Document:

Form of Warrant to Purchase Series D-2 Preferred Stock

 EXHIBIT 4.5 

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 IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO SUCH SECURITIES UNDER SAID ACT OR AN OPINION
OF COUNSEL, SATISFACTORY TO THE COMPANY, THAT SUCH REGISTRATION IS NOT REQUIRED. 
 WARRANT TO PURCHASE STOCK 

 

			
	 Company:
	  	Sutro Biopharma, Inc., a Delaware corporation
	 Number of Shares:
	  	______________ (Subject to Section 1.7)
	 Type/Series of Stock:
	  	Series D-2 Preferred Stock (Subject to Section 1.7)
	 Warrant Price:
	  	$__________ per share (Subject to Section 1.7)
	 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 of even date herewith among _____________________, as Lender and Collateral Agent, the Lenders from
time to time party thereto, including _______________________, and the Company (as modified, amended and/or restated from time to time, the “Loan Agreement”).

 THIS WARRANT CERTIFIES THAT, for good and valuable consideration, ______________ (“______”
and, 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. 

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 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 
 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. 

  
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 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 (i) any consolidation, merger or
acquisition in which the Company is a constituent party (but excluding any merger effected solely for the purpose of reincorporating into another state), or any other corporate reorganization (including, without limitation, any consolidation, merger
or acquisition in which a subsidiary of the Company is a constituent party and the Company issues shares of its capital stock pursuant to such merger, consolidation or acquisition), in which, in each case, the stockholders of the Company immediately
prior to such consolidation, merger, acquisition or reorganization, own less than 50% of the voting power of the surviving or successor entity or its parent immediately after such consolidation, merger, acquisition or reorganization; (ii) any
transaction or series of related transactions to which the Company is a party in which in excess of fifty percent (50%) of the Company’s voting power is transferred, excluding any consolidation or merger effected solely for the purpose of
reincorporating into another state; or (iii) any sale, lease, transfer, exclusive license or other disposition by the Company or any subsidiary or subsidiaries of the Company of all or substantially all of the assets of the Company and its
subsidiaries taken as a whole (or, if substantially all of the assets of the Company and its subsidiaries taken as a whole are held by one or more subsidiaries, the sale or disposition (whether by consolidation, merger, conversion or otherwise) of
such subsidiaries of the Company or all or substantially all of the assets of such subsidiaries), except where such sale, lease, transfer, exclusive license or other disposition is made to the Company or one or more wholly owned subsidiaries of the
Company. Notwithstanding the foregoing, no transaction or series of related transactions principally for bona fide equity financing purposes in which cash is received by the Company or indebtedness of the Company is cancelled or converted, or a
combination thereof, nor the transfer by any stockholder of shares of the Company’s capital stock to any third party in a transaction or series of related transactions to which the Company is not a party, shall be an Acquisition for purposes of
this Warrant. 
 (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. 

  
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 (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) following the closing of such Acquisition, Holder would not be restricted from publicly re-selling all of the issuer’s shares
and/or other securities that would be received by Holder in such Acquisition were Holder to exercise or convert this Warrant in full on or prior to the closing of such Acquisition, except to the extent that any such restriction (x) arises
solely under federal or state securities laws, rules or regulations, and (y) does not extend beyond six (6) months from the closing of such Acquisition. 

