Document:

EX-10.9

 Exhibit 10.9 

PRINCIPIA BIOPHARMA INC. 
 April 23,
2011      
 Martin Babler 

Re:    Executive Employment Terms 

Dear Martin: 
 On behalf of the Board of Directors (the
“Board”) of Principia Biopharma Inc. (the “Company”), I am pleased to offer you employment at the Company on the terms set forth in this offer letter agreement (the “Agreement”). Your employment
shall commence on Monday April 25, 2011 or another date mutually agreed between you and the Company. 
 Employment and Board Positions and Duties

 You will be employed in the executive position of Chief Executive Officer, and you shall perform the duties of such position as are
customary, as specified in the Bylaws of the Company, and as may be required by the Board. You will report to the Board and you will be based in the Company’s corporate headquarters in [South San Francisco], California. In addition, promptly
after the commencement of your employment, the Company will use its best efforts to appoint you to serve as a member of the Company’s Board in the “CEO seat” on the Board, to serve in such capacity while you continue to serve as the
Company’s Chief Executive Officer. You agree to resign from the Board in the event that your employment terminates for any reason (whether such termination is at your request or the Company’s request), with such resignation to be effective
no later than your employment termination date. 
 During your employment with the Company, you will devote your full-time best efforts and business time
and attention to the business of the Company. 
 Your employment relationship with the Company shall also be governed by the general employment policies and
practices of the Company (except that if the terms of this letter differ from or are in conflict with the Company’s general employment policies or practices, this letter will control), and you will be required to abide by the general employment
policies and practices of the Company. The Board reserves the right to change your position, duties, reporting relationship, work location, and the Company’s general employment policies and procedures, from time to time in its discretion. 

Base Salary and Annual Bonus 
 Your base salary will be
paid at the initial rate of $26,666.66 per month (an annual rate of $320,000), less payroll deductions and withholdings. You will be paid your base salary on a semi-monthly basis, on the Company’s normal payroll schedule. As an exempt salaried
employee, you will be required to work the Company’s normal business hours, and such additional time as appropriate for your work assignments and positions. You will not be eligible for overtime premiums. 

 Martin Babler 

April 23, 2011 
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 In addition to base salary, you will be eligible for a discretionary annual performance bonus of up to thirty
percent (30%) of your annual base salary in effect during the bonus year; the bonus amount for 2011 will be prorated based on your length of employment in 2011. The bonus will be based upon the Board’s assessment of your performance and of the
Company’s attainment of objectives as determined by the Board in its sole discretion. Following your hire, the Board will determine the applicable performance objectives for you and the Company for 2011. Bonus payments, if any, will be subject
to applicable payroll deductions and withholdings. Following the close of each calendar year, the Board will determine whether you have earned a performance bonus, and the amount of any performance bonus, based on its assessment of achievement of
the applicable objectives. No amount of the performance bonus is guaranteed, and you must be an employee in good standing on the bonus payment date to be eligible to receive a bonus. If your employment terminates for any reason prior to the date
that the bonus payment is scheduled to be paid (regardless of whether at your request, or the Company’s request), then you will not be eligible for a performance bonus. The performance bonus, if earned, will be paid no later than March 15
of the calendar year after the year to which it relates. Your compensation (including base salary and bonus eligibility) will be reviewed on an annual or more frequent basis by the Board (or any authorized committee thereof), and are subject to
change in the discretion of the Board (or any authorized committee thereof). 
 Employee Benefits 

As a regular, full-time employee, you will be eligible to participate in the Company’s standard employee benefits (pursuant to the terms and conditions of
the benefit plans and applicable policies). In addition, you will accrue vacation at the initial rate of four (4) weeks (or twenty (20) business days) per year, subject to the terms of the Company’s vacation policy. Your accrual of
unused vacation will be subject to a maximum accrual cap of ten (10) days, and you will cease to accrue any additional vacation if your balance of accrued and unused vacation reaches this maximum cap, following which, you will not recommence
vacation accrual until you take vacation and your balance drops below the maximum cap. The Company may modify employee benefits from time to time in its discretion. 

Stock Options 
 Subject to approval by the Board, the
Company shall grant you an option under the Company’s Amended and Restated 2008 Equity Incentive Plan (the “Equity Plan”) to purchase 641,163 shares of the Company’s Common Stock (equivalent to four percent (4%) of the
issued and outstanding shares, outstanding options, warrants and other equity rights, and all shares reserved for issuance under the Equity Plan (the “Fully Diluted Cap”)) (the “Option”) at fair market value as
determined by the Board as of the date of grant. The Option will be governed in full by the Equity Plan and your grant agreement. The Option will be subject to a four-year vesting period subject to your continued service with the Company (as defined
in the Equity Plan), with twenty-five percent (25%) of the shares subject to the Option vesting on the one year anniversary of your vesting commencement date, and one-forty-eighth (1/48th) of the shares
subject to the Option vesting for each month of your continued service thereafter. 
 Your Option grant will be subject to anti-dilution protection to the
following extent, in addition to any applicable anti-dilution provisions of the Equity Plan:
 (A) In the event that, and upon completion by the
Company of the second and third tranches (excluding any put right closings in connection with such tranches) of that certain Series A Preferred Stock Financing (each, a “Series A Financing Tranche”), in accordance with the terms of
that certain Series A Preferred Stock Purchase Agreement, made as of February 15, 2011 (the “Series A Purchase Agreement”), the 

 Martin Babler 

April 23, 2011 
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Company will grant you as necessary, upon each closing of such Series A Financing Tranche, additional stock options (or, if mutually agreeable, stock awards) on substantially similar terms, but
with a vesting commencement date equal to the grant date and excluding further anti-dilution protection under this paragraph) to purchase or receive shares, as the case may be, of the Company’s common stock such that your total number
of option shares (including the original Option and such additional grant and both vested and unvested option or stock award shares) shall equal (i) with respect to the second tranche, four and
one-quarter percent (4.25%) of the Fully-Diluted Cap on the date of closing of such second tranche, and (ii) with respect to the third tranche, four and one-half
percent (4.5%) of the Fully-Diluted Cap on the date of closing of such third tranche; and 
 (B) In the event that the Company meets the milestones set
forth in the Series A Purchase Agreement to trigger the second and/or third tranches of the Series A Financing, and the Company executes a licensing, partnering or similar deal with a strategic partner (a “Strategic Transaction”)
such that, upon the request of the Company, the Investors (as defined in the Series A Purchase Agreement) holding at least seventy-five percent (75)% of then outstanding Series A Preferred Stock agree to permanently waive their right to participate
in either of such second or third tranche, as the case may be, under the Series A Purchase Agreement (each an “Effective Participation Waiver”), then the Company will grant you as necessary additional options (or, if mutually
agreeable, stock awards) to purchase or receive shares, as the case may be, of the Company’s common stock such that your total number of option shares (including the original Option and such additional grant and both vested and
unvested option or stock award shares) shall equal either four and one-quarter percent (4.25%) of the Fully Diluted Cap on the date of such Effective Participation Waiver (in the case of a Strategic
Transaction in lieu of the second tranche) or four and one-half percent (4.5%) of the Fully Diluted Cap on the date of such Effective Participation Waiver (in the case of a Strategic Transaction in lieu of the
third tranche), 
 (each of clause (A) and (B) above, an “Anti-dilution Adjustment”), provided, however, that the
right to receive such Anti-dilution Adjustment shall terminate and be of no further force and effect upon the earlier of (i) the closing of an initial public offering of the Company’s common stock and (ii) the date that is five
(5) years from the date hereof. Further, you shall have the right to early exercise the Option and any additional options granted pursuant to the Anti-dilution Adjustment. 

