Forms of grant notice, stock option agreement and notice of exercise under the Principia Biopharma Inc. 2008 Equity Incentive Plan

Exhibit 10.3

PRINCIPIA BIOPHARMA INC.

AMENDED AND RESTATED

2008 EQUITY INCENTIVE PLAN

STOCK OPTION AGREEMENT

Pursuant to its Amended and Restated 2008 Equity Incentive Plan, as amended from time to time (the “Plan”), Principia Biopharma Inc., a Delaware corporation (the “Company”), hereby grants to the Optionee listed below (“Optionee”), an option to purchase the number of shares of the Company’s Common Stock set forth below, subject to the terms and conditions of the Plan and this Stock Option Agreement (this “Option Agreement”). Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Option Agreement.

I. NOTICE OF STOCK OPTION GRANT

1.

* Options shall be considered incentive stock options to the extent permissible under law, with the remaining portion to be nonqualified stock options.

II. AGREEMENT

1. Grant of Option. The Company hereby grants to the Optionee an Option to purchase the number of shares of Common Stock (the “Shares”) set forth in the Notice of Grant, at the exercise price per share set forth in the Notice of Grant (the “Exercise Price”). Notwithstanding anything to the contrary anywhere else in this Option Agreement, this grant of an Option is subject to the terms, definitions and provisions of the Plan, which is incorporated herein by reference.

If designated in the Notice of Grant as an Incentive Stock Option, this Option is intended to qualify as an Incentive Stock Option as defined in Section 422 of the Code; provided, however, that to the extent that the aggregate Fair Market Value of the Common Stock with respect to which Incentive Stock Options (within the meaning of Code Section 422, but without regard to Code Section 422(d)), including the Option, are exercisable for the first time by Optionee during any calendar year (under the Plan and all other incentive stock option plans of the Company (or any “parent corporation” or “subsidiary corporation” thereof within the meaning of Code Sections 424(e) or 424(f), respectively)) exceeds $100,000, such options shall be treated as not qualifying under Code Section 422, but rather shall be treated as Non-Qualified Stock Options to the extent required by Code Section 422. The rule set forth in the preceding sentence shall be applied by taking options into account in the order in which they were granted. For purposes of these rules, the Fair Market Value of the Common Stock shall be determined as of the time the option with respect to such stock is granted.

2. Exercise of Option. This Option is exercisable as follows:

(a) Right to Exercise.

2.

(i) This Option shall be exercisable cumulatively according to the vesting schedule set out in the Notice of Grant. For purposes of this Option Agreement, Shares subject to this Option shall vest based on Optionee’s continued status as a Service Provider, unless otherwise determined by the Administrator.

(ii) This Option may not be exercised for a fraction of a Share.

(iii) In the event of Optionee’s death, Disability or other termination of the Optionee’s status as a Service Provider, the exercisability of the Option shall be governed by Sections 7, 8 and 9 hereof.

(iv) In the event the exercise of the Option following the termination of the Optionee’s status as a Service Provider would be prohibited at any time solely because the issuance of shares would violate the registration requirements under the Securities Act of 1933, as amended (the “Securities Act”), then the Option shall terminate on the earlier of (i) the Term/Expiration Date of the Option as set forth in the Notice of Grant or (ii) the expiration of a period of three (3) months after the termination of the Optionee’s status as a Service Provider during which the exercise of the Option would not be in violation of such registration requirements.

(v) In no event may this Option be exercised after the Term/Expiration Date of this Option as set forth in the Notice of Grant.

(b) Method of Exercise.

(i) This Option shall be exercisable by written notice to the Company (in the form attached as Exhibit A) (the “Exercise Notice”), or, if early exercise is permitted in the Notice of Grant, pursuant to an Early Exercise Stock Purchase Agreement (in the form attached as Exhibit C) (the “Early Exercise Agreement”). The Exercise Notice shall state the number of Shares for which the Option is being exercised, and such other representations and agreements with respect to such Shares of Common Stock as may be required by the Company pursuant to the provisions of the Plan. The Exercise Notice shall be signed by Optionee and shall be delivered in person or by certified mail to the Secretary of the Company or such other authorized representative of the Company.

(ii) The Exercise Notice (or Early Exercise Agreement, if applicable) shall be accompanied by payment of the Exercise Price, including payment of any applicable withholding tax.

(iii) Any Shares issuable upon exercise of this Option shall be subject to the Company’s standard Voting Agreement, as may be amended from time to time (the “Voting Agreement”). As a condition to exercise, Optionee shall have executed, as a Common Holder, a copy of the Voting Agreement, and such Voting Agreement shall remain in effect for so long as any Shares issued hereunder remain outstanding. The terms of the Voting Agreement are incorporated herein by this reference.

(iv) No Shares shall be issued pursuant to the exercise of an Option unless such issuance and such exercise comply with all relevant provisions of law and the requirements of any stock exchange upon which the Shares may then be listed. Assuming such compliance, for income tax purposes the Shares shall be considered transferred to Optionee on the date on which the Option is exercised with respect to such Shares.

3.

3. Optionee’s Representations. If the Shares purchasable pursuant to the exercise of this Option have not been registered under the Securities Act, at the time this Option is exercised, Optionee shall, if required by the Company, concurrently with the exercise of all or any portion of this Option, deliver to the Company his or her Investment Representation Statement in the form attached hereto as Exhibit B.

4. Lock-Up Period. Optionee hereby agrees that if so requested by the Company or any representative of the underwriters (the “Managing Underwriter”) in connection with any registration of the offering of any securities of the Company under the Securities Act, Optionee shall not sell or otherwise transfer any Shares or other securities of the Company during the 180-day period (or such longer period as may be requested in writing by the Managing Underwriter and agreed to in writing by the Company) (the “Market Standoff Period”) following the effective date of a registration statement of the Company filed under the Securities Act; provided, however, that such restriction shall apply only to the first registration statement of the Company to become effective under the Securities Act that includes securities to be sold on behalf of the Company to the public in an underwritten public offering under the Securities Act.    The Company may impose stop-transfer instructions with respect to securities subject to the foregoing restrictions until the end of such Market Standoff Period and these restrictions shall be binding on any transferee of such Shares. Notwithstanding the foregoing, the 180-day period may be extended for up to such number of additional days as is deemed necessary by the Company or the Managing Underwriter to continue coverage by research analysts in accordance with NASD Rule 2711 or any successor rule.

5. Method of Payment. Payment of the Exercise Price shall be by any of the following, or a combination thereof, at the election of the Optionee:

(a) cash;

(b) check;

(c) with the consent of the Administrator, a full recourse promissory note bearing interest (at no less than such rate as is a market rate of interest and which then precludes the imputation of interest under the Code), payable upon such terms as may be prescribed by the Administrator and structured to comply with Applicable Laws;

(d) with the consent of the Administrator, surrender of other Shares of Common Stock of the Company which have a Fair Market Value on the date of surrender equal to the Exercise Price of the Shares as to which the Option is being exercised;

(e) with the consent of the Administrator, surrendered Shares issuable upon the exercise of the Option having a Fair Market Value on the date of exercise equal to the aggregate Exercise Price of the Option or exercised portion thereof;

(f) with the consent of the Administrator, property of any kind which constitutes good and valuable consideration;

4.