1.7 Adjustment to Class of Shares; Number of Shares; Warrant Price; Adjustments Cumulative. If, upon the closing of
the Next Equity Financing, the Next Equity Financing Price shall be less than the Warrant Price in effect as of immediately prior thereto, then the “Class” shall be Next Equity Financing Securities from and after such closing, subject to
adjustment thereafter from time to time in accordance with the provisions of this Warrant and the “Warrant Price” shall be the Next Equity Financing Price from and after such closing, subject to adjustment thereafter from time to time in
accordance with the provisions of this Warrant; provided, that upon such date, if any, as the “Class” becomes Next Equity Financing Securities pursuant to this sentence, this Warrant shall be exercisable for such number of shares of such
Class as shall equal (i) _______________________ ($______________), divided by (ii) the Next Equity Financing Price, subject to adjustment thereafter from time to time in accordance with the provisions of this Warrant. As used herein (i)
“Next Equity Financing” means the first sale or issuance by the Company on or after the Issue Date of this Warrant set forth above, in a single transaction or series of related transactions, of shares of its convertible preferred stock or
other senior equity securities to one or more investors for cash for financing purposes; (ii) “Next Equity Financing Securities” means the type, class and series of convertible preferred stock or other senior equity security sold or issued
by the Company in the Next Equity Financing; and (iii) “Next Equity Financing Price” means the lowest price per share for which Next Equity Financing Securities are sold or issued by the Company in the Next Equity Financing (not including
any price per share applied in connection with the conversion of debt in such Next Equity Financing). 
 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,

  
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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 (i) the fair market value (as determined in accordance with Section 1.3 above) of a full Share, less (ii) the then-effective Warrant Price. 

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. 

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. 

  
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 (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 
 (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. 

SECTION 4. REPRESENTATIONS AND 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. 

  
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 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. 

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 an exemption from such registration and qualification is otherwise available. Holder is
aware of the provisions of Rule 144 promulgated under the Act. 
 4.6 Market Stand-off
Agreement. The Holder agrees that the Shares shall be subject to the Lock-up Agreement provisions in Section 11 of the Second Amended and Restated Investors’ Rights Agreement dated as of
__________________ by and among the Company and certain stockholders of the Company. 
 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; Automatic Cashless Exercise 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, Eastern 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. 

  
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 5.2 Legends. Each certificate evidencing Shares (and each certificate evidencing the
securities issued upon conversion of any 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 IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THE SHARES UNDER SAID ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE ISSUER,
THAT SUCH REGISTRATION IS NOT REQUIRED. 
 5.3 Compliance with Securities Laws on Transfer. This Warrant and the Shares issued 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
Holder to provide an opinion of counsel if the transfer is to an 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, _______ may transfer all or part of this Warrant to one or more of _______’s affiliates (each, an “_______ Affiliate”), by execution of an Assignment
substantially in the form of Appendix 2. Subject to the provisions of Article 5.3 and upon providing the Company with written notice, __________, any such ________Affiliate and any subsequent Holder, may transfer all or part of this Warrant or the
Shares issuable upon exercise of this Warrant (or the Shares issuable directly or indirectly, upon conversion of the Shares, if any) to any other transferee, provided, however, in connection with any such transfer, the __________ Affiliate(s) 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). 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: ___________________ 

  
 7 

 Notice to the Company shall be addressed as follows until Holder receives notice of a change in
address: 
 Sutro Biopharma, Inc. 

310 Utah Street, Suite 150 

South San Francisco, CA 94080 

Attn: Edward Albini 
 Email:

 With a copy (which shall not constitute notice) to: 

Fenwick & West LLP 

555 California Street 
 12th
Floor 
 San Francisco, CA 94104 

Attn: Matthew S. Rossiter 

Telephone: 
 Facsimile: 

Email: 
 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 Attorneys’ 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] 

  
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 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:	 	 

  

  
 [Signature Page to
Warrant to Purchase Stock] 

 APPENDIX 1 

NOTICE OF EXERCISE 
 1. The
undersigned Holder hereby exercises its right to 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 the order of the Company enclosed herewith
			
		  	[    ]	  	Wire transfer of 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 

 APPENDIX 2 

ASSIGNMENT 
 For
value received, ________________ hereby sells, assigns and transfers unto 

Name:         [________________ TRANSFEREE] 

Address:                   
                              

Tax ID:
                                         
                   ] 
 that certain
Warrant to Purchase Stock issued by Sutro Biopharma, Inc. (the “Company”), on _________________ (the “Warrant”) together with all rights, title and interest therein. 

 

			
	                                    
                    

 
			
		
	By:	 	 

 
			
		
	Name:	 	 

 
			
		
	Title:	 	 

Date:                   
                                         
             
 By its execution below, and for the benefit of the Company, [_______________
TRANSFEREE] makes each of the representations and warranties set forth in Article 4 of the Warrant and agrees to all other provisions of the Warrant as of the date hereof. 

