Document:

Form of Warrant to Purchase Shares of Common Stock

 EXHIBIT 4.3 

THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER
THE SECURITIES LAWS OF ANY STATE. THESE SECURITIES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED EXCEPT AS PERMITTED UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS IN ACCORDANCE WITH APPLICABLE REGISTRATION
REQUIREMENTS OR AN EXEMPTION THEREFROM. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE ISSUER THAT SUCH OFFER, SALE, TRANSFER, PLEDGE OR HYPOTHECATION OTHERWISE COMPLIES WITH THE ACT AND ANY
APPLICABLE STATE SECURITIES LAWS. THIS WARRANT MUST BE SURRENDERED TO THE COMPANY OR ITS TRANSFER AGENT AS A CONDITION PRECEDENT TO THE SALE, TRANSFER, PLEDGE OR HYPOTHECATION OF ANY INTEREST IN ANY OF THE SECURITIES REPRESENTED HEREBY. 

WARRANT TO PURCHASE SHARES OF COMMON STOCK 

of 
 SUTRO BIOPHARMA, INC.

 Dated as of
                     
 Void
after the date specified in Section 8 
  

	 No. 
	Warrant to Purchase 

                     Shares of

 Common Stock 

(subject to adjustment) 

THIS CERTIFIES THAT, for value received,
                     or his registered assigns (the “Holder”), is entitled, subject to the provisions and upon the
terms and conditions set forth herein, to purchase from Sutro Biopharma, Inc., a Delaware corporation (the “Company”), shares of the Company’s Common Stock, $0.001 par value per share (“Common
Stock”), in the amounts, at such times and at the price per share set forth in Section 1. The term “Warrant” as used herein shall include this Warrant and any warrants delivered in substitution or exchange therefor as
provided herein. This Warrant is issued to the Holder in consideration for the services rendered by                     , at the request of
                     as its designee, under the letter agreement between
                     and the Company, dated
                    , in accordance with the terms set forth therein, and is one of a series of warrants issued pursuant thereto (the
“Common Warrants”). 
 The following is a statement of the rights of the Holder and the conditions to which this
Warrant is subject, and to which Holder, by acceptance of this Warrant, agrees: 
 1. Number and Price of Shares; Exercise Period.

 (a) Number of Shares. Subject to any previous exercise of the Warrant, the Holder shall have the right to purchase up to
                     shares of Common Stock, as may be adjusted pursuant hereto (the “Shares”), prior to (or in
connection with) the expiration of this Warrant as provided in Section 8. 
 (b) Exercise Price. The exercise price per
Share shall be equal to $                    , subject to adjustment pursuant hereto (the “Exercise Price”). 

(c) Exercise Period. This Warrant shall be exercisable, in whole or in part, prior to (or in connection with) the expiration of
this Warrant as set forth in Section 8. 

 2. Exercise of the Warrant. 

(a) Exercise. The purchase rights represented by this Warrant may be exercised at the election of the Holder, in whole or in
part, in accordance with Section 1, by: 
 (i) the tender to the Company at its principal office (or such other office or agency as the
Company may designate) of a notice of exercise in the form of Exhibit A (the “Notice of Exercise”), duly completed and executed by or on behalf of the Holder, together with the surrender of this Warrant; and 

(ii) the payment to the Company of an amount equal to (x) the Exercise Price multiplied by (y) the number of Shares being
purchased, by wire transfer or certified, cashier’s or other check acceptable to the Company and payable to the order of the Company. 

(b) Net Issue Exercise. In lieu of exercising this Warrant pursuant to Section 2(a)(ii), if the fair market value of one
Share is greater than the Exercise Price (at the date of calculation as set forth below), the Holder may elect to receive a number of Shares equal to the value of this Warrant (or of any portion of this Warrant being canceled) by surrender of this
Warrant at the principal office of the Company (or such other office or agency as the Company may designate) together with a properly completed and executed Notice of Exercise reflecting such election, in which event the Company shall issue to the
Holder that number of Shares computed using the following formula: 
  

									
		  	X	  	=	  	    Y(A-B)    	  	
		  		  		  	        A	  	

 Where: 
  

					
	X	  	=	  	The number of Shares to be issued to the Holder
			
	Y	  	=	  	The number of Shares purchasable under this Warrant or, if only a portion of the Warrant is being exercised, the portion of the Warrant being canceled (at the date of such calculation)
			
	A	  	=	  	The fair market value of one Share (at the date of such calculation)
			
	B	  	=	  	The Exercise Price (as adjusted to the date of such calculation)

 For purposes of the calculation above, the fair market value of one Share shall be determined as
follows: 
 (i) If the Company’s common stock is listed on any established stock exchange or a national market system, including
without limitation the Nasdaq National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its fair market value shall be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on such exchange
or system on the day of determination, as reported in The Wall Street Journal or such other source as the Board of Directors deems reliable; 

(ii) If the Company’s common stock is regularly quoted by a recognized securities dealer but selling prices are not reported, its fair
market value shall be the mean between the high bid and low asked prices for the Company’s common stock on the day of determination; 

  
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 (iii) If the Warrant is exercised in connection with the Company’s initial public offering
of common stock, the fair market value per Share shall be the per share offering price to the public of the Company’s initial public offering; or 

(iv) In the absence of an established market for the Company’s common stock and if the Warrant is not exercised in connection with the
Company’s initial public offering of common stock, the fair market value thereof shall be determined in good faith by the Board of Directors of the Company. 

(c) Stock Certificates. The rights under this Warrant shall be deemed to have been exercised and the Shares issuable upon such
exercise shall be deemed to have been issued immediately prior to the close of business on the date this Warrant is exercised in accordance with its terms, and the person entitled to receive the Shares issuable upon such exercise shall be treated
for all purposes as the holder of record of such Shares as of the close of business on such date. As promptly as reasonably practicable on or after such date, the Company shall issue and deliver to the person or persons entitled to receive the same
a certificate or certificates for that number of shares issuable upon such exercise. In the event that the rights under this Warrant are exercised in part and have not expired, the Company shall execute and deliver a new Warrant reflecting the
number of Shares that remain subject to this Warrant. 
 (d) No Fractional Shares or Scrip. No fractional shares or scrip
representing fractional shares shall be issued upon the exercise of the rights under this Warrant. In lieu of such fractional share to which the Holder would otherwise be entitled, the Company shall make a cash payment equal to the Exercise Price
multiplied by such fraction. 
 (e) Conditional Exercise. The Holder may exercise this Warrant conditioned upon (and effective
immediately prior to) consummation of any transaction that would cause the expiration of this Warrant pursuant to Section 8 by so indicating in the notice of exercise. 

(f) Reservation of Stock. The Company agrees during the term the rights under this Warrant are exercisable to reserve and keep
available from its authorized and unissued shares of common stock for the purpose of effecting the exercise of this Warrant such number of shares as shall from time to time be sufficient to effect the exercise of the rights under this Warrant; and
if at any time the number of authorized but unissued shares of common stock shall not be sufficient for purposes of the exercise of this Warrant in accordance with its terms, without limitation of such other remedies as may be available to the
Holder, the Company will use its best efforts to take such corporate action as may be necessary to increase its authorized and unissued shares of its common stock to a number of shares as shall be sufficient for such purposes. 

3. Replacement of the Warrant. Subject to the receipt of evidence reasonably satisfactory to the Company of the loss, theft,
destruction or mutilation of this Warrant and, in the case of loss, theft or destruction, on delivery of an indemnity agreement reasonably satisfactory in form and substance to the Company or, in the case of mutilation, on surrender and cancellation
of this Warrant, the Company at the expense of the Holder shall execute and deliver, in lieu of this Warrant, a new warrant of like tenor and amount. 

4. Transfer of the Warrant. 

(a) Warrant Register. The Company shall maintain a register (the “Warrant Register”) containing the name
and address of the Holder or Holders. Until this Warrant is transferred on the Warrant Register in accordance herewith, the Company may treat the Holder as shown on the Warrant Register as the absolute owner of this Warrant for all purposes,
notwithstanding any notice to the contrary. Any Holder of this Warrant (or of any portion of this Warrant) may change its address as shown on the Warrant Register by written notice to the Company requesting a change. 

  
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 (b) Warrant Agent. The Company may appoint an agent for the purpose of maintaining
the Warrant Register referred to in Section 4(a), issuing the Shares or other securities then issuable upon the exercise of the rights under this Warrant, exchanging this Warrant, replacing this Warrant or conducting related activities. 

(c) Transferability of the Warrant. Subject to the provisions of this Warrant with respect to compliance with the Securities Act
of 1933, as amended (the “Securities Act”) and limitations on assignments and transfers, including without limitation compliance with the restrictions on transfer set forth in Section 5, title to this Warrant may be
transferred by endorsement (by the transferor and the transferee executing the assignment form attached as Exhibit B (the “Assignment Form”)) and delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery. 
 (d) Exchange of the Warrant upon a Transfer. On surrender of this Warrant (and a properly
endorsed Assignment Form) for exchange, subject to the provisions of this Warrant with respect to compliance with the Securities Act and limitations on assignments and transfers, the Company shall issue to or on the order of the Holder a new warrant
or warrants of like tenor, in the name of the Holder or as the Holder (on payment by the Holder of any applicable transfer taxes) may direct, for the number of shares issuable upon exercise hereof, and the Company shall register any such transfer
upon the Warrant Register. This Warrant (and the securities issuable upon exercise of the rights under this Warrant) must be surrendered to the Company or its warrant or transfer agent, as applicable, as a condition precedent to the sale, pledge,
hypothecation or other transfer of any interest in any of the securities represented hereby. 
 (e) Minimum Transfer. This
Warrant may not be transferred in part unless such transfer is to a transferee who, pursuant to such transfer, receives the right to purchase at least
                            
(                ) Shares hereunder (as adjusted from time to time in accordance with Section 6). 

(f) Taxes. In no event shall the Company be required to pay any tax which may be payable in respect of any transfer involved in
the issue and delivery of any certificate in a name other than that of the Holder, and the Company shall not be required to issue or deliver any such certificate unless and until the person or persons requesting the issue thereof shall have paid to
the Company the amount of such tax or shall have established to the satisfaction of the Company that such tax has been paid or is not payable. 

5. Restrictions on Transfer of the Warrant and Shares; Compliance with Securities Laws. By acceptance of this Warrant, the
Holder agrees to comply with the following: 
 (a) Restrictions on Transfers. This Warrant may not be transferred or assigned
in whole or in part without the Company’s prior written consent (which shall not be unreasonably withheld), and any attempt by Holder to transfer or assign any rights, duties or obligations that arise under this Warrant without such permission
shall be void. Any transfer of this Warrant or the Shares (the “Securities”) must be in compliance with all applicable federal and state securities laws. The Holder agrees not to make any sale, assignment, transfer, pledge or
other disposition of all or any portion of the Securities, or any beneficial interest therein, unless and until the transferee thereof has agreed in writing for the benefit of the Company to take and hold such Securities subject to, and to be bound
by, the terms and conditions set forth in this Warrant to the same extent as if the transferee were the original Holder hereunder, and 

(i) there is then in effect a registration statement under the Securities Act covering such proposed disposition and such disposition is made
in accordance with such registration statement, or 

  
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 (ii) (A) such Holder shall have given prior written notice to the Company of such Holder’s
intention to make such disposition and shall have furnished the Company with a detailed description of the manner and circumstances of the proposed disposition, (B) the transferee shall have confirmed to the satisfaction of the Company in
writing, substantially in the form of Exhibit A-1, that the Securities are being acquired (i) solely for the transferee’s own account and not as a nominee for any other party, (ii) for
investment and (iii) not with a view toward distribution or resale, and shall have confirmed such other matters related thereto as may be reasonably requested by the Company, and (C) such Holder shall have furnished the Company, at the
Holder’s expense, with (i) an opinion of counsel, reasonably satisfactory to the Company, to the effect that such disposition will not require registration of such Securities under the Securities Act or (ii) a “no action”
letter from the Securities and Exchange Commission to the effect that the transfer of such Securities without registration will not result in a recommendation by the staff of the Securities and Exchange Commission that action be taken with respect
thereto, whereupon such Holder shall be entitled to transfer such Securities in accordance with the terms of the notice delivered by the Holder to the Company. 

(b) Investment Representation Statement. Unless the rights under this Warrant are exercised pursuant to an effective
registration statement under the Securities Act that includes the Shares with respect to which the Warrant was exercised, it shall be a condition to any exercise of the rights under this Warrant that the Holder shall have confirmed to the
satisfaction of the Company in writing, substantially in the form of Exhibit A-1, that the Shares so purchased are being acquired solely for the Holder’s own account and not as a nominee for any other
party, for investment and not with a view toward distribution or resale and that the Holder shall have confirmed such other matters related thereto as may be reasonably requested by the Company. 

(c) Company’s Right of First Refusal. Notwithstanding anything to the contrary herein, before any Shares held by Holder
(which, for the purposes of this Section 5(c), shall include any transferee of Shares) may be sold or otherwise transferred (including transfer by gift or operation of law), the Company or its assignee(s) shall have a right of first refusal to
purchase the Shares on the terms and conditions set forth in this Section (the “Right of First Refusal”). 
 (i)
Notice of Proposed Transfer. The Holder of the Shares shall deliver to the Company a written notice (the “Notice”) stating: (A) the Holder’s bona fide intention to sell or otherwise transfer such Shares;
(B) the name of each proposed purchaser or other transferee (“Proposed Transferee”); (C) the number of Shares to be transferred to each Proposed Transferee; and (D) 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 the Shares at the Offered Price to the Company or its assignee(s). 

(ii) Exercise of Right of First Refusal. At any time within thirty (30) days after receipt of the Notice, the Company and/or its
assignee(s) may, by giving written notice to the Holder, elect to purchase all, but not less than all, of the Shares proposed to be transferred to any one or more of the Proposed Transferees, at the purchase price determined in accordance with
subsection (iii) below. 
 (iii) Purchase Price. The purchase price (“Purchase Price”) for the Shares
purchased by the Company or its assignee(s) under this Section 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 of Directors of the Company in good faith. 

  
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 (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 set forth in the Notice. 
 (v) Holder’s Right to
Transfer. If all of the Shares proposed in the Notice to be transferred to a given Proposed Transferee are not purchased by the Company and/or its assignee(s) as provided in this Section, 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 120 days after the date of the Notice, that any such sale or other transfer is effected in accordance with
any applicable securities laws and that the Proposed Transferee agrees in writing that the provisions of this Section 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 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 before any Shares held by the Holder may be sold or
otherwise transferred. 
 (vi) Exception for Certain Family Transfers. Anything to the contrary contained in this Section
notwithstanding, the transfer of any or all of the Shares during the Holder’s lifetime or on the Holder’s death by will or intestacy to the Holder’s immediate family or a trust for the benefit of the Holder’s immediate family
shall be exempt from the provisions of this Section. “Immediate Family” as used herein shall mean spouse, lineal descendant or antecedent, father, mother, brother or sister. In such case, the transferee or other recipient
shall receive and hold the Shares so transferred subject to the provisions of this Section, and there shall be no further transfer of such Shares except in accordance with the terms of this Section. 

(vii) Termination of Right of First Refusal. The Right of First Refusal shall terminate as to any Shares upon the expiration of this
Warrant or the occurrence of any event specified in Section 8. 
 (d) Securities Law Legend. The Securities shall (unless
otherwise permitted by the provisions of this Warrant) be stamped or imprinted with a legend substantially similar to the following (in addition to any legend required by state securities laws): 

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE
SECURITIES LAWS OF CERTAIN STATES. THESE SECURITIES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED EXCEPT AS PERMITTED UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS IN ACCORDANCE WITH APPLICABLE REGISTRATION
REQUIREMENTS OR AN EXEMPTION THEREFROM. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE ISSUER THAT SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION OTHERWISE COMPLIES WITH THE ACT AND ANY
APPLICABLE STATE SECURITIES LAWS. THIS CERTIFICATE MUST BE SURRENDERED TO THE COMPANY OR ITS TRANSFER AGENT AS A CONDITION PRECEDENT TO THE SALE, TRANSFER, PLEDGE OR HYPOTHECATION OF ANY INTEREST IN ANY OF THE SECURITIES REPRESENTED HEREBY. 