(g) following the Public Trading Date, with the consent of the Administrator, delivery of a notice that the Optionee has placed a market sell order with a broker with respect to Shares then issuable upon exercise of the Option and that the broker has been directed to pay a sufficient portion of the net proceeds of the sale to the Company in satisfaction of the aggregate Exercise Price; provided, that payment of such proceeds is then made to the Company upon settlement of such sale; or

(h) with the consent of the Administrator, any combination of the foregoing methods of payment.

6. Restrictions on Exercise. This Option may not be exercised until the Plan has been approved by the stockholders of the Company. If the issuance of Shares upon such exercise or if the method of payment for such Shares would constitute a violation of any applicable federal or state securities or other law or regulation, then the Option may also not be exercised. The Company may require Optionee to make any representation and warranty to the Company as may be required by any applicable law or regulation before allowing the Option to be exercised.

7. Termination of Relationship. If Optionee ceases to be a Service Provider (other than by reason of Optionee’s death or Disability), Optionee may exercise this Option during the Termination Period set out in the Notice of Grant, to the extent the Option was vested on the date on which Optionee ceases to be a Service Provider. To the extent that the Option is not vested on the date on which Optionee ceases to be a Service Provider, or if Optionee does not exercise this Option within the time specified herein, the Option shall terminate.

8. Disability of Optionee. If Optionee ceases to be a Service Provider as a result of his or her Disability, Optionee may exercise the Option to the extent the Option was vested at the date on which Optionee ceases to be a Service Provider, but only within twelve (12) months from such date (and in no event later than the expiration date of the term of this Option as set forth in the Notice of Grant). To the extent that the Option is not vested at the date on which Optionee ceases to be a Service Provider, or if Optionee does not exercise such Option within the time specified herein, the Option shall terminate.

9. Death of Optionee. If Optionee ceases to be a Service Provider as a result of the death of Optionee, the vested portion of the Option may be exercised at any time within twelve (12) months following the date of death (and in no event later than the expiration date of the term of this Option as set forth in the Notice of Grant) by Optionee’s estate or by a person who acquires the right to exercise the Option by bequest or inheritance. To the extent that the Option is not vested on the date of death, or if the Option is not exercised within the time specified herein, the Option shall terminate.

10. Non-Transferability of Option. This Option may not be transferred in any manner except by will or by the laws of descent or distribution. It may be exercised during the lifetime of Optionee only by Optionee. The terms of this Option shall be binding upon the executors, administrators, heirs, successors and assigns of the Optionee.

11. Term of Option. This Option may be exercised only within the term set out in the Notice of Grant.

5.

12. Restrictions on Shares. Optionee hereby agrees that Shares purchased upon the exercise of the Option shall be subject to such terms and conditions as the Administrator shall determine in its sole discretion, including, without limitation, restrictions on the transferability of Shares, and a right of first refusal in favor of the Company with respect to permitted transfers of Shares. Such terms and conditions may, in the Administrator’s sole discretion, be contained in the Exercise Notice (or Early Exercise Agreement, if applicable) with respect to the Option or in such other agreement as the Administrator shall determine and which the Optionee hereby agrees to enter into at the request of the Company. For the avoidance of doubt, as a condition to exercise, the Administrator may require, in its sole discretion, that Optionee execute as a Common Holder or otherwise agree to be bound as a Common Holder by the Company’s standard First Refusal and Co-Sale Agreement, as such agreement may be amended from time to time.

13. Rules Particular To Specific Countries.

(a) Generally. Optionee shall, if required by the Administrator, enter into an election with the Company or a Subsidiary (in a form approved by the Company) under which any liability to the Company’s (or a Subsidiary’s) Tax Liability, including, but not limited to, National Insurance Contributions (“NICs”) and the Fringe Benefit Tax (“FBT”), is transferred to and met by Optionee. For purposes of this Section 13, Tax Liability shall mean any and all liability under non-U.S. applicable laws, rules or regulations from any income tax, the Company’s (or a Subsidiary’s) NICs, FBT or similar liability and the Optionee’s NICs, FBT or similar liability that are attributable to: (A) the grant or exercise of, or any other benefit derived by the Optionee from the Option; (B) the acquisition by Optionee of the Shares on exercise of the Option; or (C) the disposal of any Shares acquired upon exercise of the Option.

(b) Tax Indemnity. Optionee shall indemnify and keep indemnified the Company and any of its Subsidiaries from and against any Tax Liability.

[Signature Page Follows]

6.

This Agreement may be executed in two or more counterparts, each of which shall be deemed an original and all of which shall constitute one document.

OPTIONEE ACKNOWLEDGES AND AGREES THAT THE VESTING OF SHARES PURSUANT TO THE OPTION HEREOF IS EARNED ONLY BY CONTINUING CONSULTANCY OR EMPLOYMENT AT THE WILL OF THE COMPANY (NOT THROUGH THE ACT OF BEING HIRED, BEING GRANTED THIS OPTION OR ACQUIRING SHARES HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT NOTHING IN THIS AGREEMENT, NOR IN THE COMPANY’S AMENDED AND RESTATED 2008 EQUITY INCENTIVE PLAN, AS AMENDED FROM TIME TO TIME, WHICH IS INCORPORATED HEREIN BY REFERENCE, SHALL CONFER UPON OPTIONEE ANY RIGHT WITH RESPECT TO CONTINUATION OF EMPLOYMENT OR CONSULTANCY BY THE COMPANY, NOR SHALL IT INTERFERE IN ANY WAY WITH OPTIONEE’S RIGHT OR THE COMPANY’S RIGHT TO TERMINATE OPTIONEE’S EMPLOYMENT OR CONSULTANCY AT ANY TIME, WITH OR WITHOUT CAUSE AND WITH OR WITHOUT PRIOR NOTICE.

Optionee acknowledges receipt of a copy of the Plan and represents that he or she is familiar with the terms and provisions thereof. Optionee hereby accepts this Option subject to all of the terms and provisions hereof. Optionee has reviewed the Plan and this Option in their entirety, has had an opportunity to obtain the advice of counsel prior to executing this Option and fully understands all provisions of the Option. Optionee hereby agrees to accept as binding, conclusive and final all decisions or interpretations of the Administrator upon any questions arising under the Plan or this Option. Optionee further agrees to notify the Company upon any change in the residence address indicated below.

SIGNATURE PAGE TO PRINCIPIA BIOPHARMA INC. STOCK OPTION AGREEMENT

EXHIBIT A

PRINCIPIA BIOPHARMA INC.

