DNTH

SEC source: 0000950170-24-007137 · ownership.xml · nonDerivative · entry 1

MOULDER LEON O JR · CIK 0001228865 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,436,745

F1 · shares: Consists of 166,667 shares of common stock purchased by Tellus BioVentures, LLC ("Tellus") from the Issuer in a private placement, which transaction is exempt from Section 16(b) in accordance with Rule 16b-3(d)(1) promulgated under the Securities Exchange Act of 1934, as amended (the "Exchange Act").

F2 · ownership.nature: The securities reported are held of record by Tellus. The Reporting Person may be deemed to have voting and dispositive control over the shares held by Tellus. The Reporting Person disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest therein.

SEC source: 0000950170-24-007136 · ownership.xml · derivative · entry 2

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 832,333

Underlying: Common Stock · 832,333 shares

Expires not disclosed

F3 · shares: Consists of Pre-Funded Warrants to purchase up to 832,333 shares of common stock purchased by Fund II from the Issuer in a private placement, which transaction is exempt from Section 16(b) in accordance with Rule 16b-3(d)(1) promulgated under the Exchange Act.

F4 · derivative.exercise_date: The Pre-Funded Warrants have no expiration date and are exercisable at any time after the date of issuance. A holder of Pre-Funded Warrants may not exercise the Pre-Funded Warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise.

F4 · derivative.expiration_date: The Pre-Funded Warrants have no expiration date and are exercisable at any time after the date of issuance. A holder of Pre-Funded Warrants may not exercise the Pre-Funded Warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise.

F5 · ownership.nature: Consists of Pre-Funded Warrants to purchase up to 832,333 shares of common stock held of record by Fund II. Fairmount is the investment manager for Fund II. The general partner of Fairmount is Fairmount GP, of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-24-007136 · ownership.xml · nonDerivative · entry 1

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 2,762,837

F1 · shares: Consists of 834,334 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II") from the Issuer in a private placement, which transaction is exempt from Section 16(b) in accordance with Rule 16b-3(d)(1) promulgated under the Securities Exchange Act of 1934, as amended (the "Exchange Act").

F2 · ownership.nature: Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 2,641,834 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0001104659-23-106378 · tm2327394-1_4seq1.xml · nonDerivative · entry 1

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,928,503

F1 · shares: Consists of 24,670 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II").

F2 · price: This transaction was executed in multiple trades at prices ranging from $13.45 to $13.645. The price reported above reflects the weighted average purchase price. The Reporting Persons hereby undertake to provide upon request to the SEC staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transaction was effected.

F3 · ownership.nature: Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 1,807,500 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0001104659-23-104808 · tm2327182-1_4seq1.xml · nonDerivative · entry 1

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,903,833

F1 · shares: Consists of 30,000 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II").

F2 · ownership.nature: Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 1,782,830 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-23-049695 · ownership.xml · nonDerivative · entry 2

Randhawa Simrat · CIK 0001992260 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 4,000

SEC source: 0000950170-23-049695 · ownership.xml · nonDerivative · entry 1

Randhawa Simrat · CIK 0001992260 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 2,000

SEC source: 0000899243-23-019370 · doc4.xml · nonDerivative · entry 1

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,873,833

F1 · shares: Consists of 30,000 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II").

F2 · ownership.nature: Consists of (i) 58,857 shares of common stock held of record by Fairmount Healthcare Fund LP ("Fund I"), (ii) 1,752,830 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-23-048022 · ownership.xml · nonDerivative · entry 2

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,843,833

F4 · shares: Consists of (i) 281 shares of common stock purchased by Fund I and (ii) 9,086 shares of common stock purchased by Fund II.

F5 · price: This transaction was executed in multiple trades at prices ranging from $10.90 to $12.50 The price reported above reflects the weighted average purchase price. The Reporting Persons hereby undertake to provide upon request to the SEC staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transaction was effected.

F6 · ownership.nature: Consists of (i) 58,857 shares of common stock held of record by Fund I, (ii) 1,722,830 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC.