 

			
	[______________ TRANSFEREE]

 
			
		
	By:	 	 

 
			
		
	Name:	 	 

 
			
		
	Title:	 	                                     
                                       ]

  
 Appendix 2 

 SCHEDULE 1 

Company Capitalization Table 

See attached 

  
 Schedule 12004 Stock Plan and forms of award agreements

 EXHIBIT 10.2 

SUTRO BIOPHARMA, INC. 

2004 STOCK PLAN 
 (as amended
May 17, 2018) 
 1. Purposes of the Plan. The purposes of this Plan are to
attract and retain the best available personnel for positions of substantial responsibility, to provide additional incentive to Employees, Directors and Consultants and to promote the success of the Company’s business. Options granted under the
Plan may be Incentive Stock Options or Nonstatutory Stock Options, as determined by the Administrator at the time of grant. Stock Purchase Rights may also be granted under the Plan. 

2. Definitions. As used herein, the following definitions shall apply: 

(a) “Administrator” means the Board or any of its Committees as shall be administering the Plan in accordance with
Section 4 hereof. 
 (b) “Applicable Laws” means the requirements relating to the administration of stock option plans
under U.S. state corporate laws, U.S. federal and state securities laws, the Code, any stock exchange or quotation system on which the Common Stock is listed or quoted and the applicable laws of any other country or jurisdiction where Options or
Stock Purchase Rights are granted under the Plan. 
 (c) “Board” means the Board of Directors of the Company. 

(d) “Change in Control” means the occurrence of any of the following events: 

(i) Any “person” (as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the “beneficial owner”
(as defined in Rule 13d-3 of the Exchange Act), directly or indirectly, of securities of the Company representing fifty percent (50%) or more of the total voting power represented by the Company’s then
outstanding voting securities, except that any change in the beneficial ownership of the securities of the Company as a result of a private financing of the Company that is approved by the Board, shall not be deemed to be a Change in Control; or

 (ii) The consummation of the sale or disposition by the Company of all or substantially all of the Company’s assets; or 

(iii) The consummation of a merger or consolidation of the Company with any other corporation, other than a merger or consolidation which
would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity or its parent) at least fifty
percent (50%) of the total voting power represented by the voting securities of the Company or such surviving entity or its parent outstanding immediately after such merger or consolidation. 

 (e) “Code” means the Internal Revenue Code of 1986, as amended. Any reference to
a section of the Code herein will be a reference to any successor or amended section of the Code. 
 (f) “Committee” means
a committee of Directors or of other individuals satisfying Applicable Laws appointed by the Board in accordance with Section 4 hereof. 

(g) “Common Stock” means the Common Stock of the Company. 

(h) “Company” means Sutro Biopharma, Inc., a Delaware corporation. 

(i) “Consultant” means any person who is engaged by the Company or any Parent or Subsidiary to render consulting or advisory
services to such entity. 
 (j) “Director” means a member of the Board. 

(k) “Disability” means total and permanent disability as defined in Section 22(e)(3) of the Code. 

(l) “Employee” means any person, including officers and Directors, employed by the Company or any Parent or Subsidiary of the
Company. Neither service as a Director nor payment of a director’s fee by the Company shall be sufficient to constitute “employment” by the Company. 

(m) “Exchange Act” means the Securities Exchange Act of 1934, as amended. 

(n) “Exchange Program” means a program under which (a) outstanding Options are surrendered or cancelled in exchange for
Options of the same type (which may have lower exercise prices and different terms), Options of a different type, and/or cash, and/or (b) the exercise price of an outstanding Option is reduced. The terms and conditions of any Exchange Program
will be determined by the Administrator in its sole discretion. 
 (o) “Fair Market Value” means, as of any date, the value
of Common Stock determined as follows: 
 (i) If the 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 Administrator deems reliable; 

(ii) If the 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 Common Stock on the day of determination; or 
 (iii) In the absence of
an established market for the Common Stock, the Fair Market Value thereof shall be determined in good faith by the Administrator. 