  
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 (e) Additional Share Legend. The Shares issued upon exercise hereof shall also be
stamped or imprinted with a legend in substantially the following form: 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
RESTRICTIONS ON TRANSFER AND A RIGHT OF FIRST REFUSAL HELD BY THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE WARRANT TO PURCHASE SHARES OF COMMON STOCK 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 TRANSFER RESTRICTIONS AND RIGHT OF FIRST REFUSAL ARE BINDING ON TRANSFEREES OF THESE SHARES. 
 THE
SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFERABILITY AND RESALE, INCLUDING A LOCK-UP PERIOD IN THE EVENT OF A PUBLIC OFFERING, AS SET FORTH IN THE WARRANT PURSUANT TO WHICH
THESE SHARES WERE ISSUED, A COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE COMPANY. 
 (f) Instructions Regarding
Transfer Restrictions. The Holder consents to the Company making a notation on its records and giving instructions to any transfer agent in order to implement the restrictions on transfer established in this Section 5. 

(g) Removal of Legend. The legend referring to federal and state securities laws identified in Section 5(d) stamped on a
certificate evidencing the Shares and the stock transfer instructions and record notations with respect to such securities shall be removed and the Company shall issue a certificate without such legend to the holder of such securities if
(i) such securities are registered under the Securities Act, or (ii) such holder provides the Company with an opinion of counsel reasonably acceptable to the Company to the effect that a sale or transfer of such securities may be made
without registration or qualification. 
 6. Adjustments. Subject to the expiration of this Warrant pursuant to
Section 8, the number and kind of shares purchasable hereunder and the Exercise Price therefor are subject to adjustment from time to time, as follows: 

(a) Merger or Reorganization. If at any time there shall be any reorganization, recapitalization, merger or consolidation (a
“Reorganization”) involving the Company (other than as otherwise provided for herein or as would cause the expiration of this Warrant under Section 8) in which shares of the Company’s stock are converted into or
exchanged for securities, cash or other property, then, as a part of such Reorganization, lawful provision shall be made so that the Holder shall thereafter be entitled to receive upon exercise of this Warrant, the kind and amount of securities,
cash or other property of the successor corporation resulting from such Reorganization, equivalent in value to that which a holder of the Shares deliverable upon exercise of this Warrant would have been entitled in such Reorganization if the right
to purchase the Shares hereunder had been exercised immediately prior to such Reorganization. In any such case, appropriate adjustment (as determined in good faith by the Board of Directors of the successor corporation) shall be made in the
application of the provisions of this Warrant with respect to the rights and interests of the Holder after such Reorganization to the end that the provisions of this Warrant shall be applicable after the event, as near as reasonably may be, in
relation to any shares or other securities deliverable after that event upon the exercise of this Warrant. 
 (b) Reclassification of
Shares. If the securities issuable upon exercise of this Warrant are changed into the same or a different number of securities of any other class or classes by reclassification, capital reorganization or otherwise (other than as otherwise
provided for herein) (a “Reclassification”), 

  
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then, in any such event, in lieu of the number of Shares which the Holder would otherwise have been entitled to receive, the Holder shall have the right thereafter to exercise this Warrant for a
number of shares of such other class or classes of stock that a holder of the number of securities deliverable upon exercise of this Warrant immediately before that change would have been entitled to receive in such Reclassification, all subject to
further adjustment as provided herein with respect to such other shares. 
 (c) Subdivisions and Combinations. In the event
that the outstanding shares of common stock are subdivided (by stock split, by payment of a stock dividend or otherwise) into a greater number of shares of such securities, the number of Shares issuable upon exercise of the rights under this Warrant
immediately prior to such subdivision shall, concurrently with the effectiveness of such subdivision, be proportionately increased, and the Exercise Price shall be proportionately decreased, and in the event that the outstanding shares of common
stock are combined (by reclassification or otherwise) into a lesser number of shares of such securities, the number of Shares issuable upon exercise of the rights under this Warrant immediately prior to such combination shall, concurrently with the
effectiveness of such combination, be proportionately decreased, and the Exercise Price shall be proportionately increased. 
 (d)
Notice of Adjustments. Upon any adjustment in accordance with this Section 6, the Company shall give notice thereof to the Holder, which notice shall state the event giving rise to the adjustment, the Exercise Price as adjusted
and the number of securities or other property purchasable upon the exercise of the rights under this Warrant, setting forth in reasonable detail the method of calculation of each. The Company shall, upon the written request of any Holder, furnish
or cause to be furnished to such Holder a certificate setting forth (i) such adjustments, (ii) the Exercise Price at the time in effect and (iii) the number of securities and the amount, if any, of other property that at the time
would be received upon exercise of this Warrant. 
 7. Notification of Certain Events. Prior to the expiration of this Warrant
pursuant to Section 8, in the event that the Company shall authorize: 
 (a) the issuance of any dividend or other distribution on the
capital stock of the Company (other than (i) dividends or distributions otherwise provided for in Section 6, (ii) repurchases of common stock issued to or held by employees, officers, directors or consultants of the Company or its
subsidiaries upon termination of their employment or services pursuant to agreements providing for the right of said repurchase; (iii) repurchases of common stock issued to or held by employees, officers, directors or consultants of the Company
or its subsidiaries pursuant to rights of first refusal or first offer contained in agreements providing for such rights; or (iv) repurchases of capital stock of the Company in connection with the settlement of disputes with any stockholder),
whether in cash, property, stock or other securities; 
 (b) the voluntary liquidation, dissolution or winding up of the Company; or 

(c) any transaction resulting in the expiration of this Warrant pursuant to Section 8(b) or 8(c); 

the Company shall send to the Holder of this Warrant at least ten (10) days prior written notice of the date on which a record shall be taken for any
such dividend or distribution specified in clause (a) or the expected effective date of any such other event specified in clause (b) or (c), as applicable. The notice provisions set forth in this section may be shortened or waived
prospectively or retrospectively by the consent of the holders of a majority of the Shares issuable upon exercise of the rights under the Common Warrants. 

8. Expiration of the Warrant. This Warrant shall expire and shall no longer be exercisable as of the earlier of: 

(a)                 , Pacific time, on
                    ; 

  
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 (b) (i) the acquisition of the Company by another entity by means of any transaction or series of
related transactions to which the Company is a party (including, without limitation, any stock acquisition, reorganization, merger or consolidation, but excluding any sale of stock for capital raising purposes and any transaction effected primarily
for purposes of changing the Company’s jurisdiction of incorporation) other than a transaction or series of related transactions in which the holders of the voting securities of the Company outstanding immediately prior to such transaction or
series of related transactions retain, immediately after such transaction or series of transactions, as a result of shares in the Company held by such holders prior to such transaction or series of transactions, at least a majority of the total
voting power represented by the outstanding voting securities of the Company or such other surviving or resulting entity (or if the Company or such other surviving or resulting entity is a wholly-owned subsidiary immediately following such
acquisition, its parent), or (ii) a sale, lease or other disposition of all or substantially all of the assets of the Company and its subsidiaries taken as a whole by means of any transaction or series of related transactions, except where such
sale, lease or other disposition is to a wholly-owned subsidiary of the Company; or 
 (c) Immediately prior to the closing of a firm
commitment underwritten public offering pursuant to an effective registration statement filed under the Securities Act covering the offering and sale of the Company’s common stock. 

9. No Rights as a Stockholder. Nothing contained herein shall entitle the Holder to any rights as a stockholder of the Company
or to be deemed the holder of any securities that may at any time be issuable on the exercise of the rights hereunder for any purpose nor shall anything contained herein be construed to confer upon the Holder, as such, any right to vote for the
election of directors or upon any matter submitted to stockholders at any meeting thereof, or to give or withhold consent to any corporate action (whether upon any recapitalization, issuance of stock, reclassification of stock, change of par value
or change of stock to no par value, consolidation, merger, conveyance or otherwise) or to receive notice of meetings, or to receive dividends or subscription rights or any other rights of a stockholder of the Company until the rights under the
Warrant shall have been exercised and the Shares purchasable upon exercise of the rights hereunder shall have become deliverable as provided herein. 

10. Market Stand-off. The Holder of this Warrant hereby agrees that such Holder shall
not sell or otherwise 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, of any common stock (or other securities) of the Company held by
the Holder (other than those included in the registration) during the one hundred eighty (180) day period following the effective date of the registration statement for the Company’s initial public offering filed under the Securities Act
(or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports and (ii) analyst recommendations and opinions, including,
but not limited to, the restrictions contained in NASD Rule 2711(f)(4) or NYSE Rule 472(f)(4), or any successor provisions or amendments thereto). The obligations described in this section shall not apply to a registration relating solely to
employee benefit plans on Form S-1 or Form S-8 or similar forms that may be promulgated in the future, or a registration relating solely to a transaction on Form S-4 or similar forms that may be promulgated in the future. The Company may impose stop-transfer instructions and may stamp each certificate with a legend as substantially set forth in Section 5(e) with respect
to the shares of common stock (or other securities) subject to the foregoing restriction until the end of such one hundred eighty (180) day (or other) period. The Holder agrees to execute a market
stand-off agreement with the underwriters in the offering in customary form consistent with the provisions of this section. 

  
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 11. Representations and Warranties of the Holder. By acceptance of this Warrant,
the Holder represents and warrants to the Company as follows: 
 (a) No Registration. The Holder understands that the
Securities have not been, and will not be, registered under the Securities Act by reason of a specific exemption from the registration provisions of the Securities Act, the availability of which depends upon, among other things, the bona fide nature
of the investment intent and the accuracy of the Holder’s representations as expressed herein or otherwise made pursuant hereto. 
 (b)
Investment Intent. The Holder is acquiring the Securities for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in connection with, any distribution thereof. The Holder has no present
intention of selling, granting any participation in, or otherwise distributing the Securities, nor does it have any contract, undertaking, agreement or arrangement for the same. 

(c) Investment Experience. The Holder has substantial experience in evaluating and investing in private placement transactions
of securities in companies similar to the Company, and has such knowledge and experience in financial or business matters so that it is capable of evaluating the merits and risks of its investment in the Company and protecting its own interests.

 (d) Speculative Nature of Investment. The Holder understands and acknowledges that the Company has a limited financial and
operating history and that its investment in the Company is highly speculative and involves substantial risks. The Holder can bear the economic risk of its investment and is able, without impairing its financial condition, to hold the Securities for
an indefinite period of time and to suffer a complete loss of its investment. 
 (e) Access to Data. The Holder has had an
opportunity to ask questions of officers of the Company, which questions were answered to its satisfaction. The Holder believes that it has received all the information that it considers necessary or appropriate for deciding whether to acquire the
Securities. The Holder understands that any such discussions, as well as any information issued by the Company, were intended to describe certain aspects of the Company’s business and prospects, but were not necessarily a thorough or exhaustive
description. The Holder acknowledges that any business plans prepared by the Company have been, and continue to be, subject to change and that any projections included in such business plans or otherwise are necessarily speculative in nature, and it
can be expected that some or all of the assumptions underlying the projections will not materialize or will vary significantly from actual results. 

(f) Accredited Investor. The Holder is an “accredited investor” within the meaning of Regulation D, Rule 501(a),
promulgated by the Securities and Exchange Commission and agrees to submit to the Company such further assurances of such status as may be reasonably requested by the Company. 

(g) Residency. The residency of the Holder (or, in the case of a partnership, corporation or other business entity, such
entity’s principal place of business) is correctly set forth on the signature page hereto. 
 (h) Restrictions on
Resales. The Holder acknowledges that the Securities must be held indefinitely unless subsequently registered under the Securities Act or an exemption from such registration is available. The Holder is aware of the provisions of Rule 144
promulgated under the Securities Act, which permit resale of shares purchased in a private placement subject to the satisfaction of certain conditions, which may include, among other things, the availability of certain current public information
about the Company; the resale occurring not less than a specified period after a party has 

  
 - 10 - 

 
purchased and paid for the security to be sold; the number of shares being sold during any three-month period not exceeding specified limitations; the sale being effected through a
“broker’s transaction,” a transaction directly with a “market maker” or a “riskless principal transaction” (as those terms are defined in the Securities Act or the Securities Exchange Act of 1934, as amended, and
the rules and regulations promulgated thereunder); and the filing of a Form 144 notice, if applicable. The Holder acknowledges and understands that the Company may not be satisfying the current public information requirement of Rule 144 at the time
the Holder wishes to sell the Securities and that, in such event, the Holder may be precluded from selling the Securities under Rule 144 even if the other applicable requirements of Rule 144 have been satisfied. The Holder acknowledges that, in the
event the applicable requirements of Rule 144 are not met, registration under the Securities Act or an exemption from registration will be required for any disposition of the Securities. The Holder understands that, although Rule 144 is not
exclusive, the Securities and Exchange Commission has expressed its opinion that persons proposing to sell restricted securities received in a private offering other than in a registered offering or pursuant to Rule 144 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 the brokers who participate in the transactions do so at their own risk. 

(i) No Public Market. The Holder understands and acknowledges that no public market now exists for any of the securities issued
by the Company and that the Company has made no assurances that a public market will ever exist for the Company’s securities. 
 (j)
Brokers and Finders. The Holder has not engaged any brokers, finders or agents in connection with the Securities, and the Company has not incurred nor will incur, directly or indirectly, as a result of any action taken by the Holder,
any liability for brokerage or finders’ fees or agents’ commissions or any similar charges in connection with the Securities. 

(k) Legal Counsel. The Holder has had the opportunity to review this Warrant, the exhibits and schedules attached hereto and the
transactions contemplated by this Warrant with its own legal counsel. The Holder is not relying on any statements or representations of the Company or its agents for legal advice with respect to this investment or the transactions contemplated by
this Warrant. 
 (l) Tax Advisors. The Holder has reviewed with its own tax advisors the U.S. federal, state and local and non-U.S. tax consequences of this investment and the transactions contemplated by this Warrant. With respect to such matters, the Holder relies solely on any such advisors and not on any statements or
representations of the Company or any of its agents, written or oral. The Holder understands that it (and not the Company) shall be responsible for its own tax liability that may arise as a result of this investment and the transactions contemplated
by this Warrant. 
 12. Code Section 409A. Under Code Section 409A, a warrant that vests after
                     (or that vested on or prior to such date but which was materially modified after
                    ) that was granted with a per Share exercise price that is determined by the Internal Revenue Service (the
“IRS”) to be less than the fair market value of a Share on the date of grant (a “discount warrant”) may be considered “deferred compensation.” A warrant that is a “discount warrant”
may result in (i) income recognition by the holder of the warrant prior to the exercise of the warrant, (ii) an additional twenty percent (20%) federal income tax, and (iii) potential penalty and interest charges. The “discount
warrant” may also result in additional state income, penalty and interest tax to the holder of the warrant. Holder acknowledges that the Company cannot guarantee and has not guaranteed that the IRS will agree that the per Share exercise price
of this Warrant equals or exceeds the fair market value of a Share on the date of grant in a later examination. Holder agrees that if the IRS determines that the Warrant was granted with a per Share exercise price that was less than the fair market
value of a Share on the date of grant, Holder will be solely responsible for Holder’s costs related to such a determination. 