AMENDED AND RESTATED

2008 EQUITY INCENTIVE PLAN

EXERCISE NOTICE

Principia Biopharma Inc.

Attention: Stock Administration

1. Exercise of Option. Effective as of today,                     ,                     , the undersigned (“Optionee”) hereby elects to exercise Optionee’s option to purchase                     shares of the Common Stock (the “Shares”) of Principia Biopharma Inc., a Delaware corporation (the “Company”), under and pursuant to the Principia Biopharma Inc. Amended and Restated 2008 Equity Incentive Plan, as amended from time to time (the “Plan”) and the Stock Option Agreement dated                     (the “Option Agreement”). Capitalized terms used herein without definition shall have the meanings given in the Option Agreement.

2. Representations of Optionee. Optionee acknowledges that Optionee has received, read and understood the Plan and the Option Agreement. Optionee agrees to abide by and be bound by their terms and conditions.

3. Rights as Stockholder. Until the stock certificate evidencing Shares purchased pursuant to the exercise of the Option is issued (as evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a stockholder shall exist with respect to Shares subject to the Option, notwithstanding the exercise of the Option. The Company shall issue (or cause to be issued) such stock certificate promptly after the Option is exercised. No adjustment will be made for a dividend or other right for which the record date is prior to the date the stock certificate is issued, except as provided in Section 13 of the Plan.

Optionee shall enjoy rights as a stockholder until such time as Optionee disposes of the Shares or the Company and/or its assignee(s) exercises the Right of First Refusal (as defined below) hereunder. Upon such exercise, Optionee shall have no further rights as a holder of the Shares so purchased except the right to receive payment for the Shares so purchased in accordance with the provisions of this Agreement, and Optionee shall forthwith cause the certificate(s) evidencing the Shares so purchased to be surrendered to the Company for transfer or cancellation.

4. Optionee’s Rights to Transfer Shares.

(a) Company’s Right of First Refusal. Before any Shares held by Optionee or any permitted transferee (each, a “Holder”) may be sold, pledged, assigned, hypothecated, transferred, or otherwise disposed of (each, a “Transfer”), the Company or its assignee(s) shall have a right of first refusal to purchase the Shares proposed to be Transferred on the terms and conditions set forth in this Section 4 (the “Right of First Refusal”).

(i) Notice of Proposed Transfer. In the event any Holder desires to Transfer any Shares, the Holder shall deliver to the Company a written notice (the “Notice”) stating: (w) the Holder’s bona fide intention to sell or otherwise Transfer such Shares; (x) the name of each proposed purchaser or other transferee (“Proposed Transferee”); (y) the number of Shares to be Transferred to each Proposed Transferee; and (z) the bona fide cash price or other consideration for which the Holder proposes to Transfer the Shares (the “Offered Price”), and the Holder shall offer such Shares at the Offered Price to the Company or its assignee(s).

(ii) Exercise of Right of First Refusal. Within thirty (30) days after receipt of the Notice, the Company and/or its assignee(s) may elect in writing to purchase all, but not less than all, of the Shares proposed to be Transferred to any one or more of the Proposed Transferees. The purchase price shall be determined in accordance with Section 4(a)(iii) hereof.

(iii) Purchase Price. The purchase price (“Purchase Price”) for the Shares repurchased under this Section 4 shall be the Offered Price. If the Offered Price includes consideration other than cash, the cash equivalent value of the non-cash consideration shall be determined by the Board in good faith.

(iv) Payment. Payment of the Purchase Price shall be made, at the option of the Company or its assignee(s), in cash (by check), by cancellation of all or a portion of any outstanding indebtedness of the Holder to the Company (or, in the case of repurchase by an assignee, to the assignee), or by any combination thereof within thirty (30) days after receipt of the Notice or in the manner and at the times mutually agreed to by the Company and the Holder.

2.

(v) Holder’s Right to Transfer. If all of the Shares proposed in the Notice to be Transferred are not purchased by the Company and/or its assignee(s) as provided in this Section 4, then the Holder may sell or otherwise Transfer such Shares to that Proposed Transferee at the Offered Price or at a higher price, provided that such sale or other Transfer is consummated within one hundred twenty (120) days after the date of the Notice and provided further that any such sale or other Transfer is effected in accordance with any applicable securities laws and the Proposed Transferee agrees in writing that the provisions of this Section 4 and the Restricted Stock Purchase Agreement, if applicable, shall continue to apply to the Shares in the hands of such Proposed Transferee. If the Shares described in the Notice are not Transferred to the Proposed Transferee within such 120-day period, a new Notice shall be given to the Company, and the Company and/or its assignees shall again be offered the Right of First Refusal as provided herein before any Shares held by the Holder may be sold or otherwise Transferred.

(b) Exception for Certain Family Transfers. Anything to the contrary contained in this Section 4 notwithstanding, the Transfer of any or all of the Shares during the Optionee’s lifetime or upon the Optionee’s death by will or intestacy to the Optionee’s Immediate Family or a trust for the benefit of the Optionee’s Immediate Family shall be exempt from the Right of First Refusal. As used herein, “Immediate Family” shall mean spouse, lineal descendant or antecedent, father, mother, brother or sister or stepchild (whether or not adopted). In such case, the transferee or other recipient shall receive and hold the Shares so Transferred subject to the provisions of this Section 4 (including the Right of First Refusal) and the Restricted Stock Purchase Agreement, if applicable, and there shall be no further Transfer of such Shares except in accordance with the terms of this Section 4.

(c) Termination of Right of First Refusal. The Right of First Refusal shall terminate as to all Shares upon a sale of Common Stock of the Company to the general public pursuant to a registration statement filed with and declared effective by the Securities and Exchange Commission under the Securities Act of 1933, as amended (a “Public Offering”).

5. Voting Agreement. As a condition to exercise, Optionee shall have executed, as a Common Holder, a copy of the Company’s standard Voting Agreement, as may be amended from time to time (the “Voting Agreement”), and such Voting Agreement shall remain in effect for so long as any Shares issued hereunder remain outstanding unless terminated earlier pursuant to its terms.

6. Transfer Restrictions. Any transfer or sale of the Shares is subject to restrictions on transfer imposed by any applicable state and federal securities laws. Any Transfer or attempted Transfer of any of the Shares not in accordance with the terms of this Agreement, including the Right of First Refusal provided in this Agreement, shall be void and the Company may enforce the terms of this Agreement by stop transfer instructions or similar actions by the Company and its agents or designees.

7. Tax Consultation. Optionee understands that Optionee may suffer adverse tax consequences as a result of Optionee’s purchase or disposition of the Shares. Optionee represents that Optionee has consulted with any tax consultants Optionee deems advisable in connection with the purchase or disposition of the Shares and that Optionee is not relying on the Company for any tax advice.

3.

