Document:

EX-10.5

 Exhibit 10.5 
  

 
 February 27, 2020 

Jonathan Lim, M.D. 
 Re: Employment Letter Agreement 

Dear Jonathan: 
 This letter will serve to
memorialize the terms of your continued employment with Erasca, Inc. (the “Company”) as provided in this employment letter agreement (this “Agreement”), effective from and after January 1, 2020.

 • DUTIES. You will serve as the Chairman of the Board of Directors of the Company
(the “Board”) and Chief Executive Officer of the Company. As Chairman and Chief Executive Officer, you shall serve and shall perform such duties as are customarily associated with such positions. You shall perform your
services at the Company’s headquarters. This is an exempt position. You shall devote approximately fifty percent (50%) of your working time and attention to the business affairs of the Company. 

• COMPENSATION. Your initial compensation will be as follows: 

 

	 	•	 	 BASE SALARY. You will receive an annual base salary of $300,000,
which reflects a prorated salary for your approximately fifty percent (50%) time commitment, for all hours worked, to be paid in accordance with the Company’s customary payroll procedures. 

 

	 	•	 	 STOCK OPTIONS. You were previously granted stock options to
purchase 375,000 shares of the Company’s common stock at an exercise price per share equal to the fair market value per share of the Company’s common stock on the date of grant (the “Stock Options”). The Stock
Options were granted pursuant to the Company’s equity incentive plan (the “Plan”). The Stock Options are subject to the terms and conditions of the Plan and your stock option agreement. The Stock Options will vest over a
four year vesting schedule, with 25% of the Stock Options vesting on the first anniversary of your commencement of employment and the remaining Stock Options vesting in 36 equal monthly installments thereafter, subject to your continued employment
or service to the Company on each such vesting date. 

  

	 	•	 	 ANNUAL BONUS. Commencing in 2020, the Board has established an annual bonus
plan, pursuant to which will be eligible to participate, subject to the terms and conditions of such plan, and your bonus target will be equal to 40% of your base salary (your “Target Bonus”). You must be employed by
the Company on the date of payment of such annual bonus in order to be eligible to receive such annual bonus. You hereby acknowledge and agree that nothing contained herein confers upon you any right to an annual bonus in any year, and that whether
the Company pays you an annual bonus and the amount of any such annual bonus will be determined by the Company in its sole discretion. 

	 	•	 	 BENEFITS. You shall be eligible to participate in all of the
employee benefit plans or programs the Company generally makes available to similarly situated employees, pursuant to the terms and conditions of such plans. The Company reserves the right to change compensation and benefits provided to its
employees from time to time in its discretion. 

  

	 	•	 	 WITHHOLDING. All amounts payable to you will be subject to appropriate payroll deductions
and withholdings. 

 • EXPENSES. You will be entitled to reimbursement for all
ordinary and reasonable out-of-pocket business expenses which are reasonably incurred by you in furtherance of the Company’s business, with appropriate
documentation and in accordance with the Company’s standard policies. 
 • SEVERANCE. 

 

	 	•	 	 ACCRUED OBLIGATIONS. If your employment terminates for any
reason, you are entitled to your fully earned but unpaid base salary, through the date such termination is effective at the rate then in effect, and all other amounts or benefits to which you are entitled under any compensation, retirement or
benefit plan of the Company at the time of your termination of employment in accordance with the terms of such plans, including, without limitation, any accrued but unpaid paid time off and any continuation of benefits required by applicable law
(the “Accrued Obligations”). 

  

	 	•	 	 NON-CIC SEVERANCE
BENEFITS. In addition to your Accrued Obligations, subject to your continued compliance with the Proprietary Information and Inventions Agreement, as described below, and the effectiveness of your Release (as
defined below), if your employment is involuntarily terminated by the Company without Cause (as defined below) (and other than by reason of your death or disability) or you resign for Good Reason (as defined below) (either such termination, a
“Qualifying Termination”), and such Qualifying Termination does not occur during the Change in Control Period (as defined below), you shall be entitled to receive, as the sole severance benefits to which you are entitled, the
benefits provided below (the “Non-CIC Severance Benefits”): 

  

	 	•	 	 An amount equal to your base salary for the Non-CIC Severance Period (as
defined below) (at the rate in effect immediately prior to the date of your termination of employment), payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than
75 days following your termination date). 

  

	 	•	 	 For the Non-CIC Severance Period (or, if earlier, the date on which the
applicable continuation period under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”) expires) (the “COBRA Coverage Period”), if you and/or your eligible dependents who
were covered under the Company’s health insurance plans as of the date of your termination of employment elect to have COBRA coverage and are eligible for such coverage, the Company shall pay for or reimburse you on a monthly basis for an
amount equal to (a) the monthly premium you and/or your covered dependents, as applicable, are required to pay for continuation coverage pursuant to COBRA for you and/or your eligible dependents, as applicable, who were covered under the
Company’s health plans as of the date of your termination of employment (calculated by reference to the premium as of the date of your termination of employment) less (b) the amount you would have had to pay to receive group health
coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of employment. If any of the Company’s health benefits are self-funded as of the date of your termination
of employment, or if the Company cannot provide the foregoing benefits in a manner that is exempt from Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), or that is otherwise compliant with
applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the foregoing monthly amount as a
taxable monthly payment for the COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without limitation, the election of such
coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment. 

	 	•	 	 CIC SEVERANCE BENEFITS. In addition to your Accrued
Obligations, subject to your continued compliance with the Proprietary Information and Inventions Agreement, as described below, and the effectiveness of your Release, if your Qualifying Termination occurs during the Change in Control Period, you
shall be entitled to receive, as the sole severance benefits to which you are entitled and in lieu of any Non-CIC Severance Benefits, the benefits provided below (the “CIC Severance
Benefits”) (and for the avoidance of doubt, in no event will you be entitled to both the Non-CIC Severance Benefits and the CIC Severance Benefits): 

 

	 	•	 	 An amount equal to your base salary for the CIC Severance Period (as defined below) (at the rate in effect
immediately prior to the date of your termination of employment), payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than 75 days following your termination
date). 

  

	 	•	 	 An amount equal to (a) (i) your Target Bonus for the year in which your date of termination occurs, divided
by (ii) 12, multiplied by (b) the number of months in the CIC Severance Period, payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than 75 days following
your termination date). 

  

	 	•	 	 For the CIC Severance Period (or, if earlier, the date on which the applicable continuation period under COBRA
expires) (the “CIC COBRA Coverage Period”), if you and/or your eligible dependents who were covered under the Company’s health insurance plans as of the date of your termination of employment elect to have COBRA coverage
and are eligible for such coverage, the Company shall pay for or reimburse you on a monthly basis for an amount equal to (a) the monthly premium you and/or your covered dependents, as applicable, are required to pay for continuation coverage
pursuant to COBRA for you and/or your eligible dependents, as applicable, who were covered under the Company’s health plans as of the date of your termination of employment (calculated by reference to the premium as of the date of your
termination of employment) less (b) the amount you would have had to pay to receive group health coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of
employment. If any of the Company’s health benefits are self-funded as of the date of your termination of employment, or if the Company cannot provide the foregoing benefits in a manner that is exempt from Section 409A of the Code, or that
is otherwise compliant with applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the
foregoing monthly amount as a taxable monthly payment for the CIC COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without
limitation, the election of such coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or
self-employment. 

  

	 	•	 	 Notwithstanding anything else set forth herein, in the Plan or in any award agreement, any unvested Stock Awards
(as defined below) then held by you (including the Stock Options and any restricted shares issued upon “early exercise” of the Stock Options) will vest on the effective date of your Release. The foregoing provisions are hereby deemed to be
a part of each Stock Award and to supersede any less favorable provision in any agreement or plan regarding such Stock Award. 

