Hack Andrew A. F.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 13

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 2,200 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 12

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 734 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 11

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,800 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 10

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 439 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 9

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,002 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 8

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 118 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 7

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 368 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 6

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,000 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 5

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 400 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 4

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 2,088 shares

Expires not disclosed

F4 · price: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

F4 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.

SEC source: 0001193125-26-004925 · ownership.xml · derivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 2,460 shares

Expires not disclosed

F3 · price: Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Upfront Cash Consideration (each, a "Cash-Out Option"), became fully vested and was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, (i) the Offer Price minus (ii) the exercise price payable per share of Common Stock underlying such Cash-Out Option.

F3 · derivative.exercise_date: Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Upfront Cash Consideration (each, a "Cash-Out Option"), became fully vested and was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, (i) the Offer Price minus (ii) the exercise price payable per share of Common Stock underlying such Cash-Out Option.

F3 · derivative.expiration_date: Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Upfront Cash Consideration (each, a "Cash-Out Option"), became fully vested and was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, (i) the Offer Price minus (ii) the exercise price payable per share of Common Stock underlying such Cash-Out Option.

SEC source: 0001193125-26-004925 · ownership.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 0

F1 · kind: Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"),

F2 · kind: (continued from footnote 1) which represents the right to receive certain contingent milestone payments of up to an aggregate of $30.25 per CVR in cash, without interest and less any applicable tax withholding, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.

F1 · price: Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"),

F2 · price: (continued from footnote 1) which represents the right to receive certain contingent milestone payments of up to an aggregate of $30.25 per CVR in cash, without interest and less any applicable tax withholding, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.

F5 · ownership.nature: Represents shares of Common Stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities"). Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. The Reporting Person is a Partner of BCLSI. As a result, the Reporting Person may be deemed to share voting and dispositive power with respect to the shares held by the Bain Capital Life Sciences Entities. The Reporting Person disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.

SEC source: 0001193125-26-004925 · ownership.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

F1 · kind: Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"),

F2 · kind: (continued from footnote 1) which represents the right to receive certain contingent milestone payments of up to an aggregate of $30.25 per CVR in cash, without interest and less any applicable tax withholding, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.

F1 · price: Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"),

F2 · price: (continued from footnote 1) which represents the right to receive certain contingent milestone payments of up to an aggregate of $30.25 per CVR in cash, without interest and less any applicable tax withholding, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.

SEC source: 0000950170-25-086364 · ownership.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 61,500

Underlying: Common Stock · 61,500 shares

Expires 2035-06-11

F1 · derivative.exercise_date: The award will vest in full on the earlier of the first anniversary of the date of grant or the date of the 2026 Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continuous service with the Issuer on such vesting date.

SEC source: 0000950170-24-136230 · ownership.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 1,447,267

F1 · ownership.nature: Represents shares of Class A Common Stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS Fund II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS Fund II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of each of BCLS Fund II and BCLS II Investco and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000950170-24-073762 · ownership.xml · derivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 3,789

Underlying: Class A Common Stock · 3,789 shares

Expires 2034-06-12

F2 · derivative.exercise_date: The shares underlying this option will vest in full on the earlier of June 12, 2025 or the date of the Issuer's next annual meeting of stockholders, subject to continued service to the Issuer through such vesting date.

SEC source: 0000950170-24-073762 · ownership.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 2,499

F1 · shares: The shares reported in this transaction represent Restricted Stock Units ("RSUs"). Each RSU represents the contingent right to receive one share of the Issuer's Class A Common Stock. 100% of the RSUs subject to this grant will vest on the earlier of June 12, 2025 or the date of the Issuer's next annual meeting of stockholders, subject to continued service to the Issuer through such vesting date.

F1 · price: The shares reported in this transaction represent Restricted Stock Units ("RSUs"). Each RSU represents the contingent right to receive one share of the Issuer's Class A Common Stock. 100% of the RSUs subject to this grant will vest on the earlier of June 12, 2025 or the date of the Issuer's next annual meeting of stockholders, subject to continued service to the Issuer through such vesting date.

SEC source: 0000950170-24-072570 · ownership.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 55,000

Underlying: Common Stock · 55,000 shares

Expires 2034-06-10

F1 · derivative.exercise_date: The award will vest in full on the earlier of the first anniversary of the date of grant or the date of the 2025 Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continuous service with the Issuer on such vesting date.

SEC source: 0000950170-24-038756 · ownership.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 2,697,267

F1 · ownership.nature: Represents shares of Class A Common Stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS Fund II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS Fund II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of each of BCLS Fund II and BCLS II Investco and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000950170-24-038756 · ownership.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 3,489,062

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $76.46 to $77.44, inclusive. The reporting person undertakes to provide to Nuvalent, Inc., any security holder of Nuvalent, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth herein.

F1 · ownership.nature: Represents shares of Class A Common Stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS Fund II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS Fund II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of each of BCLS Fund II and BCLS II Investco and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000950170-23-041402 · ownership.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 915,000

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000950170-23-028682 · ownership.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 15,000

Underlying: Class A Common Stock · 15,000 shares

Expires 2033-06-15

F1 · derivative.exercise_date: The shares underlying this option shall vest in full on the earlier of June 15, 2024 or the date of Nuvalent, Inc.'s next annual meeting of stockholders, subject to continued service to Nuvalent, Inc. through the applicable vesting date.

SEC source: 0000899243-23-015776 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 2,415,000

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-23-015378 · doc4.xml · derivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,355

Underlying: Common Stock · 18,355 shares

Expires 2033-06-07

F2 · derivative.exercise_date: The award will vest in full on the earlier of the first anniversary of the date of grant or the date of the 2024 Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continuous service with the Issuer on such vesting date.

