EX-10.3





 Exhibit 10.3 

THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

(AS ADOPTED ON SEPTEMBER 23, 2021) 












 THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

ARTICLE 1.    INTRODUCTION. 

The Board adopted the Plan to become effective immediately, although no Awards may be granted prior to the IPO Date. The purpose of the Plan is
to promote the long-term success of the Company and the creation of stockholder value by (a) encouraging Service Providers to focus on critical long-range corporate objectives, (b) encouraging the attraction and retention of Service
Providers with exceptional qualifications and (c) linking Service Providers directly to stockholder interests through increased stock ownership. The Plan seeks to achieve this purpose by providing for Awards in the form of Options (which may be
ISOs or NSOs), SARs, Restricted Shares and Restricted Stock Units. Capitalized terms used in this Plan are defined in Article 14. 
 ARTICLE
2.    ADMINISTRATION. 
 2.1    General. The Plan may be administered by the Board or one
or more Committees to which the Board (or an authorized Board committee) has delegated authority. If administration is delegated to a Committee, the Committee shall have the powers theretofore possessed by the Board, including, to the extent
permitted by applicable law, the power to delegate to a subcommittee any of the administrative powers the Committee is authorized to exercise (and references in this Plan to either the Board or the Administrator shall hereafter also encompass the
Committee or subcommittee, as applicable). The Board may abolish the Committee’s delegation at any time and the Board shall at all times also retain the authority it has delegated to the Committee. The Administrator shall comply with rules and
regulations applicable to it, including under the rules of any exchange on which the Common Shares are traded, and shall have the authority and be responsible for such functions as have been assigned to it. 

2.2    Section 16. To the extent desirable to qualify transactions hereunder as exempt under Exchange Act
Rule 16b-3, the transactions contemplated hereunder will be approved by the entire Board or a Committee of two or more “non-employee directors” within the
meaning of Exchange Act Rule 16b-3. 
 2.3    Powers of
Administrator. Subject to the terms of the Plan, and in the case of a Committee, subject to the specific duties delegated to the Committee, the Administrator shall have the authority to (a) select the Service Providers who are to receive
Awards under the Plan, (b) determine the type, number, vesting requirements and other features and conditions of such Awards, (c) interpret the Plan and Awards granted under the Plan, (d) determine whether, when and to what extent an
Award has become vested and/or exercisable and whether any performance-based vesting conditions have been satisfied, (e) make, amend and rescind rules relating to the Plan and Awards granted under the Plan, including rules relating to sub-plans established for the purposes of satisfying applicable foreign laws or for qualifying for favorable tax treatment under applicable foreign laws, (f) impose such restrictions, conditions or limitations
as it determines appropriate as to the timing and manner of any resales by a Participant of any Common Shares issued pursuant to an Award, including restrictions under an insider trading policy and restrictions as to the use of a specified brokerage
firm for such resales, and (g) make all other decisions relating to the operation of the Plan and Awards granted under the Plan. In addition, with regard to the terms and conditions of Awards granted to Service Providers outside of the United
States, the Administrator may vary from the provisions of the Plan (other than any requiring stockholder approval pursuant to Section 13.3) to the extent it determines it necessary and appropriate to do so. 












 2.4    Effect of Administrator’s Decisions. The
Administrator’s decisions, determinations and interpretations shall be final and binding on all interested parties. 

2.5    Governing Law. The Plan, and all claims or causes of action (whether in contract, tort or statute)
that may be based upon, arise out of or relate to the Plan or any Award, shall be governed by, and enforced in accordance with, the internal laws of the State of Delaware, without giving effect to any laws, rules or provisions of the State of
Delaware that would cause the application of the laws, rules or provisions of any jurisdiction other than the State of Delaware. 
 ARTICLE
3.    SHARES AVAILABLE FOR GRANTS. 
 3.1    Basic Limitation. Common Shares issued
pursuant to the Plan may be authorized but unissued shares or treasury shares. The aggregate number of Common Shares issued under the Plan shall not exceed the sum of (a) 4,395,080 Common Shares, plus (b) up to 4,699,003 Common Shares
(i) subject to awards granted under the Predecessor Plan that are outstanding on the IPO Date and that subsequently are forfeited, expire or lapse unexercised or unsettled and (ii) issued pursuant to awards granted under the Predecessor
Plan that are outstanding on the IPO Date and that are subsequently forfeited to or reacquired by the Company, and (c) the additional Common Shares described in Articles 3.2 and 3.3. The Company shall reserve and keep available such
number of Common Shares as will be sufficient to satisfy the requirements of the Plan. The numerical limitations in this Article 3.1 shall be subject to adjustment pursuant to Article 9. 

3.2    Annual Increase in Shares. On the first day of
each fiscal year of the Company during the term of the Plan, commencing on January 1, 2023 and ending on (and including) January 1, 2031, the aggregate number of Common Shares that may be issued under the Plan shall automatically increase
by a number equal to the lesser of (a) five percent (5%) of the total number of Common Shares actually issued and outstanding on the last day of the preceding fiscal year, or (b) a number of Common Shares determined by the
Board. 
 3.3    Shares Returned to Reserve. To the extent that Options, SARs, Restricted Stock Units or
other Awards are forfeited, cancelled or expire for any reason before being exercised or settled in full, the Common Shares subject to such Awards shall again become available for issuance under the Plan. If SARs are exercised or Restricted Stock
Units are settled, then only the number of Common Shares (if any) actually issued to the Participant upon exercise of such SARs or settlement of such Restricted Stock Units, as applicable, shall reduce the number of Common Shares available under
Article 3.1 and the balance shall again become available for issuance under the Plan. If Restricted Shares or Common Shares issued upon the exercise of Options are reacquired by the Company pursuant to a forfeiture provision, repurchase right
or for any other reason, then such Common Shares shall again become available for issuance under the Plan. Common Shares applied to pay the Exercise Price of Options or to satisfy tax withholding obligations related to any Award shall again become
available for issuance under the Plan. To the extent that an Award is settled in cash rather than Common Shares, the cash settlement shall not reduce the number of Shares available for issuance under the Plan. 












 3.4    Awards Not Reducing Share Reserve. To the extent
permitted under applicable exchange listing standards, any dividend equivalents paid or credited under the Plan with respect to Restricted Stock Units shall not be applied against the number of Common Shares that may be issued under the Plan,
whether or not such dividend equivalents are converted into Restricted Stock Units. In addition, Common Shares subject to Substitute Awards granted by the Company shall not reduce the number of Common Shares that may be issued under Article 3.1, nor
shall shares subject to Substitute Awards again be available for Awards under the Plan in the event of any forfeiture, expiration or cash settlement of such Substitute Awards. 

3.5    Code Section 422 Limit. Subject to adjustment in accordance with Article 9,
no more than 30,000,000 Common Shares may be issued under the Plan upon the exercise of ISOs. 
 ARTICLE 4.    ELIGIBILITY. 

4.1    Incentive Stock Options. Only Employees who are common-law
employees of the Company, a Parent or a Subsidiary shall be eligible for the grant of ISOs. In addition, an Employee who owns more than 10% of the total combined voting power of all classes of outstanding stock of the Company or any of its Parents
or Subsidiaries shall not be eligible for the grant of an ISO unless the additional requirements set forth in Code Section 422(c)(5) are satisfied. 

4.2    Other Awards. Awards other than ISOs may be granted to both Employees and other Service
Providers. 
 ARTICLE 5.    OPTIONS. 

5.1    Stock Option Agreement. Each grant of an Option under the Plan shall be evidenced by a Stock Option
Agreement between the Optionee and the Company. Such Option shall be subject to all applicable terms of the Plan and may be subject to any other terms that are not inconsistent with the Plan. The Stock Option Agreement shall specify whether the
Option is intended to be an ISO or an NSO. The provisions of the various Stock Option Agreements entered into under the Plan need not be identical. 

5.2    Number of Shares. Each Stock Option Agreement shall specify the number of Common Shares subject to
the Option, which number shall adjust in accordance with Article 9. 
 5.3    Exercise Price. Each
Stock Option Agreement shall specify the Exercise Price, which shall not be less than 100% of the Fair Market Value of a Common Share on the date of grant. The preceding sentence shall not apply to an Option that is a Substitute Award granted in a
manner that would satisfy the requirements of Code Section 409A and, if applicable, Code Section 424(a). 