  
 - 11 - 

 13. Miscellaneous. 

(a) Amendments. Except as expressly provided herein, neither this Warrant nor any term hereof may be amended, waived, discharged
or terminated other than by a written instrument referencing this Warrant and signed by the Company and the holders of warrants representing not less than a majority of the Shares issuable upon exercise of any and all outstanding Common Warrants,
which majority does not need to include the consent of the Holder. Any amendment, waiver, discharge or termination effected in accordance with this Section 13(a) shall be binding upon each holder of the Common Warrants, each future holder of
such Common Warrants and the Company; provided, however, that no special consideration or inducement may be given to any such holder in connection with such consent that is not given ratably to all such holders, and that such amendment
must apply to all such holders equally and ratably in accordance with the number of shares of Common Stock issuable upon exercise of the Common Warrants. The Company shall promptly give notice to all holders of Common Warrants of any amendment
effected in accordance with this Section 13(a). 
 (b) Waivers. No waiver of any single breach or default shall be deemed
a waiver of any other breach or default theretofore or thereafter occurring. 
 (c) Notices. All notices and other
communications required or permitted hereunder shall be in writing and shall be mailed by registered or certified mail, postage prepaid, sent by facsimile or electronic mail (if to the Holder) or otherwise delivered by hand, messenger or courier
service addressed: 
 (i) if to the Holder, to the Holder at the Holder’s address, facsimile number or electronic mail address as shown
in the Company’s records, as may be updated in accordance with the provisions hereof, or until any such Holder so furnishes an address, facsimile number or electronic mail address to the Company, then to and at the address, facsimile number or
electronic mail address of the last holder of this Warrant for which the Company has contact information in its records; or 
 (ii) if to
the Company, to the attention of the President or Chief Financial Officer of the Company at the Company’s address as shown on the signature page hereto, or at such other current address as the Company shall have furnished to the Holder, with a
copy (which shall not constitute notice) to                             ,
                        . 

Each such notice or other communication shall for all purposes of this Warrant be treated as effective or having been given (i) if
delivered by hand, messenger or courier service, when delivered, or (ii) if sent by mail, at the earlier of its receipt or 72 hours after the same has been deposited in a regularly-maintained receptacle for the deposit of the United States
mail, addressed and mailed as aforesaid, or (iii) if sent by facsimile, upon confirmation of facsimile transfer or, if sent by electronic mail, upon confirmation of delivery when directed to the relevant electronic mail address. In the event of
any conflict between the Company’s books and records and this Warrant or any notice delivered hereunder, the Company’s books and records will control absent fraud or error. 

(d) Governing Law. This Warrant and all actions arising out of or in connection with this Warrant shall be governed by and
construed in accordance with the laws of the State of California, without regard to the conflicts of law provisions of the State of California, or of any other state. 

(e) Jurisdiction and Venue. Each of the Holder and the Company irrevocably consents to the exclusive jurisdiction and venue of
any court within San Mateo County, State of California, in connection with any matter based upon or arising out of this Warrant or the matters contemplated herein, and agrees that process may be served upon them in any manner authorized by the laws
of the State of California for such persons. 

  
 - 12 - 

 (f) Titles and Subtitles. The titles and subtitles used in this Warrant are used
for convenience only and are not to be considered in construing or interpreting this Warrant. All references in this Warrant to sections, paragraphs and exhibits shall, unless otherwise provided, refer to sections and paragraphs hereof and exhibits
attached hereto. 
 (g) Severability. If any provision of this Warrant becomes or is declared by a court of competent
jurisdiction to be illegal, unenforceable or void, portions of such provision, or such provision in its entirety, to the extent necessary, shall be severed from this Warrant, and such illegal, unenforceable or void provision shall be replaced with a
valid and enforceable provision that will achieve, to the extent possible, the same economic, business and other purposes of the illegal, unenforceable or void provision. The balance of this Warrant shall be enforceable in accordance with its terms.

 (h) Waiver of Jury Trial. EACH OF THE HOLDER AND THE COMPANY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ANY AND ALL
RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATED TO THIS WARRANT. If the waiver of jury trial set forth in this paragraph is not enforceable, then any claim or cause of
action arising out of or relating to this Warrant shall be settled by judicial reference pursuant to California Code of Civil Procedure Section 638 et seq. before a referee sitting without a jury, such referee to be mutually acceptable
to the parties or, if no agreement is reached, by a referee appointed by the Presiding Judge of the California Superior Court for San Mateo County. This paragraph shall not restrict the Holder or the Company from exercising remedies under the
Uniform Commercial Code or from exercising pre-judgment remedies under applicable law. 
 (i)
California Corporate Securities Law. THE SALE OF THE SECURITIES THAT ARE THE SUBJECT OF THIS WARRANT HAS NOT BEEN QUALIFIED WITH THE COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA AND THE ISSUANCE OF SUCH SECURITIES OR THE
PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION THEREFOR PRIOR TO SUCH QUALIFICATION IS UNLAWFUL, UNLESS THE SALE OF SECURITIES IS EXEMPT FROM QUALIFICATION BY SECTION 25100, 25102, OR 25105 OF THE CALIFORNIA CORPORATIONS CODE. THE RIGHTS OF ALL
PARTIES TO THIS WARRANT ARE EXPRESSLY CONDITIONED UPON THE QUALIFICATION BEING OBTAINED, UNLESS THE SALE IS SO EXEMPT. 
 (j) Rights
and Obligations Survive Exercise of the Warrant. Except as otherwise provided herein, the rights and obligations of the Company and the Holder under this Warrant shall survive exercise of this Warrant. 

(k) Entire Agreement. Except as expressly set forth herein, this Warrant (including the exhibits attached hereto) constitutes
the entire agreement and understanding of the Company and the Holder with respect to the subject matter hereof and supersedes all prior agreements and understandings relating to the subject matter hereof. 

(signature page follows) 

  
 - 13 - 

 The Company and the Holder sign this Warrant as of the date stated on the first page. 

 

			
	SUTRO BIOPHARMA, INC.

 
			
		
	By:	 	 

 
			
		
	Name:	 	 

 
			
		
	Title:	 	 

 
			
		
	Address:	 	 
		
		 	 

  

			
	AGREED AND ACKNOWLEDGED,
	
	                                   
         
	
	   

	
	Address:
	
	 
	
	Fax number:

			
		
	Email address:	 	 

 (Signature Page to Warrant to Purchase Shares Common Stock of Sutro Biopharma, Inc.) 

 EXHIBIT A 

NOTICE OF EXERCISE 
  

			
	TO:	  	    SUTRO BIOPHARMA, INC. (the “Company”)
		
	Attention:	  	    President

  

	(1)	Exercise. The undersigned elects to purchase the following pursuant to the terms of the attached warrant: 

  

					
		 	Number of shares:	  	 
			
		 	Type of security:	  	 

  

	(2)	Method of Exercise. The undersigned elects to exercise the attached warrant pursuant to: 

  

					
		 	☐	  	A cash payment, and tenders herewith payment of the purchase price for such shares in full, together with all applicable transfer taxes, if any.
			
		 	☐	  	The net issue exercise provisions of Section 2(b) of the attached warrant.

  

	(3)	Conditional Exercise. Is this a conditional exercise pursuant to Section 2(e): 

  

											
						
		 	☐	  	Yes	  	☐	  	No	  	
		
		 	If “Yes,” indicate the applicable condition:
		
		 	 

  

	(4)	Stock Certificate. Please issue a certificate or certificates representing the shares in the name of: 

  

									
					
		 	☐	  	The undersigned	 		  	
					
		 	☐	  	Other—Name:	 		  	 
					
		 		  	Address:      	 		  	 
					
		 		  		 		  	 

  

	(5)	Unexercised Portion of the Warrant. Please issue a new warrant for the unexercised portion of the attached warrant in the name of: 

 

									
					
		 	☐	  	The undersigned	 		  	
					
		 	☐	  	Other—Name:	 		  	 
					
		 		  	Address:      	 		  	 
					
		 		  		 		  	 
					
		 	☐	  	Not applicable	 		  	

  
 A-1 

	(6)	Investment Intent. The undersigned represents and warrants that the aforesaid shares are being acquired for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in
connection with, the distribution thereof, and that the undersigned has no present intention of selling, granting any participation in, or otherwise distributing the shares, nor does it have any contract, undertaking, agreement or arrangement for
the same, and all representations and warranties of the undersigned set forth in Section 11 of the attached warrant are true and correct as of the date hereof. 

 

	(7)	Investment Representation Statement and Market Stand-Off Agreement. The undersigned has executed, and delivers herewith, an Investment Representation Statement and Market Stand-Off Agreement in a form substantially similar to the form attached to the warrant as Exhibit A-1. 

 

	(8)	Consent to Receipt of Electronic Notice. Subject to the limitations set forth in Delaware General Corporation Law §232(e), the undersigned consents to the delivery of any notice to stockholders given by the
Company under the Delaware General Corporation Law or the Company’s certificate of incorporation or bylaws by (i) facsimile telecommunication to the facsimile number provided below (or to any other facsimile number for the undersigned in
the Company’s records), (ii) electronic mail to the electronic mail address provided below (or to any other electronic mail address for the undersigned in the Company’s records), (iii) posting on an electronic network together with
separate notice to the undersigned of such specific posting or (iv) any other form of electronic transmission (as defined in the Delaware General Corporation Law) directed to the undersigned. This consent may be revoked by the undersigned by
written notice to the Company and may be deemed revoked in the circumstances specified in Delaware General Corporation Law §232. 

  

	
	(Print name of the warrant holder)
	
	 
	(Signature)
	
	 
	(Name and title of signatory, if applicable)
	
	 
	(Date)
	
	 
	(Fax number)
	
	 
	(Email address)

 (Signature page to the Notice of Exercise) 

  
 A-2 

 EXHIBIT A-l 

INVESTMENT REPRESENTATION STATEMENT 

AND 
 MARKET STAND-OFF AGREEMENT 
  

							
	INVESTOR:	 		 	                                      
                                         
                                         
                                         
           	 	
				
	COMPANY:	 		 	SUTRO BIOPHARMA, INC.	 	
			
	SECURITIES:	 		 	THE WARRANT ISSUED ON                              (THE
“WARRANT”) AND THE SECURITIES ISSUED OR ISSUABLE UPON EXERCISE THEREOF
				
	DATE:	 		 	                                      
                   	 	

 In connection with the purchase or acquisition of the above-listed Securities, the undersigned Investor
represents and warrants to, and agrees with, the Company as follows: 
 1. No Registration. The Investor understands that the
Securities have not been, and will not be, registered under the Securities Act of 1933, as amended (the “Securities Act”), by reason of a specific exemption from the registration provisions of the Securities Act, the
availability of which depends upon, among other things, the bona fide nature of the investment intent and the accuracy of the Investor’s representations as expressed herein or otherwise made pursuant hereto. 

2. Investment Intent. The Investor is acquiring the Securities for investment for its own account, not as a nominee or agent, and not
with a view to, or for resale in connection with, any distribution thereof. The Investor has no present intention of selling, granting any participation in, or otherwise distributing the Securities, nor does it have any contract, undertaking,
agreement or arrangement for the same. 
 3. Investment Experience. The Investor has substantial experience in evaluating and
investing in private placement transactions of securities in companies similar to the Company, and has such knowledge and experience in financial or business matters so that it is capable of evaluating the merits and risks of its investment in the
Company and protecting its own interests. 
 4. Speculative Nature of Investment. The Investor understands and acknowledges that the
Company has a limited financial and operating history and that its investment in the Company is highly speculative and involves substantial risks. The Investor can bear the economic risk of its investment and is able, without impairing its financial
condition, to hold the Securities for an indefinite period of time and to suffer a complete loss of its investment. 
 5. Access to
Data. The Investor has had an opportunity to ask questions of officers of the Company, which questions were answered to its satisfaction. The Investor believes that it has received all the information that it considers necessary or appropriate
for deciding whether to acquire the Securities. The Investor understands that any such discussions, as well as any information issued by the Company, were intended to describe certain aspects of the Company’s business and prospects, but were
not necessarily a thorough or exhaustive description. The Investor acknowledges that any business plans prepared by the Company have been, and continue to be, subject to change and that any projections included in such business plans or otherwise
are necessarily speculative in nature, and it can be expected that some or all of the assumptions underlying the projections will not materialize or will vary significantly from actual results. 

  
 A-1-1 

 6. Accredited Investor. The Investor is an “accredited investor” within the
meaning of Regulation D, Rule 501(a), promulgated by the Securities and Exchange Commission and agrees to submit to the Company such further assurances of such status as may be reasonably requested by the Company. 

7. Residency. The residency of the Investor (or, in the case of a partnership, corporation or other business entity, such entity’s
principal place of business) is correctly set forth on the signature page hereto. 
 8. Restrictions on Resales. The Investor
acknowledges that the Securities must be held indefinitely unless subsequently registered under the Securities Act or an exemption from such registration is available. The Investor is aware of the provisions of Rule 144 promulgated under the
Securities Act, which permit resale of shares purchased in a private placement subject to the satisfaction of certain conditions, which may include, among other things, the availability of certain current public information about the Company; the
resale occurring not less than a specified period after a party has purchased and paid for the security to be sold; the number of shares being sold during any three-month period not exceeding specified limitations; the sale being effected through a
“broker’s transaction,” a transaction directly with a “market maker” or a “riskless principal transaction” (as those terms are defined in the Securities Act or the Securities Exchange Act of 1934, as amended, and
the rules and regulations promulgated thereunder); and the filing of a Form 144 notice, if applicable. The Investor acknowledges and understands that the Company may not be satisfying the current public information requirement of Rule 144 at the
time the Investor wishes to sell the Securities and that, in such event, the Investor may be precluded from selling the Securities under Rule 144 even if the other applicable requirements of Rule 144 have been satisfied. The Investor understands and
acknowledges that, in the event the applicable requirements of Rule 144 are not met, registration under the Securities Act or an exemption from registration will be required for any disposition of the Securities. The Investor understands that,
although Rule 144 is not exclusive, the Securities and Exchange Commission has expressed its opinion that persons proposing to sell restricted securities received in a private offering other than in a registered offering or pursuant to Rule 144 will
have a substantial burden of proof in establishing that an exemption from registration is available for those offers or sales and that those persons and the brokers who participate in the transactions do so at their own risk. 

9. No Public Market. The Holder understands and acknowledges that no public market now exists for any of the securities issued by the
Company and that the Company has made no assurances that a public market will ever exist for the Company’s securities. 
 10.
Brokers and Finders. The Investor has not engaged any brokers, finders or agents in connection with the Securities, and the Company has not incurred nor will incur, directly or indirectly, as a result of any action taken by the Investor, any
liability for brokerage or finders’ fees or agents’ commissions or any similar charges in connection with the Securities. 
 11.
Legal Counsel. The Investor has had the opportunity to review the Warrant, the exhibits and schedules attached thereto and the transactions contemplated by the Warrant with its own legal counsel. The Investor is not relying on any statements
or representations of the Company or its agents for legal advice with respect to this investment or the transactions contemplated by the Warrant. 

12. Tax Advisors. The Investor has reviewed with its own tax advisors the U.S. federal, state and local and non-U.S. tax consequences of this investment and the transactions contemplated by the Warrant. With respect to such matters, the Investor relies solely on such advisors and not on any statements or representations
of the Company or any of its agents, written or oral. The Investor understands that it (and not the Company) shall be responsible for its own tax liability that may arise as a result of this investment or the transactions contemplated by the
Warrant. 

  
 A-1-2 

 13. Market Stand-off. The Investor agrees that the
Investor shall not sell or otherwise 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, of any common stock (or other securities) of the
Company held by the Investor (other than those included in the registration) during the one hundred eighty (180) day period following the effective date of the registration statement for the Company’s initial public offering filed under
the Securities Act (or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports and (ii) analyst recommendations and
opinions, including, but not limited to, the restrictions contained in NASD Rule 2711(f)(4) or NYSE Rule 472(f)(4), or any successor provisions or amendments thereto. The obligations described in this section shall not apply to a registration
relating solely to employee benefit plans on Form S-1 or Form S-8 or similar forms that may be promulgated in the future, or a registration relating solely to a
transaction on Form S-4 or similar forms that may be promulgated in the future. The Company may impose stop-transfer instructions and may stamp each certificate with a legend with respect to the shares of
common stock (or other securities) subject to the foregoing restriction until the end of such one hundred eighty (180) day (or other) period. The Investor agrees to execute a market stand-off agreement
with the relevant underwriters in customary form consistent with the provisions of this section. 
 14. Company’s Right of First
Refusal. The undersigned acknowledges and agrees to be bound, or to continue to be bound, by the Company’s right of first refusal over the securities issued or issuable upon the exercise of the Warrant, as provided for in Section 5(c)
of the Warrant. 
 (signature page follows) 

  
 A-1-3 

 The Investor is signing this Investment Representation Statement and Market Stand-Off Agreement on the date first written above. 
  