	 	•	 	 As a condition to your receipt of any post-termination payments and benefits pursuant to the preceding
paragraphs, you shall execute and not revoke a general release of all claims in favor of the Company (the “Release”) in a form reasonably acceptable to the Company. In the event the Release does not become effective within
the 60-day period following the date of your termination of employment, you will not be entitled to the aforesaid payments and benefits. 

 

	 	•	 	 For purposes of this Agreement, “Cause” means any of the following: (a) your
commission of an act of fraud, embezzlement or dishonesty, or the commission of some other illegal act by you, that has a demonstrable adverse impact on the Company or any successor or affiliate thereof; (b) your conviction of, or plea of
“guilty” or “no contest” to, a felony or any crime involving fraud, dishonesty or moral turpitude under the laws of the United States or any state thereof; (c) any intentional, unauthorized use or disclosure by you of
confidential information or trade secrets of the Company or any successor or affiliate thereof; (d) your gross negligence, insubordination or material violation of any duty of loyalty to the Company or any successor or affiliate thereof, or any
other demonstrable material misconduct on your part; (e) your ongoing and repeated failure or refusal to perform or neglect of your duties as required by this Agreement or your ongoing and repeated failure or refusal to comply with the
instructions given to you by the Board, which failure, refusal or neglect continues for 15 days following your receipt of written notice from the Board stating with specificity the nature of such failure, refusal or neglect; or (f) your
willful, material breach of any Company policy or any material provision of this Agreement or the Proprietary Information and Inventions Agreement. Prior to the determination that “Cause” under clauses (d), (e) or (f) has occurred,
the Company shall (i) provide to you in writing, in reasonable detail, the reasons for the determination that such “Cause” exists, (ii) other than with respect to clause (e) above which specifies the applicable period of
time for you to remedy your breach, afford you a reasonable opportunity to remedy any such breach, (iii) provide you an opportunity to be heard prior to the final decision to terminate your employment hereunder for such “Cause” and
(iv) make any decision that such “Cause” exists in good faith. The foregoing definition shall not in any way preclude or restrict the right of the Company or any successor or affiliate thereof to discharge or dismiss you for any other
acts or omissions, but such other acts or omissions shall not be deemed, for purposes of this Agreement, to constitute grounds for termination for Cause. 

  

	 	•	 	 For purposes of this Agreement, “Change in Control” means (a) a merger or
consolidation of the Company with or into any other corporation or other entity or person, (b) a sale, lease, exchange or other transfer in one transaction or a series of related transactions of all or substantially all of the Company’s
assets, or (c) any other transaction, including the sale by the Company of new shares of its capital stock or a transfer of existing shares of capital stock of the Company, the result of which is that a third party that is not an affiliate of
the Company or its stockholders (or a group of third parties not affiliated with the Company or its stockholders) immediately prior to such transaction acquires or holds capital stock of the Company representing a majority of the Company’s
outstanding voting power immediately following such transaction; provided that the following events shall not constitute a “Change in Control”: (i) a transaction (other than a sale of all or substantially all of the Company’s
assets) in which the holders of the voting securities of the Company immediately prior to the merger or consolidation hold, directly or indirectly, at least a majority of the voting securities in the successor corporation or its parent immediately
after the merger or consolidation; (ii) a sale, lease, exchange or other transaction in one transaction or a series of related transactions of all or substantially all of the Company’s assets to an affiliate of the Company; (iii) an
initial public offering of any of the Company’s securities; (iv) a reincorporation of the Company solely to change its jurisdiction; or (v) a transaction undertaken for the primary purpose of creating a holding company that will be
owned in substantially the same proportion by the persons who held the Company’s securities immediately before such transaction. 

  

	 	•	 	 For purposes of this Agreement, “Change in Control Period” means the period
commencing on the date of a Change in Control and ending 12 months following such Change in Control. 

	 	•	 	 For purposes of this Agreement, “CIC Severance Period” means (a) if your Qualifying
Termination occurs during the Change in Control Period and prior to the first anniversary of your hire date, 4 months; (b) if your Qualifying Termination occurs during the Change in Control Period and on or after the first anniversary of your
hire date but prior to the second anniversary of your hire date, 8 months; or (c) if your Qualifying Termination occurs during the Change in Control Period and on or after the second anniversary of your hire date, 12 months.

  

	 	•	 	 For purposes of this Agreement, “Good Reason” means any of the following without your
written consent: (a) a material diminution in your authority, duties or responsibilities; (b) a material diminution in your base compensation, unless such a reduction is imposed across-the-board to senior management of the Company; (c) a material change in the geographic location at which you must perform your duties; or (d) any other action or inaction that constitutes a
material breach by the Company or any successor or affiliate of its obligations to you under this Amended Agreement. You must provide written notice to the Company of the occurrence of any of the foregoing events or conditions without your written
consent within 60 days of the occurrence of such event. The Company or any successor or affiliate shall have a period of 30 days to cure such event or condition after receipt of written notice of such event from you. Your termination of employment
by reason of resignation from employment with the Company for Good Reason must occur within 30 days following the expiration of the foregoing 30-day cure period. 

 

	 	•	 	 For purposes of this Agreement, “Non-CIC Severance
Period” means, provided your Qualifying Termination does not occur during the Change in Control Period, (a) if your Qualifying Termination occurs prior to the first anniversary of your hire date, 3 months; (b) if your
Qualifying Termination occurs on or after the first anniversary of your hire date but prior to the second anniversary of your hire date, 6 months; or (c) if your Qualifying Termination occurs on or after the second anniversary of your hire
date, 9 months. 

  

	 	•	 	 For purposes of this Agreement, “Stock Awards” means all stock options, restricted stock
and such other awards granted pursuant to the Plan or the Company’s other stock option and equity incentive award plans or agreements, as in effect from time to time, and any shares of stock issued upon exercise or settlement thereof, including
the Stock Options and any restricted shares issued upon “early exercise” of the Stock Options. 

  

	 	•	 	 To the extent applicable, this Agreement shall be interpreted in accordance with Section 409A of the Code
and Department of Treasury regulations and other interpretive guidance issued thereunder. The intent of the parties is that payments and benefits under this Agreement comply with, or be exempt from Section 409A of the Code and, accordingly, to
the maximum extent permitted, this Agreement shall be interpreted to be in compliance with such intention. To the extent that any provision in this Agreement is ambiguous as to its compliance with or exemption from Section 409A of the
Code, the provision shall be read in such a manner that no payments payable under this Agreement shall be subject to an “additional tax” as defined in Section 409A(a)(1)(B) of the Code. For purposes of Section 409A of the
Code, any right to a series of installment payments under this Agreement shall be treated as a right to a series of separate payments. For purposes of this Agreement, to the extent that the payments or benefits under this Agreement are “non-qualified deferred compensation” subject to Section 409A of the Code or as otherwise required to ensure such payments or benefits are exempt from or comply with Section 409A of the Code, all
references to your “termination of employment” shall mean your “separation from service” (as defined in Treasury Regulation Section 1.409A-1(h)) (“Separation from
Service”). If you are a “specified employee” (as defined in Section 409A of the Code), as determined by the Company in accordance with Section 409A of the Code, on the date of your Separation from Service, to
the extent that the payments or benefits under this Agreement are “non-qualified deferred compensation” subject to Section 409A of the Code and the delayed payment or distribution of all or any
portion of such amounts to which you are entitled under this Agreement is required in order to avoid a prohibited distribution under Section 409A(a)(2)(B)(i) of the Code, then such portion deferred pursuant to this paragraph shall be paid or
distributed to you in a lump sum on the earlier of (a) the date that is 6 months and one day following your Separation from Service, (b) the date of your death or (c) the earliest date as is permitted under Section 409A of the
Code. Any remaining payments due under this Agreement shall be paid as otherwise provided herein. 