5.4    Exercisability and Term. Each Stock Option Agreement shall specify the date or event when all or any
installment of the Option is to become vested and/or exercisable. The vesting and exercisability conditions applicable to the Option may include service-based conditions, performance-based conditions, such other conditions as the Administrator may
determine, or any combination of such conditions. The Stock Option Agreement shall also specify the term of the Option; provided that, except to the extent necessary to comply with applicable foreign law, the term of an Option shall in no event
exceed 10 years from the date of grant. A Stock Option Agreement may provide for accelerated vesting and/or exercisability upon certain specified events and may provide for expiration prior to the end of its term in the event of the termination
of the Optionee’s service. 












 5.5    Death of Optionee. After an Optionee’s
death, any vested and exercisable Options held by such Optionee may be exercised by his or her beneficiary or beneficiaries. Each Optionee may designate one or more beneficiaries for this purpose by filing the prescribed form with the Company. A
beneficiary designation may be changed by filing the prescribed form with the Company at any time before the Optionee’s death. If no beneficiary was designated or if no designated beneficiary survives the Optionee, then any vested and
exercisable Options held by the Optionee may be exercised by his or her estate. 
 5.6    Modification or
Assumption of Options. Within the limitations of the Plan, the Administrator may modify, reprice, extend or assume outstanding options or may accept the cancellation of outstanding options (whether granted by the Company or by another issuer) in
return for the grant of new Options for the same or a different number of shares and at the same or a different exercise price or in return for the grant of a different type of Award. The foregoing notwithstanding, no modification of an Option
shall, without the consent of the Optionee, materially impair his or her rights under such Option. 

5.7    Buyout Provisions. The Administrator may at any time (a) offer to buy out for a payment in cash
or cash equivalents an Option previously granted or (b) authorize an Optionee to elect to cash out an Option previously granted, in either case at such time and based upon such terms and conditions as the Administrator shall establish. 

5.8    Payment for Option Shares. The entire Exercise Price of Common Shares issued upon exercise of Options
shall be payable in cash or cash equivalents at the time when such Common Shares are purchased. In addition, the Administrator may, in its sole discretion and to the extent permitted by applicable law, accept payment of all or a portion of the
Exercise Price through any one or a combination of the following forms or methods: 
 (a)    Subject to any conditions or
limitations established by the Administrator, by surrendering, or attesting to the ownership of, Common Shares that are already owned by the Optionee with a value on the date of surrender equal to the aggregate exercise price of the Common Shares as
to which such Option will be exercised; 
 (b)    By delivering (on a form prescribed by the Company) an irrevocable
direction to a securities broker approved by the Company to sell all or part of the Common Shares being purchased under the Plan and to deliver all or part of the sales proceeds to the Company; 

(c)    Subject to such conditions and requirements as the Administrator may impose from time to time, through a net
exercise procedure; or 
 (d)    Through any other form or method consistent with applicable laws, regulations and
rules. 
 ARTICLE 6.    STOCK APPRECIATION RIGHTS. 

6.1    SAR Agreement. Each grant of a SAR under the Plan shall be evidenced by a SAR Agreement between the
Optionee and the Company. Such SAR shall be subject to all applicable terms of the Plan and may be subject to any other terms that are not inconsistent with the Plan. The provisions of the various SAR Agreements entered into under the Plan need not
be identical. 












 6.2    Number of Shares. Each SAR Agreement shall specify
the number of Common Shares to which the SAR pertains, which number shall adjust in accordance with Article 9. 

6.3    Exercise Price. Each SAR Agreement shall specify the Exercise Price, which shall in no event be less
than 100% of the Fair Market Value of a Common Share on the date of grant. The preceding sentence shall not apply to a SAR that is a Substitute Award granted in a manner that would satisfy the requirements of Code Section 409A. 

6.4    Exercisability and Term. Each SAR Agreement shall specify the date when all or any installment of the
SAR is to become vested and exercisable. The vesting and exercisability conditions applicable to the SAR may include service-based conditions, performance-based conditions, such other conditions as the Administrator may determine, or any combination
thereof. The SAR Agreement shall also specify the term of the SAR; provided that except to the extent necessary to comply with applicable foreign law, the term of a SAR shall not exceed 10 years from the date of grant. A SAR Agreement may provide
for accelerated vesting and exercisability upon certain specified events and may provide for expiration prior to the end of its term in the event of the termination of the Optionee’s service. 

6.5    Exercise of SARs. Upon exercise of a SAR, the Optionee (or any person having the right to exercise
the SAR after his or her death) shall receive from the Company (a) Common Shares, (b) cash or (c) a combination of Common Shares and cash, as the Administrator shall determine. The amount of cash and/or the Fair Market Value of Common
Shares received upon exercise of SARs shall, in the aggregate, not exceed the amount by which the Fair Market Value (on the date of surrender) of the Common Shares subject to the SARs exceeds the Exercise Price. If, on the date when a SAR expires,
the Exercise Price is less than the Fair Market Value on such date but any portion of such SAR has not been exercised or surrendered, then such SAR shall automatically be deemed to be exercised as of such date with respect to such portion. A SAR
Agreement may also provide for an automatic exercise of the SAR on an earlier date. 
 6.6    Death of
Optionee. After an Optionee’s death, any vested and exercisable SARs held by such Optionee may be exercised by his or her beneficiary or beneficiaries. Each Optionee may designate one or more beneficiaries for this purpose by filing
the prescribed form with the Company. A beneficiary designation may be changed by filing the prescribed form with the Company at any time before the Optionee’s death. If no beneficiary was designated or if no designated beneficiary survives the
Optionee, then any vested and exercisable SARs held by the Optionee at the time of his or her death may be exercised by his or her estate. 

6.7    Modification or Assumption of SARs. Within the limitations of the Plan, the Administrator may modify,
reprice, extend or assume outstanding stock appreciation rights or may accept the cancellation of outstanding stock appreciation rights (whether granted by the Company or by another issuer) in return for the grant of new SARs for the same or a
different number of shares and at the same or a different exercise price or in return for the grant of a different type of Award. The foregoing notwithstanding, no modification of a SAR shall, without the consent of the Optionee, materially impair
his or her rights under such SAR. 












 ARTICLE 7.    RESTRICTED SHARES. 

7.1    Restricted Stock Agreement. Each grant of Restricted Shares under the Plan shall be evidenced by a
Restricted Stock Agreement between the recipient and the Company. Such Restricted Shares shall be subject to all applicable terms of the Plan and may be subject to any other terms that are not inconsistent with the Plan. The provisions of the
various Restricted Stock Agreements entered into under the Plan need not be identical. 
 7.2    Payment for
Awards. Restricted Shares may be sold or awarded under the Plan for such consideration as the Administrator may determine, including (without limitation) cash, cash equivalents, property, cancellation of other equity awards, promissory notes,
past services and future services, and such other methods of payment as are permitted by applicable law. 

7.3    Vesting Conditions. Each Award of Restricted Shares may or may not be subject to vesting and/or other
conditions as the Administrator may determine. Vesting shall occur, in full or in installments, upon satisfaction of the conditions specified in the Restricted Stock Agreement. Vesting conditions may include service-based conditions,
performance-based conditions, such other conditions as the Administrator may determine, or any combination thereof. A Restricted Stock Agreement may provide for accelerated vesting upon certain specified events. 

7.4    Voting and Dividend Rights. The holders of Restricted Shares awarded under the Plan shall have the
same voting, dividend and other rights as the Company’s other stockholders, unless the Administrator otherwise provides. A Restricted Stock Agreement, however, may require that any cash dividends paid on Restricted Shares (a) be
accumulated and paid when such Restricted Shares vest, or (b) be invested in additional Restricted Shares. Such additional Restricted Shares shall be subject to the same conditions and restrictions as the shares subject to the Award with
respect to which the dividends were paid. In addition, unless the Administrator provides otherwise, if any dividends or other distributions are paid in Common Shares, such Common Shares shall be subject to the same restrictions on transferability
and forfeitability as the Restricted Shares with respect to which they were paid. 
 7.5    Modification or
Assumption of Restricted Shares. Within the limitations of the Plan, the Administrator may modify or assume outstanding Restricted Shares or may accept the cancellation of outstanding restricted shares (whether granted by the Company or by
another issuer) in return for the grant of new Restricted Shares for the same or a different number of shares or in return for the grant of a different type of Award. The foregoing notwithstanding, no modification of Restricted Shares shall, without
the consent of the Participant, materially impair his or her rights under such Restricted Shares. 
 ARTICLE 8.    RESTRICTED STOCK
UNITS. 
 8.1    Restricted Stock Unit Agreement. Each grant of Restricted Stock Units under the
Plan shall be evidenced by a Restricted Stock Unit Agreement between the recipient and the Company. Such Restricted Stock Units shall be subject to all applicable terms of the Plan and may be subject to any other terms that are not inconsistent with
the Plan. The provisions of the various Restricted Stock Unit Agreements entered into under the Plan need not be identical. 