8. Restrictive Legends and Stop-Transfer Orders.

(a) Legends. Optionee understands and agrees that the Company shall cause the legends set forth below or legends substantially equivalent thereto, to be placed upon any certificate(s) evidencing ownership of the Shares together with any other legends that may be required by state or federal securities laws:

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) AND MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A VOTING AGREEMENT AND CERTAIN RESTRICTIONS ON TRANSFER AND RIGHT OF FIRST REFUSAL OPTIONS HELD BY THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER. SUCH VOTING AGREEMENT AND THE TRANSFER RESTRICTIONS AND RIGHT OF FIRST REFUSAL ARE BINDING ON TRANSFEREES OF THESE SHARES.

(b) Stop-Transfer Notices. Optionee agrees that, in order to ensure compliance with the restrictions referred to herein, the Company may issue appropriate “stop transfer” instructions to its transfer agent, if any, and that, if the Company transfers its own securities, it may make appropriate notations to the same effect in its own records.

(c) Refusal to Transfer. The Company shall not be required (i) to transfer on its books any Shares that have been sold or otherwise transferred in violation of any of the provisions of this Agreement or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any purchaser or other transferee to whom such Shares shall have been so transferred.

9. Successors and Assigns. The Company may assign any of its rights under this Agreement to single or multiple assignees, and this Agreement shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Agreement shall be binding upon Optionee and his or her heirs, executors, administrators, successors and assigns.

10. Interpretation. Any dispute regarding the interpretation of this Agreement shall be submitted by Optionee or by the Company forthwith to the Company’s Board of Directors or committee thereof that is responsible for the administration of the Plan (the “Administrator”), which shall review such dispute at its next regular meeting. The resolution of such a dispute by the Administrator shall be final and binding on the Company and on Optionee.

4.

11. Governing Law; Severability. This Agreement shall be governed by and construed in accordance with the laws of the State of California excluding that body of law pertaining to conflicts of law. Should any provision of this Agreement be determined by a court of law to be illegal or unenforceable, the other provisions shall nevertheless remain effective and shall remain enforceable.

12. Notices. Any notice required or permitted hereunder shall be given in writing and shall be deemed effectively given upon personal delivery or upon deposit in the United States mail by certified mail, with postage and fees prepaid, addressed to the other party at its address as shown below beneath its signature, or to such other address as such party may designate in writing from time to time to the other party.

13. Further Instruments. The Optionee hereby agrees to execute such further instruments and to take such further action as may be reasonably necessary to carry out the purposes and intent of this Agreement including, without limitation, the Investment Representation Statement in the form attached to the Option Agreement as Exhibit B.

14. Delivery of Payment. The Optionee herewith delivers to the Company the full Exercise Price for the Shares, as well as any applicable withholding tax.

15. Entire Agreement. The Plan, the Voting Agreement and the Option Agreement are incorporated herein by reference. This Agreement, the Plan, the Voting Agreement, the Option Agreement and the Investment Representation Statement constitute the entire agreement of the parties and supersede in their entirety all prior undertakings and agreements of the Company and Optionee with respect to the subject matter hereof.

5.

EXHIBIT B

INVESTMENT REPRESENTATION STATEMENT

In connection with the purchase of the above-listed shares of Common Stock (the “Securities”) of Principia Biopharma Inc., a Delaware corporation (the “Company”), the undersigned (the “Optionee”) represents to the Company the following:

(a) Optionee is aware of the Company’s business affairs and financial condition and has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Securities. Optionee is acquiring these Securities for investment for Optionee’s own account only and not with a view to, or for resale in connection with, any “distribution” thereof within the meaning of the Securities Act of 1933, as amended (the “Securities Act”).

(b) Optionee acknowledges and understands that the Securities constitute “restricted securities” under the Securities Act and have not been registered under the Securities Act in reliance upon a specific exemption therefrom, which exemption depends upon, among other things, the bona fide nature of Optionee’s investment intent as expressed herein. Optionee understands that, in the view of the Securities and Exchange Commission, the statutory basis for such exemption may be unavailable if Optionee’s representation was predicated solely upon a present intention to hold these Securities for the minimum capital gains period specified under tax statutes, for a deferred sale, for or until an increase or decrease in the market price of the Securities, or for a period of one year or any other fixed period in the future. Optionee further understands that the Securities must be held indefinitely unless they are subsequently registered under the Securities Act or an exemption from such registration is available. Optionee further acknowledges and understands that the Company is under no obligation to register the Securities. Optionee understands that the certificate evidencing the Securities will be imprinted with a legend which prohibits the transfer of the Securities unless they are registered or such registration is not required in the opinion of counsel satisfactory to the Company and any other legend required under applicable securities laws or agreements.

(c) Optionee is familiar with the provisions of Rule 701 and Rule 144, each promulgated under the Securities Act, which, in substance, permit limited public resale of “restricted securities” acquired, directly or indirectly from the issuer thereof, in a non-public offering subject to the satisfaction of certain conditions. Rule 701 provides that if the issuer qualities under Rule 701 at the time of the grant of the Option to Optionee, the exercise will be

exempt from registration under the Securities Act. In the event the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), ninety (90) days thereafter (or such longer period as any market stand-off agreement may require) the Securities exempt under Rule 701 may under present law be resold, subject to the satisfaction of certain of the conditions specified by Rule 144, including: (1) the resale being made through a broker in an unsolicited “broker’s transaction” or in transactions directly with a market maker (as this term is defined under the Exchange Act); and, in the case of an affiliate, (2) the availability of certain public information about the Company, (3) the amount of Securities being sold during any three (3) month period not exceeding the limitations specified in Rule 144(e), and (4) the timely filing of a Form 144, if applicable.

In the event that the Company does not qualify under Rule 701 at the time of grant of the Option, then the Securities may be resold in certain limited circumstances subject to the provisions of Rule 144, which, effective as of February 15, 2008, requires the resale to occur not less than six months, or, in the event the Company is not subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, not less than one year, after the later of the date the Securities were sold by the Company or the date the Securities were sold by an affiliate of the Company, within the meaning of Rule 144; and, in the case of acquisition of the Securities by an affiliate, the satisfaction of the conditions set forth in sections (1), (2), (3) and (4) of the paragraph immediately above or, in the case of a non-affiliate who subsequently holds the Securities less than one year, the satisfaction of the conditions set forth in section (2) of the paragraph immediately above.

(d) Optionee further understands that in the event all of the applicable requirements of Rule 701 or 144 are not satisfied, registration under the Securities Act, compliance with Regulation A, or some other registration exemption will be required; and that, notwithstanding the fact that Rules 144 and 701 are not exclusive, the Staff of the Securities and Exchange Commission has expressed its opinion that persons proposing to sell private placement securities other than in a registered offering and otherwise than pursuant to Rules 144 or 701 will have a substantial burden of proof in establishing that an exemption from registration is available for such offers or sales, and that such persons and their respective brokers who participate in such transactions do so at their own risk. Optionee understands that no assurances can be given that any such other registration exemption will be available in such event.

Date: __________, ____

2.