	
	INVESTOR
	
	
	(Print name of the investor)
	
	 
	(Signature)
	
	 
	(Name and title of signatory, if applicable)
	
	 
	(Street address)
	
	 
	(City, state and ZIP)

  
 A-1-4 

 EXHIBIT B 

ASSIGNMENT FORM 
  

					
	ASSIGNOR:	 	                                      
                                         
                                         
                                         
                                  	  	
			
	COMPANY:	 	SUTRO BIOPHARMA, INC.	  	
		
	WARRANT:	 	THE WARRANT TO PURCHASE SHARES OF COMMON STOCK ISSUED ON
                                 (THE “WARRANT”)
			
	DATE:	 	                                      
                      	  	

  

	(1)	Assignment. The undersigned registered holder of the Warrant (“Assignor”) assigns and transfers to the assignee named below (“Assignee”) all of the rights of
Assignor under the Warrant, with respect to the number of shares set forth below: 

  

			
	
  Name of Assignee:                
                                         
                                         
                                         
                                         
                            

	
	
  Address of Assignee:               
                                         
                                         
                                         
                                         
                        

	
	
                       
                                         
                                         
                                         
                                         
                                         
            

	
	
  Number of Shares Assigned:             
                                         
                                         
                                         
                                         
            

 and does irrevocably constitute and appoint
                                     as attorney to make such
transfer on the books of Sutro Biopharma, Inc. (the “Company”), maintained for the purpose, with full power of substitution in the premises. 
  

	(2)	Obligations of Assignee. Assignee agrees to take and hold the Warrant and any shares of stock to be issued upon exercise of the rights thereunder (the “Securities”) subject to, and to be
bound by, the terms and conditions set forth in the Warrant to the same extent as if Assignee were the original holder thereof. 

  

	(3)	Investment Intent. Assignee represents and warrants that the Securities are being acquired for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in connection with,
the distribution thereof, and that Assignee has no present intention of selling, granting any participation in, or otherwise distributing the shares, nor does it have any contract, undertaking, agreement or arrangement for the same, and all
representations and warranties set forth in Section 11 of the Warrant are true and correct as to Assignee as of the date hereof. 

  

	(4)	Investment Representation Statement and Market Stand-Off Agreement. Assignee has executed, and delivers herewith, an Investment Representation Statement and Market Stand-Off Agreement in a form substantially similar to the form attached to the Warrant as Exhibit A-1. 

Assignor and Assignee are signing this Assignment Form on the date first set forth above. 

  
 B-1 

					
	ASSIGNOR	 		 	ASSIGNEE
			
	   
	 		 	   

	(Print name of Assignor)	 		 	(Print name of Assignee)
			
	 	 		 	 
	(Signature of Assignor)	 		 	(Signature of Assignee)
			
	 	 		 	 
	(Print name of signatory, if applicable)	 		 	(Print name of signatory, if applicable)
			
	 	 		 	 
	(Print title of signatory, if applicable)	 		 	(Print title of signatory, if applicable)
			
		 		 	
	Address:	 		 	Address:
			
	 	 		 	 
			
	 	 		 	 

  
 B-2Forms of Warrant to Purchase Series C Preferred Stock

 EXHIBIT 4.4 

THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER
THE SECURITIES LAWS OF ANY STATE. THESE SECURITIES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED EXCEPT AS PERMITTED UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS IN ACCORDANCE WITH APPLICABLE REGISTRATION
REQUIREMENTS OR AN EXEMPTION THEREFROM. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE ISSUER THAT SUCH OFFER, SALE, TRANSFER, PLEDGE OR HYPOTHECATION OTHERWISE COMPLIES WITH THE ACT AND ANY
APPLICABLE STATE SECURITIES LAWS. THIS WARRANT MUST BE SURRENDERED TO THE COMPANY OR ITS TRANSFER AGENT AS A CONDITION PRECEDENT TO THE SALE, TRANSFER, PLEDGE OR HYPOTHECATION OF ANY INTEREST IN ANY OF THE SECURITIES REPRESENTED HEREBY. 

WARRANT TO PURCHASE SHARES OF PREFERRED STOCK 

of 
 SUTRO BIOPHARMA, INC.

 Dated as of
                         

Void after the date specified in Section 8 
  

			
	No.	  	 Warrant to Purchase

Shares of
 Preferred
Stock
 (subject to adjustment)

 THIS CERTIFIES THAT, in consideration of the sum of
                            
($            ) and for other value received,                 , or its registered assigns (the
“Holder”), is entitled, subject to the provisions and upon the terms and conditions set forth herein, to purchase from Sutro Biopharma, Inc., a Delaware corporation (the “Company”), Shares (as defined
below), in the amounts, at such times and at the price per share set forth in Section 1. The term “Warrant” as used herein shall include this Warrant and any warrants delivered in substitution or exchange therefor as provided herein.
This Warrant is issued in connection with the transactions described in the Note and Warrant Purchase Agreement, dated as of
                            , by and among the Company and the purchasers described therein (the
“Purchase Agreement”). 
 The following is a statement of the rights of the Holder and the conditions to which this
Warrant is subject, and to which Holder, by acceptance of this Warrant, agrees: 
 1. Number and Price of Shares; Exercise Period.

 (a) Definition of Shares. “Shares” shall mean the class and series of preferred stock issued by
the Company to investors in a Qualified Financing (as defined below) that occurs prior to the earlier of (i)
                             or (ii) the expiration of this Warrant. If no Qualified Financing
occurs prior to the earlier of (i)                      or (ii) the expiration of this Warrant, “Shares” shall
mean Series B Preferred Stock of the Company. A “Qualified Financing” is a transaction or series of transactions pursuant to which the Company issues and sells shares of its preferred stock, with the principal purpose of
raising capital, for aggregate gross proceeds of at least $                     (including any and all amounts received upon the conversion or
cancellation of indebtedness). 
 (b) Number of Shares. Subject to any previous exercise of the Warrant, the Holder shall have
the right to purchase up to the number of Shares that equals the quotient obtained by dividing (x)
$                         by (y) the Exercise Price (as defined below), prior to (or in connection with) the
expiration of this Warrant as provided in Section 8. 

 (c) Exercise Price. The exercise price per Share shall be equal to the lowest price
per share of the Shares issued in a Qualified Financing; provided, however, that if no Qualified Financing has occurred on or prior to the earlier of (i) September 20, 2011 or (ii) the expiration of this Warrant, and if
the Shares subject to this Warrant are deemed to be Series B Preferred Stock of the Company in accordance with Section 1(a), the exercise price for the Shares subject to this Warrant shall be
                 per Share, subject to adjustment pursuant hereto (the “Exercise Price”). 

(d) Exercise Period. This Warrant shall be exercisable, in whole or in part, after the earlier of (i) the closing date of a
Qualified Financing or (ii)                              and prior to (or in connection with) the
expiration of this Warrant as set forth in Section 8. 
 2. Exercise of the Warrant. 

(a) Exercise. The purchase rights represented by this Warrant may be exercised at the election of the Holder, in whole or in
part, in accordance with Section 1, by: 
 (i) the tender to the Company at its principal office (or such other office or agency as the
Company may designate) of a notice of exercise in the form of Exhibit A (the “Notice of Exercise”), duly completed and executed by or on behalf of the Holder, together with the surrender of this Warrant; and 

(ii) the payment to the Company of an amount equal to (x) the Exercise Price multiplied by (y) the number of Shares being
purchased, by wire transfer or certified, cashier’s or other check acceptable to the Company and payable to the order of the Company. 

(b) Net Issue Exercise. In lieu of exercising this Warrant pursuant to Section 2(a)(ii), if the fair market value of one
Share is greater than the Exercise Price (at the date of calculation as set forth below), the Holder may elect to receive a number of Shares equal to the value of this Warrant (or of any portion of this Warrant being canceled) by surrender of this
Warrant at the principal office of the Company (or such other office or agency as the Company may designate) together with a properly completed and executed Notice of Exercise reflecting such election, in which event the Company shall issue to the
Holder that number of Shares computed using the following formula: 
  

									
		  	X	  	=	  	    Y (A-B)    	  	
		  		  		  	        A	  	

 Where: 
  

							
		 	X	  	=	  	The number of Shares to be issued to the Holder
				
		 	Y	  	=	  	The number of Shares purchasable under this Warrant or, if only a portion of the Warrant is being exercised, the portion of the Warrant being canceled (at the date of such calculation)
				
		 	A	  	=	  	The fair market value of one Share (at the date of such calculation)
				
		 	B	  	=	  	The Exercise Price (as adjusted to the date of such calculation)

  
 - 2 - 

 For purposes of the calculation above, the fair market value of one Share shall be determined by
the Board of Directors of the Company, acting in good faith; provided, however, that: 
 (i) where a public market exists for
the Company’s common stock at the time of such exercise, the fair market value per Share shall be the product of (x) the average of the closing bid and asked prices of the common stock or the closing price quoted on the national securities
exchange on which the common stock is listed as published in the Wall Street Journal, as applicable, for the ten (10) trading day period ending five (5) trading days prior to the date of determination of fair market value and
(y) the number of shares of common stock into which each Share is convertible at the time of such exercise, as applicable; and 
 (ii)
if the Warrant is exercised in connection with the Company’s initial public offering of common stock, the fair market value per Share shall be the product of (x) the per share offering price to the public of the Company’s initial
public offering and (y) the number of shares of common stock into which each Share is convertible at the time of such exercise, as applicable. 

(c) Stock Certificates. The rights under this Warrant shall be deemed to have been exercised and the Shares issuable upon such
exercise shall be deemed to have been issued immediately prior to the close of business on the date this Warrant is exercised in accordance with its terms, and the person entitled to receive the Shares issuable upon such exercise shall be treated
for all purposes as the holder of record of such Shares as of the close of business on such date. As promptly as reasonably practicable on or after such date, the Company shall issue and deliver to the person or persons entitled to receive the same
a certificate or certificates for that number of shares issuable upon such exercise. In the event that the rights under this Warrant are exercised in part and have not expired, the Company shall execute and deliver a new Warrant reflecting the
number of Shares that remain subject to this Warrant. 
 (d) No Fractional Shares or Scrip. No fractional shares or scrip
representing fractional shares shall be issued upon the exercise of the rights under this Warrant. In lieu of such fractional share to which the Holder would otherwise be entitled, the Company shall make a cash payment equal to the Exercise Price
multiplied by such fraction. 
 (e) Reservation of Stock. The Company agrees during the term the rights under this Warrant
are exercisable to reserve and keep available from its authorized and unissued shares of preferred stock for the purpose of effecting the exercise of this Warrant such number of shares (and shares of common stock for issuance on conversion of such
shares) as shall from time to time be sufficient to effect the exercise of the rights under this Warrant; and if at any time the number of authorized but unissued shares of preferred stock (and shares of common stock for issuance on conversion of
such shares) shall not be sufficient for purposes of the exercise of this Warrant in accordance with its terms and the conversion of the Shares, without limitation of such other remedies as may be available to the Holder, the Company will use its
best efforts to take such corporate action as may be necessary to increase its authorized and unissued shares of its preferred stock (and shares of common stock for issuance on conversion of such shares) to a number of shares as shall be sufficient
for such purposes. 
 3. Replacement of the Warrant. Subject to the receipt of evidence reasonably satisfactory to the Company
of the loss, theft, destruction or mutilation of this Warrant and, in the case of loss, theft or destruction, on delivery of an indemnity agreement reasonably satisfactory in form and substance to the Company or, in the case of mutilation, on
surrender and cancellation of this Warrant, the Company at the expense of the Holder shall execute and deliver, in lieu of this Warrant, a new warrant of like tenor and amount. 

  
 - 3 - 

 4. Transfer of the Warrant. 

(a) Warrant Register. The Company shall maintain a register (the “Warrant Register”) containing the name
and address of the Holder or Holders. Until this Warrant is transferred on the Warrant Register in accordance herewith, the Company may treat the Holder as shown on the Warrant Register as the absolute owner of this Warrant for all purposes,
notwithstanding any notice to the contrary. Any Holder of this Warrant (or of any portion of this Warrant) may change its address as shown on the Warrant Register by written notice to the Company requesting a change. 

(b) Warrant Agent. The Company may appoint an agent for the purpose of maintaining the Warrant Register referred to in
Section 4(a), issuing the Shares or other securities then issuable upon the exercise of the rights under this Warrant, exchanging this Warrant, replacing this Warrant or conducting related activities. 

(c) Transferability of the Warrant. Subject to the provisions of this Warrant with respect to compliance with the Securities Act
of 1933, as amended (the “Securities Act”) and limitations on assignments and transfers, including without limitation compliance with the restrictions on transfer set forth in Section 5, title to this Warrant may be
transferred by endorsement (by the transferor and the transferee executing the assignment form attached as Exhibit B (the “Assignment Form”)) and delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery. 
 (d) Exchange of the Warrant upon a Transfer. On surrender of this Warrant (and a properly
endorsed Assignment Form) for exchange, subject to the provisions of this Warrant with respect to compliance with the Securities Act and limitations on assignments and transfers, the Company shall issue to or on the order of the Holder a new warrant
or warrants of like tenor, in the name of the Holder or as the Holder (on payment by the Holder of any applicable transfer taxes) may direct, for the number of shares issuable upon exercise hereof, and the Company shall register any such transfer
upon the Warrant Register. This Warrant (and the securities issuable upon exercise of the rights under this Warrant) must be surrendered to the Company or its warrant or transfer agent, as applicable, as a condition precedent to the sale, pledge,
hypothecation or other transfer of any interest in any of the securities represented hereby. 
 (e) Taxes. In no event shall
the Company be required to pay any tax which may be payable in respect of any transfer involved in the issue and delivery of any certificate in a name other than that of the Holder, and the Company shall not be required to issue or deliver any such
certificate unless and until the person or persons requesting the issue thereof shall have paid to the Company the amount of such tax or shall have established to the satisfaction of the Company that such tax has been paid or is not payable. 

5. Restrictions on Transfer of the Warrant and Shares; Compliance with Securities Laws. By acceptance of this Warrant, the
Holder agrees to comply with the following: 
 (a) Restrictions on Transfers. Subject to Section 5(b), this Warrant may
not be transferred or assigned in whole or in part without the Company’s prior written consent (which shall not be unreasonably withheld), and any attempt by Holder to transfer or assign any rights, duties or obligations that arise under this
Warrant without such permission shall be void. Any transfer of this Warrant or the Shares or the shares of common stock issuable upon conversion of the Shares (the “Securities”) must be in compliance with all applicable
federal and state securities laws. The Holder agrees not to make any sale, assignment, transfer, pledge or other disposition of all or any portion of the Securities, or any beneficial interest therein, unless and until the transferee thereof has
agreed in writing for the benefit of the Company to take and hold such Securities subject to, and to be bound by, the terms and conditions set forth in this Warrant to the same extent as if the transferee were the original Holder hereunder, and 

(i) there is then in effect a registration statement under the Securities Act covering such proposed disposition and such disposition is made
in accordance with such registration statement, or 

  
 - 4 - 

 (ii) (A) such Holder shall have given prior written notice to the Company of such Holder’s
intention to make such disposition and shall have furnished the Company with a detailed description of the manner and circumstances of the proposed disposition, (B) the transferee shall have confirmed to the satisfaction of the Company in
writing, substantially in the form of Exhibit A-1, that the Securities are being acquired (i) solely for the transferee’s own account and not as a nominee for any other party, (ii) for
investment and (iii) not with a view toward distribution or resale, and shall have confirmed such other matters related thereto as may be reasonably requested by the Company, and (C) such Holder shall have furnished the Company, at the
Holder’s expense, with (i) an opinion of counsel, reasonably satisfactory to the Company, to the effect that such disposition will not require registration of such Securities under the Securities Act or (ii) a “no action”
letter from the Securities and Exchange Commission to the effect that the transfer of such Securities without registration will not result in a recommendation by the staff of the Securities and Exchange Commission that action be taken with respect
thereto, whereupon such Holder shall be entitled to transfer such Securities in accordance with the terms of the notice delivered by the Holder to the Company. 