Signing Bonus 
 As an inducement to your acceptance of
employment, you will be paid a cash signing bonus, within ten days of your date of commencement of employment, of Forty Five Thousand Dollars ($45,000) less any payroll deductions and withholding. 

Change in Control Double Trigger Option Acceleration 
 If,
on or within twelve (12) months after a Change in Control (as defined below), your employment is terminated by the Company (or its successor) other than for Cause (as defined below) or is terminated by you due to a resignation for Good Reason
(as defined below), and such termination or resignation is not due to your death or disability, then all outstanding shares subject to any stock options then held by you (including but not limited to the Option) shall vest in full effective as of
your termination or resignation date (the “Full Acceleration”). Notwithstanding the foregoing, as a pre-condition of the Full Acceleration, you must deliver to the Company, within thirty
(30) days following your termination date, a signed and dated effective, general release of all known and unknown claims in the form provided to you by the Company. 

 Martin Babler 

April 23, 2011 
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 For purposes of the above paragraph, the following definitions shall apply: 

(1)    Definition of Change in Control. “Change in Control” shall have the same definition
as Sections 2(a)(i) and 2(a)(iii) of the Equity Plan (which constitute portions of the definition of “Acquisition” under the Equity Plan). 

(2)    Definition of Cause. “Cause” for the Company (or any successor thereto) to terminate
your employment shall exist if any of the following occurs: (A) your conviction (including a guilty plea or plea of nolo contendere) of any felony, or of any other crime involving fraud, dishonesty or moral turpitude; (B) your commission
or attempted commission of or participation in a fraud or act of dishonesty against the Company; (C) your material violation of any written and fully executed contract or agreement between you and the Company, including without limitation,
material breach of this Agreement or your Proprietary Information and Inventions Agreement (discussed below), or of any Company policy, or of any statutory duty you owe to the Company; or (D) your conduct that constitutes gross insubordination
or habitual neglect of duties, provided, however, that the action or conduct described in clause (C) above and this clause (D) will constitute “Cause” only if such action or conduct causes (or is reasonably expected to
cause) harm to the Company and continues after the Board has provided you with written notice thereof and thirty (30) days opportunity to cure the same (provided that the Board is not obligated to provide such written notice and opportunity to
cure if the action or conduct is not reasonably susceptible to cure). The determination that a termination is for Cause shall be made by the Board in good faith.  

(3)    Definition of Good Reason. For purposes of this Agreement, you shall have “Good
Reason” for your resignation from your employment with the Company or its successors for up to ninety (90) days following the occurrence of one of the following events without your written consent and after having
provided thirty (30) days prior written notice and an opportunity to cure to the Company, and the Company fails to cure the event within such thirty-day cure period: (A) material reduction in your
duties (including responsibilities and/or authorities), provided, however, that a change in job position (including a change in title) shall not be deemed a “material reduction” in and of itself unless your new duties are
substantially reduced from the prior duties; (B) relocation of your principal place of employment to a place that increases your one-way commute by more than forty-five (45) miles as compared to your
then current principal place of employment immediately prior to such relocation; or (C) a reduction of at least 10% of your gross base salary (unless pursuant to a salary reduction program applicable generally to the Company’s executive
employees).  
 Compliance With Confidential Information Agreement and Company Policies; Third Party Information 

As a condition of employment, you must sign and comply with the Company’s standard form of Employee Proprietary Information and Inventions Agreement. In
addition, you will be expected to abide by the Company’s rules and policies, as may be changed from time to time within the Company’s sole discretion. 

In your work for the Company, you will be expected not to use or disclose any confidential information, including trade secrets, of any former employer or
other person to whom you have an obligation of confidentiality. Rather, you will be expected to use only that information which is generally known and used by persons with training and experience comparable to your own, which is common knowledge in
the industry or otherwise legally in the public domain, or which is otherwise provided or developed by the Company or by you in the course of your employment with the Company. By signing this letter, you

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April 23, 2011 
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represent that you are able to perform your job duties within these guidelines, and you are not in unauthorized possession of any confidential documents or other property of any former employer
or other third party. In addition, by signing below, you represent that you have disclosed to the Company in writing any agreement you may have with any third party (e.g., a former employer) which may conflict with or limit your ability to perform
your duties to the Company. 
 Outside Activities 

Throughout your employment with the Company, you may engage in civic and
not-for-profit activities so long as such activities do not interfere with the performance of your duties hereunder or present a conflict of interest with the Company.
Subject to the restrictions set forth herein and with the prior written consent of the Board, you may serve as a director of other corporations and may devote a reasonable amount of your time to other types of business or public activities not
expressly mentioned in this paragraph. The Board may rescind its consent to your service as a director of all other corporations or participation in other business or public activities, if the Board, in its sole discretion, determines that such
activities compromise or threaten to compromise the Company’s business interests or conflict with your duties to the Company. 
 During your employment
by the Company, except on behalf of the Company, you will not directly or indirectly serve as an officer, director, stockholder, employee, partner, proprietor, investor, joint venturer, associate, representative or consultant of any other person,
corporation, firm, partnership or other entity whatsoever known by you to compete with the Company (or is planning or preparing to compete with the Company), anywhere in the world, in any line of business engaged in (or planned to be engaged in) by
the Company; provided, however, that you may purchase or otherwise acquire up to (but not more than) one percent (1%) of any class of securities of any enterprise (but without participating in the activities of such enterprise) if such securities
are listed on any national or regional securities exchange. 
 At-Will Employment Relationship 

You may terminate your employment with the Company at any time and for any reason whatsoever simply by notifying the Company. Likewise, the Company may
terminate your employment at any time, with or without Cause, and with or without advance notice. Your employment at-will status can only be modified in a written agreement approved by the Board and signed by
you and a duly authorized Member of the Board. 
 Severance Benefits 

If, at any time, (a) your employment with the Company terminates due to termination without Cause by the Company (or its successor) or you resign for Good
Reason, (b) such termination is not due to your death or disability, and (c) such termination constitutes a “separation from service” (as defined under Treasury Regulation
Section 1.409A-1(h)) (a “Separation from Service”), then you shall be entitled to receive the following as your sole severance benefits (the “Severance Benefits”): 

(1)    Severance Pay. You shall be entitled to severance pay in the form of continuation of your base salary
in effect on the effective date of termination for the first six (6) months after the date of such termination. The severance shall be paid in substantially equal installments on the Company’s regular payroll schedule, subject to
standard deductions and withholdings over the six (6) month period following termination; provided, however, that no payments will be made prior to the thirtieth (30th) day following
your termination (or on such later date that the Release (as defined below) becomes effective). 

 Martin Babler 

April 23, 2011 
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On the thirtieth (30th) day following your termination date, the Company will pay you the salary continuation payments that you would have
received on or prior to such date in a lump sum under the original schedule but for the delay while waiting for the effectiveness of the Release, with the balance of the cash severance being paid as originally scheduled. 