EXHIBIT C

PRINCIPIA BIOPHARMA INC.

EARLY EXERCISE STOCK PURCHASE AGREEMENT

UNDER THE PRINCIPIA BIOPHARMA INC.

2008 AMENDED AND RESTATED EQUITY INCENTIVE PLAN

THIS AGREEMENT is made by and between PRINCIPIA BIOPHARMA INC., a Delaware corporation (the “Company”), and                      (“Purchaser”).

WITNESSETH:

WHEREAS, Purchaser holds a stock option dated                      to purchase shares of common stock (“Common Stock”) of the Company (the “Option”) pursuant to the Company’s 2008 Amended and Restated Equity Incentive Plan (the “Plan”); and

WHEREAS, the Option consists of a Stock Option Grant Notice and a Stock Option Agreement; and

WHEREAS, Purchaser desires to exercise the Option on the terms and conditions contained herein; and

WHEREAS, Purchaser wishes to take advantage of the early exercise provision of Purchaser’s Option and therefore to enter into this Agreement;

NOW, THEREFORE, IT IS AGREED between the parties as follows:

1. INCORPORATION OF PLAN AND OPTION BY REFERENCE. This Agreement is subject to all of the terms and conditions as set forth in the Plan and the Option. If there is a conflict between the terms of this Agreement and/or the Option and the terms of the Plan, the terms of the Plan shall control. If there is a conflict between the terms of this Agreement and the terms of the Option, the terms of the Option shall control. Defined terms not explicitly defined in this Agreement but defined in the Plan shall have the same definitions as in the Plan. Defined terms not explicitly defined in this Agreement or the Plan but defined in the Option shall have the same definitions as in the Option.

2. PURCHASE AND SALE OF COMMON STOCK.

(a) Agreement to purchase and sell Common Stock. Purchaser hereby agrees to purchase from the Company, and the Company hereby agrees to sell to Purchaser, shares of the Common Stock of the Company in accordance with the Notice of Exercise duly executed by Purchaser and attached hereto as Exhibit A.

1.

(b) Closing. The closing hereunder, including payment for and delivery of the Common Stock, shall occur at the offices of the Company immediately following the execution of this Agreement, or at such other time and place as the parties may mutually agree; provided, however, that if stockholder approval of the Plan is required before the Option may be exercised, then the Option may not be exercised, and the closing shall be delayed, until such stockholder approval is obtained. If such stockholder approval is not obtained within the time limit specified in the Plan, then this Agreement shall be null and void.

3. UNVESTED SHARE REPURCHASE OPTION.

(a) Repurchase Option. In the event Purchaser’s Continuous Service terminates, then the Company shall have an irrevocable option (the “Repurchase Option”) for a period of six (6) months after said termination (or in the case of shares issued upon exercise of the Option after such date of termination, within six (6) months after the date of the exercise), or such longer period as may be agreed to by the Company and Purchaser, to repurchase from Purchaser or Purchaser’s personal representative, as the case may be, those shares that Purchaser received pursuant to the exercise of the Option that have not as yet vested as of such termination date in accordance with the Vesting Schedule indicated on Purchaser’s Stock Option Grant Notice (the “Unvested Shares”).

(b) Share Repurchase Price.    The Company may repurchase all or any of the Unvested Shares at the lower of (i) the Fair Market Value of the such shares (as determined under the Plan) on the date of repurchase, or (ii) the price equal to Purchaser’s Exercise Price for such shares as indicated on Purchaser’s Stock Option Grant Notice.

4. EXERCISE OF REPURCHASE OPTION. The Repurchase Option shall be exercised by written notice signed by such person as designated by the Company, and delivered or mailed as provided herein. Such notice shall identify the number of shares of Common Stock to be purchased and shall notify Purchaser of the time, place and date for settlement of such purchase, which shall be scheduled by the Company within the term of the Repurchase Option set forth above. The Company shall be entitled to pay for any shares of Common Stock purchased pursuant to its Repurchase Option at the Company’s option in cash or by offset against any indebtedness owing to the Company by Purchaser (including without limitation any Promissory Note given in payment for the Common Stock), or by a combination of both. Upon delivery of such notice and payment of the purchase price in any of the ways described above, the Company shall become the legal and beneficial owner of the Common Stock being repurchased and all rights and interest therein or related thereto, and the Company shall have the right to transfer to its own name the Common Stock being repurchased by the Company, without further action by Purchaser.

5. CAPITALIZATION ADJUSTMENTS TO COMMON STOCK. In the event of a Capitalization Adjustment, then any and all new, substituted or additional securities or other property to which Purchaser is entitled by reason of Purchaser’s ownership of Common Stock shall be immediately subject to the Repurchase Option and be included in the word “Common Stock” for all purposes of the Repurchase Option with the same force and effect as the shares of the Common Stock presently subject to the Repurchase Option, but only to the extent the Common Stock is, at the time, covered by such Repurchase Option. While the total Option Price shall remain the same after each such event, the Option Price per share of Common Stock upon exercise of the Repurchase Option shall be appropriately adjusted.

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6. CORPORATE TRANSACTIONS. In the event of a Corporate Transaction, then the Repurchase Option may be assigned by the Company to the successor of the Company (or such successor’s parent company), if any, in connection with such Corporate Transaction. To the extent the Repurchase Option remains in effect following such Corporate Transaction, it shall apply to the new capital stock or other property received in exchange for the Common Stock in consummation of the Corporate Transaction, but only to the extent the Common Stock was at the time covered by such right. Appropriate adjustments shall be made to the price per share payable upon exercise of the Repurchase Option to reflect the Corporate Transaction upon the Company’s capital structure; provided, however, that the aggregate price payable upon exercise of the Repurchase Option shall remain the same.

7. ESCROW OF UNVESTED COMMON STOCK. As security for Purchaser’s faithful performance of the terms of this Agreement and to insure the availability for delivery of Purchaser’s Common Stock upon exercise of the Repurchase Option herein provided for, Purchaser agrees, at the closing hereunder, to deliver to and deposit with the Secretary of the Company or the Secretary’s designee (“Escrow Agent”), as Escrow Agent in this transaction, three (3) stock assignments duly endorsed (with date and number of shares blank) in the form attached hereto as Exhibit B, together with a certificate or certificates evidencing all of the Common Stock subject to the Repurchase Option; said documents are to be held by the Escrow Agent and delivered by said Escrow Agent pursuant to the Joint Escrow Instructions of the Company and Purchaser set forth in Exhibit C, attached hereto and incorporated by this reference, which instructions also shall be delivered to the Escrow Agent at the closing hereunder.

8. RIGHTS OF PURCHASER. Subject to the provisions of the Option, Purchaser shall exercise all rights and privileges of a stockholder of the Company with respect to the shares deposited in escrow. Purchaser shall be deemed to be the holder of the shares for purposes of receiving any dividends that may be paid with respect to such shares and for purposes of exercising any voting rights relating to such shares, even if some or all of such shares have not yet vested and been released from the Company’s Repurchase Option.