(b) Permitted Transfers. Permitted transfers include (i) a transfer not involving a change in beneficial ownership, or
(ii) transactions involving the distribution without consideration of Securities by any Holder to (x) a parent, subsidiary or other affiliate of a Holder that is a corporation, (y) any of the Holder’s partners, members or other
equity owners, or retired partners or members, or to the estate of any of its partners, members or other equity owners or retired partners or members, or (z) a venture capital fund that is controlled by or under common control with one or more
general partners or managing members of, or shares the same management company with, the Holder; provided, in each case, that the Holder shall give written notice to the Company of the Holder’s intention to effect such disposition and
shall have furnished the Company with a detailed description of the manner and circumstances of the proposed disposition. 
 (c)
Investment Representation Statement. Unless the rights under this Warrant are exercised pursuant to an effective registration statement under the Securities Act that includes the Shares with respect to which the Warrant was exercised,
it shall be a condition to any exercise of the rights under this Warrant that the Holder shall have confirmed to the satisfaction of the Company in writing, substantially in the form of Exhibit A-1, that the
Shares so purchased are being acquired solely for the Holder’s own account and not as a nominee for any other party, for investment and not with a view toward distribution or resale and that the Holder shall have confirmed such other matters
related thereto as may be reasonably requested by the Company. 

  
 - 5 - 

 (d) Securities Law Legend. The Securities shall (unless otherwise permitted by the
provisions of this Warrant) be stamped or imprinted with a legend substantially similar to the following (in addition to any legend required by state securities laws): 

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR UNDER THE
SECURITIES LAWS OF CERTAIN STATES. THESE SECURITIES MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED EXCEPT AS PERMITTED UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS IN ACCORDANCE WITH APPLICABLE REGISTRATION
REQUIREMENTS OR AN EXEMPTION THEREFROM. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE ISSUER THAT SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION OTHERWISE COMPLIES WITH THE ACT AND ANY
APPLICABLE STATE SECURITIES LAWS. THIS CERTIFICATE MUST BE SURRENDERED TO THE COMPANY OR ITS TRANSFER AGENT AS A CONDITION PRECEDENT TO THE SALE, TRANSFER, PLEDGE OR HYPOTHECATION OF ANY INTEREST IN ANY OF THE SECURITIES REPRESENTED HEREBY. 

(e) Market Stand-off Legend. The Shares and common stock issued upon exercise hereof or
conversion thereof shall also be stamped or imprinted with a legend in substantially the following form: 
 THE SHARES REPRESENTED BY THIS
CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFERABILITY AND RESALE, INCLUDING A LOCK-UP PERIOD IN THE EVENT OF A PUBLIC OFFERING, AS SET FORTH IN THE WARRANT PURSUANT TO WHICH THESE SHARES WERE ISSUED, A
COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE COMPANY. 
 (f) Instructions Regarding Transfer Restrictions. The
Holder consents to the Company making a notation on its records and giving instructions to any transfer agent in order to implement the restrictions on transfer established in this Section 5. 

(g) Removal of Legend. The legend referring to federal and state securities laws identified in Section 5(d) stamped on a
certificate evidencing the Shares (and the common stock issuable upon conversion thereof) and the stock transfer instructions and record notations with respect to such securities shall be removed and the Company shall issue a certificate without
such legend to the holder of such securities if (i) such securities are registered under the Securities Act, or (ii) such holder provides the Company with an opinion of counsel reasonably acceptable to the Company to the effect that a sale
or transfer of such securities may be made without registration or qualification. 
 6. Adjustments. Subject to the expiration
of this Warrant pursuant to Section 8, the number and kind of shares purchasable hereunder and the Exercise Price therefor are subject to adjustment from time to time, as follows: 

(a) Merger or Reorganization. If at any time there shall be any reorganization, recapitalization, merger or consolidation (a
“Reorganization”) involving the Company (other than as otherwise provided for herein or as would cause the expiration of this Warrant under Section 8) in which shares of the Company’s stock are converted into or
exchanged for securities, cash or other property, then, as a part of such Reorganization, lawful provision shall be made so that the Holder shall thereafter be entitled to receive upon exercise of this Warrant, the kind and amount of securities,
cash or other property of the successor corporation resulting from such Reorganization, equivalent in value to that which a holder of the Shares deliverable upon exercise of this Warrant would have been entitled in such Reorganization if the right
to purchase the Shares hereunder had been exercised immediately prior to such Reorganization. In any such case, appropriate adjustment (as determined in good faith by the Board of Directors of the successor corporation) shall be made in the
application of the provisions of this Warrant with respect to the rights and interests of the Holder after such Reorganization to the end that the provisions of this Warrant shall be applicable after the event, as near as reasonably may be, in
relation to any shares or other securities deliverable after that event upon the exercise of this Warrant. 

  
 - 6 - 

 (b) Reclassification of Shares. If the securities issuable upon exercise of this
Warrant are changed into the same or a different number of securities of any other class or classes by reclassification, capital reorganization, conversion of all outstanding shares of the relevant class or series (other than as would cause the
expiration of this Warrant pursuant to Section 8) or otherwise (other than as otherwise provided for herein) (a “Reclassification”), then, in any such event, in lieu of the number of Shares which the Holder would
otherwise have been entitled to receive, the Holder shall have the right thereafter to exercise this Warrant for a number of shares of such other class or classes of stock that a holder of the number of securities deliverable upon exercise of this
Warrant immediately before that change would have been entitled to receive in such Reclassification, all subject to further adjustment as provided herein with respect to such other shares. 

(c) Subdivisions and Combinations. In the event that the outstanding shares of the securities issuable upon exercise of this
Warrant are subdivided (by stock split, by payment of a stock dividend or otherwise) into a greater number of shares of such securities, the number of Shares issuable upon exercise of the rights under this Warrant immediately prior to such
subdivision shall, concurrently with the effectiveness of such subdivision, be proportionately increased, and the Exercise Price shall be proportionately decreased, and in the event that the outstanding shares of the securities issuable upon
exercise of this Warrant are combined (by reclassification or otherwise) into a lesser number of shares of such securities, the number of Shares issuable upon exercise of the rights under this Warrant immediately prior to such combination shall,
concurrently with the effectiveness of such combination, be proportionately decreased, and the Exercise Price shall be proportionately increased. 

(d) Notice of Adjustments. Upon any adjustment in accordance with this Section 6, the Company shall give notice thereof to
the Holder, which notice shall state the event giving rise to the adjustment, the Exercise Price as adjusted and the number of securities or other property purchasable upon the exercise of the rights under this Warrant, setting forth in reasonable
detail the method of calculation of each. The Company shall, upon the written request of any Holder, furnish or cause to be furnished to such Holder a certificate setting forth (i) such adjustments, (ii) the Exercise Price at the time in
effect and (iii) the number of securities and the amount, if any, of other property that at the time would be received upon exercise of this Warrant. 

7. Notification of Certain Events. Prior to the expiration of this Warrant pursuant to Section 8, in the event that the
Company shall authorize: 
 (a) the issuance of any dividend or other distribution on the capital stock of the Company (other than
(i) dividends or distributions otherwise provided for in Section 6, (ii) repurchases of common stock issued to or held by employees, officers, directors or consultants of the Company or its subsidiaries upon termination of their employment
or services pursuant to agreements providing for the right of said repurchase; (iii) repurchases of common stock issued to or held by employees, officers, directors or consultants of the Company or its subsidiaries pursuant to rights of first
refusal or first offer contained in agreements providing for such rights; or (iv) repurchases of capital stock of the Company in connection with the settlement of disputes with any stockholder), whether in cash, property, stock or other
securities; 
 (b) the voluntary liquidation, dissolution or winding up of the Company; or 

  
 - 7 - 

 (c) any transaction resulting in the expiration of this Warrant pursuant to Section 8(b) or
8(c); 
 the Company shall send to the Holder of this Warrant at least ten (10) days prior written notice of the date on which a record shall be taken
for any such dividend or distribution specified in clause (a) or the expected effective date of any such other event specified in clause (b) or (c), as applicable. The notice provisions set forth in this section may be shortened or waived
prospectively or retrospectively by the consent of the holders of a majority of the Shares issuable upon exercise of the rights under the Warrants. 

8. Expiration of the Warrant. This Warrant shall expire and shall no longer be exercisable as of the earlier of: 

(a) ____ p.m., Pacific time, on
                    ; 
 (b) (i)
the acquisition of the Company by another entity by means of any transaction or series of related transactions to which the Company is a party (including, without limitation, any stock acquisition, reorganization, merger or consolidation, but
excluding any sale of stock for capital raising purposes and any transaction effected primarily for purposes of changing the Company’s jurisdiction of incorporation) other than a transaction or series of related transactions in which the
holders of the voting securities of the Company outstanding immediately prior to such transaction or series of related transactions retain, immediately after such transaction or series of transactions, as a result of shares in the Company held by
such holders prior to such transaction or series of transactions, at least a majority of the total voting power represented by the outstanding voting securities of the Company or such other surviving or resulting entity (or if the Company or such
other surviving or resulting entity is a wholly-owned subsidiary immediately following such acquisition, its parent), or (ii) a sale, lease or other disposition of all or substantially all of the assets of the Company and its subsidiaries taken
as a whole by means of any transaction or series of related transactions, except where such sale, lease or other disposition is to a wholly-owned subsidiary of the Company; or 

(c) Immediately prior to the closing of a firm commitment underwritten public offering pursuant to an effective registration statement filed
under the Securities Act covering the offering and sale of the Company’s common stock. 
 9. No Rights as a Stockholder.
Nothing contained herein shall entitle the Holder to any rights as a stockholder of the Company or to be deemed the holder of any securities that may at any time be issuable on the exercise of the rights hereunder for any purpose nor shall anything
contained herein be construed to confer upon the Holder, as such, any right to vote for the election of directors or upon any matter submitted to stockholders at any meeting thereof, or to give or withhold consent to any corporate action (whether
upon any recapitalization, issuance of stock, reclassification of stock, change of par value or change of stock to no par value, consolidation, merger, conveyance or otherwise) or to receive notice of meetings, or to receive dividends or
subscription rights or any other rights of a stockholder of the Company until the rights under the Warrant shall have been exercised and the Shares purchasable upon exercise of the rights hereunder shall have become deliverable as provided herein.

 10. Market Stand-off. The Holder of this Warrant hereby agrees that such Holder
shall not sell or otherwise 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, of any common stock (or other securities) of the Company
held by the Holder (other than those included in the registration) during the one hundred eighty (180) day period following the effective date of the registration statement for the Company’s initial public offering filed under the
Securities Act (or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (i) the publication or other 

  
 - 8 - 

 
distribution of research reports and (ii) analyst recommendations and opinions, including, but not limited to, the restrictions contained in NASD Rule 2711(f)(4) or NYSE Rule 472(f)(4), or
any successor provisions or amendments thereto). The obligations described in this section shall not apply to a registration relating solely to employee benefit plans on Form S-1 or Form S-8 or similar forms that may be promulgated in the future, or a registration relating solely to a transaction on Form S-4 or similar forms that may be promulgated in the
future. The Company may impose stop-transfer instructions and may stamp each certificate with a legend as substantially set forth in Section 5(e) with respect to the shares of common stock (or other securities) subject to the foregoing
restriction until the end of such one hundred eighty (180) day (or other) period. The Holder agrees to execute a market stand-off agreement with the underwriters in the offering in customary form
consistent with the provisions of this section. 
 11. Representations and Warranties of the Holder. By acceptance of this
Warrant, the Holder represents and warrants to the Company as follows: 
 (a) No Registration. The Holder understands that the
Securities have not been, and will not be, registered under the Securities Act by reason of a specific exemption from the registration provisions of the Securities Act, the availability of which depends upon, among other things, the bona fide nature
of the investment intent and the accuracy of the Holder’s representations as expressed herein or otherwise made pursuant hereto. 
 (b)
Investment Intent. The Holder is acquiring the Securities for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in connection with, any distribution thereof. The Holder has no present
intention of selling, granting any participation in, or otherwise distributing the Securities, nor does it have any contract, undertaking, agreement or arrangement for the same. 

(c) Investment Experience. The Holder has substantial experience in evaluating and investing in private placement transactions
of securities in companies similar to the Company, and has such knowledge and experience in financial or business matters so that it is capable of evaluating the merits and risks of its investment in the Company and protecting its own interests.

 (d) Speculative Nature of Investment. The Holder understands and acknowledges that the Company has a limited financial and
operating history and that its investment in the Company is highly speculative and involves substantial risks. The Holder can bear the economic risk of its investment and is able, without impairing its financial condition, to hold the Securities for
an indefinite period of time and to suffer a complete loss of its investment. 
 (e) Access to Data. The Holder has had an
opportunity to ask questions of officers of the Company, which questions were answered to its satisfaction. The Holder believes that it has received all the information that it considers necessary or appropriate for deciding whether to acquire the
Securities. The Holder understands that any such discussions, as well as any information issued by the Company, were intended to describe certain aspects of the Company’s business and prospects, but were not necessarily a thorough or exhaustive
description. The Holder acknowledges that any business plans prepared by the Company have been, and continue to be, subject to change and that any projections included in such business plans or otherwise are necessarily speculative in nature, and it
can be expected that some or all of the assumptions underlying the projections will not materialize or will vary significantly from actual results. 

(f) Accredited Investor. The Holder is an “accredited investor” within the meaning of Regulation D, Rule 501(a),
promulgated by the Securities and Exchange Commission and agrees to submit to the Company such further assurances of such status as may be reasonably requested by the Company. 

  
 - 9 - 

 (g) Residency. The residency of the Holder (or, in the case of a partnership or
corporation, such entity’s principal place of business) is correctly set forth on the signature page hereto. 
 (h) Restrictions
on Resales. The Holder acknowledges that the Securities must be held indefinitely unless subsequently registered under the Securities Act or an exemption from such registration is available. The Holder is aware of the provisions of Rule 144
promulgated under the Securities Act, which permit resale of shares purchased in a private placement subject to the satisfaction of certain conditions, which may include, among other things, the availability of certain current public information
about the Company; the resale occurring not less than a specified period after a party has purchased and paid for the security to be sold; the number of shares being sold during any three-month period not exceeding specified limitations; the sale
being effected through a “broker’s transaction,” a transaction directly with a “market maker” or a “riskless principal transaction” (as those terms are defined in the Securities Act or the Securities Exchange Act
of 1934, as amended, and the rules and regulations promulgated thereunder); and the filing of a Form 144 notice, if applicable. The Holder acknowledges and understands that the Company may not be satisfying the current public information requirement
of Rule 144 at the time the Holder wishes to sell the Securities and that, in such event, the Holder may be precluded from selling the Securities under Rule 144 even if the other applicable requirements of Rule 144 have been satisfied. The Holder
acknowledges that, in the event the applicable requirements of Rule 144 are not met, registration under the Securities Act or an exemption from registration will be required for any disposition of the Securities. The Holder understands that,
although Rule 144 is not exclusive, the Securities and Exchange Commission has expressed its opinion that persons proposing to sell restricted securities received in a private offering other than in a registered offering or pursuant to Rule 144 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 the brokers who participate in the transactions do so at their own risk. 

(i) No Public Market. The Holder understands and acknowledges that no public market now exists for any of the securities issued
by the Company and that the Company has made no assurances that a public market will ever exist for the Company’s securities. 
 (j)
Brokers and Finders. The Holder has not engaged any brokers, finders or agents in connection with the Securities, and the Company has not incurred nor will incur, directly or indirectly, as a result of any action taken by the Holder,
any liability for brokerage or finders’ fees or agents’ commissions or any similar charges in connection with the Securities. 