(2)    Stock Option Vesting. Any unvested stock options outstanding as of the termination date (including
the Option, to the extent not fully vested) will be subject to accelerated vesting, effective as of the termination date, with respect to an additional number of options that would have vested over a six-month
period (for example, 6/48th of the total options for option grants with a four year vesting schedule). 

(3)    COBRA Payments. If you timely elect continued coverage under federal COBRA laws or comparable state
insurance laws (collectively, “COBRA”), then the Company shall reimburse the cost of your COBRA premiums necessary to continue your medical insurance coverage in effect for yourself and your eligible dependents on the termination
date for the first six (6) months of such coverage (provided that such COBRA reimbursement shall terminate on such earlier date as you are no longer eligible for COBRA coverage or you become eligible for group medical insurance coverage
through a new employer). You are required to provide prompt written notice to the Company of other employment you obtain during the six-month period following the termination date, including notice of whether
you are eligible for group medical insurance coverage through your new employer. Notwithstanding the foregoing, if the Company determines in its sole discretion that it cannot provide the foregoing COBRA reimbursement benefit without potentially
violating applicable law (including, without limitation, Section 2716 of the Public Health Service Act), the Company shall in lieu thereof provide to you a taxable monthly payment in an amount equal to the monthly COBRA premium that you would
be required to pay to continue your group medical insurance coverage in effect on the date of your termination (which amount shall be based on the premium for the first month of COBRA coverage), which payments shall continue for the same time period
that the Company otherwise would have provided reimbursement of your COBRA payments (e.g. through no later than six (6) months after your termination). 

The Severance Benefits are conditional upon (a) your continuing to comply with your continuing obligations to the Company, including obligations under
your Proprietary Information and Inventions Agreement; and (b) your delivering to the Company, within thirty (30) days following your termination date, a signed and dated effective, general release of all known and unknown claims in
the form provided to you by the Company (the “Release”). 
 IRS Section 409A 

It is intended that the Severance Benefits satisfy, to the greatest extent possible, the exemptions from the application of Internal Revenue Code
Section 409A provided under Treasury Regulations 1.409A-1(b)(4), 1.409A-1(b)(5) and 1.409A-1(b)(9), and this letter will be
construed to the greatest extent possible as consistent with those provisions. For purposes of Code Section 409A (including, without limitation, for purposes of Treasury Regulation
Section 1.409A-2(b)(2)(iii)), your right to receive installment payments under this letter shall be treated as a right to receive a series of separate payments and, accordingly, each installment payment
hereunder shall at all times be considered a separate and distinct payment. Notwithstanding any provision to the contrary in this letter, if you are deemed by the Company at the time of your Separation from Service to be a “specified
employee” for purposes of Code Section 409A(a)(2)(B)(i), to the extent delayed commencement of any portion of the severance benefits to which you are entitled under this letter is required in order to avoid a prohibited distribution under
Code Section 409A(a)(2)(B)(i), such portion of your benefits shall not be provided to you prior to the earlier of (i) the 

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expiration of the six-month period measured from the date of your Separation from Service with the Company or (ii) the date of your death. Upon the
first business day following the expiration of the applicable Code Section 409A(a)(2)(B)(i) period, all payments deferred pursuant to this paragraph shall be paid in a lump sum to you, and any remaining payments due under this letter shall be
paid as otherwise provided herein. 
 Dispute Resolution 

To ensure the rapid and economical resolution of disputes that may arise in connection with your employment with the Company, you and the Company agree that
any and all disputes, claims, or causes of action, in law or equity, including but not limited to statutory claims, arising from or relating to the enforcement, breach, performance, or interpretation of this letter agreement, your employment with
the Company, or the termination of your employment, shall be resolved, to the fullest extent permitted by law, by final, binding and confidential arbitration before a single arbitrator held in San Francisco, California and conducted by JAMS, Inc.
(“JAMS”) or its successor, under JAMS’ then applicable rules. By agreeing to this arbitration procedure, both you and the Company waive the right to resolve any such dispute through a trial by jury or judge or by
administrative proceeding. You will have the right to be represented by legal counsel at any arbitration proceeding. The arbitrator shall: (1) have the authority to compel adequate discovery for the resolution of the dispute and to award
such relief as would otherwise be available under applicable law in a court proceeding; and (2) issue a written statement signed by the arbitrator regarding the disposition of each claim and the relief, if any, awarded as to each claim, the
reasons for the award, and the arbitrator’s essential findings and conclusions on which the award is based. The Company shall bear JAMS’ arbitration fees and administrative costs in excess of the court filing fees that you would be
required to pay if the dispute was litigated in civil court. Nothing in this Agreement shall prevent either you or the Company from obtaining injunctive relief in court to prevent irreparable harm pending the conclusion of any such arbitration. Any
awards or orders in such arbitrations may be entered and enforced as judgments in the federal and state courts of any competent jurisdiction. 

Miscellaneous 
 As required by federal law, this offer is
contingent upon satisfactory proof of your identity and right to work in the United States. In addition, this offer and your employment are subject to satisfactory background check and references check, and you agree to cooperate fully with the
Company in completing any requested authorizations for the background and references check. 
 This letter, together with your Proprietary Information and
Inventions Agreement, forms the complete and exclusive statement of your employment agreement with the Company. It supersedes any other agreements or promises made to you by anyone, whether oral or written. Changes in your employment terms, other
than those changes expressly reserved to the Company’s or Board’s discretion in this letter, require a written modification approved by the Board and signed by a duly authorized Member of the Board. This Agreement will bind the heirs,
personal representatives, successors and assigns of both you and the Company, and inure to the benefit of both you and the Company, their heirs, successors and assigns. If any provision of this Agreement is determined to be invalid or unenforceable,
in whole or in part, this determination shall not affect any other provision of this Agreement and the provision in question shall be modified so as to be rendered enforceable in a manner consistent with the intent of the parties insofar as possible
under applicable law. This Agreement shall be construed and enforced in accordance with the laws of the State of California without regard to conflicts of law principles. Any ambiguity in this Agreement shall not be construed against either party as
the drafter. Any waiver of a 

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April 23, 2011 
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breach of this Agreement, or rights hereunder, shall be in writing and shall not be deemed to be a waiver of any successive breach or rights hereunder. This Agreement may be executed in
counterparts which shall be deemed to be part of one original, and facsimile signatures shall be equivalent to original signatures. 
 Please sign and date
this letter and return it to me as soon as practicable if you wish to accept employment at the Company under the terms described above. I would be happy to discuss any questions that you may have about these terms. 

We are delighted to be making this offer and the Board looks forward to your favorable reply and to a productive and enjoyable work relationship. 