	 	•	 	 To the extent that the payments or benefits under this Agreement are
“non-qualified deferred compensation” subject to Section 409A of the Code, if the period during which you may deliver the Release required hereunder spans two calendar years, the payment of your
post-termination benefits shall occur on the later of (a) January 1 of the second calendar year, or (b) the first regularly-scheduled payroll date following the date your Release becomes effective. 

 

	 	•	 	 Any reimbursement of expenses or in-kind benefits payable under this
Agreement shall be made in accordance with Treasury Regulation Section 1.409A-3(i)(1)(iv) and shall be paid on or before the last day of your taxable year following the taxable year in which you
incurred the expenses. The amount of expenses reimbursed or in-kind benefits payable in one year shall not affect the amount eligible for reimbursement or in-kind
benefits payable in any other taxable year of yours, and your right to reimbursement for such amounts shall not be subject to liquidation or exchange for any other benefit. 

• SECTION 280G TREATMENT. 

 

	 	•	 	 In the event that any payment or benefit received or to be received by you pursuant to the terms of any plan,
arrangement or agreement (including any payment or benefit received in connection with a change of control or the termination of your employment) (all such payments and benefits being hereinafter referred to as the “Total
Payments”) would be subject (in whole or part) to the excise tax (the “Excise Tax”) imposed under Section 4999 of the Code, then the Total Payments shall be reduced to the extent necessary so that no portion
of the Total Payments is subject to the Excise Tax but only if (a) the net amount of such Total Payments, as so reduced (after subtracting the amount of federal, state and local income taxes on such reduced Total Payments and after taking into
account the phase out of itemized deductions and personal exemptions attributable to such reduced Total Payments) is greater than or equal to (b) the net amount of such Total Payments without such reduction (after subtracting the net amount of
federal, state and local income taxes on such Total Payments and the amount of Excise Tax to which you would be subject in respect of such unreduced Total Payments and after taking into account the phase out of itemized deductions and personal
exemptions attributable to such unreduced Total Payments); provided, however, that this sentence shall not apply if, immediately before the change in ownership or control on which such Total Payments are contingent or otherwise relate,
no stock in the Company is readily tradeable on an established securities market or otherwise (as determined in accordance with Treasury Reg. Section 1.280G-1 Q&A 6). The Total Payments shall be
reduced in the following order: (i) reduction of any cash severance payments otherwise payable to you that are exempt from Section 409A of the Code, (ii) reduction of any other cash payments or benefits otherwise payable to you that
are exempt from Section 409A of the Code, but excluding any payment attributable to the acceleration of vesting or payment with respect to any equity award with respect to the Company’s common stock that is exempt from Section 409A of
the Code, (iii) reduction of any other payments or benefits otherwise payable to you on a pro-rata basis or such other manner that complies with Section 409A of the Code, but excluding any payment
attributable to the acceleration of vesting and payment with respect to any equity award with respect to the Company’s common stock that is exempt from Section 409A of the Code, and (iv) reduction of any payments attributable to the
acceleration of vesting or payment with respect to any equity award with respect to the Company’s common stock that is exempt from Section 409A of the Code; provided, in case of clauses (ii), (iii) and (iv), that reduction of any payments
or benefits attributable to the acceleration of vesting of Company equity awards shall be first applied to Company equity awards that would otherwise vest last in time. The foregoing reductions shall be made in a manner that results in the maximum
economic benefit to you on an after-tax basis and, to the extent economically equivalent payments or benefits are subject to reduction, in a pro rata manner. 

	 	•	 	 All determinations regarding the application of this “Section 280G Treatment” section shall be
made by an accounting firm or consulting group with nationally recognized standing and substantial expertise and experience in performing calculations regarding the applicability of Section 280G of the Code and the Excise Tax retained by the
Company prior to the date of the applicable change in control (the “280G Firm”). For purposes of determining whether and the extent to which the Total Payments will be subject to the Excise Tax, (a) no portion of the
Total Payments shall be taken into account which, in the written opinion of the 280G Firm, (i) does not constitute a “parachute payment” within the meaning of Section 280G(b)(2) of the Code (including by reason of
Section 280G(b)(4)(A) of the Code) and, in calculating the Excise Tax, or (ii) constitutes reasonable compensation for services actually rendered, within the meaning of Section 280G(b)(4)(B) of the Code, in excess of the “base
amount” (as defined in Section 280G(b)(3) of the Code) allocable to such reasonable compensation, (b) no portion of the Total Payments the receipt or enjoyment of which you shall have waived at such time and in such manner as not to
constitute a “payment” within the meaning of Section 280G(b) of the Code shall be taken into account, and (c) the value of any non-cash benefit or any deferred payment or benefit included
in the Total Payments shall be determined by the 280G Firm in accordance with the principles of Sections 280G(d)(3) and (4) of the Code. All determinations related to the calculations to be performed pursuant to this this
“Section 280G Treatment” section shall be done by the 280G Firm. 

  

	 	•	 	 The 280G Firm will be directed to submit its determination and detailed supporting calculations to both you and
the Company within 15 days after notification from either the Company or you that you may receive payments which may be “parachute payments.” You and the Company will each provide the 280G Firm access to and copies of any books, records,
and documents in their possession as may be reasonably requested by the 280G Firm, and otherwise cooperate with the 280G Firm in connection with the preparation and issuance of the determinations and calculations contemplated by this Agreement. The
fees and expenses of the 280G Firm for its services in connection with the determinations and calculations contemplated by this Agreement will be borne by the Company. 

 

	 	•	 	 Notwithstanding the foregoing, if any portion of the Total Payments would not be subject to the Excise Tax if the
stockholder approval requirements of Section 280G(b)(5) of the Code are satisfied, subject to your waiver of the rights to such portion of the Total Payments in accordance with and to the extent required by Section 280G of the Code with
respect to any portion of the Total Payments that would otherwise be subject to excise tax imposed by Section 4999 of the Code (before giving effect to any reduction in the Total Payments contemplated above), the Company shall use its
reasonable best efforts to cause such payments to be submitted for such approval prior to the event giving rise to such payments. To the extent the Company submits any payment or benefit payable to you under this Agreement or otherwise to the
Company’s stockholders for approval in accordance with Treasury Reg. Section 1.280G-1 Q&A 7, the foregoing provisions under this “Section 280G Treatment” section shall not apply
following such submission and such payments and benefits will be treated in accordance with the results of such vote, except that any reduction in, or waiver of, such payments or benefits required by such vote will be applied without any application
of discretion by you and in the order prescribed in the preceding paragraph. 