(k) Legal Counsel. The Holder has had the opportunity to review this Warrant, the exhibits and schedules attached hereto and the
transactions contemplated by this Warrant with its own legal counsel. The Holder is not relying on any statements or representations of the Company or its agents for legal advice with respect to this investment or the transactions contemplated by
this Warrant. 
 (l) Tax Advisors. The Holder has reviewed with its own tax advisors the U.S. federal, state and local and non-U.S. tax consequences of this investment and the transactions contemplated by this Warrant. With respect to such matters, the Holder relies solely on any such advisors and not on any statements or
representations of the Company or any of its agents, written or oral. The Holder understands that it (and not the Company) shall be responsible for its own tax liability that may arise as a result of this investment and the transactions contemplated
by this Warrant. 
 12. Miscellaneous. 

(a) Amendments. Except as expressly provided herein, neither this Warrant nor any term hereof may be amended, waived, discharged
or terminated other than by a written instrument referencing this Warrant and signed by the Company and the holders of warrants representing not less than 

  
 - 10 - 

 
a majority of the Shares issuable upon exercise of any and all outstanding Warrants, which majority does not need to include the consent of the Holder. Any amendment, waiver, discharge or
termination effected in accordance with this Section 12(a) shall be binding upon each holder of the Warrants, each future holder of such Warrants and the Company; provided, however, that no special consideration or inducement may
be given to any such holder in connection with such consent that is not given ratably to all such holders, and that such amendment must apply to all such holders equally and ratably in accordance with the number of shares of Stock issuable upon
exercise of the Warrants. The Company shall promptly give notice to all holders of Warrants of any amendment effected in accordance with this Section 12(a). 

(b) Waivers. No waiver of any single breach or default shall be deemed a waiver of any other breach or default theretofore or
thereafter occurring. 
 (c) Notices. All notices and other communications required or permitted hereunder shall be in writing
and shall be mailed by registered or certified mail, postage prepaid, sent by facsimile or electronic mail (if to the Holder) or otherwise delivered by hand, messenger or courier service addressed: 

(i) if to the Holder, to the Holder at the Holder’s address, facsimile number or electronic mail address as shown in the Company’s
records, as may be updated in accordance with the provisions hereof, or until any such Holder so furnishes an address, facsimile number or electronic mail address to the Company, then to and at the address, facsimile number or electronic mail
address of the last holder of this Warrant for which the Company has contact information in its records; or 
 (ii) if to the Company, to
the attention of the President or Chief Financial Officer of the Company at the Company’s address as shown on the signature page hereto, or at such other address as the Company shall have furnished to the Holder, with a copy to Kenneth A.
Clark, Wilson Sonsini Goodrich & Rosati, P.C., 650 Page Mill Road, Palo Alto, CA 94301. 
 Each such notice or other communication
shall for all purposes of this Warrant be treated as effective or having been given (i) if delivered by hand, messenger or courier service, when delivered, or (ii) if sent by mail, at the earlier of its receipt or 72 hours after the same
has been deposited in a regularly-maintained receptacle for the deposit of the United States mail, addressed and mailed as aforesaid, or (iii) if sent by facsimile, upon confirmation of facsimile transfer or, if sent by electronic mail, upon
confirmation of delivery when directed to the relevant electronic mail address. In the event of any conflict between the Company’s books and records and this Warrant or any notice delivered hereunder, the Company’s books and records will
control absent fraud or error. 
 (d) Governing Law. This Warrant and all actions arising out of or in connection with this
Warrant shall be governed by and construed in accordance with the laws of the State of California, without regard to the conflicts of law provisions of the State of California, or of any other state. 

(e) Jurisdiction and Venue. Each of the Holder and the Company irrevocably consents to the exclusive jurisdiction and venue of
any court within Santa Clara County, State of California, in connection with any matter based upon or arising out of this Warrant or the matters contemplated herein, and agrees that process may be served upon them in any manner authorized by the
laws of the State of California for such persons. 
 (f) Titles and Subtitles. The titles and subtitles used in this Warrant
are used for convenience only and are not to be considered in construing or interpreting this Warrant. All references in this Warrant to sections, paragraphs and exhibits shall, unless otherwise provided, refer to sections and paragraphs hereof and
exhibits attached hereto. 

  
 - 11 - 

 (g) Severability. If any provision of this Warrant becomes or is declared by a
court of competent jurisdiction to be illegal, unenforceable or void, portions of such provision, or such provision in its entirety, to the extent necessary, shall be severed from this Warrant, and such illegal, unenforceable or void provision shall
be replaced with a valid and enforceable provision that will achieve, to the extent possible, the same economic, business and other purposes of the illegal, unenforceable or void provision. The balance of this Warrant shall be enforceable in
accordance with its terms. 
 (h) Waiver of Jury Trial. EACH OF THE HOLDER AND THE COMPANY WAIVES, TO THE FULLEST EXTENT
PERMITTED BY LAW, ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATED TO THIS WARRANT. If the waiver of jury trial set forth in this paragraph is not enforceable,
then any claim or cause of action arising out of or relating to this Warrant shall be settled by judicial reference pursuant to California Code of Civil Procedure Section 638 et seq. before a referee sitting without a jury, such referee
to be mutually acceptable to the parties or, if no agreement is reached, by a referee appointed by the Presiding Judge of the California Superior Court for Santa Clara County. This paragraph shall not restrict the Holder or the Company from
exercising remedies under the Uniform Commercial Code or from exercising pre-judgment remedies under applicable law. 

(i) California Corporate Securities Law. THE SALE OF THE SECURITIES THAT ARE THE SUBJECT OF THIS WARRANT HAS NOT BEEN QUALIFIED
WITH THE COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA AND THE ISSUANCE OF SUCH SECURITIES OR THE PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION THEREFOR PRIOR TO SUCH QUALIFICATION IS UNLAWFUL, UNLESS THE SALE OF SECURITIES IS EXEMPT
FROM QUALIFICATION BY SECTION 25100, 25102, OR 25105 OF THE CALIFORNIA CORPORATIONS CODE. THE RIGHTS OF ALL PARTIES TO THIS WARRANT ARE EXPRESSLY CONDITIONED UPON THE QUALIFICATION BEING OBTAINED, UNLESS THE SALE IS SO EXEMPT. 

(j) Rights and Obligations Survive Exercise of the Warrant. Except as otherwise provided herein, the rights and obligations of
the Company and the Holder under this Warrant shall survive exercise of this Warrant. 
 (k) Entire Agreement. Except as
expressly set forth herein, this Warrant (including the exhibits attached hereto) constitutes the entire agreement and understanding of the Company and the Holder with respect to the subject matter hereof and supersede all prior agreements and
understandings relating to the subject matter hereof. 
 (signature page follows) 

  
 - 12 - 

 The Company and the Holder sign this Warrant as of the date stated on the first page. 

 

			
	SUTRO BIOPHARMA, INC.

 
			
		
	By:	 	 

 
			
		
	Name:	 	 

 
			
		
	Title:	 	 

 
			
		
	Address:	 	
	
	 310 Utah Avenue, Suite 150
 South
San Francisco, CA 94080

  

	
	AGREED AND ACKNOWLEDGED,
	
	   

	
	Address:
	
	Fax number:
	
	Email address:

 (Signature Page to Warrant to Purchase Shares of Preferred Stock of Sutro Biopharma, Inc.) 

 EXHIBIT A 

NOTICE OF EXERCISE 
  

			
	TO: SUTRO BIOPHARMA, INC. (the “Company”)
	
	Attention: President

  

	(1)	Exercise. The undersigned elects to purchase the following pursuant to the terms of the attached warrant: 

  

					
		 	Number of shares:	  	 
			
		 	Type of security:	  	 

  

	(2)	Method of Exercise. The undersigned elects to exercise the attached warrant pursuant to: 

  

					
		 	☐	  	A cash payment, and tenders herewith payment of the purchase price for such shares in full, together with all applicable transfer taxes, if any.
			
		 	☐	  	The net issue exercise provisions of Section 2(b) of the attached warrant.

  

	(3)	Stock Certificate. Please issue a certificate or certificates representing the shares in the name of: 

  

									
		 	☐	  	The undersigned	 		  	
					
		 	☐	  	Other—Name:	 		  	 
					
		 		  	Address:	 		  	 
					
		 		  		 		  	 

  

	(4)	Unexercised Portion of the Warrant. Please issue a new warrant for the unexercised portion of the attached warrant in the name of: 

 

									
		 	☐	  	The undersigned	  		  	
					
		 	☐	  	Other—Name:	  		  	 
					
		 		  	Address:	  		  	 
					
		 		  		  		  	 
					
		 	☐	  	Not applicable	  		  	

  

	(5)	Investment Intent. The undersigned represents and warrants that the aforesaid shares are being acquired for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in
connection with, the distribution thereof, and that the undersigned has no present intention of selling, granting any participation in, or otherwise distributing the shares, nor does it have any contract, undertaking, agreement or arrangement for
the same, and all representations and warranties of the undersigned set forth in Section 11 of the attached warrant are true and correct as of the date hereof. 

  
 A-1 

	(6)	Investment Representation Statement and Market Stand-Off Agreement. The undersigned has executed, and delivers herewith, an Investment Representation Statement and Market Stand-Off Agreement in a form substantially similar to the form attached to the warrant as Exhibit A-1. 

 

	(7)	Consent to Receipt of Electronic Notice. Subject to the limitations set forth in Delaware General Corporation Law §232(e), the undersigned consents to the delivery of any notice to stockholders given by the
Company under the Delaware General Corporation Law or the Company’s certificate of incorporation or bylaws by (i) facsimile telecommunication to the facsimile number provided below (or to any other facsimile number for the undersigned in
the Company’s records), (ii) electronic mail to the electronic mail address provided below (or to any other electronic mail address for the undersigned in the Company’s records), (iii) posting on an electronic network together with
separate notice to the undersigned of such specific posting or (iv) any other form of electronic transmission (as defined in the Delaware General Corporation Law) directed to the undersigned. This consent may be revoked by the undersigned by
written notice to the Company and may be deemed revoked in the circumstances specified in Delaware General Corporation Law §232. 

  

	
	(Print name of the warrant holder)
	
	 
	(Signature)
	
	 
	(Name and title of signatory, if applicable)
	
	 
	(Date)
	
	 
	(Fax number)
	
	 
	(Email address)

 (Signature page to the Notice of Exercise) 

  
 A-2 

 EXHIBIT A-1 

INVESTMENT REPRESENTATION STATEMENT 

AND 
 MARKET STAND-OFF AGREEMENT 
  

					
			
	INVESTOR:	 	                                      
                                         
                                         
                                         
                         	 	
			
	COMPANY:	 	SUTRO BIOPHARMA, INC.	 	
			
	SECURITIES:	 	THE WARRANT ISSUED ON
                                        
(THE “WARRANT”) AND THE SECURITIES ISSUED OR ISSUABLE UPON EXERCISE THEREOF (INCLUDING UPON SUBSEQUENT CONVERSION OF THOSE SECURITIES)	 	
			
	DATE:	 	                                      
                   	 	

 In connection with the purchase or acquisition of the above-listed Securities, the undersigned Investor
represents and warrants to, and agrees with, the Company as follows: 
 1. No Registration. The Investor understands that the
Securities have not been, and will not be, registered under the Securities Act of 1933, as amended (the “Securities Act”), by reason of a specific exemption from the registration provisions of the Securities Act, the
availability of which depends upon, among other things, the bona fide nature of the investment intent and the accuracy of the Investor’s representations as expressed herein or otherwise made pursuant hereto. 

2. Investment Intent. The Investor is acquiring the Securities for investment for its own account, not as a nominee or agent, and not
with a view to, or for resale in connection with, any distribution thereof. The Investor has no present intention of selling, granting any participation in, or otherwise distributing the Securities, nor does it have any contract, undertaking,
agreement or arrangement for the same. 
 3. Investment Experience. The Investor has substantial experience in evaluating and
investing in private placement transactions of securities in companies similar to the Company, and has such knowledge and experience in financial or business matters so that it is capable of evaluating the merits and risks of its investment in the
Company and protecting its own interests. 
 4. Speculative Nature of Investment. The Investor understands and acknowledges that the
Company has a limited financial and operating history and that its investment in the Company is highly speculative and involves substantial risks. The Investor can bear the economic risk of its investment and is able, without impairing its financial
condition, to hold the Securities for an indefinite period of time and to suffer a complete loss of its investment. 
 5. Access to
Data. The Investor has had an opportunity to ask questions of officers of the Company, which questions were answered to its satisfaction. The Investor believes that it has received all the information that it considers necessary or appropriate
for deciding whether to acquire the Securities. The Investor understands that any such discussions, as well as any information issued by the Company, were intended to describe certain aspects of the Company’s business and prospects, but were
not necessarily a thorough or exhaustive description. The Investor acknowledges that any business plans prepared by the 

  
 A-1-1 

 
Company have been, and continue to be, subject to change and that any projections included in such business plans or otherwise are necessarily speculative in nature, and it can be expected that
some or all of the assumptions underlying the projections will not materialize or will vary significantly from actual results. 
 6.
Accredited Investor. The Investor is an “accredited investor” within the meaning of Regulation D, Rule 501(a), promulgated by the Securities and Exchange Commission and agrees to submit to the Company such further assurances of such
status as may be reasonably requested by the Company. 
 7. Residency. The residency of the Investor (or, in the case of a
partnership or corporation, such entity’s principal place of business) is correctly set forth on the signature page hereto. 
 8.
Restrictions on Resales. The Investor acknowledges that the Securities must be held indefinitely unless subsequently registered under the Securities Act or an exemption from such registration is available. The Investor is aware of the
provisions of Rule 144 promulgated under the Securities Act, which permit resale of shares purchased in a private placement subject to the satisfaction of certain conditions, which may include, among other things, the availability of certain current
public information about the Company; the resale occurring not less than a specified period after a party has purchased and paid for the security to be sold; the number of shares being sold during any three-month period not exceeding specified
limitations; the sale being effected through a “broker’s transaction,” a transaction directly with a “market maker” or a “riskless principal transaction” (as those terms are defined in the Securities Act or the
Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder); and the filing of a Form 144 notice, if applicable. The Investor acknowledges and understands that the Company may not be satisfying the current
public information requirement of Rule 144 at the time the Investor wishes to sell the Securities and that, in such event, the Investor may be precluded from selling the Securities under Rule 144 even if the other applicable requirements of Rule 144
have been satisfied. The Investor understands and acknowledges that, in the event the applicable requirements of Rule 144 are not met, registration under the Securities Act or an exemption from registration will be required for any disposition of
the Securities. The Investor understands that, although Rule 144 is not exclusive, the Securities and Exchange Commission has expressed its opinion that persons proposing to sell restricted securities received in a private offering other than in a
registered offering or pursuant to Rule 144 will have a substantial burden of proof in establishing that an exemption from registration is available for those offers or sales and that those persons and the brokers who participate in the transactions
do so at their own risk. 
 9. No Public Market. The Holder understands and acknowledges that no public market now exists for any of
the securities issued by the Company and that the Company has made no assurances that a public market will ever exist for the Company’s securities. 

10. Brokers and Finders. The Investor has not engaged any brokers, finders or agents in connection with the Securities, and the Company
has not incurred nor will incur, directly or indirectly, as a result of any action taken by the Investor, any liability for brokerage or finders’ fees or agents’ commissions or any similar charges in connection with the Securities. 

11. Legal Counsel. The Investor has had the opportunity to review the Warrant, the exhibits and schedules attached thereto and the
transactions contemplated by the Warrant with its own legal counsel. The Investor is not relying on any statements or representations of the Company or its agents for legal advice with respect to this investment or the transactions contemplated by
the Warrant. 
 12. Tax Advisors. The Investor has reviewed with its own tax advisors the U.S. federal, state and local and non-U.S. tax consequences of this investment and the transactions contemplated by the Warrant. With respect to such matters, the Investor relies solely on such advisors and not on any statements or representations
of the Company or any of its agents, written or oral. The Investor understands that it (and not the Company) shall be responsible for its own tax liability that may arise as a result of this investment or the transactions contemplated by the
Warrant. 