Sincerely, 
  

	
	 /s/ Srini Akkaraju

	Srini Akkaraju
	Chairman, Board of Directors

 Reviewed, Understood, and Accepted: 
  

							
	 /s/ Martin Babler
	 		  		 	
	Martin Babler	 		  	DateEX-10.10

 Exhibit 10.10 

Principia Biopharma, Inc. 
 Suite 302 

400 East Jamie Court 
 South San Francisco, CA 94080 

November 26, 2013 
 Chris Chai 

 

	Re:	 Offer of Employment 

Dear Chris: 
 Principia Biopharma Inc. a
Delaware corporation (the “Company”), is pleased to offer you the position of Chief Financial Officer, on the following terms: 
 Employment
and Duties 
 In your position as Chief Financial Officer, you will be responsible for leading and running Principia’s finance
organization, and as a member of the executive leadership team contribute to corporate strategy and represent the organization to investors. You will also be asked to perform other duties determined by or in collaboration with the Chief Executive
Officer of the Company (“CEO”). This is a full time position. You will report to Martin Babler, CEO and will principally work from our facility located in South San Francisco. Subject to your right to receive severance upon a resignation
for Good Reason (as defined herein), the Company may change your position, duties, work location or reporting structure from time to time in its discretion. 

Base Salary and Annual Bonus 
 You will be
paid a base salary at the annual rate of $280,000.00 less standard payroll deductions and all required withholdings. Your salary will be paid twice per month and otherwise in accordance with the Company’s standard payroll policies. 

 In addition to your salary, each year you will be eligible to earn an annual cash bonus (the
“Annual Bonus”) in accordance with the Company’s bonus guidelines. Whether you receive an Annual Bonus for any given year, and the amount of any such Annual Bonus, shall be determined by the Company’s Board of Directors (the
“Board”) in its sole discretion based upon the Company’s performance and your individual attainment of agreed upon performance objectives during the applicable year, as well as such other criteria that the Board deems relevant.
Performance objectives will be set no later than ninety (90) days after the start of the relevant year. Any Annual Bonus awarded by the Board shall be paid no later than March 15th of the year following the applicable bonus year. You are
only eligible to earn an Annual Bonus if you are employed by the Company on the day any such Annual Bonus is paid. Therefore, in the event you leave the Company’s employment for any reason prior to the date any Annual Bonus is paid, you
will not have earned, and will not receive, any such Annual Bonus (including a prorated amount). 
 Stock Options 

As an additional incentive to join the Company, subject to approval by the Board, you will be granted an unvested option to purchase 752,000
(seven hundred and fifty two thousand) shares of common stock of the Company (which the Company acknowledges and agrees constitutes 1.50% of the Company’s fully diluted equity as of the option grant date) pursuant to the Company’s 2008
Equity Incentive Plan (the “Plan”), at a per share exercise price equal to the fair market value of the Company’s common stock on the date of grant (the “Option”). The Option will be an incentive stock option (ISO) to the
extent permitted by law. The Option shall vest and become exercisable as to twenty-five percent (25%) of the Shares subject to the Option on the first anniversary of your employment start date, and as to 1/48th of the Shares subject to the Option in equal monthly installments thereafter on each monthly anniversary of your employment start date, with such vesting subject to your continuous employment by the
Company through the applicable vesting date. The Option shall be subject to the terms and conditions of the Plan and the Company’s standard form of stock option agreement. 

In connection with the Company’s next financing transaction, you will be eligible for a second option grant, with all terms and
conditions of such option (including the number of shares) to be determined by the Board in its sole discretion. 
 Employee Benefits 

You shall be entitled to the Company’s basic employment benefits generally available to all Company employees. You shall be entitled to
participate in all incentive, savings and retirement plans, practices, policies and programs maintained or sponsored by the Company from time to time for the benefit of its employees, subject to the terms and conditions of the applicable plans. You
will be eligible for standard benefits, such as medical, dental and vision insurance, sick leave, vacations and holidays to the extent applicable generally available to all Company employees. Details about these benefits are provided in an Employee
Handbook and in Summary Plan Descriptions, which have been prepared by the Company and made available for your review. 

 Compliance with Confidential Information Agreement and Company Policies 

As a condition of employment, you will be required to (i) sign and comply with a Proprietary Information and Invention Assignment
Agreement, a copy of which is attached hereto as Exhibit A, which, among other things, prohibits unauthorized use or disclosure of Company proprietary information, (ii) sign and return a satisfactory
I-9 Immigration form providing sufficient documentation establishing your employment eligibility in the United States, and (iii) provide satisfactory proof of your identity as required by United States
law. By signing below, you represent that your performance of services to the Company will not violate any duty which you may have to any other person or entity (such as a present or former employer), including obligations concerning providing
services (whether or not competitive) to others, confidentiality of proprietary information and assignment of inventions, ideas, patents or copyrights, and you agree that you will not do anything in the performance of services hereunder that would
violate any such duty. You will be expected to abide by the Company rules and regulations and acknowledge in writing that you have read the Company’s Employee Handbook. 

Change in Control Double Trigger Option Acceleration 

If, on or within twelve (12) months after a Change in Control (as defined below), your employment is terminated by the Company (or its
successor) other than for Cause (as defined below) or by you due to a resignation for Good Reason (as defined below), and such termination or resignation is not due to your death or disability, then all outstanding shares subject to any stock
options or other equity awards then held by you (including, but not limited to, the Option) shall vest in full effective as of immediately prior to your termination (the “Full Acceleration”). Notwithstanding the foregoing, as a
precondition of the Full Acceleration, you must deliver to the Company, within (30) days following your termination date, a signed and dated effective, general release of all known and unknown claims in the form provided to you by the Company.

 For the purposes of the above paragraph, the following definitions shall apply: 

(1)    Definition of Change in Control 

“Change in Control” shall have the same definition as Sections 2(a)(i) and 2(a)(iii) of the Equity Plan (which constitutes portions
of the definition of “Acquisition” under the Equity Plan). 
 (2)    Definition of Cause 

“Cause” for the Company (or any successor thereto) to terminate your employment shall exist if any of the following occurs:
(A) your conviction (including a guilty plea of nolo contendere) of any felony, or of any other crime involving fraud, dishonesty or moral turpitude; (B) your commission or attempted commission of or participation in a fraud act or act of
dishonesty against the Company; (C) your material violation of any written and fully executed contract or agreement between you and the Company, including, without limitation, material breach of this agreement, or your Proprietary Information
and Inventions Agreement, or of any 

 
Company policy, or of any statutory duty you owe to the Company; or (D) your conduct that constitutes gross insubordination or habitual neglect of duties; provided, however, that the action
or conduct described in clauses (C) and (D) above will constitute “Cause” only if such action or conduct causes (or is reasonably expected to cause) harm to the Company and continues after the Board has provided you with written
notice thereof and thirty (30) days opportunity to cure the same (provided that the Board is not obligated to provide such written notice and opportunity to cure if the action or conduct is not reasonably susceptible to cure). The determination
that a termination is for Cause shall be made by the Board in good faith. 
 (3)    Definition of Good Reason 

For purposes of this Agreement, you shall have “Good Reason” for your resignation from your employment with the Company or its
successors for up to ninety (90) days following the occurrence of one of the following events without your written consent and after having provided thirty (30) days prior written notice and an opportunity to cure to the Company, and the
Company fails to cure the event within such thirty-day cure period: (A) material reduction in your duties (including responsibilities and/or authorities), provided, however, that a change in job position
(including a change in title) shall not be deemed a “material reduction” in and of itself unless your new duties are substantially reduced from prior duties; (B) relocation of your principal place of employment to a place that
increases your one-way commute by more than forty-five (45) miles as compared to your then current place of employment immediately prior to such relocation; or (C) a reduction of at least 10% of your
gross base salary (unless pursuant to a salary reduction program applicable generally to the Company’s executive employees). 
 Severance Benefits

