Deerfield Special Situations Fund, L.P.

SEC source: 0001193805-21-001014 · e620792_4-mirum.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · * Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · * Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · * Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · * Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · * Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 0

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $15.81 to $15.91, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-21-000999 · e620783_4-mirum.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · * Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · * Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · * Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · * Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · * Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 99,325

F3 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $15.84 to $15.955, inclusive.

F4 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F5 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-21-000999 · e620783_4-mirum.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · * Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · * Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · * Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · * Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · * Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 106,162

F2 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $16.185 to $16.345, inclusive.

F4 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F5 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-21-000999 · e620783_4-mirum.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · * Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · * Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · * Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · * Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · * Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · * Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 155,401

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $16.85 to $17.55, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes 1 and 2 of this Form 4.

F4 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F5 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-001376 · e619146_4-cabaletta.xml · derivative · entry 5

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 464,253 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-001376 · e619146_4-cabaletta.xml · derivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 464,253 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F1 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-001376 · e619146_4-cabaletta.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 700,000

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-001376 · e619146_4-cabaletta.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 464,253

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-001376 · e619146_4-cabaletta.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 464,253

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series B Preferred Stock automatically converted into 0.66666667 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-1.5 reverse stock split of the Issuer's common stock effected by the Issuer on October 16, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000911 · e619107_4-ft.xml · derivative · entry 5

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 472,860 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000911 · e619107_4-ft.xml · derivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 472,860 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F1 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000911 · e619107_4-ft.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 285,714

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000911 · e619107_4-ft.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 472,860

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000911 · e619107_4-ft.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 472,860

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.148467077 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-6.7355 reverse stock split of the Issuer's common stock effected by the Issuer on September 20, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund IV, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt IV, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · derivative · entry 6

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 1,558,456 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · derivative.exercise_date: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · derivative.expiration_date: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · derivative · entry 5

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Healthcare Innovations Fund, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 1,558,456 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · derivative.exercise_date: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F1 · derivative.expiration_date: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · nonDerivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 166,000

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 1,724,456

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund IV, L.P.

Disclosed balance after: 1,558,456

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000660 · e618569_4-mirum.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt HIF, L.P. · CIK 0001665736 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt IV, L.P. · CIK 0001713467 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund IV, L.P. · CIK 0001680307 · 10% owner · Possible Member of 10% Group

Deerfield Healthcare Innovations Fund, L.P. · CIK 0001646981 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Healthcare Innovations Fund, L.P.

Disclosed balance after: 1,558,456

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series A Preferred Stock automatically converted into 0.125 shares of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-8 reverse stock split of the common stock effected by the Issuer on July 3, 2019).

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt IV, L.P. is the general partner of Deerfield Private Design Fund IV, L.P. ("Fund IV"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. ("Deerfield Special Situations"). Deerfield Mgmt HIF, L.P. is the general partner of Deerfield Healthcare Innovations Fund, L.P. (collectively with Fund IV and Deerfield Special Situations, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P., Deerfield Mgmt IV, L.P., Deerfield Mgmt HIF, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000616 · e618541_4-aclaris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 3,159,165

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $2.50 to $2.98, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000616 · e618541_4-aclaris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 964,101

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $2.50 to $2.98, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000603 · e618536_4-aclaris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 3,749,966

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.505, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000603 · e618536_4-aclaris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,072,775

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.505, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 6

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 3,751,318

F5 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.58, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 5

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,073,127

F5 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.58, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 3,792,168

F4 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.67, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,083,761

F4 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.67, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 3,842,345

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.89, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1), (4) and (5) of this Form 4.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000599 · e618533_4-aclaris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,096,824

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $4.50 to $4.89, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1), (4) and (5) of this Form 4.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000485 · e618447_4-aclaris.xml · nonDerivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,166,959

F4 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $6.00 to $6.12, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000485 · e618447_4-aclaris.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 4,111,747

F4 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $6.00 to $6.12, inclusive.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000485 · e618447_4-aclaris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 1,238,828

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $6.00 to $6.61, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) and (4) of this Form 4.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000485 · e618447_4-aclaris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · Possible Member of a 10% Group

DEERFIELD PARTNERS, L.P. · CIK 0001301041 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 4,220,443

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $6.00 to $6.61, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) and (4) of this Form 4.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · derivative · entry 11

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 23,333 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · derivative · entry 10

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 132,740 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · derivative · entry 9

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund III, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 23,333 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · derivative · entry 8

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund III, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 132,740 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 7

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Partners, L.P.

Disclosed balance after: 10,000

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 6

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 166,073

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 5

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund III, L.P.

Disclosed balance after: 166,073

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 4

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 156,073

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · balance_after: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 132,740

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · balance_after: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund III, L.P.

Disclosed balance after: 156,073

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · price: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F2 · balance_after: Each share of Series C Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000271 · e618284_4-swav.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Private Design Fund III, L.P.

Disclosed balance after: 132,740

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F1 · balance_after: Each share of Series B Preferred Stock automatically converted into one share of the Issuer's common stock upon the closing of the Issuer's initial public offering (on an adjusted basis, after giving effect to the 1-for-12.2 reverse stock split effected by the Issuer on February 22, 2019).

F3 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. and Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F4 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000209 · e618226_4-xeris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 856,470

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000209 · e618226_4-xeris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 857,821

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $15.00 to $15.25, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000117 · e618211_4-xeris.xml · nonDerivative · entry 3

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 863,711

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000117 · e618211_4-xeris.xml · nonDerivative · entry 2

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 873,120

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

SEC source: 0001193805-19-000117 · e618211_4-xeris.xml · nonDerivative · entry 1

Flynn James E · CIK 0001352546 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt L.P. · CIK 0001010823 · 10% owner · Possible Member of 10% Group

DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C) · CIK 0001009258 · 10% owner · Possible Member of 10% Group

Deerfield Special Situations Fund, L.P. · CIK 0001354395 · 10% owner · Possible Member of 10% Group

Deerfield Mgmt III, L.P. · CIK 0001610540 · 10% owner · Possible Member of 10% Group

Deerfield Private Design Fund III, L.P. · CIK 0001603333 · 10% owner · Possible Member of 10% Group

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · Through Deerfield Special Situations Fund, L.P.

Disclosed balance after: 873,520

F1 · price: The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $15.00 to $15.13, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2 · ownership.nature: This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.

F3 · ownership.nature: In accordance with Instruction 4(b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.