9. LIMITATIONS ON TRANSFER. In addition to any other limitation on transfer created by applicable securities laws, Purchaser shall not sell, assign, hypothecate, donate, encumber or otherwise dispose of any interest in the Common Stock while the Common Stock is subject to the Repurchase Option. After any Common Stock has been released from the Repurchase Option, Purchaser shall not sell, assign, hypothecate, donate, encumber or otherwise dispose of any interest in the Common Stock except in compliance with the provisions herein and applicable securities laws. Furthermore, the Common Stock shall be subject to any right of first refusal in favor of the Company or its assignees that may be contained in the Company’s Bylaws.

10. RESTRICTIVE LEGENDS. All certificates representing the Common Stock shall have endorsed thereon legends in substantially the following forms (in addition to any other legend which may be required by other agreements between the parties hereto):

(a) “THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO AN OPTION SET FORTH IN AN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER, OR SUCH HOLDER’S PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT THE PRINCIPAL OFFICE OF THIS COMPANY. ANY TRANSFER OR ATTEMPTED TRANSFER OF ANY SHARES SUBJECT TO SUCH OPTION IS VOID WITHOUT THE PRIOR EXPRESS WRITTEN CONSENT OF THE COMPANY.”

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(b) “THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 AS AMENDED. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THE SECURITIES UNDER SAID ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.”

(c) Any legend required by appropriate blue sky officials.

11. INVESTMENT REPRESENTATIONS. In connection with the purchase of the Common Stock, Purchaser represents to the Company the following:

(a) Purchaser is aware of the Company’s business affairs and financial condition and has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Common Stock. Purchaser is acquiring the Common Stock for investment for Purchaser’s own account only and not with a view to, or for resale in connection with, any “distribution” thereof within the meaning of the Securities Act.

(b) Purchaser understands that the Common Stock has not been registered under the Securities Act by reason of a specific exemption therefrom, which exemption depends upon, among other things, the bona fide nature of Purchaser’s investment intent as expressed herein.

(c) Purchaser further acknowledges and understands that the Common Stock must be held indefinitely unless the Common Stock is subsequently registered under the Securities Act or an exemption from such registration is available. Purchaser further acknowledges and understands that the Company is under no obligation to register the Common Stock. Purchaser understands that the certificate evidencing the Common Stock will be imprinted with a legend that prohibits the transfer of the Common Stock unless the Common Stock is registered or such registration is not required in the opinion of counsel for the Company.

(d) Purchaser is familiar with the provisions of Rules 144 and 701, under the Securities Act, as in effect from time to time, which, in substance, permit limited public resale of “restricted securities” acquired, directly or indirectly, from the issuer thereof (or from an affiliate of such issuer), in a non-public offering subject to the satisfaction of certain conditions. Rule 701 provides that if the issuer qualifies under Rule 701 at the time of issuance of the securities, such issuance will be exempt from registration under the Securities Act. In the event the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the securities exempt under Rule 701 may be sold by Purchaser ninety (90) days thereafter, subject to the satisfaction of certain of the conditions specified by Rule 144 and the market stand-off provision described in Purchaser’s Stock Option Agreement.

(e) In the event that the sale of the Common Stock does not qualify under Rule 701 at the time of purchase, then the Common Stock may be resold by Purchaser in certain limited circumstances subject to the provisions of Rule 144, which requires, among other things: (i) the availability of certain public information about the Company, and (ii) the resale occurring following the required holding period under Rule 144 after Purchaser has purchased, and made full payment of (within the meaning of Rule 144), the securities to be sold.

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(f) Purchaser further understands that at the time Purchaser wishes to sell the Common Stock there may be no public market upon which to make such a sale, and that, even if such a public market then exists, the Company may not be satisfying the current public current information requirements of Rule 144 or 701, and that, in such event, Purchaser would be precluded from selling the Common Stock under Rule 144 or 701 even if the minimum holding period requirement had been satisfied.

12. MARKET STAND-OFF AGREEMENT. By exercising the Option, Purchaser agrees not to sell, dispose of, transfer, make any short sale of, grant any option for the purchase of, or enter into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company held by Purchaser, for a period of one hundred eighty (180) days following the effective date of a registration statement of the Company filed under the Securities Act or such longer period as necessary to permit compliance with NASD Rule 2711 or NYSE Member Rule 472 and similar rules or regulations (the “Lock-Up Period”); provided, however, that nothing shall prevent the exercise of the Repurchase Option during the Lock-Up Period. Purchaser further agrees to execute and deliver such other agreements as may be reasonably requested by the Company and/or the underwriter(s) that are consistent with the foregoing or that are necessary to give further effect thereto. In order to enforce the foregoing covenant, the Company may impose stop-transfer instructions with respect to Purchaser’s shares of Common Stock until the end of such period. The underwriters of the Company’s stock are intended third party beneficiaries of this Section 12 and shall have the right, power and authority to enforce the provisions hereof as though they were a party hereto.

13. SECTION 83(b) ELECTION.    Purchaser understands that Section 83(a) of the Code taxes as ordinary income the difference between the amount paid for the Common Stock and the fair market value of the Common Stock as of the date any restrictions on the Common Stock lapse. In this context, “restriction” includes the right of the Company to buy back the Common Stock pursuant to the Repurchase Option set forth above. Purchaser understands that Purchaser may elect to be taxed at the time the Common Stock is purchased, rather than when and as the Repurchase Option expires, by filing an election under Section 83(b) (an “83(b) Election”) of the Code with the Internal Revenue Service within thirty (30) days of the date of purchase. Even if the fair market value of the Common Stock at the time of the execution of this Agreement equals the amount paid for the Common Stock, the 83(b) Election must be made to avoid income under Section 83(a) in the future. Purchaser understands that failure to file such an 83(b) Election in a timely manner may result in adverse tax consequences for Purchaser. Purchaser further understands that Purchaser must file an additional copy of such 83(b) Election with his or her federal income tax return for the calendar year in which the date of this Agreement falls. Purchaser acknowledges that the foregoing is only a summary of the effect of United States federal income taxation with respect to purchase of the Common Stock hereunder, and does not purport to be complete. Purchaser further acknowledges that the Company has directed Purchaser to seek independent advice regarding the applicable provisions of the Code, the income tax laws of any municipality, state or foreign country in which Purchaser may reside, and the tax consequences of Purchaser’s death. Purchaser assumes all responsibility for filing an 83(b) Election and paying all taxes resulting from such election or the lapse of the restrictions on the Common Stock.

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14. REFUSAL TO TRANSFER. The Company shall not be required (a) to transfer on its books any shares of Common Stock of the Company which shall have been transferred in violation of any of the provisions set forth in this Agreement, or (b) to treat as owner of such shares or to accord the right to vote as such owner or to pay dividends to any transferee to whom such shares shall have been so transferred.