 If, at any time, (a) your employment with the Company terminates due to termination without Cause by the Company (or its
successor) or you resign for Good Reason and (b) such termination is not due to your death or disability, then, upon your “separation from service” (as defined under Treasury Regulation
Section 1.409A-1(h)) (a “Separation from Service”), then you shall be entitled to receive the following as your sole severance benefits (the “Severance Benefits”): 

(1)    Severance Pay 

You shall be entitled to severance pay in the form of continuation of your base salary in effect on the effective date of termination for the
first six (6) months after the date of such termination. The severance shall be paid in substantially equal installments on the Company’s regular payroll schedule, subject to standard deductions and withholdings over the six (6) month
period following termination; provided, however, that no payments will be made prior to the thirtieth (30th) day following your termination (or on such later date that the Release (as defined
below) becomes effective). On the thirtieth (30th) day following your termination date, the Company 

 
will pay you the salary continuation payments that you would have received on or prior to such date in a lump sum under the original schedule but for the thirty
(30)-day delay while waiting for the effectiveness of the Release (as defined below), with the balance of the cash severance being paid as originally scheduled. 

(2)    Stock Option Vesting 

Any unvested stock options and other equity awards (if any) outstanding as of the termination date (including the Option, to the extent not
fully vested) will be subject to accelerated vesting, effective as of the termination date, with respect to an additional number of options that would have vested over a six month period following your termination had your employment not been
terminated (for example 6/48th of the total options for option grants with a four year vesting schedule). 

(3)    Health Benefits 

For the six month period immediately following the Termination Date you will receive reimbursement by the company of the share of the premiums
for continuation of medical and dental benefits under COBRA that are paid by the Company for active and similarly-situated employees who receive the same type of coverage, assuming you elect and are eligible for such coverage (provided, that, any
such reimbursement shall cease upon you becoming eligible for coverage under a subsequent employer’s plans). 
 The Severance Benefits
are conditional upon (a) your continuing to comply with your continuing obligations under your Proprietary Information and Inventions Agreement; and b) your delivering to the Company, within thirty (30) days following your termination
date, a signed and dated effective, general release of all known and unknown claims in the form provided to you by the Company. 

Notwithstanding anything to the contrary in this Agreement, no compensation or benefits, including without limitation any Severance Benefits,
shall be paid to you during the 6-month period following your Separation from Service to the extent that (i) you are a specified employee (within the meaning of Internal Revenue Code Section 409A
(together with the regulations and other guidance thereunder, “Section 409A”)) and (ii) the Company makes a good faith determination that paying such amounts at the time or times indicated in this Agreement would be a prohibited
distribution under Section 409A(a)(2)(B)(i) of the Code. If the payment of any such amounts is delayed as a result of the previous sentence, then the Company will pay you the cumulative amount that would have otherwise been payable to you
during such 6-month period in a lump sum on the first business day after such six-month period (or such earlier date upon which such amount can be paid under
Section 409A of the Code without resulting in a prohibited distribution). For purposes of Section 409A, any right to a series of installment payments pursuant to this Agreement, including without limitation any severance payments, will be
treated as a right to a series of separate payments. 

 At-will Employment Relationship and Dispute Resolution 

Notwithstanding any of the above, your employment with the Company is “at will”. This means you may terminate your employment with
the Company at any time and for any reason whatsoever simply by notifying the Company. Likewise, the Company may terminate your employment at any time and for any reason whatsoever, with or without cause or advance notice (but subject to the
severance provisions contained herein). This at-will employment relationship cannot be changed except in a writing signed by a Company officer or by a duly authorized member of the Board. To ensure the rapid
and economical resolution of disputes that may arise in connection with your employment, you and the Company agree that any and all disputes, claims, or causes of action, in law or equity, arising from or relating to the enforcement, breach,
performance, execution, or interpretation of this agreement, your employment, or the termination of your employment, shall be resolved, to the fullest extent permitted by law, by final, binding and confidential arbitration in San Francisco,
California conducted before a single arbitrator by Judicial Arbitration and Mediation Services, Inc. (“JAMS”) or its successor, under the then applicable JAMS rules. By agreeing to this arbitration procedure, both you and the Company waive
the right to resolve any such dispute through a trial by jury or judge or by administrative proceeding. The arbitrator shall: (a) have the authority to compel adequate discovery for the resolution of the dispute and to award such relief as
would otherwise be permitted by law; and (b) issue a written arbitration decision including the arbitrator’s essential findings and conclusions and a statement of the award. The Company shall pay all JAMS’ arbitration fees. Nothing in
this letter agreement shall prevent either you or the Company from obtaining injunctive relief in court if necessary to prevent irreparable harm pending the conclusion of any arbitration. 

The employment terms in this letter supersede any other agreements or promises made to you by anyone, whether oral or written, and comprise
the final, complete and exclusive agreement between you and the Company. As required by law, this offer is subject to satisfactory proof of your right to work in the United States. 

If you accept this offer, this Agreement (together with its Exhibits), your option agreements and the Proprietary Information and Invention
Assignment Agreement, shall constitute the complete agreement between you and Company with respect to the terms and conditions of your employment. Any prior or contemporaneous representations (whether oral or written) not contained in this letter or
the Proprietary Information and Invention Assignment Agreement or contrary to those contained in this letter or the Proprietary Information and Invention Assignment Agreement, that may have been made to you are expressly cancelled and superseded by
this offer. Except as otherwise specified herein, the terms and conditions of your employment may not be changed, except in another letter or written agreement, signed by you and the Chief Executive Officer or other responsible officer of the
Company. 

 Please sign and date this letter, and return it to me by December 2, 2013 if you wish
to accept employment at the Company under the terms described above. If you accept our offer, we would like you to commence your employment with us by no later than December 9, 2013. 

We look forward to your favorable reply and to a productive and enjoyable work relationship. 

 

			
	Sincerely,	 	

 
			
	
	PRINCIPIA BIOPHARMA INC.

 
			
		
	By:	 	 /s/ Martin Babler

	Name:	 	Martin Babler
	Title:	 	CEO

  

	
	Accepted by:
	
	 /s/ Chris Chai

	Chris Chai
	
	November 26, 2013
	Date

 Exhibit A 

Proprietary Information and Invention Assignment Agreement 

 PRINCIPIA BIOPHARMA INC. 

PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT 

In consideration of my employment by Principia Biopharma Inc. (the “Company”) (the definition of “Company”
for the purposes of this Agreement shall include the Company, its affiliates, and subsidiaries) and access to Proprietary Information (defined below) being given to me by the Company, I hereby agree to this Proprietary Information and Inventions
Agreement (“Agreement”) as follows: 
 1.    Proprietary Information. The term
“Proprietary Information” shall mean trade secrets, research, inventions, confidential knowledge, data or any other information or materials that the Company treats or considers as proprietary, whether or not such Proprietary
Information is patentable or copyrightable, however it is embodied and irrespective of whether it is labeled as “proprietary” or “confidential”. By way of illustration but not limitation, “Proprietary
Information” includes (a) inventions, trade secrets, know-how, ideas, confidential knowledge, chemical structures, compositions, pharmaceutical formulations, methods of administration and
synthesis, improvements, discoveries, developments, processes, designs, techniques, formulas, formulations, source and object codes, data, programs, other works of authorship; organisms, plasmids, cosmids, bacteriophages, expression vectors, cells,
cell lines, tissues, materials, substrates, media, delivery methods or transfection methods, assays, compounds, peptides, proteins, DNA, RNA, and their constructs, and sequence, genomic, and structural information relating thereto; crystals,
optically active materials, ceramics, metals, metal oxides, and organic and inorganic chemical, biological and other material and their progeny, clones and derivatives and salt forms (hereinafter the Proprietary Information found at paragraph 1(a)
shall collectively be referred to as “Inventions”); and (b) information regarding the Company’s plans for research, development, manufacturing, engineering, new products, marketing and selling, the Company’s business
plans, budgets and unpublished financial statements, licenses, prices and costs, suppliers and customers; and information regarding the skills and compensation of other employees of the Company. 

2.    Recognition of Company’s Rights; Nondisclosure. I acknowledge that as a result of my
responsibilities at the Company, I am likely to be exposed and given access to the Proprietary Information of the Company. I understand and agree that my access to the Proprietary Information is for the sole and exclusive purpose of producing
technology and performing other work for the benefit of the Company and that the Company has a substantial ongoing investment in the development of such Proprietary Information which would be injured irreparably if this Agreement were breached. At
all times during the term of my employment and thereafter, I will hold the Company’s Proprietary Information in the strictest confidence and will not, except with the written permission of the Chief Executive Officer of the Company, disclose
(which term throughout this Agreement includes, but is not limited to, lecturing upon or publishing) any such Proprietary Information to anyone other than Company personnel who need to know such information in connection with their work for the
Company or use such Proprietary Information except in connection with any work for the Company. 
 I further acknowledge that Proprietary
Information is solely the property of the Company and I agree that at no time either during the period of my employment nor thereafter will I challenge or engage in any other acts which question or impugn the validity or ownership of the
Company’s 

 
rights in any Proprietary Information. I further acknowledge that any and all improvements or modifications to Proprietary Information that I make, conceive, develop or reduce to practice or to
specific form, whether alone or in conjunction with others, either during or after the period of my employment with the Company shall constitute Proprietary Information. 

3.    Third Party Information. I understand, in addition, that the Company has received and in the future
will receive from third parties confidential or proprietary information (“Third Party Information”) subject to a duty on the Company’s part to maintain the confidentiality of such information and to use it only for certain
limited purposes. During the term of my employment and thereafter, I will hold all Third Party Information in the strictest confidence and will not disclose (to anyone other than Company personnel who need to know such information in connection with
their work for the Company) or use, except in connection with my work for the Company, any Third Party Information unless expressly authorized by an officer of the Company in writing. 

4.    Assignment of Inventions. 

(a)    Except as provided below in paragraph 4(b) of this Agreement, I hereby assign to the Company all my right, title and
interest in and to any and all Inventions whether or not patentable or registrable under copyright or similar statutes, that I make or conceive or reduce to practice or reduce to specific form or learn, either alone or jointly with others, in the
course of my employment by the Company, whether developed in whole or in part using the company’s equipment, supplies, facilities, trade secret information or Proprietary Information; or relating at the time of conception or reduction to
practice to the Company’s business, or actual or demonstrably anticipated research or development of the Company; or resulting from any work performed by me for the Company (collectively, the “Employment Inventions”). I
recognize that this Agreement does not require assignment of any invention which qualifies fully for protection under Section2870 of the California Labor Code (hereinafter “Section 2870”), which provides as
follows: 
 (i)    Any provision in an employment agreement which provides that an employee shall assign, or offer to
assign, any of his or her rights in an invention to his or her employer shall not apply to an invention that the employee developed entirely on his or her own time without using the employer’s equipment, supplies, facilities, or trade secret
information except for those inventions that either: 
 (1)    relate at the time of conception or reduction to
practice of the invention to the employer’s business, or actual or demonstrably anticipated research or development of the employer; or 

(2)    result from any work performed by the employee for the employer. 

(ii)    To the extent a provision in an employment agreement purports to require an employee to assign an invention
otherwise excluded from being required to be assigned under subdivision (a), the provision is against the public policy of this state and is unenforceable. 

(b)    I have set forth on Exhibit A attached hereto, a complete list of all restrictions, express or implied,
which would prevent me from complying with all of the requirements of paragraph 4(a) of this Agreement in whole or in part. If full disclosure of such restrictions, express or implied, in Exhibit A would cause me to violate any prior
confidentiality 

  
 2 

 
agreement, I understand that I am to describe such restrictions in Exhibit A at the most specific level possible without violating any such restrictions. Exhibit A is incorporated
into this Agreement by reference as if fully set forth herein. I will promptly inform the Company in writing of any such restrictions that arise between the time I sign this Agreement and the time my employment with the Company commences. 

(c)    I also assign to or assign as directed by the Company all my right, title and interest in and to all Employment
Inventions, full title to which is required to be in the United States by a contract between the Company and the United States or any of its agencies. 

(d)    I acknowledge that all original works of authorship which are made by me (solely or jointly with others) within the
scope of my employment and which are protectable by copyright are “works made for hire,” as that term is defined in the United States Copyright Act (17 U.S.C., Section 101). 

5.    Enforcement of Proprietary Rights. To assist the Company in exercising its ownership rights to all
Proprietary Information or Employment Inventions that I make, conceive, reduce to practice or to specific form, alter or modify, I will, if requested by the Company, execute, verify and deliver assignments of all rights in the United States and
elsewhere, including but not limited to patent and copyright rights, in such Proprietary Information or Employment Inventions to the Company or its designees. I will also assist the Company in every proper way to obtain and from time to time enforce
its United States and foreign rights relating to Proprietary Information or Employment Inventions in any and all countries, irrespective of whether I had any role in the development or modification of such Proprietary Information or Employment
Inventions. To that end, I will execute, verify and deliver such documents and perform such other acts (including appearances as a witness) as the Company may reasonably request for use in applying for, obtaining, perfecting, evidencing, sustaining
and enforcing such proprietary rights and the assignment thereof to the Company. My obligation to assist the Company with respect to all its rights in Proprietary Information or Employment Inventions in any and all countries shall continue beyond
the termination of my employment, but the Company shall compensate me at a reasonable rate after my termination for the time actually spent by me at the Company’s request on such assistance. 

In the event the Company is unable for any reason, after good faith and all reasonable effort, to secure my signature on any document needed
in connection with the actions specified in this Section 5, I hereby irrevocably designate and appoint the Company and its duly authorized officers and agents as my agent and attorney in fact, to act for and in my behalf to execute, verify and
file any such documents and to do all other lawfully permitted acts to further the purposes of the preceding paragraph thereon with the same legal force and effect as if executed by me. I hereby waive and quitclaim to the Company any and all claims,
of any nature whatsoever, which I now or may hereafter have for infringement of any proprietary rights assigned hereunder to the Company. 