8.2    Payment for Awards. To the extent that an Award is granted in the form of Restricted Stock Units, no
cash consideration shall be required of the Award recipients. 












 8.3    Vesting Conditions. Each Award of Restricted Stock
Units may or may not be subject to vesting, as determined by the Administrator. Vesting shall occur, in full or in installments, upon satisfaction of the conditions specified in the Restricted Stock Unit Agreement. Vesting conditions may include
service-based conditions, performance-based conditions, such other conditions as the Administrator may determine, or any combination thereof. A Restricted Stock Unit Agreement may provide for accelerated vesting upon certain specified events. 

8.4    Voting and Dividend Rights. The holders of Restricted Stock Units shall have no voting rights. Prior
to settlement or forfeiture, Restricted Stock Units awarded under the Plan may, at the Administrator’s discretion, provide for a right to dividend equivalents. Such right entitles the holder to be credited with an amount equal to all cash
dividends paid on one Common Share while the Restricted Stock Unit is outstanding. Dividend equivalents may be converted into additional Restricted Stock Units. Settlement of dividend equivalents may be made in the form of cash, in the form of
Common Shares, or in a combination of both. Prior to distribution, any dividend equivalents shall be subject to the same conditions and restrictions as the Restricted Stock Units to which they attach. 

8.5    Form and Time of Settlement of Restricted Stock Units. Settlement of vested Restricted
Stock Units may be made in the form of (a) cash, (b) Common Shares or (c) any combination of both, as determined by the Administrator. The actual number of Restricted Stock Units eligible for settlement may be larger or smaller than
the number included in the original Award, based on predetermined performance factors. Methods of converting Restricted Stock Units into cash may include (without limitation) a method based on the average value of Common Shares over a series of
trading days. Vested Restricted Stock Units shall be settled in such manner and at such time(s) as specified in the Restricted Stock Unit Agreement. Until an Award of Restricted Stock Units is settled, the number of such Restricted Stock Units shall
be subject to adjustment pursuant to Article 9. 
 8.6    Death of Recipient. Any Restricted Stock
Units that become payable after the recipient’s death shall be distributed to the recipient’s beneficiary or beneficiaries. Each recipient of Restricted Stock Units under the Plan may designate one or more beneficiaries for this purpose by
filing the prescribed form with the Company. A beneficiary designation may be changed by filing the prescribed form with the Company at any time before the Award recipient’s death. If no beneficiary was designated or if no designated
beneficiary survives the Award recipient, then any Restricted Stock Units that become payable after the recipient’s death shall be distributed to the recipient’s estate. 

8.7    Modification or Assumption of Restricted Stock Units. Within the limitations of the
Plan, the Administrator may modify or assume outstanding restricted stock units or may accept the cancellation of outstanding restricted stock units (whether granted by the Company or by another issuer) in return for the grant of new Restricted
Stock Units for the same or a different number of shares or in return for the grant of a different type of Award. The foregoing notwithstanding, no modification of a Restricted Stock Unit shall, without the consent of the Participant, materially
impair his or her rights under such Restricted Stock Unit. 
 8.8    Creditors’ Rights.
A holder of Restricted Stock Units shall have no rights other than those of a general creditor of the Company. Restricted Stock Units represent an unfunded and unsecured obligation of the Company, subject to the terms and conditions of the
applicable Restricted Stock Unit Agreement. 












 ARTICLE 9.    ADJUSTMENTS; DISSOLUTIONS AND LIQUIDATIONS; CORPORATE TRANSACTIONS.

 9.1    Adjustments. In the event of a subdivision of the outstanding Common Shares, a declaration of
a dividend payable in Common Shares, a combination or consolidation of the outstanding Common Shares (by reclassification or otherwise) into a lesser number of Common Shares or any other increase or decrease in the number of issued Common Shares
effected without receipt of consideration by the Company, proportionate adjustments shall be made to the following: 

(a)    The number and kind of shares available for issuance under Article 3, including the numerical share limits in
Articles 3.1 and 3.5; 
 (b)    The number and kind of shares covered by each outstanding Option, SAR and Restricted
Stock Unit; and/or 
 (c)    The Exercise Price applicable to each outstanding Option and SAR, and the repurchase price,
if any, applicable to Restricted Shares. 
 In the event of a declaration of an extraordinary dividend payable in a form other than Common Shares in an
amount that has a material effect on the price of Common Shares, a recapitalization, a spin-off or a similar occurrence, the Administrator may make such adjustments as it, in its sole discretion, deems
appropriate to the foregoing. Any adjustment in the number of shares subject to an Award under this Article 9.1 shall be rounded down to the nearest whole share, although the Administrator in its sole discretion may make a cash payment in lieu of a
fractional share. Except as provided in this Article 9, a Participant shall have no rights by reason of any issuance by the Company of stock of any class or securities convertible into stock of any class, any subdivision or consolidation of
shares of stock of any class, the payment of any stock dividend or any other increase or decrease in the number of shares of stock of any class. 

9.2    Dissolution or Liquidation. To the extent not previously exercised or settled, Options, SARs and
Restricted Stock Units shall terminate immediately prior to the dissolution or liquidation of the Company. 

9.3    Corporate Transactions. In the event that the Company is a party to a merger, consolidation, or a
Change in Control (other than one described in Article 14.7(d)), all Common Shares acquired under the Plan and all Awards outstanding on the effective date of the transaction shall be treated in the manner described in the definitive transaction
agreement (or, in the event the transaction does not entail a definitive agreement to which the Company is party, in the manner determined by the Administrator, with such determination having final and binding effect on all parties), which agreement
or determination need not treat all Awards (or portions thereof) in an identical manner. Unless an Award Agreement provides otherwise, the treatment specified in the transaction agreement or by the Administrator may include (without limitation) one
or more of the following with respect to each outstanding Award: 
 (a)    The continuation of such
outstanding Award by the Company (if the Company is the surviving entity); 












 (b)    The assumption of such outstanding Award by the
surviving entity or its parent, provided that the assumption of an Option or a SAR shall comply with applicable tax requirements; 

(c)    The substitution by the surviving entity or its parent of an equivalent award for such outstanding
Award (including, but not limited to, an award to acquire the same consideration paid to the holders of Common Shares in the transaction), provided that the substitution of an Option or a SAR shall comply with applicable tax requirements; 

(d)    In the case of an Option or SAR, the cancellation of such Award without payment of any
consideration. An Optionee shall be able to exercise his or her outstanding Option or SAR, to the extent such Option or SAR is then vested or becomes vested as of the effective time of the transaction, during a period of not less than five full
business days preceding the closing date of the transaction, unless (i) a shorter period is required to permit a timely closing of the transaction and (ii) such shorter period still offers the Optionee a reasonable opportunity to exercise
such Option or SAR; 
 (e)    The cancellation of such Award and a payment to the Participant with
respect to each share subject to the portion of the Award that is vested or becomes vested as of the effective time of the transaction equal to the excess of (A) the value, as determined by the Administrator in its absolute discretion, of
the property (including cash) received by the holder of a Common Share as a result of the transaction, over (if applicable) (B) the per-share Exercise Price of such Award (such excess, if any, the “Spread”). Such payment
shall be made in the form of cash, cash equivalents, or securities of the surviving entity or its parent having a value equal to the Spread. In addition, any escrow, holdback, earn-out or similar
provisions in the transaction agreement may apply to such payment to the same extent and in the same manner as such provisions apply to the holders of Common Shares. If the Spread applicable to an Award (whether or not vested) is zero
or a negative number, then the Award may be cancelled without making a payment to the Participant. In the event that an Award is subject to Code Section 409A, the payment described in this clause (e) shall be made on the settlement date
specified in the applicable Award Agreement, provided that settlement may be accelerated in accordance with Treasury Regulation Section 1.409A-3(j)(4); or 

(f)    The assignment of any reacquisition or repurchase rights held by the Company in respect of an Award
of Restricted Shares to the surviving entity or its parent, with corresponding proportionate adjustments made to the price per share to be paid upon exercise of any such reacquisition or repurchase rights. 