SEC source: 0000950170-23-048022 · ownership.xml · nonDerivative · entry 1

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,834,466

F1 · shares: Consists of (i) 447 shares of common stock purchased by Fairmount Healthcare Fund LP ("Fund I") and (ii) 14,440 shares of common stock purchased by Fairmount Healthcare Fund II LP ("Fund II").

F2 · price: This transaction was executed in multiple trades at prices ranging from $10.415 to $11.00. The price reported above reflects the weighted average purchase price. The Reporting Persons hereby undertake to provide upon request to the SEC staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transaction was effected.

F3 · ownership.nature: Consists of (i) 58,576 shares of common stock held of record by Fund I, (ii) 1,713,744 shares of common stock held of record by Fund II and (iii) 62,146 shares of common stock held of record by Fairmount SPV III, LLC. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fund I and Fund II and is the Class A Member for Fairmount SPV III, LLC. The general partner of Fairmount is Fairmount Funds Management GP LLC ("Fairmount GP"), of which Peter Harwin and Tomas Kiselak are the managing members. Fairmount, Fairmount GP, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-23-048029 · ownership.xml · derivative · entry 1

Meng Lei · CIK 0001992281 · Director

Avidity Partners Management LP · CIK 0001791827 · Director

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

F2 · ownership.nature: Under Ms. Meng's arrangement with Avidity Partners Management LP (the "Avidity"), Ms. Meng holds the option for the benefit of clients of Avidity. Ms. Meng is obligated to turn over to the Avidity any net cash or stock received from the option for the benefit of Avidity. Ms. Meng therefore disclaims beneficial ownership of the option and underlying common stock. The reported shares may be deemed to beneficially owned by (i) Avidity Partners Management LP, (ii) Avidity Partners Management (GP) LLC, the general partner of Avidity Partners Management LP and (iii) each of David Witzke and Michael Gregory, the managing members of Avidity Partners Management (GP) LLC. Under Ms. Meng's arrangement with Avidity Partners Management LP (the "Avidity"), Ms. Meng holds the option for the benefit of clients of Avidity.

F3 · ownership.nature: Ms. Meng is obligated to turn over to the Avidity any net cash or stock received from the option for the benefit of Avidity. Ms. Meng therefore disclaims beneficial ownership of the option and underlying common stock. The reported shares may be deemed to beneficially owned by (i) Avidity Partners Management LP, (ii) Avidity Partners Management (GP) LLC, the general partner of Avidity Partners Management LP and (iii) each of David Witzke and Michael Gregory, the managing members of Avidity Partners Management (GP) LLC.

F4 · ownership.nature: As of the date hereof, Avidity Partners Management (GP) LLC, David Witzke and Michael Gregory have not yet received the applicable EDGAR codes required to make filings with the Securities and Exchange Commission; however, such Reporting Persons have applied for the applicable codes and will supplement this Form 4 once such codes are available.

SEC source: 0000899243-23-018866 · doc4.xml · derivative · entry 1

Soteropoulos Paula · CIK 0001692444 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

SEC source: 0000899243-23-018869 · doc4.xml · derivative · entry 1

Violin Jonathan · CIK 0001730615 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

SEC source: 0000950170-23-048022 · ownership.xml · derivative · entry 3

Fairmount Funds Management LLC · CIK 0001802528 · Director · 10% owner

Kiselak Tomas · CIK 0001830177 · Director · 10% owner

Harwin Peter Evan · CIK 0001663607 · Director · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F7 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

F8 · ownership.nature: Under Mr. Kiselak's arrangement with Fairmount Funds Management LLC (the "Adviser"), Mr. Kiselak holds the option for one or more investment vehicles managed by the Adviser (each, a "Fairmount Fund"). Mr. Kiselak is obligated to turn over to the Adviser any net cash or stock received from the option for the benefit of such Fairmount Fund. Mr. Kiselak therefore disclaims beneficial ownership of the option and underlying common stock.