6.    Obligation to Keep Company Informed. I will promptly disclose to the Company fully and in writing and
will hold in trust for the sole right and benefit of the Company any and all Employment Inventions that I make, conceive, develop or reduce to practice or to specific form, whether alone or in conjunction with others, during or after the period of
my employment with the Company. In addition, after any termination of my employment, I will promptly disclose to the Company fully and in writing, the full particulars of all patent applications filed by me which disclose or claim Proprietary
Information or Employment Inventions. 

  
 3 

 I will also promptly disclose to the Company fully and in writing any inventions containing
or disclosing Proprietary Information that I believe fully qualify for protection under Section 2870; and I will at that time provide to the Company in writing all evidence necessary to substantiate that belief. I understand that the Company
will keep in confidence and will not disclose to third parties without my consent any proprietary information disclosed in writing to the Company pursuant to this Agreement relating to Inventions that qualify fully for protection under the
provisions of Section 2870. I will preserve the confidentiality of any Employment Invention that does not fully qualify for protection under Section 2870. 

7.    Prior Inventions. The term “Prior Inventions” shall mean any and all trade secrets, know-how, ideas, confidential knowledge, chemical structures, compositions, pharmaceutical formulations, methods of administration and synthesis, improvements, discoveries, developments, processes, designs,
techniques, formulas, formulations, source and object codes, data, programs, other works of authorship; organisms, plasmids, cosmids, bacteriophages, expression vectors, cells, cell lines, tissues, materials, substrates, media, delivery methods or
transfection methods, assays, compounds, peptides, proteins, DNA, RNA, and their constructs, and sequence, genomic, and structural information relating thereto; crystals, optically active materials, ceramics, metals, metal oxides, and organic and
inorganic chemical, biological and other material and their progeny, clones and derivatives and salt forms, which I have, alone or jointly with others, conceived, developed or reduced to practice or caused to be conceived, developed or reduced to
practice prior to the commencement of my employment with the Company. To preclude any possible uncertainty over what is a Prior Invention, I have set forth on Exhibit B attached hereto a complete list of all Prior Inventions that I consider
to be in whole or part my property or the property of third parties, and that I wish to have excluded from the scope of this Agreement. If full disclosure of any such Prior Invention on Exhibit B would cause me to violate any prior
confidentiality agreement, I understand that I am to describe such Prior Inventions in Exhibit B at the most specific level possible without violating any such prior confidentiality agreements. Exhibit B is incorporated into this
Agreement as if fully set forth herein. I will promptly inform the Company in writing of any Prior Inventions that occur between the time I sign this Agreement and the time my employment with the Company commences. 

8.    Unauthorized Use or Disclosure. I shall immediately notify my supervisor or any officer of the Company
if I learn of any possible unauthorized use or disclosure of Proprietary Information and shall cooperate fully with the Company to enforce the provisions of this Agreement. 

9.    Authorized Disclosure. Should I be subject to any governmental, administrative or court order or
action purporting to require or authorize the disclosure of any Proprietary Information, in whole or in part, I will immediately notify the Company’s legal department and will immediately provide the Company with all documents and other
pertinent information in my possession or control to permit the Company to take such steps as it deems necessary in its sole discretion to block or pursue the confidentiality of such disclosure. 

  
 4 

 10.    Additional Activities. I agree that during the
period of my employment by the Company I will not, without the Company’s express written consent, engage in any employment or business activity other than for the Company, except as may be provided in any written agreement between me and an
authorized officer of the Company with the Company executed as of the same date, and for the period of my employment by the Company and for one (1) year after the date of termination of my employment by the Company I will not use any
Proprietary Information in order to (i) induce any employee of the Company to leave the employ of the Company or (ii) solicit the business of any client or customer of the Company (other than on behalf of the Company) with whom I had
contact during the course of my employment with the Company. 
 11.    No Improper Use of Materials. I
acknowledge that the Company forbids me to use or disclose any information that is proprietary to any competitor of the Company or to any other third party. Therefore, during my employment by the Company, I will not use or disclose any confidential
information or trade secrets, if any, of any former employer or any other person to whom I have an obligation of confidentiality and I will not bring onto the premises of the Company any unpublished documents or any property belonging to any former
employer or any other person to whom I have an obligation of confidentiality unless consented to in writing by that former employer or person. To preclude any possible uncertainty, I have set forth on Exhibit C attached hereto, a complete
list of all devices, materials, and documents of a former employer or other person or institution to whom I have an obligation of confidentiality that may be used in providing services to the Company pursuant to the express written authorization of
my former employer or such other person. I will promptly notify the Company in writing of any devices, materials, and documents that are called for in Exhibit C that arise between the time I sign this Agreement and the time my employment with
the Company commences. Exhibit C is incorporated into this Agreement by reference as if fully set forth herein. In addition, I will not seek nor knowingly use any information from job applicants, Company employees or other third parties,
including but not limited to vendors, that is confidential to the present or former employers of such applicants or former employers of the employees or to such third parties. 

12.    No Conflicting Obligation. I represent that my performance of all the terms of this Agreement and as
an employee of the Company does not and will not breach any agreement to keep in confidence information acquired by me in confidence or in trust prior to my employment by the Company. I have not entered into, and I agree I will not enter into, any
agreement either written or oral in conflict herewith. 
 13.    Return of Company Materials. When I leave
the employ of the Company, I will deliver to the Company any and all copies and originals of drawings, notes, memoranda, lab notebooks, specifications, correspondence (including email and quickmail messages), devices, equipment, formulas, documents,
molecules, cells, organisms, plasmids, cosmids, bacteriophages, expression vectors, cell lines, peptides, proteins, DNA, RNA, and their constructs, and sequence, genomic, and structural information relating thereto; crystals, optically active
materials, ceramics, metals, metal oxides, and organic and inorganic chemical, biological and other material and their progeny, clones and derivatives and salt forms and any other material containing or disclosing any Inventions, Employment
Inventions, Proprietary Information or Third Party Information. I further agree that any property situated on the Company’s premises and owned by the Company, including disks and other storage media, quickmail, email, voicemail, filing cabinets
or other work areas, is subject to inspection by Company personnel at any time with or without notice. Prior to leaving, I will reasonably cooperate with the Company in completing and signing the Company’s documentation for separating staff
members. 

  
 5 

 14.    Name and License. I hereby grant to the Company a non-exclusive worldwide license to use my name and likeness on or in connection with any advertising and promotional materials distributed by or on behalf of the Company in any medium while serving as an employee or
director of the Company or thereafter, if such materials describe my prior role as employee or director of the Company or thereafter, if such material describes my prior role as an employee or director of the Company. 

15.    Potential Liability. I have been informed and acknowledge that the unauthorized taking of the
Company’s trade secrets (a) could result in civil liability under California Civil Code Section 3426, and that, if willful, could result in an award for triple the amount of the Company’s damages and attorneys’ fees; and
(b) is a crime under California Penal Code Section 499c(c), punishable by imprisonment for a time not exceeding one year, or by a fine not exceeding five thousand dollars ($5,000), or by both. 

16.    Legal and Equitable Remedies. Because my services are personal and unique and because I may have
access to and become acquainted with the Proprietary Information of the Company, and due to the irreparable injury which would be suffered by the Company as a result of a breach of this Agreement, the Company shall have the right to enforce this
Agreement and any of its provisions by injunction, specific performance or other equitable relief, without bond and without prejudice to any other rights and remedies that the Company may have for a breach of this Agreement. 