SEC source: 0000899243-23-015378 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,467

F1 · shares: Represents a restricted stock unit ("RSU") award. Each RSU represents the contingent right to receive one share of Common Stock of the Issuer.

F2 · shares: The award will vest in full on the earlier of the first anniversary of the date of grant or the date of the 2024 Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continuous service with the Issuer on such vesting date.

SEC source: 0000899243-23-014173 · doc4.xml · derivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 22,500

Underlying: Common Stock · 22,500 shares

Expires 2030-05-25

F3 · derivative.exercise_date: This option grant fully vests and becomes exercisable one year from date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date.

SEC source: 0000899243-23-014173 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 10,714

F1 · shares: These securities are restricted stock units ("RSUs"). Each RSU represents a contingent right to receive one share of DVAX Common Stock. The RSU will fully vest one year from the date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date. The release of RSU shares shall be mandatorily deferred six months and one day after the Reporting Person no longer provides services to the Company.

F2 · balance_after: The Reporting Person has reported prior awards of RSUs in Table II of Form 4. The total reported in Column 5 includes 5,357 newly awarded RSUs and 5,357 RSUs previously reported in Table II.

SEC source: 0000899243-23-013349 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnotes

Disclosed balance after: 2,915,000

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Partner of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-037989 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 3,915,000

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-034893 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 3,577,267

F3 · shares: On November 3, 2022, BCLS II Investco purchased 149,253 shares of the Issuer's Class A Common Stock at a price of $33.50 per share in an underwritten public offering.

F1 · ownership.nature: Represents securities held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCLS II Investco, LP ("BCLS II Investco") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS II and BCLS II Investco, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-029005 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 5,415,000

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. By virtue of the relationships described in this footnote, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-023141 · doc4.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 20,000

Underlying: Class A Common Stock · 20,000 shares

Expires 2032-06-16

F1 · derivative.exercise_date: The shares underlying this option shall vest in full on the earlier of June 16, 2023 or the date of Nuvalent, Inc.'s next annual meeting of stockholders, subject to continued service to Nuvalent, Inc. through the applicable vesting date.

SEC source: 0000899243-22-021967 · doc4.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 45,000

Underlying: Common Stock · 45,000 shares

Expires 2032-06-08

F1 · derivative.exercise_date: The option vests in full on the earlier of the first anniversary of the date of grant or the date of the 2023 Annual Meeting of Stockholders of Mersana Therapeutics, Inc., subject to the reporting person's continued service on such vesting date.

SEC source: 0000899243-22-020726 · doc4.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,663,673

F4 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.175 to $3.200, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-020726 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,648,913

F3 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.215 to $3.300, inclusive. The reporting person undertakes to provide to Mersana Therapeutics, Inc., any security holder of Mersana Therapeutics, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnotes (3) and (4) to this Form 4.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019801 · doc4.xml · nonDerivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,568,154

F5 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.150 to $3.200, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019955 · doc4.xml · derivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 22,500

Underlying: Common Stock · 22,500 shares

Expires 2029-05-25

F2 · derivative.exercise_date: This option grant fully vests and becomes exercisable one year from date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date.

SEC source: 0000899243-22-019955 · doc4.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 5,357

Underlying: Common Stock · 5,357 shares

Expires not disclosed

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of common stock. The RSU will fully vest one year from the date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date. The release of RSU shares shall be mandatorily deferred until the Reporting Person no longer provides services to the Company.

F1 · derivative.exercise_date: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of common stock. The RSU will fully vest one year from the date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date. The release of RSU shares shall be mandatorily deferred until the Reporting Person no longer provides services to the Company.

F1 · derivative.expiration_date: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of common stock. The RSU will fully vest one year from the date of grant, provided that Reporting Person continues to provide services to the Company through such vesting date. The release of RSU shares shall be mandatorily deferred until the Reporting Person no longer provides services to the Company.

SEC source: 0000899243-22-019801 · doc4.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,493,154

F4 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.100 to $3.200, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019801 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,402,999

F3 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.210 to $3.350, inclusive. The reporting person undertakes to provide to Mersana Therapeutics, Inc., any security holder of Mersana Therapeutics, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnotes (3) through (5) to this Form 4.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019274 · doc4.xml · nonDerivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,302,999

F5 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.345 to $3.350, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019274 · doc4.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,287,400

F4 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.374 to $3.505, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-019274 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,187,400

F3 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.375 to $3.595, inclusive. The reporting person undertakes to provide to Mersana Therapeutics, Inc., any security holder of Mersana Therapeutics, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnotes (3) through (5) to this Form 4.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-018652 · doc4.xml · nonDerivative · entry 3

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 8,087,400

F5 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.290 to $3.405, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-018652 · doc4.xml · nonDerivative · entry 2

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 7,876,132

F4 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $3.160 to $3.200, inclusive.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-018652 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 7,872,692

F3 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.910 to $3.150, inclusive. The reporting person undertakes to provide to Mersana Therapeutics, Inc., any security holder of Mersana Therapeutics, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnotes (3) through (5) to this Form 4.

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-014811 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 7,737,400

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-014730 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 7,120,116

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-005224 · doc4.xml · nonDerivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnotes

Disclosed balance after: 6,522,030

F1 · ownership.nature: Represents shares of common stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").

F2 · ownership.nature: Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. Dr. Hack is a Managing Director of BCLSI. As a result, Dr. Hack may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. Dr. Hack disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

SEC source: 0000899243-22-001013 · doc4.xml · derivative · entry 1

Hack Andrew A. F. · CIK 0001657434 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,995

Underlying: Common Stock · 10,995 shares

Expires 2032-01-02

F1 · derivative.exercise_date: The option becomes exercisable in equal quarterly installments on the last day of each calendar quarter of 2022.