Unless an Award Agreement provides otherwise, each outstanding Award held by a Participant who remains a Service Provider as of the effective time of a
merger, consolidation or Change in Control (other than one described in Article 14.7(d)) (a “Current Participant”) shall become fully vested and, if applicable, exercisable (with any performance-based vesting conditions applicable
to an Award deemed achieved at 100% of target levels) immediately prior to the effective time of the transaction. However, the prior sentence shall not apply, and an outstanding Award shall not become vested and, if applicable,
exercisable, if and to the extent the Award is continued, assumed or substituted as provided for in clauses (a), (b) or (c) above.    In addition, the prior two sentences shall not apply to an Award held by a
Participant who is not a Current Participant, unless an Award Agreement provides otherwise or unless the Company and the acquirer agree otherwise. 












 For avoidance of doubt, the Administrator shall have the discretion, exercisable either at the time an Award
is granted or at any time while the Award remains outstanding, to provide for the acceleration of vesting upon the occurrence of a Change in Control, whether or not the Award is to be assumed or replaced in the transaction, or in connection with a
termination of the Participant’s service following a transaction. 
 Any action taken under this Article 9.3 shall either preserve an Award’s
status as exempt from Code Section 409A or comply with Code Section 409A. 
 ARTICLE 10.    OTHER AWARDS. 

Subject in all events to the limitations under Article 3 above as to the number of Common Shares available for issuance under this Plan, the
Company may grant other forms of Awards not specifically described herein and may grant awards under other plans or programs, where such awards are settled in the form of Common Shares issued under this Plan. Such Common Shares shall be treated for
all purposes under the Plan like Common Shares issued in settlement of Restricted Stock Units and shall, when issued, reduce the number of Common Shares available under Article 3. 

ARTICLE 11.    LIMITATION ON RIGHTS. 

11.1    Retention Rights. Neither the Plan nor any Award granted under the Plan shall be deemed to give any
individual a right to remain a Service Provider. The Company and its Parents, Subsidiaries and Affiliates reserve the right to terminate the service of any Service Provider at any time, with or without cause, subject to applicable laws, the
Company’s certificate of incorporation and by-laws and a written employment agreement (if any). 

11.2    Stockholders’ Rights. Except as set forth in Article 7.4 or 8.4 above, a
Participant shall have no dividend rights, voting rights or other rights as a stockholder with respect to any Common Shares covered by his or her Award prior to the time when a stock certificate for such Common Shares is issued or, if applicable,
the time when he or she becomes entitled to receive such Common Shares by filing any required notice of exercise and paying any required Exercise Price. No adjustment shall be made for cash dividends or other rights for which the record date is
prior to such time, except as expressly provided in the Plan. 
 11.3    Regulatory Requirements. Any
other provision of the Plan notwithstanding, the obligation of the Company to issue Common Shares under the Plan shall be subject to all applicable laws, rules and regulations and such approval by any regulatory body as may be required. The Company
reserves the right to restrict, in whole or in part, the delivery of Common Shares pursuant to any Award prior to the satisfaction of all legal requirements relating to the issuance of such Common Shares, to their registration, qualification or
listing or to an exemption from registration, qualification or listing. The inability of the Company to obtain authority from any regulatory body having jurisdiction, which authority is deemed necessary by the Company’s counsel to be necessary
to the lawful issuance and sale of any Common Shares hereunder, will relieve the Company of any liability in respect of the failure to issue or sell such Common Shares as to which such requisite authority will not have been obtained. 












 11.4    Transferability of Awards. The
Administrator may, in its sole discretion, permit transfer of an Award in a manner consistent with applicable law. Unless otherwise determined by the Administrator, Awards shall be transferable by a Participant only by (a) beneficiary
designation, (b) a will or (c) the laws of descent and distribution; provided that, in any event, an ISO may only be transferred by will or by the laws of descent and distribution and may be exercised during the lifetime of the
Optionee only by the Optionee or by the Optionee’s guardian or legal representative 
 11.5    Recoupment
Policy. All Awards granted under the Plan, all amounts paid under the Plan and all Common Shares issued under the Plan shall be subject to recoupment, clawback or recovery by the Company in accordance with applicable law and with Company policy
(whenever adopted) regarding same, whether or not such policy is intended to satisfy the requirements of the Dodd-Frank Wall Street Reform and Consumer Protection Act, the Sarbanes-Oxley Act, or other applicable law, as well as any implementing
regulations and/or listing standards thereunder. 
 11.6    Other Conditions and Restrictions on Common
Shares. Any Common Shares issued under the Plan shall be subject to such forfeiture conditions, rights of repurchase, rights of first refusal, other transfer restrictions and such other terms and conditions as the Administrator may determine.
Such conditions and restrictions shall be set forth in the applicable Award Agreement and shall apply in addition to any restrictions that may apply to holders of Common Shares generally. In addition, Common Shares issued under the Plan shall be
subject to such conditions and restrictions imposed either by applicable law or by Company policy, as adopted from time to time, designed to ensure compliance with applicable law or laws with which the Company determines in its sole discretion to
comply including in order to maintain any statutory, regulatory or tax advantage. 
 ARTICLE 12.    TAXES. 

12.1    General. It is a condition to each Award under the Plan that a Participant or his or her successor
shall make arrangements satisfactory to the Company for the satisfaction of any federal, state, local or foreign withholding tax obligations that arise in connection with any Award granted under the Plan. The Company shall not be required to issue
any Common Shares or make any cash payment under the Plan unless such obligations are satisfied. 

12.2    Share Withholding. To the extent that applicable law subjects a Participant to tax withholding
obligations, the Administrator may permit such Participant to satisfy all or part of such obligations by having the Company withhold all or a portion of any Common Shares that otherwise would be issued to him or her or by surrendering all or a
portion of any Common Shares that he or she previously acquired. Such Common Shares shall be valued on the date when they are withheld or surrendered. Any payment of taxes by assigning Common Shares to the Company may be subject to restrictions
including any restrictions required by the SEC, accounting or other rules. 
 12.3    Section 409A
Matters. Except as otherwise expressly set forth in an Award Agreement, it is intended that Awards granted under the Plan either be exempt from, or comply with, the requirements of Code Section 409A. To the extent an Award is subject to
Code Section 409A (a “409A Award”), the terms of the Plan, the Award and any written agreement governing the Award shall be interpreted to comply with the requirements of Code Section 409A so that the Award is not subject
to additional tax or interest under Code Section 409A, unless the Administrator expressly provides otherwise. In the event that any (i) provision of the Plan or an Award Agreement, (ii) Award, payment, transaction or (iii) other
action or arrangement contemplated by the provisions of the Plan is determined by the Administrator to not comply with the applicable requirements of Code Section 409A, the Administrator shall have the authority to take such actions and to make
such changes to the Plan or an Award Agreement as the Administrator deems necessary to comply with such requirements; provided, however, that no such action shall materially impair a Participant’s rights under an Award without the consent of
the affected Participant. A 409A Award shall be subject to such additional rules and requirements as specified by the Administrator from time to time in order for it to comply with the requirements of Code Section 409A. No payment that
constitutes deferred compensation under Code Section 409A that would otherwise be made under the Plan or an Award Agreement upon a termination of service will be made or provided unless and until such termination is also a “separation from
service,” as determined in accordance with Code Section 409A. If any amount under a 409A Award is payable upon a “separation from service” to an individual who is considered a “specified employee” (as each term is
defined under Code Section 409A), then no such payment shall be made prior to the date that is the earlier of (i) six months and one day after the Participant’s separation from service or (ii) the Participant’s death, but
only to the extent such delay is necessary to prevent such payment from being subject to Code Section 409A(a)(1). For purposes of Code Section 409A, a Participant’s right to receive any installment payments pursuant to this Plan or
any Award granted hereunder shall be treated as a right to receive a series of separate and distinct payments. For the avoidance of doubt, each applicable tranche of Common Shares subject to vesting under any Award shall be considered a right to
receive a series of separate and distinct payments. 












 12.4    Limitation on Liability. Neither the Company nor
any person serving as Administrator shall have any liability to a Participant in the event an Award held by the Participant fails to achieve its intended characterization under applicable tax law. 

ARTICLE 13.    FUTURE OF THE PLAN. 

13.1    Term of the Plan. The Plan, as set forth herein, shall become effective on the date of its adoption
by the Board, subject to approval of the Company’s stockholders under Article 13.3 below. The Plan shall terminate automatically 10 years after the date when the Board adopted the Plan. 