SEC source: 0000899243-23-018867 · doc4.xml · derivative · entry 1

Lawton Alison Frances · CIK 0001542650 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

SEC source: 0000899243-23-018863 · doc4.xml · derivative · entry 1

McGeorge Anne · CIK 0001779934 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

SEC source: 0000899243-23-018862 · doc4.xml · derivative · entry 1

MOULDER LEON O JR · CIK 0001228865 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,500

Underlying: Common Stock · 6,500 shares

Expires 2033-09-10

F1 · derivative.exercise_date: This option represents a right to purchase a total of 6,500 shares of the Issuer's common stock, which will vest in full on the date that is the earlier of (i) the Issuer's 2024 Annual Meeting of Stockholders and (ii) September 11, 2024, subject to the Reporting Person's continued service to the Issuer.

SEC source: 0000899243-23-004411 · doc4.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,058,204

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.801 to $0.893, inclusive. The reporting person undertakes 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 this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-23-004411 · doc4.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,558,204

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.808 to $0.86, inclusive. The reporting person undertakes 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 this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-22-037424 · doc4.xml · nonDerivative · entry 1

Stants Kristen · CIK 0001805727 · Chief People Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,264

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of June 1, 2022 through November 30, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 1, 2022.

SEC source: 0000899243-22-037435 · doc4.xml · nonDerivative · entry 1

Beetham Thomas W. · CIK 0001741382 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 19,897

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of June 1, 2022 through November 30, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 1, 2022.

SEC source: 0000899243-22-037433 · doc4.xml · nonDerivative · entry 1

Mahoney Stephen F. · CIK 0001741389 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 17,264

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of June 1, 2022 through November 30, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 1, 2022.

SEC source: 0000899243-22-037432 · doc4.xml · nonDerivative · entry 1

Deardorf Caren · CIK 0001871152 · Chief Commercial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 19,762

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of June 1, 2022 through November 30, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 1, 2022.

SEC source: 0000899243-22-037431 · doc4.xml · nonDerivative · entry 1

GARDNER JASON · CIK 0001741286 · Director · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 292,872

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of June 1, 2022 through November 30, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on June 1, 2022.

SEC source: 0000899243-22-028910 · doc4.xml · derivative · entry 1

VASCONCELLES MICHAEL · CIK 0001734755 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 40,000

Underlying: Common Stock · 40,000 shares

Expires 2032-08-14

F1 · derivative.exercise_date: This option shall vest and become exercisable over three years, with 33% of this option vesting on August 15, 2023, and the remainder vesting in 24 equal monthly installments thereafter.

SEC source: 0000899243-22-027272 · doc4.xml · derivative · entry 1

Humphrey Jeffrey · CIK 0001816944 · Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 75,000

Underlying: Common Stock · 75,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027265 · doc4.xml · derivative · entry 1

Stants Kristen · CIK 0001805727 · Chief People Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 85,000

Underlying: Common Stock · 85,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027275 · doc4.xml · derivative · entry 1

Olson Lisa · CIK 0001824009 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 100,000

Underlying: Common Stock · 100,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027273 · doc4.xml · derivative · entry 1

Beetham Thomas W. · CIK 0001741382 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 75,000

Underlying: Common Stock · 75,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027271 · doc4.xml · derivative · entry 1

GARDNER JASON · CIK 0001741286 · Director · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 187,500

Underlying: Common Stock · 187,500 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027270 · doc4.xml · derivative · entry 1

Nichols David Wayne · CIK 0001857488 · Chief Technical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 75,000

Underlying: Common Stock · 75,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027264 · doc4.xml · derivative · entry 1

Deardorf Caren · CIK 0001871152 · Chief Commercial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 75,000

Underlying: Common Stock · 75,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-027266 · doc4.xml · derivative · entry 1

Mahoney Stephen F. · CIK 0001741389 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 130,000

Underlying: Common Stock · 130,000 shares

Expires 2032-07-31

F1 · derivative.exercise_date: This option shall vest and become exercisable in 16 equal quarterly installments beginning on the first quarter following the vesting commencement date. The vesting commencement date is August 1, 2022.