  
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 (p) “Incentive Stock Option” means an Option intended to qualify as an incentive
stock option within the meaning of Section 422 of the Code. 
 (q) “Nonstatutory Stock Option” means an Option not
intended to qualify as an Incentive Stock Option. 
 (r) “Option” means a stock option granted pursuant to the Plan. 

(s) “Option Agreement” means a written or electronic agreement between the Company and an Optionee evidencing the terms and
conditions of an individual Option grant. The Option Agreement is subject to the terms and conditions of the Plan. 
 (t)
“Optioned Stock” means the Common Stock subject to an Option or a Stock Purchase Right. 
 (u)
“Optionee” means the holder of an outstanding Option or Stock Purchase Right granted under the Plan. 
 (v)
“Parent” means a “parent corporation,” whether now or hereafter existing, as defined in Section 424(e) of the Code. 

(w) “Plan” means this 2004 Stock Plan. 

(x) “Restricted Stock” means Shares issued pursuant to a Stock Purchase Right or Shares of restricted stock issued pursuant
to an Option. 
 (y) “Restricted Stock Purchase Agreement” means a written or electronic agreement between the Company and
the Optionee evidencing the terms and restrictions applying to Shares purchased under a Stock Purchase Right. The Restricted Stock Purchase Agreement is subject to the terms and conditions of the Plan and the notice of grant. 

(z) “Securities Act” means the Securities Act of 1933, as amended. 

(aa) “Service Provider” means an Employee, Director or Consultant. 

(bb) “Share” means a share of the Common Stock, as adjusted in accordance with Section 13 below. 

(cc) “Stock Purchase Right” means a right to purchase Common Stock pursuant to Section 11 below. 

(dd) “Subsidiary” means a “subsidiary corporation,” whether now or hereafter existing, as defined in
Section 424(f) of the Code. 
 3.
Stock Subject to the Plan. Subject to the provisions of Section 13 of the Plan, the maximum aggregate number of Shares that may be subject to Options or Stock
Purchase Rights and sold under the Plan is 105,854,931 Shares. The Shares may be authorized but unissued, or reacquired Common Stock. 

  
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 If an Option or Stock Purchase Right expires or becomes unexercisable without having been
exercised in full, or is surrendered pursuant to an Exchange Program, the unpurchased Shares that were subject thereto shall become available for future grant or sale under the Plan (unless the Plan has terminated). However, Shares that have
actually been issued under the Plan, upon exercise of either an Option or Stock Purchase Right, shall not be returned to the Plan and shall not become available for future distribution under the Plan, except that if unvested Shares of Restricted
Stock are repurchased by the Company at their original purchase price, such Shares shall become available for future grant under the Plan. 

4. Administration of the Plan. 

(a) Administrator. The Plan shall be administered by the Board or a Committee appointed by the Board, which Committee shall be
constituted to comply with Applicable Laws. 
 (b)
Powers of the Administrator. Subject to the provisions of the Plan and, in the case of a Committee, the specific duties delegated by the Board to such Committee, and subject to the
approval of any relevant authorities, the Administrator shall have the authority in its discretion: 
 (i) to determine the Fair Market
Value; 
 (ii) to select the Service Providers to whom Options and Stock Purchase Rights may from time to time be granted hereunder; 

(iii) to determine the number of Shares to be covered by each such award granted hereunder; 

(iv) to approve forms of agreement for use under the Plan; 

(v) to determine the terms and conditions of any Option or Stock Purchase Right granted hereunder. Such terms and conditions include, but are
not limited to, the exercise price, the time or times when Options or Stock Purchase Rights may be exercised (which may be based on performance criteria), any vesting acceleration or waiver of forfeiture restrictions, and any restriction or
limitation regarding any Option or Stock Purchase Right or the Common Stock relating thereto, based in each case on such factors as the Administrator, in its sole discretion, shall determine; 

(vi) to institute an Exchange Program; 