 • COMPANY
POLICIES AND PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT. As an employee of the Company, you shall be expected to abide by all of the
Company’s policies and procedures and the Company’s employee handbook, if any. You have executed and agree to abide by the terms of the Company’s form of Proprietary Information and Inventions Agreement, which shall survive
termination of your employment with the Company and the termination of this Agreement. You acknowledge that a remedy at law for any breach or threatened breach by you of the provisions of the Proprietary Information and Inventions Agreement would be
inadequate, and you 

 
therefore agree that the Company shall be entitled to injunctive relief in case of any such breach or threatened breach. The Company may modify, revoke, suspend or terminate any of the terms,
plans, policies and/or procedures described in the employee handbook, if any, or as otherwise communicated to you, in whole or part, at any time, with or without notice. Notwithstanding the foregoing, or anything contained in the Proprietary
Information and Inventions Agreement, you acknowledge that you will not be held criminally or civilly liable for (a) the disclosure of confidential or proprietary information that is made in confidence to a government official or to an attorney
solely for the purpose of reporting or investigating a suspected violation of law, or (b) disclosure of confidential or proprietary information in a made in a complaint or other document filed in a lawsuit or other proceeding under seal or
pursuant to court order. 
 • OTHER AGREEMENTS. You represent and agree that your performance of
your duties for the Company shall not violate any agreements, obligations or understandings that you may have with any third party or prior employer. You agree not to make any unauthorized disclosure or use, on behalf of the Company, of any
confidential information belonging to any of your former employers. You also represent that you are not in unauthorized possession of any materials containing a third party’s confidential and proprietary information. While employed by the
Company, you will not engage in any business activity in competition with the Company nor make preparations to do so. In the event that you wish to undertake a business activity outside the scope of your employment by the Company, which activity you
believe entails no conflict with the Company’s activities, you agree to inform the Company of your intentions prior to the initiation of such outside business activity, and you furthermore agree to abide by the Company’s decision as to
whether or not there is no conflict. If, in the Company’s sole determination, a conflict exists or is likely to develop, you agree not to undertake such outside business activity. 

• AT-WILL EMPLOYMENT. Your employment with
the Company will be “at-will” at all times, meaning that either you or the Company will be entitled to terminate your employment at any time and for any reason, with or without Cause. Any contrary
representations that may have been made to you are superseded by this offer. This Agreement in no way represents a fixed-term employment contract. This is the full and complete agreement between you and the Company on this term. Although your job
duties, title, compensation and benefits, as well as the Company’s personnel policies and procedures, may change from time to time, the “at will” nature of your employment may only be changed in an express written agreement signed by
you and a duly authorized officer of the Company. 
 •
NON-INTERFERENCE. While employed by the Company, and for one year immediately following the date on which you terminate employment or otherwise cease providing services to
the Company, you agree not to interfere with the business of the Company by (a) soliciting or attempting to solicit any employee or consultant of the Company to terminate such employee’s or consultant’s employment or service in order
to become an employee, consultant or independent contractor to or for any other person or entity or (b) soliciting or attempting to solicit any vendor, supplier, customer or other person or entity either directly or indirectly, to direct his,
her or its purchase of the Company’s products and/or services to any person, firm, corporation, institution or other entity in competition with the business of the Company. Your duties under this paragraph shall survive termination of your
employment with the Company and the termination of this Agreement. 
 • DISPUTE
RESOLUTION. Unless otherwise prohibited by law or specified below, all disputes, claims and causes of action, in law or equity, arising from or relating to this Agreement or its enforcement, performance, breach, or
interpretation shall be resolved solely and exclusively by final and binding arbitration held in San Diego, California through Judicial Arbitration & Mediation Services/Endispute (“JAMS”) under the then existing JAMS
arbitration rules. The rules may be found online at www.jamsadr.com or upon written request to the Company. This paragraph is intended to be the exclusive method for resolving any and all claims by the parties against each other relating to your
employment; provided that you will retain the right to file administrative charges with or seek relief through any government agency of competent jurisdiction, and to participate in any government investigation, including but not limited to
(a) claims for workers’ compensation, state disability insurance or unemployment insurance; (b) claims for unpaid wages or waiting time penalties brought before the California Division of Labor Standards Enforcement (provided
that any appeal from an award or from denial of an award of wages and/or waiting time penalties shall be arbitrated pursuant to the terms of this paragraph; and (c) claims for administrative relief from the United States Equal Employment
Opportunity Commission and/or the California Department of Fair Employment and Housing (or any similar agency in any applicable jurisdiction other than California); provided, further, that you will not be entitled to obtain any
monetary relief through such agencies other than workers’ compensation benefits or unemployment insurance benefits. Further, nothing in this paragraph is intended to prevent either party from obtaining injunctive relief in court to prevent
irreparable harm pending the 

 
conclusion of any such arbitration, including without limitation injunctive relief, in any court of competent jurisdiction pursuant to California Code of Civil Procedure § 1281.8 or any
similar statute of an applicable jurisdiction. Seeking any such relief shall not be deemed to be a waiver of such party’s right to compel arbitration. Each party in any such arbitration shall be responsible for its own attorneys’ fees,
costs and necessary disbursement; provided, however, that if one party refuses to arbitrate and the other party seeks to compel arbitration by court order, if such other party prevails, it shall be entitled to recover reasonable
attorneys’ fees, costs and necessary disbursements. Each party warrants that it has had the opportunity to be represented by counsel in the negotiation and execution of this Agreement, including the attorneys’ fees provision herein. Both
you and the Company expressly waive your right to a jury trial. 
 • SEVERABILITY.
Whenever possible, each provision of this Agreement will be interpreted in such manner as to be effective and valid under applicable law, but if any provision of this Agreement is held to be invalid, illegal or unenforceable in any respect under any
applicable law or rule in any jurisdiction, such invalidity, illegality or unenforceability will not affect any other provision or any other jurisdiction, but this Agreement will be reformed, construed and enforced in such jurisdiction as if such
invalid, illegal or unenforceable provisions had never been contained herein. 
 • SUCCESSORS AND
ASSIGNS. This Agreement is intended to bind and inure to the benefit of and be enforceable by you and the Company, and their respective successors, assigns, heirs, executors and administrators, except
that you may not assign any of your duties hereunder and you may not assign any of your rights hereunder, without the written consent of the Company, which shall not be withheld unreasonably. 

• ENTIRE AGREEMENT. This Agreement and the Proprietary Information and Inventions Agreement
constitute the complete, final and exclusive embodiment of the entire agreement between you and the Company with respect to the terms and conditions of your employment specified herein and therein. This Agreement and the Proprietary Information and
Inventions Agreement supersede any other such promises, warranties, representations or agreements between you and the Company. This Agreement may not be amended or modified except by a written instrument signed by you and a duly authorized officer
of the Company. 
 • GOVERNING LAW. This Agreement will be governed by and construed in accordance
with the laws of the State of California without regard to the conflicts of law provisions thereof. 
 If you choose to accept this
Agreement under the terms described above, please acknowledge your acceptance of by returning a signed copy of this Agreement to our attention. 

 Sincerely, 

Erasca, Inc. 
  

			
		 	 /s/ Jonathan Lim

	Name: Jonathan Lim, M.D.
	Title: Chief Executive Officer

 Agreed and Accepted:  

I have read and understood this Agreement and hereby acknowledge, accept and agree to the terms as set forth above and further acknowledge and
agree that no other commitments were made to me in connection with this Agreement except as specifically set forth herein.  
  

							
	 /s/ Jonathan Lim
	 		  	Date:	  	 February 27, 2020

	Jonathan Lim, M.D.EX-10.6

 Exhibit 10.6 
  

 
 February 5, 2020 
 David
Chacko 
  

	Re:	 Restated Employment Offer Letter 

Dear David: 
 You are currently a party to an
employment offer letter with Erasca, Inc. (the “Company”) dated April 19, 2019 (the “Original Agreement”). You and the Company hereby agree to amend and restate the Original Agreement to add
certain severance benefits, as provided in this amended employment offer letter (this “Amended Agreement”), effective from and after January 1, 2020. 