  
 A-1-2 

 13. Market Stand-off. The Investor agrees that the
Investor shall not sell or otherwise 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, of any common stock (or other securities) of the
Company held by the Investor (other than those included in the registration) during the one hundred eighty (180) day period following the effective date of the registration statement for the Company’s initial public offering filed under
the Securities Act (or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports and (ii) analyst recommendations and
opinions, including, but not limited to, the restrictions contained in NASD Rule 2711(f)(4) or NYSE Rule 472(f)(4), or any successor provisions or amendments thereto). The obligations described in this section shall not apply to a registration
relating solely to employee benefit plans on Form S-1 or Form S-8 or similar forms that may be promulgated in the future, or a registration relating solely to a
transaction on Form S-4 or similar forms that may be promulgated in the future. The Company may impose stop-transfer instructions and may stamp each certificate with a legend with respect to the shares of
common stock (or other securities) subject to the foregoing restriction until the end of such one hundred eighty (180) day (or other) period. The Investor agrees to execute a market stand-off agreement
with the relevant underwriters in customary form consistent with the provisions of this section. 
 (signature page follows) 

  
 A-1-3 

 The Investor is signing this Investment Representation Statement and Market Stand-Off Agreement on the date first written above. 
  

	
	INVESTOR
	
	
	(Print name of the investor)
	
	 
	(Signature)
	
	 
	(Name and title of signatory, if applicable)
	
	 
	(Street address)
	
	 
	(City, state and ZIP)

  
 A-1-4 

 EXHIBIT B 

ASSIGNMENT FORM 
  

							
				
	ASSIGNOR:	 		 	                                      
                                         
                                         
                                         
                         	 	
				
	COMPANY:	 		 	SUTRO BIOPHARMA, INC.	 	
				
	WARRANT:	 		 	THE WARRANT TO PURCHASE SHARES OF PREFERRED STOCK ISSUED ON
                                 (THE “WARRANT”)	 	
				
	DATE:	 		 	                                      
                   	 	

  

	(1)	Assignment. The undersigned registered holder of the Warrant (“Assignor”) assigns and transfers to the assignee named below (“Assignee”) all of the rights of
Assignor under the Warrant, with respect to the number of shares set forth below: 

  

			
	
  Name of Assignee:                
                                         
                                         
                                         
                                         
                            

	
	
  Address of Assignee:               
                                         
                                         
                                         
                                         
                        

	
	
                       
                                         
                                         
                                         
                                         
                                         
            

	
	
  Number of Shares Assigned:             
                                         
                                         
                                         
                                         
            

 and does irrevocably constitute and appoint
                                     as attorney to make such
transfer on the books of Sutro Biopharma, Inc., maintained for the purpose, with full power of substitution in the premises. 
  

	(2)	Obligations of Assignee. Assignee agrees to take and hold the Warrant and any shares of stock to be issued upon exercise of the rights thereunder (and any shares issuable upon conversion thereof) (the
“Securities”) subject to, and to be bound by, the terms and conditions set forth in the Warrant to the same extent as if Assignee were the original holder thereof. 

 

	(3)	Investment Intent. Assignee represents and warrants that the Securities are being acquired for investment for its own account, not as a nominee or agent, and not with a view to, or for resale in connection with,
the distribution thereof, and that Assignee has no present intention of selling, granting any participation in, or otherwise distributing the shares, nor does it have any contract, undertaking, agreement or arrangement for the same, and all
representations and warranties set forth in Section 11 of the Warrant are true and correct as to Assignee as of the date hereof. 

  

	(4)	Investment Representation Statement and Market Stand-Off Agreement. Assignee has executed, and delivers herewith, an Investment Representation Statement and Market Stand-Off Agreement in a form substantially similar to the form attached to the Warrant as Exhibit A-1. 

  
 B-1 

 Assignor and Assignee are signing this Assignment Form on the date first set forth above. 

 

					
	ASSIGNOR	 		 	ASSIGNEE
			
	 	 		 	 
	(Print name of Assignor)	 		 	(Print name of Assignee)
			
	 	 		 	 
	(Signature of Assignor)	 		 	(Signature of Assignee)
			
	 	 		 	 
	(Print name of signatory, if applicable)	 		 	(Print name of signatory, if applicable)
			
	 	 		 	 
	(Print title of signatory, if applicable)	 		 	(Print title of signatory, if applicable)
			
	 Address:
	 		 	 Address:

			
	 	 		 	 
			
	 	 		 	 

  
 B-2 

 THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE “ACT”), OR THE SECURITIES LAWS OF ANY STATE AND, EXCEPT AS SET FORTH IN SECTIONS 5.3 AND 5.4 BELOW, MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED UNLESS AND UNTIL REGISTERED UNDER SAID ACT AND LAWS
OR IN THE OPINION OF LEGAL COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE COMPANY, SUCH OFFER, SALE, PLEDGE OR OTHER TRANSFER IS EXEMPT FROM SUCH REGISTRATION. 

WARRANT TO PURCHASE STOCK 
  

					
	Company:	 		  	SUTRO BIOPHARMA, INC.
	Number of Shares:	 		  	That number of Shares (rounded down to the nearest whole number) which could be purchased by taking $                    ,
divided by the Warrant Price (the “Initial Shares”), plus all Additional Shares which Holder is entitled to purchase pursuant to Section 1.7.
	Type/Series of Stock:	 		  	Series C Preferred Stock
	Warrant Price:	 		  	$                 per share
	Issue Date:	 		  	                                
	Expiration Date:	 		  	                                 See also
Section 5.1(b).
	Credit Facility:	 		  	This Warrant to Purchase Stock (“Warrant”) is issued in connection with that certain Loan and Security Agreement dated as of even date herewith between
                                         
            and the Company (as amended, modified, supplemented or restated, the “Loan Agreement”).

 THIS WARRANT CERTIFIES THAT, for good and valuable
consideration,                                     (together
with any successor or permitted assignee or transferee of this Warrant or of any shares issued upon exercise hereof, “Holder”) is entitled to purchase the number of fully paid and
non-assessable shares (the “Shares”) of the above-stated Type/Series of Stock (the “Class”) of the above-named company (the “Company”) at
the above-stated Warrant Price, all as set forth above and as adjusted pursuant to Section 2 of this Warrant, subject to the provisions and upon the terms and conditions set forth in this Warrant. Reference is made to Section 5.4 of this
Warrant whereby                                      shall
transfer this Warrant to its parent company,
                                    . 

SECTION 1. EXERCISE. 
 1.1
Method of Exercise. Holder may at any time and from time to time exercise this Warrant, in whole or in part, by delivering to the Company the original of this Warrant together with a duly executed Notice of Exercise in substantially the form
attached hereto as Appendix 1 and, unless Holder is exercising this Warrant pursuant to a cashless exercise as set forth in Section 1.2, a check, wire transfer of same-day funds (to an account designated
by the Company), or other form of payment acceptable to the Company for the aggregate Warrant Price for the Shares being purchased. 
 1.2
Cashless Exercise. On any exercise of this Warrant, in lieu of payment of the aggregate Warrant Price in the manner as specified in Section 1.1 above, but otherwise in accordance with the requirements of Section 1.1, Holder may
elect to receive Shares equal to the value of this Warrant, or portion hereof as to which this Warrant is being exercised. Thereupon, the Company shall issue to the Holder such number of fully paid and
non-assessable Shares as are computed using the following formula: 
 X = Y(A-B)/A 

  
 1 

 where: 
  

					
		 	X =	  	the number of Shares to be issued to the Holder;
			
		 	Y =	  	the number of Shares with respect to which this Warrant is being exercised (inclusive of the Shares surrendered to the Company in payment of the aggregate Warrant Price);
			
		 	A =	  	the Fair Market Value (as determined pursuant to Section 1.3 below) of one Share; and
			
		 	B =	  	the Warrant Price.

 1.3 Fair Market Value. If the Company’s common stock is then traded or quoted on a nationally
recognized securities exchange, inter-dealer quotation system or over-the-counter market (a “Trading Market”) and the Class is common stock,
the fair market value of a Share shall be the closing price or last sale price of a share of common stock reported for the Business Day immediately before the date on which Holder delivers this Warrant together with its Notice of Exercise to the
Company. If the Company’s common stock is then traded in a Trading Market and the Class is a series of the Company’s convertible preferred stock, the fair market value of a Share shall be the closing price or last sale price of a
share of the Company’s common stock reported for the Business Day immediately before the date on which Holder delivers this Warrant together with its Notice of Exercise to the Company multiplied by the number of shares of the Company’s
common stock into which a Share is then convertible. If the Company’s common stock is not traded in a Trading Market, the Board of Directors of the Company shall determine the fair market value of a Share in its reasonable good faith judgment.

 1.4 Delivery of Certificate and New Warrant. Within a reasonable time after Holder exercises this Warrant in the manner set forth
in Section 1.1 or 1.2 above, the Company shall deliver to Holder a certificate representing the Shares issued to Holder upon such exercise and, if this Warrant has not been fully exercised and has not expired, a new warrant of like tenor
representing the Shares not so acquired. 
 1.5 Replacement of Warrant. On receipt of evidence reasonably satisfactory to the Company
of the loss, theft, destruction or mutilation of this Warrant and, in the case of loss, theft or destruction, on delivery of an indemnity agreement reasonably satisfactory in form, substance and amount to the Company or, in the case of mutilation,
on surrender of this Warrant to the Company for cancellation, the Company shall, within a reasonable time, execute and deliver to Holder, in lieu of this Warrant, a new warrant of like tenor and amount. 

1.6 Treatment of Warrant Upon Acquisition of Company. 

(a) Acquisition. For the purpose of this Warrant, “Acquisition” means any transaction or series of related
transactions involving: (i) the sale, lease, exclusive license, or other disposition of all or substantially all of the assets of the Company; (ii) any merger or consolidation of the Company into or with another person or entity (other
than a merger or consolidation effected exclusively to change the Company’s domicile), or any other corporate reorganization, in which the stockholders of the Company in their capacity as such immediately prior to such merger, consolidation or
reorganization, own less than a majority of the Company’s (or the surviving or successor entity’s) outstanding voting power immediately after such merger, consolidation or reorganization; or (iii) any sale or other transfer by the
stockholders of the Company of shares representing at least a majority of the Company’s then-total outstanding combined voting power. 

  
 2 

 (b) Treatment of Warrant at Acquisition. In the event of an Acquisition in which the
consideration to be received by the Company’s stockholders consists solely of cash, solely of Marketable Securities or a combination of cash and Marketable Securities (a “Cash/Public Acquisition”), either (i) Holder
shall exercise this Warrant pursuant to Section 1.1 and/or 1.2 and such exercise will be deemed effective immediately prior to and contingent upon the consummation of such Acquisition or (ii) if Holder elects not to exercise the Warrant,
this Warrant will expire immediately prior to the consummation of such Acquisition. 
 (c) The Company shall provide Holder with written
notice of its request relating to the Cash/Public Acquisition (together with such reasonable information as Holder may reasonably require regarding the treatment of this Warrant in connection with such contemplated Cash/Public Acquisition giving
rise to such notice), which is to be delivered to Holder not less than seven (7) Business Days prior to the closing of the proposed Cash/Public Acquisition. In the event the Company does not provide such notice, then if, immediately prior to
the Cash/Public Acquisition, the fair market value of one Share (or other security issuable upon the exercise hereof) as determined in accordance with Section 1.3 above would be greater than the Warrant Price in effect on such date, then this
Warrant shall automatically be deemed on and as of such date to be exercised pursuant to Section 1.2 above as to all Shares (or such other securities) for which it shall not previously have been exercised, and the Company shall promptly notify
the Holder of the number of Shares (or such other securities) issued upon such exercise to the Holder and Holder shall be deemed to have restated each of the representations and warranties in Section 4 of the Warrant as the date thereof. 

(d) Upon the closing of any Acquisition other than a Cash/Public Acquisition defined above, the acquiring, surviving or successor entity shall
assume the obligations of this Warrant, and this Warrant shall thereafter be exercisable for the same securities and/or other property as would have been paid for the Shares issuable upon exercise of the unexercised portion of this Warrant as if
such Shares were outstanding on and as of the closing of such Acquisition, subject to further adjustment from time to time in accordance with the provisions of this Warrant. 

(e) As used in this Warrant, “Marketable Securities” means securities meeting all of the following requirements:
(i) the issuer thereof is then subject to the reporting requirements of Section 13 or Section 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and is then current in its filing of
all required reports and other information under the Act and the Exchange Act; (ii) the class and series of shares or other security of the issuer that would be received by Holder in connection with the Acquisition were Holder to exercise this
Warrant on or prior to the closing thereof is then traded in a Trading Market, and (iii) Holder would not be restricted by contract or by applicable federal and state securities laws from publicly
re-selling, within six (6) months following the closing of such Acquisition, all of the issuer’s shares and/or other securities that would be received by Holder in such Acquisition were Holder to
exercise this Warrant in full on or prior to the closing of such Acquisition. 
 1.7 Additional Shares. In addition to the Initial
Shares granted to Holder on the Issue Date, at the time of the funding of the Tranche Two Equipment Advance (as defined in the Loan Agreement), the Company shall be deemed to have automatically granted to Holder, in addition to the number of Shares
which this Warrant can otherwise be exercised for by Holder, the right to purchase that number of additional Shares (rounded down to the nearest whole number) which could be purchased by taking
$                                    , divided by the Warrant
Price (such additional Shares being called the “Additional Shares”). 

  
 3 

 SECTION 2. ADJUSTMENTS TO THE SHARES AND WARRANT PRICE. 

2.1 Stock Dividends, Splits, Etc. If the Company declares or pays a dividend or distribution on the outstanding shares of the
Class payable in common stock or other securities or property (other than cash), then upon exercise of this Warrant, for each Share acquired, Holder shall receive, without additional cost to Holder, the total number and kind of securities and
property which Holder would have received had Holder owned the Shares of record as of the date the dividend or distribution occurred. If the Company subdivides the outstanding shares of the Class by reclassification or otherwise into a greater
number of shares, the number of Shares purchasable hereunder shall be proportionately increased and the Warrant Price shall be proportionately decreased. If the outstanding shares of the Class are combined or consolidated, by reclassification
or otherwise, into a lesser number of shares, the Warrant Price shall be proportionately increased and the number of Shares shall be proportionately decreased. 

2.2 Reclassification, Exchange, Combinations or Substitution. Upon any event whereby all of the outstanding shares of the
Class are reclassified, exchanged, combined, substituted, or replaced for, into, with or by Company securities of a different class and/or series, then from and after the consummation of such event, this Warrant will be exercisable for the
number, class and series of Company securities that Holder would have received had the Shares been outstanding on and as of the consummation of such event, and subject to further adjustment thereafter from time to time in accordance with the
provisions of this Warrant. The provisions of this Section 2.2 shall similarly apply to successive reclassifications, exchanges, combinations substitutions, replacements or other similar events. 

2.3 Conversion of Preferred Stock. If the Class is a class and series of the Company’s convertible preferred stock, in the
event that all outstanding shares of the Class are converted, automatically or by action of the holders thereof, into common stock pursuant to the provisions of the Company’s Certificate of Incorporation, including, without limitation, in
connection with the Company’s initial, underwritten public offering and sale of its common stock pursuant to an effective registration statement under the Act (the “IPO”), then from and after the date on which all
outstanding shares of the Class have been so converted, this Warrant shall be exercisable for such number of shares of common stock into which the Shares would have been converted had the Shares been outstanding on the date of such conversion,
and the Warrant Price shall equal the Warrant Price in effect as of immediately prior to such conversion divided by the number of shares of common stock into which one Share would have been converted, all subject to further adjustment thereafter
from time to time in accordance with the provisions of this Warrant. 
 2.4 Adjustments for Diluting Issuances. Without duplication
of any adjustment otherwise provided for in this Section 2, the number of shares of common stock issuable upon conversion of the Shares shall be subject to anti-dilution adjustment from time to time in the manner set forth in the Company’s
Articles or Certificate of Incorporation as if the Shares were issued and outstanding on and as of the date of any such required adjustment. 