SEC source: 0000899243-22-024669 · doc4.xml · derivative · entry 1

McGeorge Anne · CIK 0001779934 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-024681 · doc4.xml · derivative · entry 1

Booth Bruce · CIK 0001451612 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

F2 · ownership.direct: This option was granted to the Reporting Person, a director of the Issuer. The proceeds of any sale of shares of common stock issued to the Reporting Person upon exercise of this option will be transferred to Atlas Venture Life Science Advisors, LLC and as such, the Reporting Person disclaims ownership of such securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, except to the extent of his pecuniary interest therein, if any.

SEC source: 0000899243-22-024676 · doc4.xml · derivative · entry 1

Daniel Thomas O · CIK 0001538894 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-024675 · doc4.xml · derivative · entry 1

Lawton Alison Frances · CIK 0001542650 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-024673 · doc4.xml · derivative · entry 1

RONNEBERG AMY L · CIK 0001380292 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-024671 · doc4.xml · derivative · entry 1

Albers Jeffrey W. · CIK 0001638474 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-024670 · doc4.xml · derivative · entry 1

Scadden David · CIK 0001707715 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Common Stock · 20,000 shares

Expires 2032-06-27

F1 · derivative.exercise_date: This option shall vest and become exercisable in full upon the earlier to occur of (a) June 28, 2023 or (b) the next annual meeting of the Issuer's stockholders.

SEC source: 0000899243-22-021186 · doc4.xml · nonDerivative · entry 1

Stants Kristen · CIK 0001805727 · Chief People Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 17,264

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of December 1, 2021 through May 31, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on May 31, 2022.

SEC source: 0000899243-22-021185 · doc4.xml · nonDerivative · entry 1

Deardorf Caren · CIK 0001871152 · Chief Commercial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 16,762

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of December 1, 2021 through May 31, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on May 31, 2022.

SEC source: 0000899243-22-021184 · doc4.xml · nonDerivative · entry 1

GARDNER JASON · CIK 0001741286 · Director · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 289,872

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of December 1, 2021 through May 31, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on May 31, 2022.

SEC source: 0000899243-22-021182 · doc4.xml · nonDerivative · entry 1

Beetham Thomas W. · CIK 0001741382 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 16,897

F1 · kind: The reporting person is voluntarily reporting the acquisition of shares of the Issuer's common stock pursuant to the Magenta Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the "ESPP") for the ESPP purchase period of December 1, 2021 through May 31, 2022. This transaction is exempt under both Rule 16b-3(c) and Rule 16b-3(d).

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the Issuer's common stock on May 31, 2022.

SEC source: 0000899243-22-018819 · doc4.xml · derivative · entry 1

Humphrey Jeffrey · CIK 0001816944 · Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Common Stock · 50,000 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.

SEC source: 0000899243-22-018812 · doc4.xml · derivative · entry 1

Stants Kristen · CIK 0001805727 · Chief People Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Common Stock · 50,000 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.

SEC source: 0000899243-22-018822 · doc4.xml · derivative · entry 1

Olson Lisa · CIK 0001824009 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Common Stock · 50,000 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.

SEC source: 0000899243-22-018817 · doc4.xml · derivative · entry 1

GARDNER JASON · CIK 0001741286 · Director · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 162,500

Underlying: Common Stock · 162,500 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.

SEC source: 0000899243-22-018807 · doc4.xml · derivative · entry 1

Nichols David Wayne · CIK 0001857488 · Chief Technical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Common Stock · 50,000 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.

SEC source: 0000899243-22-018804 · doc4.xml · derivative · entry 1

Mahoney Stephen F. · CIK 0001741389 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 62,500

Underlying: Common Stock · 62,500 shares

Expires 2032-05-16

F1 · derivative.exercise_date: This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022.