• DUTIES. You shall serve and shall perform such duties as are customarily associated
with the position of Chief Business Officer and such other duties as are assigned to you, reporting to Jonathan Lim, CEO. You shall perform your services on a full-time basis at the Company’s headquarters. This is an exempt position. 

 • EXCLUSIVE SERVICES. You shall perform your services on a
full-time basis at the Company’s headquarters and devote your full working time and attention to the business affairs of the Company and its affiliates. Subject to the terms of the Company’s form of Proprietary Information and Inventions
Agreement, as described below, this shall not preclude you from (a) devoting time to personal and family investments, (b) participating in industry associations, or (c) serving on up to one outside board with the approval of the Chief
Executive Officer of the Company or the Board of Directors of the Company (the “Company”), provided such activities do not interfere with your duties to the Company, as determined in good faith by the Chief Executive Officer
of the Company or the Board. 
 • COMPENSATION. Your initial compensation will be as follows: 

 

	 	•	 	 BASE SALARY. You will receive an annual base salary of $314,000,
which reflects a merit increase effective January 1, 2020, for all hours worked, to be paid in accordance with the Company’s customary payroll procedures. 

 

	 	•	 	 STOCK OPTIONS. You were previously granted
stock options to purchase 875,000 shares of the Company’s common stock at an exercise price per share equal to the fair market value per share of the Company’s common stock on the date of grant (the “Stock
Options”). The Stock Options were granted pursuant to the Company’s equity incentive plan (the “Plan”). The Stock Options are subject to the terms and conditions of the Plan and your stock option agreement.
The Stock Options will vest over a four year vesting schedule, with 25% of the Stock Options vesting on the first anniversary of your commencement of employment and the remaining Stock Options vesting in 36 equal monthly installments thereafter,
subject to your continued employment or service to the Company on each such vesting date. 

  

	 	•	 	 ANNUAL BONUS. Commencing in 2020, the Board has established an annual bonus
plan, pursuant to which will be eligible to participate, subject to the terms and conditions of such plan, and your bonus target will be equal to 30% of your base salary (your “Target Bonus”). You must be employed by
the Company on the date of payment of such annual bonus in order to be eligible to receive such annual bonus. You hereby acknowledge and agree that nothing contained herein confers upon you any right to an annual bonus in any year, and that whether
the Company pays you an annual bonus and the amount of any such annual bonus will be determined by the Company in its sole discretion. 

	 	•	 	 BENEFITS. You shall be eligible to participate in all of the
employee benefit plans or programs the Company generally makes available to similarly situated employees, pursuant to the terms and conditions of such plans. You will initially be entitled to 18 days of paid time off each year, accruing on a
semi-monthly basis, and all holidays observed by the Company each year. The Company reserves the right to change compensation and benefits provided to its employees from time to time in its discretion. 

 

	 	•	 	 WITHHOLDING. All amounts payable to you will be subject to appropriate payroll deductions
and withholdings. 

 • EXPENSES. You will be entitled to reimbursement for all ordinary and
reasonable out-of-pocket business expenses which are reasonably incurred by you in furtherance of the Company’s business, with appropriate documentation and in
accordance with the Company’s standard policies. 
 • SEVERANCE. 

 

	 	•	 	 ACCRUED OBLIGATIONS. If your employment terminates for any
reason, you are entitled to your fully earned but unpaid base salary, through the date such termination is effective at the rate then in effect, and all other amounts or benefits to which you are entitled under any compensation, retirement or
benefit plan of the Company at the time of your termination of employment in accordance with the terms of such plans, including, without limitation, any accrued but unpaid paid time off and any continuation of benefits required by applicable law
(the “Accrued Obligations”). 

  

	 	•	 	 NON-CIC SEVERANCE
BENEFITS. In addition to your Accrued Obligations, subject to your continued compliance with the Proprietary Information and Inventions Agreement, as described below, and the effectiveness of your Release (as
defined below), if your employment is involuntarily terminated by the Company without Cause (as defined below) (and other than by reason of your death or disability) or you resign for Good Reason (as defined below) (either such termination, a
“Qualifying Termination”), and such Qualifying Termination does not occur during the Change in Control Period (as defined below), you shall be entitled to receive, as the sole severance benefits to which you are entitled, the
benefits provided below (the “Non-CIC Severance Benefits”): 

  

	 	•	 	 An amount equal to your base salary for the Non-CIC Severance Period (as
defined below) (at the rate in effect immediately prior to the date of your termination of employment), payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than
75 days following your termination date). 

  

	 	•	 	 For the Non-CIC Severance Period (or, if earlier, the date on which the
applicable continuation period under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”) expires) (the “COBRA Coverage Period”), if you and/or your eligible dependents who
were covered under the Company’s health insurance plans as of the date of your termination of employment elect to have COBRA coverage and are eligible for such coverage, the Company shall pay for or reimburse you on a monthly basis for an
amount equal to (a) the monthly premium you and/or your covered dependents, as applicable, are required to pay for continuation coverage pursuant to COBRA for you and/or your eligible dependents, as applicable, who were covered under the
Company’s health plans as of the date of your termination of employment (calculated by reference to the premium as of the date of your termination of employment) less (b) the amount you would have had to pay to receive group health
coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of employment. If any of the Company’s health benefits are self-funded as of the date of your termination
of employment, or if the Company cannot 

	 	 
provide the foregoing benefits in a manner that is exempt from Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), or that is otherwise
compliant with applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the foregoing monthly
amount as a taxable monthly payment for the COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without limitation, the election
of such coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment.

  

	 	•	 	 CIC SEVERANCE BENEFITS. In addition to your Accrued
Obligations, subject to your continued compliance with the Proprietary Information and Inventions Agreement, as described below, and the effectiveness of your Release, if your Qualifying Termination occurs during the Change in Control Period, you
shall be entitled to receive, as the sole severance benefits to which you are entitled and in lieu of any Non-CIC Severance Benefits, the benefits provided below (the “CIC Severance
Benefits”) (and for the avoidance of doubt, in no event will you be entitled to both the Non-CIC Severance Benefits and the CIC Severance Benefits): 

 

	 	•	 	 An amount equal to your base salary for the CIC Severance Period (as defined below) (at the rate in effect
immediately prior to the date of your termination of employment), payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than 75 days following your termination
date). 

  

	 	•	 	 An amount equal to (a) (i) your Target Bonus for the year in which your date of termination occurs, divided
by (ii) 12, multiplied by (b) the number of months in the CIC Severance Period, payable in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective (but in no event more than 75 days following
your termination date). 

  

	 	•	 	 For the CIC Severance Period (or, if earlier, the date on which the applicable continuation period under COBRA
expires) (the “CIC COBRA Coverage Period”), if you and/or your eligible dependents who were covered under the Company’s health insurance plans as of the date of your termination of employment elect to have COBRA coverage
and are eligible for such coverage, the Company shall pay for or reimburse you on a monthly basis for an amount equal to (a) the monthly premium you and/or your covered dependents, as applicable, are required to pay for continuation coverage
pursuant to COBRA for you and/or your eligible dependents, as applicable, who were covered under the Company’s health plans as of the date of your termination of employment (calculated by reference to the premium as of the date of your
termination of employment) less (b) the amount you would have had to pay to receive group health coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of
employment. If any of the Company’s health benefits are self-funded as of the date of your termination of employment, or if the Company cannot provide the foregoing benefits in a manner that is exempt from Section 409A of the Code, or that
is otherwise compliant with applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the
foregoing monthly amount as a taxable monthly payment for the CIC COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without
limitation, the election of such coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or
self-employment. 