13.2    Amendment or Termination. The Board may, at any time and for any reason, amend or terminate the
Plan. No Awards shall be granted under the Plan after the termination thereof. The termination of the Plan, or any amendment thereof, shall not affect any Award previously granted under the Plan. 

13.3    Stockholder Approval. To the extent required by applicable law, the Plan will be subject to the
approval of the Company’s stockholders within 12 months of its adoption date. An amendment of the Plan shall be subject to the approval of the Company’s stockholders only to the extent required by applicable laws, regulations or rules.













 ARTICLE 14.    DEFINITIONS. 

14.1    “Administrator” means the Board or any Committee administering the Plan in accordance with
Article 2. 
 14.2    “Affiliate” means any entity other than a Subsidiary, if the Company
and/or one or more Subsidiaries own not less than 50% of such entity. 
 14.3    “Award” means
any award granted under the Plan, including as an Option, a SAR, a Restricted Share award, a Restricted Stock Unit award or another form of equity-based compensation award. 

14.4    “Award Agreement” means a Stock Option Agreement, a SAR Agreement, a Restricted Stock
Agreement, a Restricted Stock Unit Agreement or such other agreement evidencing an Award granted under the Plan. 

14.5    “Board” means the Company’s Board of Directors, as constituted from time to time and,
where the context so requires, reference to the “Board” may refer to a Committee to whom the Board has delegated authority to administer any aspect of this Plan. 

14.6    “Change in Control” means: 

(a)    Any “person” (as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the
“beneficial owner” (as defined in Rule 13d-3 of the Exchange Act), directly or indirectly, of securities of the Company representing more than fifty percent (50%) of the total voting power
represented by the Company’s then-outstanding voting securities; 
 (b)    The consummation of the sale or
disposition by the Company of all or substantially all of the Company’s assets; 
 (c)    The consummation of a
merger or consolidation of the Company with or into any other entity, other than a merger or consolidation which would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining
outstanding or by being converted into voting securities of the surviving entity or its parent) more than fifty percent (50%) of the total voting power represented by the voting securities of the Company or such surviving entity or its parent
outstanding immediately after such merger or consolidation; or 
 (d)    Individuals who are members of the Board (the
“Incumbent Board”) cease for any reason to constitute at least a majority of the members of the Board over a period of 12 months; provided, however, that if the appointment or election (or nomination for election) of any new Board
member was approved or recommended by a majority vote of the members of the Incumbent Board then still in office, such new member shall, for purposes of this Plan, be considered as a member of the Incumbent Board. 

A transaction shall not constitute a Change in Control if its sole purpose is to change the state of the Company’s incorporation or to create a holding
company that will be owned in substantially the same proportions by the persons who held the Company’s securities immediately before such transaction. In addition, if a Change in Control constitutes a payment event with respect to any
Award which provides for a deferral of compensation and is subject to Code Section 409A, then notwithstanding anything to the contrary in the Plan or applicable Award Agreement the transaction with respect to such Award must also constitute a
“change in control event” as defined in Treasury Regulation Section 1.409A-3(i)(5) to the extent required by Code Section 409A. 












 14.7    “Code” means the Internal Revenue Code
of 1986, as amended. 
 14.8    “Code Section 409A” means Section 409A
of the Code and the Treasury Regulations and other guidance issued thereunder. 

14.9    “Committee” means a committee of one or more members of the Board, or of other individuals
satisfying applicable laws, appointed by the Board to administer the Plan. 
 14.10    “Common
Share” means one share of the Company’s [common stock]. 
 14.11    “Company”
means Theseus Pharmaceuticals, Inc., a Delaware corporation. 
 14.12    “Consultant” means a
consultant or adviser who provides bona fide services to the Company, a Parent, a Subsidiary or an Affiliate as an independent contractor and who qualifies as a consultant or advisor under Instruction A.1.(a)(1) of Form S-8 under the Securities Act. 
 14.13    “Employee” means a common-law employee of the Company, a Parent, a Subsidiary or an Affiliate. 

14.14    “Exchange Act” means the Securities Exchange Act of 1934, as amended. 

14.15    “Exercise Price,” in the case of an Option, means the amount for which one Common Share
may be purchased upon exercise of such Option, as specified in the applicable Stock Option Agreement. “Exercise Price,” in the case of a SAR, means an amount, as specified in the applicable SAR Agreement, which is subtracted from the Fair
Market Value of one Common Share in determining the amount payable upon exercise of such SAR. 

14.16    “Fair Market Value” means the closing price of a Common Share on any established stock
exchange or a national market system on the applicable date or, if the applicable date is not a trading day, on the last trading day prior to the applicable date, as reported in a source that the Administrator deems reliable. If Common Shares are
not traded on an established stock exchange or a national market system, the Fair Market Value shall be determined by the Administrator in good faith on such basis as it deems appropriate. The Administrator’s determination shall be conclusive
and binding on all persons. Notwithstanding the foregoing, the determination of Fair Market Value in all cases shall be in accordance with the requirements set forth under Section 409A of the Code to the extent necessary for an Award to
comply with, or be exempt from, Section 409A of the Code. 
 14.17    “IPO Date” means the
effective date of the registration statement filed by the Company with the Securities and Exchange Commission for its initial offering of the Common Shares to the public. 

14.18    “ISO” means an incentive stock option described in Code Section 422(b). 

14.19    “NSO” means a stock option not described in Code Sections 422 or 423. 












 14.20    “Option” means an ISO or NSO granted
under the Plan and entitling the holder to purchase Common Shares. 
 14.21    “Optionee” means
an individual or estate holding an Option or SAR. 
 14.22    “Outside Director” means a member
of the Board who is not an Employee. 
 14.23    “Parent” means any corporation (other than the
Company) in an unbroken chain of corporations ending with the Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations
in such chain. A corporation that attains the status of a Parent on a date after the adoption of the Plan shall be considered a Parent commencing as of such date. 

14.24    “Participant” means an individual or estate holding an Award. 

14.25    “Plan” means this Theseus Pharmaceuticals, Inc. 2021 Equity Incentive Plan, as amended
from time to time. 
 14.26    “Predecessor Plan” means the Theseus Pharmaceuticals, Inc. 2018
Stock Plan, as amended. 
 14.27    “Restricted Share” means a Common Share awarded under
Article 7 of the Plan. 
 14.28    “Restricted Stock Agreement” means the agreement consistent
with the terms of the Plan between the Company and the recipient of a Restricted Share that contains the terms, conditions and restrictions pertaining to such Restricted Share. 

14.29    “Restricted Stock Unit” means a bookkeeping entry representing the equivalent of one
Common Share, as awarded under the Plan. 
 14.30    “Restricted Stock Unit Agreement” means the
agreement consistent with the terms of the Plan between the Company and the recipient of a Restricted Stock Unit that contains the terms, conditions and restrictions pertaining to such Restricted Stock Unit. 

14.31    “SAR” means a stock appreciation right granted under the Plan. 

14.32    “SAR Agreement” means the agreement consistent with the terms of the Plan between the
Company and an Optionee that contains the terms, conditions and restrictions pertaining to his or her SAR. 

14.33    “Securities Act” means the Securities Act of 1933, as amended. 

14.34    “Service Provider” means any individual who is an Employee, Outside Director or
Consultant, including any prospective Employee, Outside Director or Consultant who has accepted an offer of employment or service and will be an Employee, Outside Director or Consultant after the commencement of their service. 












 14.35    “Stock Option Agreement” means the
agreement consistent with the terms of the Plan between the Company and an Optionee that contains the terms, conditions and restrictions pertaining to his or her Option. 

14.36    “Subsidiary” means any corporation (other than the Company) in an unbroken chain of
corporations beginning with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations
in such chain. A corporation that attains the status of a Subsidiary on a date after the adoption of the Plan shall be considered a Subsidiary commencing as of such date. 

14.37    “Substitute Awards” means Awards or Common Shares issued by the Company in assumption of,
or substitution or exchange for, awards previously granted, or the right or obligation to make future awards, in each case by an entity acquired by the Company or any Affiliate or with which the Company or any Affiliate combines to the extent
permitted by the applicable exchange listing requirements. 












 THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

NOTICE OF STOCK OPTION GRANT 

You have been granted the following option to purchase Common Shares of Theseus Pharmaceuticals, Inc. (the “Company”) on the terms and conditions
set out below: 
  

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option (U.S. Tax Status):	  	Nonstatutory Stock Option
		
	Exercise Price per Share:	  	US$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Vesting Commencement Date:	  	«VestDay»
		
	Vesting Schedule:	  	This option shall vest and become exercisable with respect to the first 25% of the shares subject to this option on the Vesting Date (as defined below) occurring in the fiscal quarter that contains the first anniversary of the
Vesting Commencement Date, and this option shall vest and become exercisable with respect to an additional 6.25% of the shares subject to this option quarterly thereafter on the corresponding Vesting Date occurring in each fiscal quarter thereafter,
in each case, subject to your continuous service as an Employee or Consultant (“Service”) through each such date. “Vesting Date” means each of March 20, June 20, September 20 and December 20.
		
	Expiration Date:	  	«ExpDate». This option expires earlier if your Service terminates earlier, as described in the Stock Option Agreement, and may terminate earlier in connection with certain corporate transactions as described in Article 9
of the Plan.


 You and the Company agree that this option is granted under and governed by the terms and conditions of the
Company’s 2021 Equity Incentive Plan (the “Plan”) and the Stock Option Agreement (including, if applicable, the Appendix for Non-U.S. Participants), both of which are attached to, and made a
part of, this document. Capitalized terms not otherwise defined herein shall have the meanings assigned to such terms in the Plan. 
 The Company may, in
its sole discretion, decide to deliver any documents related to options awarded under the Plan, future options that may be awarded under the Plan and all other documents that the Company is required to deliver to security holders (including annual
reports and proxy statements) by email or other electronic means (including by posting them on a website maintained by the Company or a third party under contract with the Company). You hereby consent to receive such documents by electronic delivery
and agree to participate in the Plan through any on-line or electronic system established and maintained by the Company or another third party designated by the Company. You acknowledge that you may incur
costs in connection with any such delivery by means of electronic transmission, including the cost of accessing the Internet and printing fees, and that an interruption of Internet access may interfere with your ability to access the documents. 

You further agree to comply with the Company’s insider trading policy when selling Common Shares. 












 THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

STOCK OPTION AGREEMENT 

 

			
	Grant of Option	  	 Subject to all of the terms and conditions set forth in the Notice of Stock Option Grant (the “Grant Notice”), this Stock Option
Agreement (the “Agreement”) and the Plan, the Company has granted you an option to purchase up to the total number of shares specified in the Grant Notice at the exercise price indicated in the Grant Notice.

All capitalized terms used in this Agreement shall have the meanings assigned to them in this Agreement, the Grant Notice or the Plan.

		
	U.S. Tax Treatment	  	This option is intended to be a nonstatutory stock option, as provided in the Grant Notice.
		
	Vesting	  	 This option vests and becomes exercisable in accordance with the vesting schedule set forth in the Grant Notice.

In no event will this option vest or become exercisable for additional shares after your Service has terminated for any reason unless expressly provided in a
written agreement between you and the Company.

		
	Term of Option	  	This option expires in any event at the close of business at Company headquarters on the day before the 10th anniversary of the Date of Grant, as shown in the Grant Notice. (This option will expire earlier if your Service terminates
earlier, as described below, and this option may be terminated earlier as provided in Article 9 of the Plan.)
		
	Termination of Service	  	If your Service terminates for any reason, this option will expire to the extent it is unvested as of your termination date and does not vest as a result of your termination of Service. The Company determines whether and when your
Service terminates for all purposes of this option.
		
	Regular Termination	  	If your Service terminates for any reason except death or total and permanent disability, then this option, to the extent vested as of your termination date, will expire at the close of business at Company headquarters on the date
three months after your termination date.














			
		
	Death	  	If your Service terminates as a result of your death, then this option, to the extent vested as of the date of your death, will expire at the close of business at Company headquarters on the date twelve months after the date of
death.
		
	Disability	  	 If your Service terminates because of your total and permanent disability, then this option, to the extent vested as of your termination
date, will expire at the close of business at Company headquarters on the date six months after your termination date.
 For all purposes under this
Agreement, “total and permanent disability” means that you are unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has
lasted, or can be expected to last, for a continuous period of not less than one year.

		
	Leaves of Absence and Part-Time Work	  	 For purposes of this option, your Service does not terminate when you go on a military leave, a sick leave or another bona fide leave
of absence, if the leave was approved by the Company in writing. However, except as otherwise determined by the Company, your Service terminates when the approved leave ends, unless you immediately return to active work.

 
 If you go on an unpaid leave of absence that lasts more than 30 days, then, to the
extent permitted by applicable law, the vesting schedule specified in the Grant Notice will be suspended on the thirty-first day of such unpaid leave, and this option will not vest or become exercisable with respect to any additional shares during
the remainder of such leave. Vesting will resume when you return to active Service. If you go on a paid leave of absence, the vesting schedule specified in the Notice of Stock Option Grant may be adjusted and/or suspended in accordance with the
Company’s leave of absence policy or the terms of your leave.
  
 If you commence
working on a part-time basis, the Company may adjust the vesting schedule so that the rate of vesting is commensurate with your reduced work schedule.















			
	Restrictions on Exercise/Compliance with Law	  	 The Company will not permit you to exercise this option if the issuance of shares at that time would violate any law or regulation.

 
 Notwithstanding any other provision in the Plan or this Agreement, unless there is an
available exemption from registration, qualification or other legal requirement applicable to the Company’s shares, the Company shall not be required to permit the exercise of this option and/or delivery of Company shares prior to the
completion of any registration or qualification of the shares under any local, state, national or federal securities law or under rulings or regulations of the Securities and Exchange Commission (“SEC”) or of any other governmental body,
or prior to obtaining any approval or other clearance from any local, state, national or federal governmental agency, which registration, qualification or approval the Company shall, in its absolute discretion, deem necessary or advisable. You
understand that the Company is under no obligation to register or qualify the Company’s shares with the SEC or any state securities commission or to seek approval or clearance from any governmental authority for the issuance or sale of the
shares.

		
	Notice of Exercise	  	 When you wish to exercise this option, you must notify the Company by filing the proper “Notice of Exercise” form at the address
given on the form or, if the Company has designated a third party to administer the Plan, you must notify such third party in the manner such third party requires. Your notice must specify how many shares you wish to purchase. The notice will be
effective when the Company receives it.
  
 However, if you wish to exercise this option
by executing a same-day sale (as described below), you must follow the instructions of the Company and the broker who will execute the sale.

 
 If someone else wants to exercise this option after your death, that person must prove
to the Company’s satisfaction that he or she is entitled to do so.
  
 You may only
exercise your option for whole shares.















			
	Form of Payment	  	 When you submit your notice of exercise, you must make arrangements for the payment of the option exercise price for the shares that you are
purchasing. To the extent permitted by applicable law, payment may be made in one (or a combination of two or more) of the following forms:

  

•   By delivering to the Company your personal check, a cashier’s check or a money order,
or arranging for a wire transfer.
  

•   By giving to a securities broker approved by the Company irrevocable directions to sell all
or part of your option shares and to deliver to the Company, from the sale proceeds, an amount sufficient to pay the option exercise price and any Tax-Related Items (as defined below). (The balance of the sale
proceeds, if any, will be delivered to you.) The directions must be given in accordance with the instructions of the Company and the broker. This exercise method is sometimes called a “same-day
sale.”
  
 The Company may permit other forms of payment in its discretion to the
extent permitted by the Plan.


  

			
	Withholding Taxes	  	 Regardless of any action the Company (or, if applicable, the Parent, Subsidiary or Affiliate employing or retaining you (the
“Employer”)) takes with respect to any or all income tax, social insurance, payroll tax, payment on account or other tax-related items related to the participation in the Plan and legally applicable
to you (“Tax-Related Items”), you acknowledge that the ultimate liability for all Tax-Related Items is and remains your responsibility and may exceed the
amount actually withheld by the Company and/or the Employer. You further acknowledge that the Company and the Employer (1) make no representations or undertakings regarding the treatment of any
Tax-Related Items in connection with any aspect of the options, including, but not limited to, the grant, vesting or exercise of the option, the issuance of shares upon exercise of the option, the subsequent
sale of shares acquired pursuant to such exercise and the receipt of any dividends and/or any dividend equivalents; and (2) do not commit to and are under no obligation to structure the terms of the option or any aspect of the option to reduce
or eliminate your liability for Tax-Related Items or achieve any particular tax result. Further, if you are subject to tax in more than one jurisdiction, you acknowledge that the Company and/or the Employer
may be required to withhold or account for Tax-Related Items in more than one jurisdiction.
  