2.5 No Fractional Share. No fractional Share shall be issuable upon exercise of this Warrant and the number of Shares to be issued
shall be rounded down to the nearest whole Share. If a fractional Share interest arises upon any exercise of the Warrant, the Company shall eliminate such fractional Share interest by paying Holder in cash the amount computed by multiplying the
fractional interest by the fair market value (as determined in accordance with Section 1.3 above) of a full Share. 
 2.6
Notice/Certificate as to Adjustments. Upon each adjustment of the Warrant Price, Class and/or number of Shares, the Company, at the Company’s expense, shall notify Holder in writing within a reasonable time setting forth the
adjustments to the Warrant Price, Class and/or number of Shares and facts upon which such adjustment is based. The Company shall, upon written request from Holder, furnish Holder with a certificate of its Chief Financial Officer, including
computations of such adjustment and the Warrant Price, Class and number of Shares in effect upon the date of such adjustment. 

  
 4 

 SECTION 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY. 

3.1 Representations and Warranties. The Company represents and warrants to, and agrees with, the Holder as follows: 

(a) The initial Warrant Price referenced on the first page of this Warrant is not greater than the price per share at which shares of the
Class were last sold and issued prior to the Issue Date hereof in an arms-length transaction in which at least $                     of
such shares were sold. 
 (b) All Shares which may be issued upon the exercise of this Warrant, and all securities, if any, issuable upon
conversion of the Shares, shall, upon issuance, be duly authorized, validly issued, fully paid and non-assessable, and free of any liens and encumbrances except for restrictions on transfer provided for herein
or under applicable federal and state securities laws. The Company covenants that it shall at all times cause to be reserved and kept available out of its authorized and unissued capital stock such number of shares of the Class, common stock and
other securities as will be sufficient to permit the exercise in full of this Warrant and the conversion of the Shares into common stock or such other securities. 

(c) The Company’s capitalization table attached hereto as Schedule 1 is true and complete, in all material respects, as of the Issue
Date. 
 3.2 Notice of Certain Events. If the Company proposes at any time to: 

(a) declare any dividend or distribution upon the outstanding shares of the Class or common stock, whether in cash, property, stock, or
other securities and whether or not a regular cash dividend; 
 (b) offer for subscription or sale pro rata to the holders of the
outstanding shares of the Class any additional shares of any class or series of the Company’s stock (other than pursuant to contractual pre-emptive rights); 

(c) effect any reclassification, exchange, combination, substitution, reorganization or recapitalization of the outstanding shares of the
Class; 
 (d) effect an Acquisition or to liquidate, dissolve or wind up; or 

(e) effect an IPO; 
 then, in connection with
each such event, the Company shall give Holder: 
 (1) at least seven (7) Business Days prior written notice of the date
on which a record will be taken for such dividend, distribution, or subscription rights (and specifying the date on which the holders of outstanding shares of the Class will be entitled thereto) or for determining rights to vote, if any, in
respect of the matters referred to in (a) and (b) above; 
 (2) in the case of the matters referred to in (c) and
(d) above at least seven (7) Business Days prior written notice of the date when the same will take place (and specifying the date on which the holders of outstanding shares of the Class will be entitled to exchange their shares for the
securities or other property deliverable upon the occurrence of such event); and 

  
 5 

 (3) with respect to the IPO, at least seven (7) Business Days prior written
notice of the date on which the Company proposes to file its registration statement in connection therewith. 
 Reference is made to Section 1.6(c)
whereby this Warrant will be deemed to be exercised pursuant to Section 1.2 hereof if the Company does not give written notice to Holder of a Cash/Public Acquisition as required by the terms hereof. Company will also provide information
requested by Holder that is reasonably necessary to enable Holder to comply with Holder’s accounting or reporting requirements. 
 3.3
Registration Under Securities Act of 1933, as amended. The Company agrees that the Shares or, if the Shares are convertible into common stock of the Company, such common stock, shall have certain “piggyback” and “S-3” registration rights in parity with the investors pursuant to and as set forth in the Company’s Amended and Restated Investors’ Rights Agreement dated November 5, 2010 (the
“Rights Agreement”), which rights shall be effective as of the date that the Company receives the requisite investor consent and an executed amendment to the Rights Agreement from Holder substantially in the form attached hereto as
Exhibit A, joining the Holder as a party to the Rights Agreement, which shall occur no later than the earlier of (a) the Company’s next financing round, or (b) upon any exercise or conversion of this Warrant.
The provisions set forth in the Rights Agreement or similar agreement relating to the above in effect as of the Issue Date may not be amended, modified or waived without the prior written consent of Holder unless such amendment, modification or
waiver affects the rights associated with the Shares in the same manner as such amendment, modification, or waiver affects the rights associated with all other shares of the same series and class as the Shares granted to Holder. 

SECTION 4. REPRESENTATIONS, WARRANTIES OF THE HOLDER. 

The Holder represents and warrants to the Company as follows: 

4.1 Purchase for Own Account. This Warrant and the securities to be acquired upon exercise of this Warrant by Holder are being acquired
for investment for Holder’s account, not as a nominee or agent, and not with a view to the public resale or distribution within the meaning of the Act. Holder also represents that it has not been formed for the specific purpose of acquiring
this Warrant or the Shares. 
 4.2 Disclosure of Information. Holder is aware of the Company’s business affairs and financial
condition and has received or has had full access to all the information it considers necessary or appropriate to make an informed investment decision with respect to the acquisition of this Warrant and its underlying securities. Holder further has
had an opportunity to ask questions and receive answers from the Company regarding the terms and conditions of the offering of this Warrant and its underlying securities and to obtain additional information (to the extent the Company possessed such
information or could acquire it without unreasonable effort or expense) necessary to verify any information furnished to Holder or to which Holder has access. 

4.3 Investment Experience. Holder understands that the purchase of this Warrant and its underlying securities involves substantial
risk. Holder has experience as an investor in securities of companies in the development stage and acknowledges that Holder can bear the economic risk of such Holder’s investment in this Warrant and its underlying securities and has such
knowledge and experience in financial or business matters that Holder is capable of evaluating the merits and risks of its investment in this Warrant and its underlying securities and/or has a preexisting personal or business relationship with the
Company and certain of its officers, directors or controlling persons of a nature and duration that enables Holder to be aware of the character, business acumen and financial circumstances of such persons. 

  
 6 

 4.4 Accredited Investor Status. Holder is an “accredited investor” within the
meaning of Regulation D promulgated under the Act. 
 4.5 The Act. Holder understands that this Warrant and the Shares issuable upon
exercise hereof have not been registered under the Act in reliance upon a specific exemption therefrom, which exemption depends upon, among other things, the bona fide nature of the Holder’s investment intent as expressed herein. Holder
understands that this Warrant and the Shares issued upon any exercise hereof must be held indefinitely unless subsequently registered under the Act and qualified under applicable state securities laws, or unless exemption from such registration and
qualification are otherwise available. Holder is aware of the provisions of Rule 144 promulgated under the Act. 
 4.6 Lock-Up Agreement. The Holder agrees that the Shares shall be subject to the Lock-Up provisions in Section 11 of the Rights Agreement. 

4.7 No Voting Rights. Holder, as a Holder of this Warrant, will not have any voting rights until the exercise of this Warrant. 

SECTION 5. MISCELLANEOUS. 

5.1 Term and Automatic Conversion Upon Expiration. 

(a) Term. Subject to the provisions of Section 1.6 above, this Warrant is exercisable in whole or in part at any time and from
time to time on or before 6:00 PM, Pacific time, on the Expiration Date and shall be void thereafter. 
 (b) Automatic Cashless Exercise
upon Expiration. In the event that, upon the Expiration Date, the fair market value of one Share (or other security issuable upon the exercise hereof) as determined in accordance with Section 1.3 above is greater than the Warrant Price in
effect on such date, then this Warrant shall automatically be deemed on and as of such date to be exercised pursuant to Section 1.2 above as to all Shares (or such other securities) for which it shall not previously have been exercised, and the
Company shall, within a reasonable time, deliver a certificate representing the Shares (or such other securities) issued upon such exercise to Holder. 

5.2 Legends. The Shares (and the securities issuable, directly or indirectly, upon conversion of the Shares, if any) shall be imprinted
with a legend in substantially the following form: 
 THE SHARES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED (THE “ACT”), OR THE SECURITIES LAWS OF ANY STATE AND, EXCEPT AS SET FORTH IN THAT CERTAIN WARRANT TO PURCHASE STOCK ISSUED BY THE ISSUER TO
                        
DATED                                     MAY NOT BE OFFERED,
SOLD, PLEDGED OR OTHERWISE TRANSFERRED UNLESS AND UNTIL REGISTERED UNDER SAID ACT AND LAWS OR IN THE OPINION OF LEGAL COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE ISSUER, SUCH OFFER, SALE, PLEDGE OR OTHER TRANSFER IS EXEMPT FROM SUCH
REGISTRATION. 

  
 7 

 The Shares issuable upon exercise of this Warrant (and the securities issuable, directly or
indirectly, upon conversion of the Shares, if any) shall also be imprinted with the legends described in, and required by, the Rights Agreement. 

5.3 Compliance with Securities Laws on Transfer. This Warrant and the Shares issuable upon exercise of this Warrant (and the securities
issuable, directly or indirectly, upon conversion of the Shares, if any) may not be transferred or assigned in whole or in part except in compliance with applicable federal and state securities laws by the transferor and the transferee (including,
without limitation, the delivery of investment representation letters and legal opinions reasonably satisfactory to the Company, as reasonably requested by the Company). The Company shall not require
                                     to provide an opinion of
counsel if the transfer is to
                                    
(                                        
parent company) or any other affiliate of Holder, provided that any such transferee is an “accredited investor” as defined in Regulation D promulgated under the Act. Additionally, the Company shall also not require an opinion of counsel if
there is no material question as to the availability of Rule 144 promulgated under the Act. 
 5.4 Transfer Procedure. After receipt
by                                      of the executed
Warrant,                                      will transfer
all of this Warrant to its parent company,
                                    . By its acceptance of
this Warrant,
                                        
hereby makes to the Company each of the representations and warranties set forth in Section 4 hereof and agrees to be bound by all of the terms and conditions of this Warrant as if the original Holder hereof. Subject to the provisions of
Section 5.3 and upon providing the Company with written notice,
                                        
and any subsequent Holder may transfer all or part of this Warrant or the Shares issuable upon exercise of this Warrant (or the securities issuable directly or indirectly, upon conversion of the Shares, if any) to any transferee, provided, however,
in connection with any such transfer,
                                         
    or any subsequent Holder will give the Company notice of the portion of the Warrant being transferred with the name, address and taxpayer identification number of the transferee and Holder will surrender this Warrant to the
Company for reissuance to the transferee(s) (and Holder if applicable); and provided further, that any subsequent transferee other than
                                        
shall agree in writing with the Company to be bound by all of the terms and conditions of this Warrant. Notwithstanding any contrary provision herein, at all times prior to the IPO, Holder may not, without the Company’s prior written consent,
transfer this Warrant or any portion hereof, or any Shares issued upon any exercise hereof, or any shares or other securities issued upon any conversion of any Shares issued upon any exercise hereof, to any person or entity who directly competes
with the Company, except in connection with an Acquisition of the Company by such a direct competitor. 
 5.5 Notices. All notices
and other communications hereunder from the Company to the Holder, or vice versa, shall be deemed delivered and effective (i) when given personally, (ii) on the third (3rd) Business Day
after being mailed by first-class registered or certified mail, postage prepaid, (iii) upon actual receipt if given by facsimile or electronic mail and such receipt is confirmed in writing by the recipient, or (iv) on the first Business
Day following delivery to a reliable overnight courier service, courier fee prepaid, in any case at such address as may have been furnished to the Company or Holder, as the case may be, in writing by the Company or such Holder from time to time in
accordance with the provisions of this Section 5.5. All notices to Holder shall be addressed as follows until the Company receives notice of a change of address in connection with a transfer or otherwise: 

 

					
		 	 	 	
		 	Attn:                                     
    	 	
		 	 	 	
			
		 	Telephone:                               	 	
		 	Facsimile:                                	 	
		 	Email address:                         	 	

  
 8 

 Notice to the Company shall be addressed as follows until Holder receives notice of a change in
address: 
  

					
		 	Sutro Biopharma, Inc.	 	
		 	310 Utah Ave., Suite 150	 	
		 	South San Francisco, California 94080	 	
		 	Attn: Jay Shukert, Chief Financial Officer	 	
		 	Telephone:
                                         
                    	 	
		 	Facsimile:
                                         
                     	 	
		 	Email address:
                                         
              	 	
			
		 	With a copy (which shall not constitute notice) to:	 	
			
		 	 	 	
		 	 	 	
		 	 	 	
		 	Attn:                                     
                                   	 	
		 	Facsimile:
                                         
                     	 	
		 	Email address:
                                         
              	 	

 5.6 Waiver. This Warrant and any term hereof may be changed, waived, discharged or terminated (either
generally or in a particular instance and either retroactively or prospectively) only by an instrument in writing signed by the party against which enforcement of such change, waiver, discharge or termination is sought. 

5.7 Attorney’s Fees. In the event of any dispute between the parties concerning the terms and provisions of this Warrant, the
party prevailing in such dispute shall be entitled to collect from the other party all costs incurred in such dispute, including reasonable attorneys’ fees. 

5.8 Counterparts; Facsimile/Electronic Signatures. This Warrant may be executed in counterparts, all of which together shall constitute
one and the same agreement. Any signature page delivered electronically or by facsimile shall be binding to the same extent as an original signature page with regards to any agreement subject to the terms hereof or any amendment thereto. 

5.9 Governing Law. This Warrant shall be governed by and construed in accordance with the laws of the State of California, without
giving effect to its principles regarding conflicts of law. 
 5.10 Headings. The headings in this Warrant are for purposes of
reference only and shall not limit or otherwise affect the meaning of any provision of this Warrant. 
 5.11 Business Days.
“Business Day” is any day that is not a Saturday, Sunday or a day on which
                                 is closed. 

[Remainder of page left blank intentionally] 

[Signature page follows] 

  
 9 

 IN WITNESS WHEREOF, the parties have caused this Warrant to Purchase Stock to be executed by
their duly authorized representatives effective as of the Issue Date written above. 
  

			
	“COMPANY”
	
	SUTRO BIOPHARMA, INC.
		
	By:	 	 
		
	Name:	 	 
		 	(Print)
		
	Title:	 	
	
	“HOLDER”
	
	 
		
	By:	 	 
		
	Name:	 	 
		 	(Print)
	Title:	 	

  
 10 

 APPENDIX 1 

NOTICE OF EXERCISE 
 1. The
undersigned Holder hereby exercises its right purchase ____________ shares of the Common/Series ____ Preferred [circle one] Stock of Sutro Biopharma, Inc. (the “Company”) in accordance with the attached Warrant To Purchase
Stock, and tenders payment of the aggregate Warrant Price for such shares as follows: 
  

					
		 	[    ]	  	 check in the amount of $_________ payable to order of the Company enclosed herewith

			
		 	[    ]	  	 Wire transfer of $_________ in immediately available funds to the Company’s account

			
		 	[    ]	  	 Cashless Exercise pursuant to Section 1.2 of the Warrant

			
		 	[    ]	  	 Other
[Describe]                                       
                                         
    

 2. Please issue a certificate or certificates representing the Shares in the name specified below: 

 

					
			
		 		  	                                      
                                         
                                 
			
		 		  	 Holder’s Name

			
		 		  	                                      
                                         
                                 
			
		 		  	                                      
                                         
                                 
			
		 		  	 (Address)

 3. By its execution below and for the benefit of the Company, Holder hereby restates each of the
representations and warranties in Section 4 of the Warrant to Purchase Stock as of the date hereof. 
  

			
	HOLDER:
	 

 
			
		
	By:	 	 

 
			
		
	Name:	 	 

 
			
		
	Title:	 	 

 
			
		
	(Date):	 	 

  
 Appendix 1 

 SCHEDULE 1 

Company Capitalization Table 

 EXHIBIT A 

FORM OF AMENDMENT TO INVESTOR RIGHTS AGREEMENT 

  
 Exhibit A

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