XLO

SEC source: 0000899243-21-041580 · doc4.xml · nonDerivative · entry 3

RiverVest Venture Fund IV, L.P. · CIK 0001725443 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,441,444

F4 · kind: RiverVest IV purchased the shares in the Issuer's initial public offering.

F4 · shares: RiverVest IV purchased the shares in the Issuer's initial public offering.

F2 · ownership.nature: The shares held by RiverVest Venture Fund IV, L.P. ("RiverVest IV") are indirectly held by RiverVest Venture Partners IV, L.P. ("RiverVest Partners IV"), which is the general partner of RiverVest IV. RiverVest Venture Partners IV, LLC is the general partner of RiverVest Partners IV.

F3 · ownership.nature: The individual managers of RiverVest Ventures Partners IV, LLC are Jay Schmelter, John P. McKearn, Ph.D. and Niall O'Donnell. RiverVest Partners IV, RiverVest Venture Partners IV, LLC and each of the individual managers share voting and dispositive power with regard to the securities directly held by RiverVest Venture Fund IV, L.P.

F4 · ownership.nature: RiverVest IV purchased the shares in the Issuer's initial public offering.

SEC source: 0000899243-21-041580 · doc4.xml · nonDerivative · entry 2

RiverVest Venture Fund IV, L.P. · CIK 0001725443 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,191,444

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 and Series C Preferred Stock automatically converted into 1 share of the Issuer's common stock upon the closing of the Issuer's initial public offering on October 26, 2021. The shares have no expiration date.

F2 · ownership.nature: The shares held by RiverVest Venture Fund IV, L.P. ("RiverVest IV") are indirectly held by RiverVest Venture Partners IV, L.P. ("RiverVest Partners IV"), which is the general partner of RiverVest IV. RiverVest Venture Partners IV, LLC is the general partner of RiverVest Partners IV.

F3 · ownership.nature: The individual managers of RiverVest Ventures Partners IV, LLC are Jay Schmelter, John P. McKearn, Ph.D. and Niall O'Donnell. RiverVest Partners IV, RiverVest Venture Partners IV, LLC and each of the individual managers share voting and dispositive power with regard to the securities directly held by RiverVest Venture Fund IV, L.P.

SEC source: 0000899243-21-041580 · doc4.xml · nonDerivative · entry 1

RiverVest Venture Fund IV, L.P. · CIK 0001725443 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 832,120

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 and Series C Preferred Stock automatically converted into 1 share of the Issuer's common stock upon the closing of the Issuer's initial public offering on October 26, 2021. The shares have no expiration date.

F2 · ownership.nature: The shares held by RiverVest Venture Fund IV, L.P. ("RiverVest IV") are indirectly held by RiverVest Venture Partners IV, L.P. ("RiverVest Partners IV"), which is the general partner of RiverVest IV. RiverVest Venture Partners IV, LLC is the general partner of RiverVest Partners IV.

F3 · ownership.nature: The individual managers of RiverVest Ventures Partners IV, LLC are Jay Schmelter, John P. McKearn, Ph.D. and Niall O'Donnell. RiverVest Partners IV, RiverVest Venture Partners IV, LLC and each of the individual managers share voting and dispositive power with regard to the securities directly held by RiverVest Venture Fund IV, L.P.

SEC source: 0001104659-21-130030 · tm2130646-26_4seq1.xml · derivative · entry 4

Merck KGaA · CIK 0001764133 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 0

Underlying: Common Stock · 264,765 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.

F3 · derivative.exercise_price: The Series C Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series C Preferred Stock had no expiration date.

F3 · price: The Series C Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series C Preferred Stock had no expiration date.

F3 · derivative.exercise_date: The Series C Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series C Preferred Stock had no expiration date.

F3 · derivative.expiration_date: The Series C Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series C Preferred Stock had no expiration date.

F2 · ownership.nature: The shares are held directly by Merck Ventures B.V. Merck Ventures B.V. is a wholly owned indirect subsidiary of Merck KGaA, a publicly traded company. Merck KGaA may be deemed to have sole voting and dispositive power with respect to the shares held by Merck Ventures B.V.

SEC source: 0001104659-21-130030 · tm2130646-26_4seq1.xml · derivative · entry 3

Merck KGaA · CIK 0001764133 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 0

Underlying: Common Stock · 416,060 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: The Series B Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date.

F1 · price: The Series B Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date.

F1 · derivative.exercise_date: The Series B Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date.