You will not be allowed to exercise this option unless you make arrangements acceptable to the Company and/or the Employer to pay any Tax-Related Items that the Company and/or the Employer determine must be withheld. These arrangements include payment in cash or via the same-day sale procedure described
above. With the Company’s consent, these arrangements may also include (a) withholding shares of Company stock that otherwise would be issued to you when you exercise this option with a value equal to withholding taxes,
(b) surrendering shares that you previously acquired with a value equal to the withholding taxes, or (c) withholding cash from other compensation. The value of withheld or surrendered shares, determined as of the date when taxes otherwise
would have been withheld in cash, will be applied to the Tax-Related Items.















			
		
	Restrictions on Resale	  	You agree not to sell any option shares at a time when applicable laws, Company policies or an agreement between the Company and its underwriters prohibit a sale. This restriction will apply as long as your Service continues and for
such period of time after the termination of your Service as the Company may specify.
		
	Transfer of Option	  	 Prior to your death, only you may exercise this option. You cannot transfer or assign this option. For instance, you may not sell this option
or use it as security for a loan. If you attempt to do any of these things, this option will immediately become invalid. You may, however, dispose of this option in your will or by means of a written beneficiary designation (if authorized by the
Company and to the extent such beneficiary designation is valid under applicable law) which must be filed with the Company on the proper form; provided, however, that your beneficiary or a representative of your estate acknowledges and agrees in
writing in a form reasonably acceptable to the Company, to be bound by the provisions of this Agreement and the Plan as if such beneficiary or representative of the estate were you.

Regardless of any marital property settlement agreement, the Company is not obligated to honor a notice of exercise from your former spouse, nor is the Company
obligated to recognize your former spouse’s interest in your option in any other way.

		
	No Retention Rights	  	Your option or this Agreement does not give you the right to be retained by the Company, a Parent, Subsidiary, or an Affiliate in any capacity. The Company and its Parents, Subsidiaries, and Affiliates reserve the right to terminate
your Service at any time, with or without cause.
		
	Stockholder Rights	  	You, or your estate or heirs, have no rights as a stockholder of the Company until you have exercised this option by giving the required notice to the Company, paying the exercise price, and satisfying any applicable Tax-Related Items. No adjustments are made for dividends or other rights if the applicable record date occurs before you exercise this option, except as described in the Plan.
		
	Recoupment Policy	  	This option, and the shares acquired upon exercise of this option, shall be subject to any Company recoupment or clawback policy in effect from time to time.
		
	Adjustments	  	In the event of a stock split, a stock dividend or a similar change in the Common Shares, the number of shares covered by this option and the exercise price per share will be adjusted pursuant to the Plan.














			
		
	Effect of Significant Corporate Transactions	  	If the Company is a party to a merger, consolidation, or certain change in control transactions, then this option will be subject to the applicable provisions of Article 9 of the Plan.
		
	Applicable Law	  	This Agreement, and all claims or causes of action (whether in contract, tort or statute) that may be based upon, arise out of or relate to this Agreement, shall be governed by, and enforced in accordance with, the internal laws of
the State of Delaware, without giving effect to any laws, rules or provisions of the State of Delaware that would cause the application of the laws, rules or provisions of any jurisdiction other than the State of Delaware.
		
	The Plan and Other Agreements	  	 The text of the Plan is incorporated in this Agreement by reference.

This Plan, this Agreement (including, if applicable, the Appendix for Non-U.S. Participants) and the Grant Notice
constitute the entire understanding between you and the Company regarding this option. Any prior agreements, commitments or negotiations concerning this option are superseded. This Agreement may be amended only by another written agreement between
the parties.


 BY ACCEPTING THIS OPTION GRANT, YOU AGREE TO ALL OF THE TERMS AND CONDITIONS DESCRIBED ABOVE AND IN THE PLAN
(INCLUDING THE TERMS OF ANY APPLICABLE APPENDIX INCORPORATED HEREIN BY REFERENCE). 












 THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

NOTICE OF RESTRICTED STOCK UNIT AWARD 

You have been granted Restricted Stock Units (“RSUs”), each representing the right to receive one Common Share of Theseus Pharmaceuticals, Inc. (the
“Company”) on the following terms and conditions: 
  

			
	Name of Recipient:	  	«Name»
		
	Total Number of RSUs Granted:	  	«TotalRSUs»
		
	Date of Grant:	  	«DateGrant»
		
	Vesting Commencement Date	  	«VestCommDate»
		
	Vesting Schedule:	  	25% of the RSUs subject to this award will vest on the RSU Vesting Date (as defined below) occurring in the fiscal quarter that contains the first anniversary of the Vesting Commencement Date and an additional 6.25% of the RSUs
subject to this award will vest quarterly thereafter on the corresponding RSU Vesting Date occurring in each fiscal quarter thereafter, in each case, subject to your continuous service as an Employee or Consultant (“Service”) through each
such date. “RSU Vesting Date” means each of March 20, June 20, September 20 and December 20.


 You and the Company agree that these RSUs are granted under and governed by the terms and conditions of the
Company’s 2021 Equity Incentive Plan (the “Plan”) and the Restricted Stock Unit Agreement (including, if applicable, the Appendix for Non-U.S. Participants), both of which are attached to, and
made a part of, this document. Capitalized terms not otherwise defined herein shall have the meanings assigned to such terms in the Plan. 
 The Company
may, in its sole discretion, decide to deliver any documents related to RSUs awarded under the Plan, future RSUs that may be awarded under the Plan (if any) and all documents that the Company is required to deliver to security holders (including
annual reports and proxy statements) by email or other electronic means (including posting them on a website maintained by the Company or a third party under contract with the Company). You hereby consent to receive such documents by electronic
delivery and agree to participate in the Plan through any on-line or electronic system established and maintained by the Company or another third party designated by the Company. You acknowledge that you may
incur costs in connection with any such delivery by means of electronic transmission, including the cost of accessing the Internet and printing fees, and that an interruption of Internet access may interfere with your ability to access the
documents. 
 You further agree to comply with the Company’s insider trading policy when selling Common Shares. 












 THESEUS PHARMACEUTICALS, INC. 

2021 EQUITY INCENTIVE PLAN 

RESTRICTED STOCK UNIT AGREEMENT 

 

			
		
	Grant of RSUs	  	 Subject to all of the terms and conditions set forth in the Notice of Restricted Stock Unit Award (the “Grant Notice”), this
Restricted Stock Unit Agreement (including, if applicable, the Appendix for Non-U.S. Participants) (the “Agreement”) and the Plan, the Company has granted to you the number of RSUs set forth in the
Grant Notice.
 All capitalized terms used in this Agreement shall have the meanings assigned to them in this Agreement, the Grant Notice or the
Plan.

		
	Nature of RSUs	  	Your RSUs are bookkeeping entries. They represent only the Company’s unfunded and unsecured promise to issue Common Shares on a future date. As a holder of RSUs, you have no rights other than the rights of a general creditor of
the Company.
		
	Payment for RSUs	  	No payment is required for the RSUs that you are receiving.
		
	Vesting	  	 The RSUs vest in accordance with the vesting schedule set forth in the Grant Notice.

In no event will any additional RSUs vest after your Service has terminated for any reason unless expressly provided in a written agreement between you and the
Company.
 The Company determines whether and when your Service terminates for all purposes of your RSUs.

		
	Termination of Service/Forfeiture	  	If your Service terminates for any reason, then your RSUs will be forfeited to the extent that they have not vested before the termination date and do not vest as a result of the termination of your Service. This means that any RSUs
that have not vested under this Agreement will be cancelled immediately. You will receive no payment for RSUs that are forfeited.
		
	Leaves of Absence and Part-Time Work	  	For purposes of this award, your Service does not terminate when you go on a military leave, a sick leave or another bona fide leave of absence, if the leave was approved by the Company in writing. However, except as
otherwise determined by the Company, your Service terminates when the approved leave ends, unless you immediately return to active work.














			
		
		  	 If you go on an unpaid leave of absence that lasts more than thirty days, then, to the extent permitted by applicable law, the vesting
schedule specified in the Grant Notice will be suspended on the thirty-first day of such unpaid leave, and this award will not vest with respect to any additional RSUs during the remainder of such leave. Vesting will resume when you return to active
Service. If you go on a paid leave of absence, the vesting schedule specified in the Grant Notice may be suspended and/or adjusted in accordance with the Company’s leave of absence policy or the terms of your leave.