	 	•	 	 Notwithstanding anything else set forth herein, in the Plan or in any award agreement, any unvested Stock Awards
(as defined below) then held by you (including the Stock Options) will vest on the effective date of your Release. The foregoing provisions are hereby deemed to be a part of each Stock Award and to supersede any less favorable provision in any
agreement or plan regarding such Stock Award. 

  

	 	•	 	 As a condition to your receipt of any post-termination payments and benefits pursuant to the preceding
paragraphs, you shall execute and not revoke a general release of all claims in favor of the Company (the “Release”) in a form reasonably acceptable to the Company. In the event the Release does not become effective within
the 60-day period following the date of your termination of employment, you will not be entitled to the aforesaid payments and benefits. 

 

	 	•	 	 For purposes of this Amended Agreement, “Cause” means any of the following: (a) your
commission of an act of fraud, embezzlement or dishonesty, or the commission of some other illegal act by you, that has a demonstrable adverse impact on the Company or any successor or affiliate thereof; (b) your conviction of, or plea of
“guilty” or “no contest” to, a felony or any crime involving fraud, dishonesty or moral turpitude under the laws of the United States or any state thereof; (c) any intentional, unauthorized use or disclosure by you of
confidential information or trade secrets of the Company or any successor or affiliate thereof; (d) your gross negligence, insubordination or material violation of any duty of loyalty to the Company or any successor or affiliate thereof, or any
other demonstrable material misconduct on your part; (e) your ongoing and repeated failure or refusal to perform or neglect of your duties as required by this Amended Agreement or your ongoing and repeated failure or refusal to comply with the
instructions given to you by the Chief Executive Officer of the Company or the Board, which failure, refusal or neglect continues for 15 days following your receipt of written notice from the Chief Executive Officer of the Company or the Board
stating with specificity the nature of such failure, refusal or neglect; or (f) your willful, material breach of any Company policy or any material provision of this Amended Agreement or the Proprietary Information and Inventions Agreement.
Prior to the determination that “Cause” under clauses (d), (e) or (f) has occurred, the Company shall (i) provide to you in writing, in reasonable detail, the reasons for the determination that such “Cause” exists,
(ii) other than with respect to clause (e) above which specifies the applicable period of time for you to remedy your breach, afford you a reasonable opportunity to remedy any such breach, (iii) provide you an opportunity to be heard
prior to the final decision to terminate your employment hereunder for such “Cause” and (iv) make any decision that such “Cause” exists in good faith. The foregoing definition shall not in any way preclude or restrict the
right of the Company or any successor or affiliate thereof to discharge or dismiss you for any other acts or omissions, but such other acts or omissions shall not be deemed, for purposes of this Amended Agreement, to constitute grounds for
termination for Cause. 

  

	 	•	 	 For purposes of this Amended Agreement, “Change in Control” means (a) a merger or
consolidation of the Company with or into any other corporation or other entity or person, (b) a sale, lease, exchange or other transfer in one transaction or a series of related transactions of all or substantially all of the Company’s
assets, or (c) any other transaction, including the sale by the Company of new shares of its capital stock or a transfer of existing shares of capital stock of the Company, the result of which is that a third party that is not an affiliate of
the Company or its stockholders (or a group of third parties not affiliated with the Company or its stockholders) immediately prior to such transaction acquires or holds capital stock of the Company representing a majority of the Company’s
outstanding voting power immediately following such transaction; provided that the following events shall not constitute a “Change in Control”: (i) a transaction (other than a sale of all or substantially all of the Company’s
assets) in which the holders of the voting securities of the Company immediately prior to the merger or consolidation hold, directly or indirectly, at least a majority of the voting securities in the successor corporation or its parent

	 	 
immediately after the merger or consolidation; (ii) a sale, lease, exchange or other transaction in one transaction or a series of related transactions of all or substantially all of the
Company’s assets to an affiliate of the Company; (iii) an initial public offering of any of the Company’s securities; (iv) a reincorporation of the Company solely to change its jurisdiction; or (v) a transaction undertaken
for the primary purpose of creating a holding company that will be owned in substantially the same proportion by the persons who held the Company’s securities immediately before such transaction. 

 

	 	•	 	 For purposes of this Amended Agreement, “Change in Control Period” means the
period commencing on the date of a Change in Control and ending 12 months following such Change in Control. 

  

	 	•	 	 For purposes of this Amended Agreement, “CIC Severance Period” means (a) if your
Qualifying Termination occurs during the Change in Control Period and prior to the first anniversary of your hire date, 3 months; (b) if your Qualifying Termination occurs during the Change in Control Period and on or after the first
anniversary of your hire date but prior to the second anniversary of your hire date, 6 months; or (c) if your Qualifying Termination occurs during the Change in Control Period and on or after the second anniversary of your hire date, 9 months.

  

	 	•	 	 For purposes of this Amended Agreement, “Good Reason” means any of the following without
your written consent: (a) a material diminution in your authority, duties or responsibilities; (b) a material diminution in your base compensation, unless such a reduction is imposed across-the-board to senior management of the Company; (c) a material change in the geographic location at which you must perform your duties; or (d) any other action or inaction that constitutes a
material breach by the Company or any successor or affiliate of its obligations to you under this Amended Agreement. You must provide written notice to the Company of the occurrence of any of the foregoing events or conditions without your written
consent within 60 days of the occurrence of such event. The Company or any successor or affiliate shall have a period of 30 days to cure such event or condition after receipt of written notice of such event from you. Your termination of employment
by reason of resignation from employment with the Company for Good Reason must occur within 30 days following the expiration of the foregoing 30-day cure period. 

 

	 	•	 	 For purposes of this Amended Agreement, “Non-CIC Severance
Period” means, provided your Qualifying Termination does not occur during the Change in Control Period, (a) if your Qualifying Termination occurs prior to the first anniversary of your hire date, 2 months; (b) if your
Qualifying Termination occurs on or after the first anniversary of your hire date but prior to the second anniversary of your hire date, 4 months; or (c) if your Qualifying Termination occurs on or after the second anniversary of your hire
date, 6 months. 

  

	 	•	 	 For purposes of this Amended Agreement, “Stock Awards” means all stock options,
restricted stock and such other awards granted pursuant to the Plan or the Company’s other stock option and equity incentive award plans or agreements, as in effect from time to time, and any shares of stock issued upon exercise or settlement
thereof, including the Stock Options. 

  

	 	•	 	 To the extent applicable, this Amended Agreement shall be interpreted in accordance with Section 409A of the
Code and Department of Treasury regulations and other interpretive guidance issued thereunder. The intent of the parties is that payments and benefits under this Amended Agreement comply with, or be exempt from Section 409A of the Code and,
accordingly, to the maximum extent permitted, this Amended Agreement shall be interpreted to be in compliance with such intention. To the extent that any provision in this Amended Agreement is ambiguous as to its compliance with or exemption
from Section 409A of the Code, the provision shall be read in such a manner that no payments payable under this Amended Agreement shall be subject to an “additional tax” as defined in Section 409A(a)(1)(B) of the Code. For
purposes of Section 409A of the Code, any right to a series of installment payments under this Amended Agreement shall be treated as a right to a series of separate payments. For

	 	 
purposes of this Amended Agreement, to the extent that the payments or benefits under this Amended Agreement are “non-qualified deferred
compensation” subject to Section 409A of the Code or as otherwise required to ensure such payments or benefits are exempt from or comply with Section 409A of the Code, all references to your “termination of employment” shall
mean your “separation from service” (as defined in Treasury Regulation Section 1.409A-1(h)) (“Separation from Service”). If you are a “specified
employee” (as defined in Section 409A of the Code), as determined by the Company in accordance with Section 409A of the Code, on the date of your Separation from Service, to the extent that the payments or benefits under this Amended
Agreement are “non-qualified deferred compensation” subject to Section 409A of the Code and the delayed payment or distribution of all or any portion of such amounts to which you are entitled
under this Amended Agreement is required in order to avoid a prohibited distribution under Section 409A(a)(2)(B)(i) of the Code, then such portion deferred pursuant to this paragraph shall be paid or distributed to you in a lump sum on the
earlier of (a) the date that is 6 months and one day following your Separation from Service, (b) the date of your death or (c) the earliest date as is permitted under Section 409A of the Code. Any remaining payments due under
this Amended Agreement shall be paid as otherwise provided herein. 