(vii) to prescribe, amend and rescind rules and regulations relating to the Plan, including rules and regulations relating to sub-plans established for the purpose of satisfying applicable foreign laws; 
 (viii) to allow Optionees
to satisfy withholding tax obligations by electing to have the Company withhold from the Shares to be issued upon exercise of an Option or Stock Purchase Right that number of Shares having a Fair Market Value equal to the minimum amount required to
be withheld. The Fair Market Value of the Shares to be withheld shall be determined on the date that the amount of tax to be withheld is to be determined. All elections by Optionees to have Shares withheld for this purpose shall be made in such form
and under such conditions as the Administrator may deem necessary or advisable; and 

  
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 (ix) to construe and interpret the terms of the Plan and Options granted pursuant to the Plan.

 (c) Effect of Administrator’s Decision. All decisions,
determinations and interpretations of the Administrator shall be final and binding on all Optionees. 
 5. Eligibility. Nonstatutory
Stock Options and Stock Purchase Rights may be granted to Service Providers. Incentive Stock Options may be granted only to Employees. 
 6.
Limitations. 
 (a) Incentive Stock Option Limit. Each Option shall be designated in the Option Agreement as either an
Incentive Stock Option or a Nonstatutory Stock Option. However, notwithstanding such designation, to the extent that the aggregate Fair Market Value of the Shares with respect to which Incentive Stock Options are exercisable for the first time by
the Optionee during any calendar year (under all plans of the Company and any Parent or Subsidiary) exceeds $100,000, such Options shall be treated as Nonstatutory Stock Options. For purposes of this Section 6(a), Incentive Stock Options shall
be taken into account in the order in which they were granted. The Fair Market Value of the Shares shall be determined as of the time the Option with respect to such Shares is granted. 

(b) At-Will Employment. Neither the Plan nor any Option or Stock Purchase Right shall confer
upon any Optionee any right with respect to continuing the Optionee’s relationship as a Service Provider with the Company, nor shall it interfere in any way with his or her right or the Company’s right to terminate such relationship at any
time, with or without cause, and with or without notice. 
 7. Term of Plan. Subject to
stockholder approval in accordance with Section 19, the Plan shall become effective upon its adoption by the Board. Unless sooner terminated under Section 15, it shall continue in effect for a term of ten (10) years from the later of
(i) the effective date of the Plan, or (ii) the earlier of the most recent Board or stockholder approval of an increase in the number of Shares reserved for issuance under the Plan. 

8. Term of Option. The term of each Option shall be stated in the Option Agreement; provided, however, that the term shall be no more
than ten (10) years from the date of grant thereof. In the case of an Incentive Stock Option granted to an Optionee who, at the time the Option is granted, owns stock representing more than ten percent (10%) of the voting power of all classes
of stock of the Company or any Parent or Subsidiary, the term of the Option shall be five (5) years from the date of grant or such shorter term as may be provided in the Option Agreement. 

  
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 9. Option Exercise Price and Consideration. 

(a) Exercise Price. The per share exercise price for the Shares to be issued upon exercise of an Option shall be such price as is
determined by the Administrator, but shall be subject to the following: 
 (i) In the case of an Incentive Stock Option 

(A) granted to an Employee who, at the time of grant of such Option, owns stock representing more than ten percent (10%) of the voting power
of all classes of stock of the Company or any Parent or Subsidiary, the exercise price shall be no less than 110% of the Fair Market Value per Share on the date of grant. 

(B) granted to any other Employee, the per Share exercise price shall be no less than 100% of the Fair Market Value per Share on the date of
grant. 
 (ii) In the case of a Nonstatutory Stock Option 

(A) granted to a Service Provider who, at the time of grant of such Option, owns stock representing more than ten percent (10%) of the voting
power of all classes of stock of the Company or any Parent or Subsidiary, the exercise price shall be no less than 110% of the Fair Market Value per Share on the date of grant. 