If you commence working on a part-time basis, the Company may adjust the vesting schedule so that the rate of vesting is commensurate with your reduced work
schedule.

		
	Settlement of RSUs	  	 Each RSU will be settled as soon as practicable on or following the date when it vests, but in any event within 60 days following the vesting
date (unless you and the Company have agreed in writing to a later settlement date pursuant to procedures the Company may prescribe at its discretion). In no event will you be permitted, directly or indirectly, to specify the taxable year of
settlement of any RSUs subject to this award.
 At the time of settlement, you will receive one Common Share for each vested RSU.

No fractional shares will be issued upon settlement.

		
	Section 409A	  	 Unless you and the Company have agreed to a deferred settlement date (pursuant to procedures that the Company may prescribe at its
discretion), settlement of these restricted stock units is intended to be exempt from the application of Code Section 409A pursuant to Treasury Regulation 1.409A-1(b)(4) and shall be administered and
interpreted in a manner that complies with such exception.
  
 Notwithstanding the
foregoing, if it is determined that settlement of these RSUs is not exempt from Code Section 409A and the Company determines that you are a “specified employee,” as defined in the regulations under Code Section 409A at the time
of your “separation from service,” as defined in Treasury Regulation Section 1.409A-1(h), then this paragraph will apply. If this paragraph applies, and the event triggering settlement is your
“separation from service,” then any RSUs that otherwise would have been settled during the first six months following your “separation from service” will instead be settled on the first business day following the earlier of
(i) the six-month anniversary of your separation from service or (ii) your death.
  

Each installment of RSUs that vests is hereby designated as a separate payment for purposes of Code Section 409A.















			
		
	No Voting Rights or Dividends	  	Your RSUs carry neither voting rights nor rights to cash dividends. You have no rights as a stockholder of the Company unless and until your RSUs are settled by issuing Common Shares.
		
	RSUs Nontransferable	  	 You may not sell, transfer, assign, pledge or otherwise dispose of any RSUs. For instance, you may not use your RSUs as security for a
loan.
 In addition, regardless of any marital property settlement agreement, the Company is not obligated to recognize your former spouse’s interest in
your RSUs in any way.

		
	Beneficiary Designation	  	You may dispose of your RSUs in a written beneficiary designation if authorized by the Company and to the extent such beneficiary designation is valid under applicable law. Any beneficiary designation must be filed with the Company
on the proper form. It will be recognized only if it has been received at the Company’s headquarters before your death. If you file no beneficiary designation or if none of your designated beneficiaries survives you, then your estate will
receive any vested RSUs that you hold at the time of your death.
		
	Withholding Taxes	  	Regardless of any action the Company (or, if applicable, the Parent, Subsidiary or Affiliate employing or retaining you (the “Employer”)) takes with respect to any or all income tax, social insurance, payroll tax, payment
on account or other tax-related items related to the participation in the Plan and legally applicable to you (“Tax-Related Items”), you acknowledge that the
ultimate liability for all Tax-Related Items is and remains your responsibility and may exceed the amount actually withheld by the Company and/or the Employer. You further acknowledge that the Company and the
Employer (1) make no representations or undertakings regarding the treatment of any Tax-Related Items in connection with any aspect of the RSUs, including, but not limited to, the grant or vesting of the
RSUs, the issuance of shares upon vesting of the RSUs, the subsequent sale of shares acquired pursuant to such vesting and the receipt of any dividends and/or any dividend equivalents; and (2) do not commit to and are under no obligation to
structure the terms of the RSUs or any aspect of the RSUs to reduce or eliminate your liability for Tax-Related Items or achieve any particular tax result. Further, if you are subject to tax in more than one
jurisdiction, you acknowledge that the Company and/or the Employer may be required to withhold or account for Tax-Related Items in more than one jurisdiction.














			
		  	 No shares will be distributed to you unless you have made arrangements satisfactory to the Company and/or the Employer for the payment of any
Tax-Related Items that the Company and/or the Employer determine must be withheld. In this regard, you authorize the Company, at its sole discretion, to satisfy your
Tax-Related Items by one or a combination of the following:
  

•   Withholding the amount of any Tax-Related Items
from your wages or other cash compensation paid to you by the Company and/or the Employer.
  

•   Instructing a brokerage firm selected by the Company for this purpose to sell on your
behalf a number of whole shares of Company stock to be issued to you when the RSUs are settled that the Company determines are appropriate to generate cash proceeds sufficient to satisfy the Tax-Related Items.
You acknowledge that the Company or its designee is under no obligation to arrange for such sale at any particular price. Regardless of whether the Company arranges for such sale, you will be responsible for all fees and other costs of sale, and you
agree to indemnify and hold the Company harmless from any losses, costs, damages or expenses relating to any such sale.
  

•   Withholding shares of Company stock that would otherwise be issued to you when the RSUs are
settled equal in value to the Tax-Related Items. The fair market value of the withheld shares, determined as of the date when taxes otherwise would have been withheld in cash, will be applied to the Tax-Related Items.
  

•   Any other means approved by the Company.

 
 You agree to pay to the Company in cash any amount of
Tax-Related Items that the Company does not elect to satisfy by the means described above. To the extent you fail to make satisfactory arrangements for the payment of any required withholding taxes, you will
permanently forfeit the applicable RSUs.


  

			
		
	Restrictions on Issuance	  	 The Company will not issue any shares to you if the issuance of shares at that time would violate any law or regulation.

 
 Notwithstanding any other provision in the Plan or this Agreement, unless there is an
available exemption from registration, qualification or other legal requirement applicable to Common Shares, the Company shall not be required to issue any shares to you prior to the completion of any registration or qualification of the shares
under any local, state, national or federal securities law or under rulings or regulations of the Securities and Exchange Commission (“SEC”) or of any other governmental body, or prior to obtaining any approval or other clearance from any
local, state, national or federal governmental agency, which registration, qualification or approval the Company shall, in its absolute discretion, deem necessary or advisable. You understand that the Company is under no obligation to register or
qualify the Company’s shares with the SEC or any state securities commission or to seek approval or clearance from any governmental authority for the issuance or sale of the
shares.















			
		
	Restrictions on Resale	  	You agree not to sell any shares at a time when applicable laws, Company policies or an agreement between the Company and its underwriters prohibit a sale. This restriction will apply as long as your Service continues and for such
period of time after the termination of your Service as the Company may specify.
		
	No Retention Rights	  	Your award or this Agreement does not give you the right to be retained by the Company, a Parent, Subsidiary, or an Affiliate in any capacity. The Company and its Parents, Subsidiaries, and Affiliates reserve the right to terminate
your Service at any time, with or without cause.
		
	Adjustments	  	In the event of a stock split, a stock dividend or a similar change in Common Shares, the number of your RSUs will be adjusted pursuant to the Plan.
		
	Effect of Significant Corporate Transactions	  	If the Company is a party to a merger, consolidation, or certain change in control transactions, then your RSUs will be subject to the applicable provisions of Article 9 of the Plan, provided that any action taken must either
(a) preserve the exemption of your RSUs from Code Section 409A or (b) comply with Code Section 409A.
		
	Recoupment Policy	  	This award, and the shares acquired upon settlement of this award, shall be subject to any Company recoupment or clawback policy in effect from time to time.
		
	Applicable Law	  	This Agreement, and all claims or causes of action (whether in contract, tort or statute) that may be based upon, arise out of or relate to this Agreement, shall be governed by, and enforced in accordance with, the internal laws of
the State of Delaware, without giving effect to any laws, rules or provisions of the State of Delaware that would cause the application of the laws, rules or provisions of any jurisdiction other than the State of Delaware.
		
	The Plan and Other Agreements	  	 The text of the Plan is incorporated in this Agreement by reference.

 
 The Plan, this Agreement (including, if applicable, any Appendix for Non-U.S. Participants) and the Grant Notice constitute the entire understanding between you and the Company regarding this award. Any prior agreements, commitments or negotiations concerning this award are
superseded. This Agreement may be amended only by another written agreement between the parties.














 BY ACCEPTING THIS RSU AWARD, YOU AGREE TO ALL OF THE 

TERMS AND CONDITIONS DESCRIBED ABOVE AND IN THE PLAN 

(INCLUDING THE TERMS OF ANY APPLICABLE APPENDIX 

INCORPORATED HEREIN BY REFERENCE).