  

	 	•	 	 To the extent that the payments or benefits under this Amended Agreement are
“non-qualified deferred compensation” subject to Section 409A of the Code, if the period during which you may deliver the Release required hereunder spans two calendar years, the payment of your
post-termination benefits shall occur on the later of (a) January 1 of the second calendar year, or (b) the first regularly-scheduled payroll date following the date your Release becomes effective. 

 

	 	•	 	 Any reimbursement of expenses or in-kind benefits payable under this
Amended Agreement shall be made in accordance with Treasury Regulation Section 1.409A-3(i)(1)(iv) and shall be paid on or before the last day of your taxable year following the taxable year in
which you incurred the expenses. The amount of expenses reimbursed or in-kind benefits payable in one year shall not affect the amount eligible for reimbursement or
in-kind benefits payable in any other taxable year of yours, and your right to reimbursement for such amounts shall not be subject to liquidation or exchange for any other benefit. 

• SECTION 280G TREATMENT. 

 

	 	•	 	 In the event that any payment or benefit received or to be received by you pursuant to the terms of any plan,
arrangement or agreement (including any payment or benefit received in connection with a change of control or the termination of your employment) (all such payments and benefits being hereinafter referred to as the “Total
Payments”) would be subject (in whole or part) to the excise tax (the “Excise Tax”) imposed under Section 4999 of the Code, then the Total Payments shall be reduced to the extent necessary so that no portion
of the Total Payments is subject to the Excise Tax but only if (a) the net amount of such Total Payments, as so reduced (after subtracting the amount of federal, state and local income taxes on such reduced Total Payments and after taking into
account the phase out of itemized deductions and personal exemptions attributable to such reduced Total Payments) is greater than or equal to (b) the net amount of such Total Payments without such reduction (after subtracting the net amount of
federal, state and local income taxes on such Total Payments and the amount of Excise Tax to which you would be subject in respect of such unreduced Total Payments and after taking into account the phase out of itemized deductions and personal
exemptions attributable to such unreduced Total Payments); provided, however, that this sentence shall not apply if, immediately before the change in ownership or control on which such Total Payments are contingent or otherwise relate,
no stock in the Company is readily tradeable on an established securities market or otherwise (as determined in accordance with Treasury Reg. Section 1.280G-1 Q&A 6). The Total Payments shall be
reduced in the following order: (i) reduction of any cash severance payments otherwise payable to you that are exempt from Section 409A of the Code, (ii) reduction of any other cash payments or benefits otherwise payable to you that
are exempt from Section 409A of the Code, but excluding any payment attributable to the acceleration of vesting or payment with respect to 

	 	 
any equity award with respect to the Company’s common stock that is exempt from Section 409A of the Code, (iii) reduction of any other payments or benefits otherwise payable to you
on a pro-rata basis or such other manner that complies with Section 409A of the Code, but excluding any payment attributable to the acceleration of vesting and payment with respect to any equity award
with respect to the Company’s common stock that is exempt from Section 409A of the Code, and (iv) reduction of any payments attributable to the acceleration of vesting or payment with respect to any equity award with respect to the
Company’s common stock that is exempt from Section 409A of the Code; provided, in case of clauses (ii), (iii) and (iv), that reduction of any payments or benefits attributable to the acceleration of vesting of Company equity awards shall
be first applied to Company equity awards that would otherwise vest last in time. The foregoing reductions shall be made in a manner that results in the maximum economic benefit to you on an after-tax basis
and, to the extent economically equivalent payments or benefits are subject to reduction, in a pro rata manner. 

  

	 	•	 	 All determinations regarding the application of this “Section 280G Treatment” section shall be
made by an accounting firm or consulting group with nationally recognized standing and substantial expertise and experience in performing calculations regarding the applicability of Section 280G of the Code and the Excise Tax retained by the
Company prior to the date of the applicable change in control (the “280G Firm”). For purposes of determining whether and the extent to which the Total Payments will be subject to the Excise Tax, (a) no portion of the
Total Payments shall be taken into account which, in the written opinion of the 280G Firm, (i) does not constitute a “parachute payment” within the meaning of Section 280G(b)(2) of the Code (including by reason of
Section 280G(b)(4)(A) of the Code) and, in calculating the Excise Tax, or (ii) constitutes reasonable compensation for services actually rendered, within the meaning of Section 280G(b)(4)(B) of the Code, in excess of the “base
amount” (as defined in Section 280G(b)(3) of the Code) allocable to such reasonable compensation, (b) no portion of the Total Payments the receipt or enjoyment of which you shall have waived at such time and in such manner as not to
constitute a “payment” within the meaning of Section 280G(b) of the Code shall be taken into account, and (c) the value of any non-cash benefit or any deferred payment or benefit included
in the Total Payments shall be determined by the 280G Firm in accordance with the principles of Sections 280G(d)(3) and (4) of the Code. All determinations related to the calculations to be performed pursuant to this this
“Section 280G Treatment” section shall be done by the 280G Firm. 

  

	 	•	 	 The 280G Firm will be directed to submit its determination and detailed supporting calculations to both you and
the Company within 15 days after notification from either the Company or you that you may receive payments which may be “parachute payments.” You and the Company will each provide the 280G Firm access to and copies of any books, records,
and documents in their possession as may be reasonably requested by the 280G Firm, and otherwise cooperate with the 280G Firm in connection with the preparation and issuance of the determinations and calculations contemplated by this Amended
Agreement. The fees and expenses of the 280G Firm for its services in connection with the determinations and calculations contemplated by this Amended Agreement will be borne by the Company. 

 

	 	•	 	 Notwithstanding the foregoing, if any portion of the Total Payments would not be subject to the Excise Tax if the
stockholder approval requirements of Section 280G(b)(5) of the Code are satisfied, subject to your waiver of the rights to such portion of the Total Payments in accordance with and to the extent required by Section 280G of the Code with
respect to any portion of the Total Payments that would otherwise be subject to excise tax imposed by Section 4999 of the Code (before giving effect to any reduction in the Total Payments contemplated above), the Company shall use its
reasonable best efforts to cause such payments to be submitted for such approval prior to the event giving rise to such payments. To the extent the Company submits any payment or benefit payable to you under this Amended Agreement or otherwise to
the Company’s stockholders for approval in accordance with Treasury Reg. Section 1.280G-1 Q&A 7, the foregoing provisions under this “Section 280G Treatment” section shall not
apply following such submission and such payments and benefits will be treated in accordance with the results of such vote, except that any reduction in, or waiver of, such payments or benefits required by such vote will be applied without any
application of discretion by you and in the order prescribed in the preceding paragraph. 