15. NO EMPLOYMENT RIGHTS. This Agreement is not an employment contract and nothing in this Agreement shall affect in any manner whatsoever the right or power of the Company or its Affiliates to terminate Purchaser’s employment for any reason at any time, with or without cause and with or without notice.

16. MISCELLANEOUS.

(a) Notices. All notices required or permitted hereunder shall be in writing and shall be deemed effectively given: (a) upon personal delivery to the party to be notified, (b) when sent by confirmed facsimile if sent during normal business hours of the recipient, and if not during normal business hours of the recipient, then on the next business day, (c) five (5) calendar days after having been sent by registered or certified mail, return receipt requested, postage prepaid, or (d) one (1) business day after deposit with a nationally recognized overnight courier, specifying next day delivery, with written verification of receipt. All communications shall be sent to the other party hereto at such party’s address hereinafter set forth on the signature page hereof, or at such other address as such party may designate by ten (10) days advance written notice to the other party hereto.

(b) Successors and Assigns. This Agreement shall inure to the benefit of the successors and assigns of the Company and, subject to the restrictions on transfer herein set forth, be binding upon Purchaser, Purchaser’s successors, and assigns. The Company may assign the Repurchase Option hereunder at any time or from time to time, in whole or in part.

(c) Attorneys’ Fees; Specific Performance. Purchaser shall reimburse the Company for all costs incurred by the Company in enforcing the performance of, or protecting its rights under, any part of this Agreement, including reasonable costs of investigation and attorneys’ fees. It is the intention of the parties that the Company, upon exercise of the Repurchase Option and payment for the shares repurchased, pursuant to the terms of this Agreement, shall be entitled to receive the Common Stock, in specie, in order to have such Common Stock available for future issuance without dilution of the holdings of other stockholders. Furthermore, it is expressly agreed between the parties that money damages are inadequate to compensate the Company for the Common Stock and that the Company shall, upon proper exercise of the Repurchase Option, be entitled to specific enforcement of its rights to purchase and receive said Common Stock.

(d) Governing Law; Venue. This Agreement shall be governed by and construed in accordance with the laws of the State of California. The parties agree that any action brought by either party to interpret or enforce any provision of this Agreement shall be brought in, and each party agrees to, and does hereby, submit to the jurisdiction and venue of, the appropriate state or federal court for the district encompassing the Company’s principal place of business.

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(e) Further Execution. The parties agree to take all such further action(s) as may reasonably be necessary to carry out and consummate this Agreement as soon as practicable, and to take whatever steps may be necessary to obtain any governmental approval in connection with or otherwise qualify the issuance of the securities that are the subject of this Agreement.

(f) Independent Counsel. Purchaser acknowledges that this Agreement has been prepared on behalf of the Company by Cooley LLP, counsel to the Company and that Cooley LLP does not represent, and is not acting on behalf of, Purchaser. Purchaser has been provided with an opportunity to consult with Purchaser’s own counsel with respect to this Agreement.

(g) Entire Agreement; Amendment. This Agreement constitutes the entire agreement between the parties with respect to the subject matter hereof and supersedes and merges all prior agreements or understandings, whether written or oral. This Agreement may not be amended, modified or revoked, in whole or in part, except by an agreement in writing signed by each of the parties hereto.

(h) Severability. If one or more provisions of this Agreement are held to be unenforceable under applicable law, the parties agree to renegotiate such provision in good faith. In the event that the parties cannot reach a mutually agreeable and enforceable replacement for such provision, then (i) such provision shall be excluded from this Agreement, (ii) the balance of the Agreement shall be interpreted as if such provision were so excluded and (iii) the balance of the Agreement shall be enforceable in accordance with its terms.

(i) Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original and all of which together shall constitute one instrument.

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of                    .

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ATTACHMENTS:

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EXHIBIT A

NOTICE OF EXERCISE

Principia Biopharma Inc.

Date of Exercise: _______________

Ladies and Gentlemen:

This constitutes notice under my stock option that I elect to purchase the number of shares for the price set forth below.

By this exercise, I agree (i) to provide such additional documents as you may require pursuant to the terms of the PRINCIPIA BIOPHARMA INC. 2008 AMENDED AND RESTATED EQUITY INCENTIVE PLAN, (ii) to provide for the payment by me to you (in the manner designated by you) of your withholding obligation, if any, relating to the exercise of this option, and (iii) if this exercise relates to an incentive stock option, to notify you in writing within fifteen (15) days after the date of any disposition of any of the shares of Common Stock issued upon exercise of this option that occurs within two (2) years after the date of grant of this option or within one (1) year after such shares of Common Stock are issued upon exercise of this option.

I hereby make the following certifications and representations with respect to the number of shares of Common Stock of the Company listed above (the “Shares”), which are being acquired by me for my own account upon exercise of the Option as set forth above:

I acknowledge that the Shares have not been registered under the Securities Act of 1933, as amended (the “Securities Act”), and are deemed to constitute “restricted securities” under Rule 701 and Rule 144 promulgated under the Securities Act. I warrant and represent to the Company that I have no present intention of distributing or selling said Shares, except as permitted under the Securities Act and any applicable state securities laws.

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I further acknowledge that I will not be able to resell the Shares for at least ninety days (90) after the stock of the Company becomes publicly traded (i.e., subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934) under Rule 701 and that more restrictive conditions apply to affiliates of the Company under Rule 144.

I further acknowledge that all certificates representing any of the Shares subject to the provisions of the Option shall have endorsed thereon appropriate legends reflecting the foregoing limitations, as well as any legends reflecting restrictions pursuant to the Company’s Articles of Incorporation, Bylaws and/or applicable securities laws.

I further agree that, if required by the Company (or a representative of the underwriters) in connection with the first underwritten registration of the offering of any securities of the Company under the Securities Act, I will not sell, dispose of, transfer, make any short sale of, grant any option for the purchase of, or enter into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company for a period of one hundred eighty (180) days following the effective date of a registration statement of the Company filed under the Securities Act or such longer period as necessary to permit compliance with NASD Rule 2711 or NYSE Member Rule 472 and similar rules and regulations (the “Lock-Up Period”). I further agree to execute and deliver such other agreements as may be reasonably requested by the Company and/or the underwriter(s) that are consistent with the foregoing or that are necessary to give further effect thereto. In order to enforce the foregoing covenant, the Company may impose stop-transfer instructions with respect to securities subject to the foregoing restrictions until the end of such period.

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EXHIBIT B

STOCK ASSIGNMENT SEPARATE FROM CERTIFICATE

FOR VALUE RECEIVED,                          hereby sells, assigns and transfers unto PRINCIPIA BIOPHARMA INC., a Delaware corporation (the “Company”), pursuant to the Repurchase Option under that certain Early Exercise Stock Purchase Agreement, dated                      by and between the undersigned and the Company (the “Agreement”),                         (                    ) shares of Common Stock of the Company standing in the undersigned’s name on the books of the Company represented by Certificate No(s).                     and does hereby irrevocably constitute and appoint the Company’s Secretary attorney-in-fact to transfer said Common Stock on the books of the Company with full power of substitution in the premises. This Assignment may be used only in accordance with and subject to the terms and conditions of the Agreement, in connection with the repurchase of shares of Common Stock issued to the undersigned pursuant to the Agreement, and only to the extent that such shares remain subject to the Company’s Repurchase Option under the Agreement.