17.    Notices. Any notices required or permitted hereunder shall be given to the appropriate party at the
address specified below or at such other address as the party shall specify in writing. Such notice shall be deemed given upon personal delivery to the appropriate address or if sent by certified or registered mail, three days after the date of
mailing. 
 18.    Employment at Will. I understand and agree that my employment with the Company is at-will. Therefore, my employment can terminate, with or without cause, and with or without notice, at any time, at my option or the Company’s option, and that the Company can terminate or change all other
terms and conditions of my employment, with or without cause, and with or without notice, at any time. I understand that the nature of my employment relationship with the Company will be governed by this paragraph and that this paragraph constitutes
the entire agreement, arrangement, and understanding between me and the Company on this subject matter and supersedes any prior or contemporaneous agreement, arrangement, and understanding on this subject matter. This
at-will relationship will remain in effect throughout my employment with the Company or any of its subsidiaries or affiliates, unless it is modified by a written agreement signed by both the Company’s
President and me which expressly alters it. This at-will relationship may not be modified by any oral or implied agreement, or by any Company policies, practices or patterns or conduct. 

19.    General Provisions. 

(a)    Governing Law and Forum. This Agreement will be governed by and construed according to the substantive laws of the
State of California without resort to conflict of law principles and I hereby consent to the jurisdiction of the courts of California, both state and federal, for any claim sounding in tort or contract or created by state or federal law related in
any way to my or the Company’s rights and obligations under the Agreement. 

  
 6 

 (b)    Entire Agreement. This Agreement, including all
exhibits hereto, is the final, complete and exclusive agreement of the parties with respect to the subject matter hereof and supersedes and merges all prior discussions between us. No modification of or amendment to this Agreement, nor any waiver of
any rights under this Agreement, will be effective unless in writing signed by the party to be charged. Any subsequent change or changes in my duties, salary or compensation will not affect the validity or scope of this Agreement. As used in this
Agreement, the period of my employment includes any time during which I may be retained by the Company as a consultant. 

(c)    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 prohibited by or invalid under applicable law, such provision will be ineffective only to the extent of such prohibition or invalidity, without
invalidating the remainder of this Agreement. 
 (d)    Assignment. This Agreement may not be assigned by
me but is fully assignable by the Company. 
 (e)    Successors and Assigns. This Agreement will be
binding upon my heirs, executors, administrators and other legal representatives and will be for the benefit of the Company, its successors, and its assigns. 

(f)    Survival. The provisions of this Agreement shall survive the termination of my employment and the
assignment of this Agreement by the Company to any successor in interest or other assignee. 

(g)    Waiver. No waiver by the Company of any breach of this Agreement shall be a waiver of any preceding
or succeeding breach. No waiver by the Company of any right under this Agreement shall be construed as a waiver of any other right. The Company shall not be required to give notice to enforce strict adherence to all terms of this Agreement. 

(h)    Effective Date. Agreement shall be effective as of the earliest of (1) the first day of my
employment by the Company; or (2) the first day of my use of, the facilities, technology, expertise, data, or Proprietary Information of the Company; or (3) the day I sign this Agreement. 

  
 7 

 (i)    Descriptive Headings. The descriptive headings of
this Agreement are for convenience only, and shall be of no force or effect in construing or interpreting any of the provisions of this Agreement. 

I UNDERSTAND THAT THIS AGREEMENT AFFECTS MY RIGHTS TO INVENTIONS I MIGHT HAVE MADE DURING MY PAST EMPLOYMENT. AND MAKE DURING MY EMPLOYMENT,
AND RESTRICTS MY RIGHT TO DISCLOSE OR USE THE COMPANY’S PROPRIETARY INFORMATION DURING OR SUBSEQUENT TO MY EMPLOYMENT. 
 I HAVE READ
THIS AGREEMENT CAREFULLY AND UNDERSTAND ITS TERMS. I HAVE COMPLETELY FILLED OUT EXHIBITS A, B. AND C AND SIGNED AND DATED ALL EXHIBITS TO THIS AGREEMENT. 

IN WITNESS WHEREOF, the parties have duly executed this Agreement as of the day and year first set forth above. 

 

							
	COMPANY:	  		  		  	EMPLOYEE:
	 PRINCIPIA BIOPHARMA INC.

a Delaware corporation
	  		  	
				
	By:	  	 /s/ Martin Babler
	  		  	 /s/ Christopher Y. Chai

	Name:	  	Martin Babler	  		  	Name: Christopher Y. Chai
	Title:	  	CEO	  		  	
	Address:	  	400 East Jamie Court. Ste 302	  		  	Address:
	 	  	South San Francisco CA 94080	  	 	  	 

 EXHIBIT A 

Principia Biopharma Inc.. 
 400 East Jamie Court Suite 302 

South San Francisco, CA 94080 
 Attention: Board of Directors

 Directors: 
 The following is a complete list of all
restrictions which would prevent me. in whole or in part. from assigning- to or as directed by the Company (as defined in the attached Agreement) all my right, title and interest in and to any and all Employment Inventions (as required by
paragraph 4 of the Agreement): 
  

					
		 	☒	  	No restrictions.
			
		 	☐	  	Restrictions:
			
		 		  	  

			
		 		  	  

			
		 	☐	  	Number of additional sheets attached.

 Date: November 26, 2013 
  

	
	Very truly yours,
	
	 Christopher Y. Chai

	Print Name
	
	 /s/ Christopher Y. Chai

	Signature

 EXHIBIT B 

Principia Biopharma Inc.. 
 400 East Jamie Court Suite 302 

South San Francisco, CA 94080 
 Attention: Board of Directors

 Directors: 
 The following is a complete list of all Prior
Inventions (as defined in the attached Agreement): 
  

					
		 	☒	  	No Prior Inventions
			
		 	☐	  	Prior Inventions:
			
		 		  	  

			
		 		  	  

			
		 	☐	  	Number of additional sheets attached.

 Date: November 26, 2013 
  

	
	Very truly yours,
	
	 Christopher Y. Chai

	Print Name
	
	 /s/ Christopher Y. Chai

	Signature

 EXHIBIT C 

Principia Biopharma Inc.. 
 250 Golden Hills Drive 

Portola Valley, CA 94028 
 Attention: Board of Directors 

Directors: 
 I propose to bring or have already brought to my
employment with the Company (as defined in the attached Agreement) the following devices. materials and documents of my former employer(s) or other person(s) or institution(s) to whom I have an obligation of confidentiality that are not generally
available to the public, which materials and documents may be used in providing services to the Company pursuant to the express written authorization of my former employer(s) or such other person(s) or institution(s) (copies of all such
authorizations are attached hereto): 
  

					
		 	☒	  	No materials.
			
		 	☐	  	Materials:
			
		 		  	  

			
		 		  	  

			
		 	☐	  	Number of additional sheets attached.
			
		 	☐	  	Number of pages of authorizations attached.

 Date: November 26, 2013 
  

	
	Very truly yours,
	
	 Christopher Y. Chai

	Print Name
	
	 /s/ Christopher Y. Chai

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