 • COMPANY POLICIES AND
PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT. As an employee of the Company, you shall be expected to abide by all of the Company’s policies and procedures and
the Company’s employee handbook, if any. You have executed and agree to abide by the terms of the Company’s form of Proprietary Information and Inventions Agreement, which shall survive termination of your employment with the Company and
the termination of this Amended Agreement. You acknowledge that a remedy at law for any breach or threatened breach by you of the provisions of the Proprietary Information and Inventions Agreement would be inadequate, and you therefore agree that
the Company shall be entitled to injunctive relief in case of any such breach or threatened breach. The Company may modify, revoke, suspend or terminate any of the terms, plans, policies and/or procedures described in the employee handbook, if any,
or as otherwise communicated to you, in whole or part, at any time, with or without notice. Notwithstanding the foregoing, or anything contained in the Proprietary Information and Inventions Agreement, you acknowledge that you will not be held
criminally or civilly liable for (a) the disclosure of confidential or proprietary information that is made in confidence to a government official or to an attorney solely for the purpose of reporting or investigating a suspected violation of
law, or (b) disclosure of confidential or proprietary information in a made in a complaint or other document filed in a lawsuit or other proceeding under seal or pursuant to court order. 

• OTHER AGREEMENTS. You represent and agree that your performance of your duties for the Company
shall not violate any agreements, obligations or understandings that you may have with any third party or prior employer. You agree not to make any unauthorized disclosure or use, on behalf of the Company, of any confidential information belonging
to any of your former employers. You also represent that you are not in unauthorized possession of any materials containing a third party’s confidential and proprietary information. While employed by the Company, you will not engage in any
business activity in competition with the Company nor make preparations to do so. In the event that you wish to undertake a business activity outside the scope of your employment by the Company, which activity you believe entails no conflict with
the Company’s activities, you agree to inform the Company of your intentions prior to the initiation of such outside business activity, and you furthermore agree to abide by the Company’s decision as to whether or not there is no conflict.
If, in the Company’s sole determination, a conflict exists or is likely to develop, you agree not to undertake such outside business activity. 

• AT-WILL EMPLOYMENT. Your employment with
the Company will be “at-will” at all times, meaning that either you or the Company will be entitled to terminate your employment at any time and for any reason, with or without Cause. Any contrary
representations that may have been made to you are superseded by this offer. This Amended Agreement in no way represents a fixed-term employment contract. This is the full and complete agreement between you and the Company on this term. Although
your job duties, title, compensation and benefits, as well as the Company’s personnel policies and procedures, may change from time to time, the “at will” nature of your employment may only be changed in an express written agreement
signed by you and a duly authorized officer of the Company. 
 •
NON-INTERFERENCE. While employed by the Company, and for one year immediately following the date on which you terminate employment or otherwise cease providing services to
the Company, you agree not to interfere with the business of the Company by (a) soliciting or attempting to solicit any employee or consultant of the Company to terminate such employee’s or consultant’s employment or service in order
to become an employee, consultant or independent contractor to or for any other person or entity or (b) soliciting or attempting to solicit any vendor, supplier, customer or other person or entity either directly or indirectly, to direct his,
her or its purchase of the Company’s products and/or services to any person, firm, corporation, institution or other entity in competition with the business of the Company. Your duties under this paragraph shall survive termination of your
employment with the Company and the termination of this Amended Agreement. 
 • DISPUTE
RESOLUTION. Unless otherwise prohibited by law or specified below, all disputes, claims and causes of action, in law or equity, arising from or relating to this Amended Agreement or its enforcement, performance,
breach, or interpretation shall be resolved solely and exclusively by final and binding arbitration held in San Diego, California through Judicial Arbitration & Mediation Services/Endispute (“JAMS”) under the then
existing JAMS arbitration rules. The rules may be found online at www.jamsadr.com or upon written request to the Company. This 

 
paragraph is intended to be the exclusive method for resolving any and all claims by the parties against each other relating to your employment; provided that you will retain the right to
file administrative charges with or seek relief through any government agency of competent jurisdiction, and to participate in any government investigation, including but not limited to (a) claims for workers’ compensation, state
disability insurance or unemployment insurance; (b) claims for unpaid wages or waiting time penalties brought before the California Division of Labor Standards Enforcement (provided that any appeal from an award or from denial of an
award of wages and/or waiting time penalties shall be arbitrated pursuant to the terms of this paragraph; and (c) claims for administrative relief from the United States Equal Employment Opportunity Commission and/or the California Department
of Fair Employment and Housing (or any similar agency in any applicable jurisdiction other than California); provided, further, that you will not be entitled to obtain any monetary relief through such agencies other than workers’
compensation benefits or unemployment insurance benefits. Further, nothing in this paragraph is intended to prevent either party from obtaining injunctive relief in court to prevent irreparable harm pending the conclusion of any such arbitration,
including without limitation injunctive relief, in any court of competent jurisdiction pursuant to California Code of Civil Procedure § 1281.8 or any similar statute of an applicable jurisdiction. Seeking any such relief shall not be deemed to
be a waiver of such party’s right to compel arbitration.    Each party in any such arbitration shall be responsible for its own attorneys’ fees, costs and necessary disbursement; provided, however, that if one
party refuses to arbitrate and the other party seeks to compel arbitration by court order, if such other party prevails, it shall be entitled to recover reasonable attorneys’ fees, costs and necessary disbursements. Each party warrants that it
has had the opportunity to be represented by counsel in the negotiation and execution of this Amended Agreement, including the attorneys’ fees provision herein. Both you and the Company expressly waive your right to a jury trial. 

• SEVERABILITY. Whenever possible, each provision of this Amended Agreement will be
interpreted in such manner as to be effective and valid under applicable law, but if any provision of this Amended Agreement is held to be invalid, illegal or unenforceable in any respect under any applicable law or rule in any jurisdiction, such
invalidity, illegality or unenforceability will not affect any other provision or any other jurisdiction, but this Amended Agreement will be reformed, construed and enforced in such jurisdiction as if such invalid, illegal or unenforceable
provisions had never been contained herein. 
 • SUCCESSORS AND
ASSIGNS. This Amended Agreement is intended to bind and inure to the benefit of and be enforceable by you and the Company, and their respective successors, assigns, heirs, executors and administrators,
except that you may not assign any of your duties hereunder and you may not assign any of your rights hereunder, without the written consent of the Company, which shall not be withheld unreasonably. 

• ENTIRE AGREEMENT. This Amended Agreement and the Proprietary Information and Inventions Agreement
constitute the complete, final and exclusive embodiment of the entire agreement between you and the Company with respect to the terms and conditions of your employment specified herein and therein, including, without limitation, the Original
Agreement. This Amended Agreement and the Proprietary Information and Inventions Agreement supersede any other such promises, warranties, representations or agreements between you and the Company. This Amended Agreement may not be amended or
modified except by a written instrument signed by you and a duly authorized officer of the Company. 
 • GOVERNING
LAW. This Amended Agreement will be governed by and construed in accordance with the laws of the State of California without regard to the conflicts of law provisions thereof. 

If you choose to accept this Amended Agreement under the terms described above, please acknowledge your acceptance of by returning a signed copy of this
Amended Agreement to our attention. 

 Sincerely, 

Erasca, Inc. 
  

			
		 	/s/ Jonathan Lim
	  

	Name:	 	Jonathan Lim, M.D.
	Title:	 	Chairman, CEO and Co-Founder

 Agreed and Accepted:  

I have read and understood this Amended Agreement and hereby acknowledge, accept and agree to the terms as set forth above and further
acknowledge and agree that no other commitments were made to me in connection with this Amended Agreement except as specifically set forth herein.  
  

									
	 /s/ David Chacko
	 	            	  	 Date: 
	 	 March 20,
2020                                
	  	
                   
     

	David Chacko

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