F1 · derivative.expiration_date: The Series B Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date.

F2 · ownership.nature: The shares are held directly by Merck Ventures B.V. Merck Ventures B.V. is a wholly owned indirect subsidiary of Merck KGaA, a publicly traded company. Merck KGaA may be deemed to have sole voting and dispositive power with respect to the shares held by Merck Ventures B.V.

SEC source: 0001104659-21-130030 · tm2130646-26_4seq1.xml · nonDerivative · entry 2

Merck KGaA · CIK 0001764133 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 680,825

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.

F3 · price: The Series C Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series C Preferred Stock had no expiration date.

F2 · ownership.nature: The shares are held directly by Merck Ventures B.V. Merck Ventures B.V. is a wholly owned indirect subsidiary of Merck KGaA, a publicly traded company. Merck KGaA may be deemed to have sole voting and dispositive power with respect to the shares held by Merck Ventures B.V.

SEC source: 0001104659-21-130030 · tm2130646-26_4seq1.xml · nonDerivative · entry 1

Merck KGaA · CIK 0001764133 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 416,060

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: The Series B Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on a 9.5:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date.

F2 · ownership.nature: The shares are held directly by Merck Ventures B.V. Merck Ventures B.V. is a wholly owned indirect subsidiary of Merck KGaA, a publicly traded company. Merck KGaA may be deemed to have sole voting and dispositive power with respect to the shares held by Merck Ventures B.V.

SEC source: 0000315066-21-001812 · primary_doc.xml · derivative · entry 11

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Advisors Fund IV LP

Disclosed balance after: 0

Underlying: Common Stock · 4,465 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · derivative · entry 10

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · Impresa Fund III Limited Partnership

Disclosed balance after: 0

Underlying: Common Stock · 372,215 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · derivative · entry 9

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 0

Underlying: Common Stock · 28,703 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · derivative · entry 8

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 0

Underlying: Common Stock · 686,499 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · derivative · entry 7

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 0

Underlying: Common Stock · 789,473 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · nonDerivative · entry 6

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Advisors Fund IV LP

Disclosed balance after: 4,465

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · nonDerivative · entry 5

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · Impresa Fund III Limited Partnership

Disclosed balance after: 372,215

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · nonDerivative · entry 4

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 1,530,990

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · nonDerivative · entry 3

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 1,502,287

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000315066-21-001812 · primary_doc.xml · nonDerivative · entry 2

FMR LLC · CIK 0000315066 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund IV LP

Disclosed balance after: 815,788

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000318989-21-000078 · primary_doc.xml · derivative · entry 2

FIL Ltd · CIK 0000318989 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · Eight Roads Investments

Disclosed balance after: 0

Underlying: Common Stock · 218,705 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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · price: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.exercise_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

F1 · derivative.expiration_date: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0000318989-21-000078 · primary_doc.xml · nonDerivative · entry 1

FIL Ltd · CIK 0000318989 · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · Eight Roads Investments

Disclosed balance after: 218,705

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: On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of Series B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.

SEC source: 0001193805-21-001508 · e621041_4-xilio.xml · derivative · 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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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 V, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 756,472 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 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0001193805-21-001508 · e621041_4-xilio.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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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: 0

Underlying: Common Stock · 756,472 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 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · price: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · derivative.exercise_date: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

F1 · derivative.expiration_date: Each share of Series C Preferred Stock automatically converted into 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0001193805-21-001508 · e621041_4-xilio.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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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 V, L.P.

Disclosed balance after: 1,143,972

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0001193805-21-001508 · e621041_4-xilio.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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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: 1,143,972

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0001193805-21-001508 · e621041_4-xilio.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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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 V, L.P.

Disclosed balance after: 756,472

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 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0001193805-21-001508 · e621041_4-xilio.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 PARTNERS, L.P. · CIK 0001301041 · 10% owner · Possible Member of 10% Group

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

Deerfield Mgmt V, L.P. · CIK 0001876688 · 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: 756,472

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 0.1053 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-9.5 reverse split of the Issuer's common stock effected by the Issuer on October 15, 2021).