Dated: _______________

(INSTRUCTION: Please do not fill in any blanks other than the “Signature” line and the “Print Name” line.)

EXHIBIT C

JOINT ESCROW INSTRUCTIONS

Secretary

Principia Biopharma Inc.

400 East Jamie Court, Ste. 302

South San Francisco, CA 94080

Dear Sir or Madam:

As Escrow Agent for both PRINCIPIA BIOPHARMA INC., a Delaware corporation (“Company”), and the undersigned purchaser of Common Stock of the Company (“Purchaser”), you are hereby authorized and directed to hold the documents delivered to you pursuant to the terms of that certain Early Exercise Stock Purchase Agreement (“Agreement”), dated                          to which a copy of these Joint Escrow Instructions is attached as Exhibit C, in accordance with the following instructions:

1. In the event the Company or an assignee shall elect to exercise the Repurchase Option set forth in the Agreement, the Company or its assignee will give to Purchaser and you a written notice specifying the number of shares of Common Stock to be purchased, the purchase price, and the time for a closing hereunder at the principal office of the Company. Purchaser and the Company hereby irrevocably authorize and direct you to close the transaction contemplated by such notice in accordance with the terms of said notice.

At the closing you are directed (a) to date any stock assignments necessary for the transfer in question, (b) to fill in the number of shares being transferred, and (c) to deliver same, together with the certificate evidencing the shares of Common Stock to be transferred, to the Company against the simultaneous delivery to you of the purchase price (which may include suitable acknowledgment of cancellation of indebtedness) of the number of shares of Common Stock being purchased pursuant to the exercise of the Repurchase Option.

Purchaser irrevocably authorizes the Company to deposit with you any certificates evidencing shares of Common Stock to be held by you hereunder and any additions and substitutions to said shares as specified in the Agreement. Purchaser does hereby irrevocably constitute and appoint you as the Purchaser’s attorney-in-fact and agent for the term of this escrow to execute with respect to such securities and other property all documents of assignment and/or transfer and all stock certificates necessary or appropriate to make all securities negotiable and complete any transaction herein contemplated.

This escrow shall terminate and the shares of stock held hereunder shall be released in full upon the later of (a) the expiration or exercise in full of the Repurchase Option, whichever occurs first, and (b) the payment in full of all principal and interest due and payable under the promissory note attached to the Agreement, if any.

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If at the time of termination of this escrow you should have in your possession any documents, securities, or other property belonging to Purchaser, you shall deliver all of same to Purchaser and shall be discharged of all further obligations hereunder; provided, however, that if at the time of termination of this escrow you are advised by the Company that the property subject to this escrow is the subject of a pledge or other security agreement, you shall deliver all such property to the pledgeholder or other person designated by the Company.

Except as otherwise provided in these Joint Escrow Instructions, your duties hereunder may be altered, amended, modified or revoked only by a writing signed by all of the parties hereto.

You shall be obligated only for the performance of such duties as are specifically set forth herein and may rely and shall be protected in relying or refraining from acting on any instrument reasonably believed by you to be genuine and to have been signed or presented by the proper party or parties or their assignees. You shall not be personally liable for any act you may do or omit to do hereunder as Escrow Agent or as attorney-in-fact for Purchaser while acting in good faith and any act done or omitted by you pursuant to the advice of your own attorneys shall be conclusive evidence of such good faith.

You are hereby expressly authorized to disregard any and all warnings given by any of the parties hereto or by any other person or corporation, excepting only orders or process of courts of law, and are hereby expressly authorized to comply with and obey orders, judgments or decrees of any court. In case you obey or comply with any such order, judgment or decree of any court, you shall not be liable to any of the parties hereto or to any other person, firm or corporation by reason of such compliance, notwithstanding any such order, judgment or decree being subsequently reversed, modified, annulled, set aside, vacated or found to have been entered without jurisdiction.

You shall not be liable in any respect on account of the identity, authority or rights of the parties executing or delivering or purporting to execute or deliver the Agreement or any documents or papers deposited or called for hereunder.

You shall not be liable for the outlawing of any rights under any statute of limitations with respect to these Joint Escrow Instructions or any documents deposited with you.

Your responsibilities as Escrow Agent hereunder shall terminate if you shall cease to be Secretary of the Company or if you shall resign by written notice to the Company party. In the event of any such termination, the Secretary of the Corporation shall automatically become the successor Escrow Agent unless the Company shall appoint another successor Escrow Agent, and Purchaser hereby confirms the appointment of such successor as Purchaser’s attorney-in-fact and agent to the full extent of your appointment.

If you reasonably require other or further instruments in connection with these Joint Escrow Instructions or obligations in respect hereto, the necessary parties hereto shall join in furnishing such instruments.

It is understood and agreed that should any dispute arise with respect to the delivery and/or ownership or right of possession of the securities, you are authorized and directed to retain in your possession without liability to anyone all or any part of said securities until such dispute shall have been settled either by mutual written agreement of the parties concerned or by a final order, decree or judgment of a court of competent jurisdiction after the time for appeal has expired and no appeal has been perfected, but you shall be under no duty whatsoever to institute or defend any such proceedings.

Any notice required or permitted hereunder shall be given in writing and shall be deemed effectively given upon personal delivery, including delivery by express courier or five days after deposit in the United States Post Office, by registered or certified mail with postage and fees prepaid, addressed to each of the other parties hereunto entitled at the following addresses, or at such other addresses as a party may designate by ten days’ advance written notice to each of the other parties hereto:

By signing these Joint Escrow Instructions you become a party hereto only for the purpose of said Joint Escrow Instructions; you do not become a party to the Agreement.

You shall be entitled to employ such legal counsel and other experts (including without limitation the firm of Cooley LLP) as you may deem necessary properly to advise you in connection with your obligations hereunder. You may rely upon the advice of such counsel, and may pay such counsel reasonable compensation therefor. The Company shall be responsible for all fees generated by such legal counsel in connection with your obligations hereunder.

This instrument shall be binding upon and inure to the benefit of the parties hereto and their respective successors and permitted assigns. It is understood and agreed that references to “you” or “your” herein refer to the original Escrow Agent and to any and all successor Escrow Agents. It is understood and agreed that the Company may at any time or from time to time assign its rights under the Agreement and these Joint Escrow Instructions in whole or in part.

This Agreement shall be governed by and interpreted and determined in accordance with the laws of the State of California, as such laws are applied by California courts to contracts made and to be performed entirely in California by residents of that state.