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. (the "Fund"). Deerfield Mgmt V, L.P. is the general partner of Deerfield Private Design Fund V, L.P. ("Fund V"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (together with Fund V, 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 V, 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 Fund 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: 0000899243-21-041838 · doc4.xml · derivative · entry 8

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 302,588 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-041838 · doc4.xml · derivative · entry 7

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 302,588 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

SEC source: 0000899243-21-041838 · doc4.xml · derivative · entry 6

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 998,544 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-041838 · doc4.xml · derivative · entry 5

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 998,544 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

SEC source: 0000899243-21-041838 · doc4.xml · nonDerivative · entry 4

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 1,301,132

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-041838 · doc4.xml · nonDerivative · entry 3

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,301,132

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

SEC source: 0000899243-21-041838 · doc4.xml · nonDerivative · entry 2

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 998,544

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-041838 · doc4.xml · nonDerivative · entry 1

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 998,544

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

SEC source: 0000899243-21-042710 · doc4a.xml · derivative · entry 10

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 302,588 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-042710 · doc4a.xml · derivative · entry 9

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 302,588 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

SEC source: 0000899243-21-042710 · doc4a.xml · derivative · entry 8

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 998,544 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-042710 · doc4a.xml · derivative · entry 7

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 998,544 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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.exercise_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F1 · derivative.expiration_date: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 6

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 1,613,632

F4 · shares: This Form 4 has been amended to include 312,500 shares of Common Stock purchased by SV7 Impact Medicine Fund LP in connection with Xilio's initial public offering.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 5

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,613,632

F4 · shares: This Form 4 has been amended to include 312,500 shares of Common Stock purchased by SV7 Impact Medicine Fund LP in connection with Xilio's initial public offering.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 4

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 1,301,132

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 3

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,301,132

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 2

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 998,544

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

F3 · ownership.nature: Consists of shares of Common Stock held by SV7 Impact Medicine Fund LP, via its general partner, SV7 (IMF) GP LLP. Catherine Bingham, Michael Ross, who is a member of Xilio's board of directors, and Houman Ashrafian are members of the investment committee of SV7 (IMF) GP LLP, which has voting and investment power with respect to the shares, and may be deemed to beneficially own such shares. SV7 (IMF) GP LLP and Ms. Bingham, Mr. Ross and Mr. Ashrafian each disclaim beneficial ownership of such shares except to the extent of their pecuniary interest therein. The address of SV7 Impact Medicine Fund LP is 71 Kingsway, London, WC2B 6ST, United Kingdom.

SEC source: 0000899243-21-042710 · doc4a.xml · nonDerivative · entry 1

SV7 Impact Medicine Fund LP · CIK 0001780602 · 10% owner

SV7 (IMF) GP LLP · CIK 0001889859 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 998,544

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: The Series B Convertible Preferred Stock and the Series C Convertible Preferred Stock converted into Xilio Therapeutics, Inc. Common Stock on a 0.1053-for-1 basis and had no expiration date.

F2 · balance_after: Reflects a 1-for-9.5 reverse stock split which became effective October 15, 2021.

SEC source: 0001104659-21-129571 · tm2130646-22_4seq1.xml · derivative · entry 1

Ross Michael Jay · CIK 0001254452 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 26,400

Underlying: Common Stock · 26,400 shares

Expires 2031-10-20

F1 · derivative.exercise_date: The option award was granted on October 21, 2021 and will vest in three equal installments on October 21, 2022, October 21, 2023 and October 21, 2024.

SEC source: 0001104659-21-129570 · tm2130646-21_4seq1.xml · derivative · entry 1

Huber Martin H. Jr. · CIK 0001653276 · President of R&D and CMO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 157,058

Underlying: Common Stock · 157,058 shares

Expires 2031-10-20

F1 · derivative.exercise_date: The option award was granted on October 21, 2021 and will begin to vest on November 1, 2021 and continue to vest in equal monthly installments thereafter until October 1, 2025.

SEC source: 0001104659-21-129572 · tm2130646-23_4seq1.xml · derivative · entry 1

Russo Rene · CIK 0001722066 · Director · CEO and President · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,041

Underlying: Common Stock · 50,041 shares

Expires 2031-10-20

F1 · derivative.exercise_date: The option award was granted on October 21, 2021 and shall begin to vest on November 1, 2021 and continue to vest in equal monthly installments thereafter until October 1, 2025.

SEC source: 0001104659-21-129565 · tm2130646-20_4seq1.xml · derivative · entry 1

Giovine Salvatore · CIK 0001887790 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 28,755

Underlying: Common Stock · 28,755 shares

Expires 2031-10-20

F1 · derivative.exercise_date: The option award was granted on October 21, 2021 and shall begin to vest on November 1, 2021 and continue to vest in equal monthly installments thereafter until October 1, 2025.