(B) granted to any other Service Provider, the per Share exercise price shall be no less than 85% of the Fair Market Value per Share on the
date of grant. 
 (iii) Notwithstanding the foregoing, Options may be granted with a per Share exercise price other than as required above
in accordance with and pursuant to a transaction described in Section 424 of the Code. 
 (b) Forms of Consideration. The
consideration to be paid for the Shares to be issued upon exercise of an Option, including the method of payment, shall be determined by the Administrator (and, in the case of an Incentive Stock Option, shall be determined at the time of grant).
Such consideration may consist of, without limitation, (1) cash, (2) check, (3) promissory note, (4) other Shares, provided Shares acquired directly from the Company (x) have been owned by the Optionee, and not subject to a
substantial risk of forfeiture, for more than six months on the date of surrender, and (y) have a Fair Market Value on the date of surrender equal to the aggregate exercise price of the Shares as to which such Option shall be exercised,
(5) consideration received by the Company under a cashless exercise program implemented by the Company in connection with the Plan, or (6) any combination of the foregoing methods of payment. In making its determination as to the type of
consideration to accept, the Administrator shall consider if acceptance of such consideration may be reasonably expected to benefit the Company. 

  
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 10. Exercise of Option. 

(a) Procedure for Exercise; Rights as a Stockholder. Any Option granted hereunder shall be
exercisable according to the terms hereof at such times and under such conditions as determined by the Administrator and set forth in the Option Agreement. An Option may not be exercised for a fraction of a Share. Except in the case of Options
granted to officers, Directors and Consultants, Options shall become exercisable at a rate of no less than 20% per year over five (5) years from the date the Options are granted. 

An Option shall be deemed exercised when the Company receives (i) written or electronic notice of exercise (in accordance with the
Option Agreement) from the person entitled to exercise the Option, and (ii) full payment for the Shares with respect to which the Option is exercised. Full payment may consist of any consideration and method of payment authorized by the
Administrator and permitted by the Option Agreement and the Plan. Shares issued upon exercise of an Option shall be issued in the name of the Optionee or, if requested by the Optionee, in the name of the Optionee and his or her spouse. Until the
Shares are issued (as evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a stockholder shall exist with respect to the
Shares, notwithstanding the exercise of the Option. The Company shall issue (or cause to be issued) such Shares promptly after the Option is exercised. No adjustment will be made for a dividend or other right for which the record date is prior to
the date the Shares are issued, except as provided in Section 13 of the Plan. 
 Exercise of an Option in any manner shall result in a
decrease in the number of Shares thereafter available, both for purposes of the Plan and for sale under the Option, by the number of Shares as to which the Option is exercised. 

(b) Termination of Relationship as a Service Provider. If an Optionee ceases to be a Service Provider, such Optionee
may exercise his or her Option within thirty (30) days of termination, or such longer period of time as specified in the Option Agreement, to the extent that the Option is vested on the date of termination (but in no event later than the
expiration of the term of the Option as set forth in the Option Agreement). Unless the Administrator provides otherwise, if on the date of termination the Optionee is not vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall revert to the Plan. If, after termination, the Optionee does not exercise his or her Option within the time specified by the Administrator, the Option shall terminate, and the Shares covered by such Option shall revert to
the Plan. 
 (c) Disability of Optionee. If an Optionee ceases to be a Service Provider as a result of the Optionee’s
Disability, the Optionee may exercise his or her Option within six (6) months of termination, or such longer period of time as specified in the Option Agreement, to the extent the Option is vested on the date of termination (but in no event
later than the expiration of the term of such Option as set forth in the Option Agreement). Unless the Administrator provides otherwise, if on the date of termination the Optionee is not vested as to his or her entire Option, the Shares covered by
the unvested portion of the Option shall revert to the Plan. If, after termination, the Optionee does not exercise his or her Option within the time specified herein, the Option shall terminate, and the Shares covered by such Option shall revert to
the Plan. 

  
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 (d) Death of Optionee. If an Optionee dies while a
Service Provider, the Option may be exercised within six (6) months following Optionee’s death, or such longer period of time as specified in the Option Agreement, to the extent that the Option is vested on the date of death (but in no
event later than the expiration of the term of such Option as set forth in the Option Agreement) by the Optionee’s designated beneficiary, provided such beneficiary has been designated prior to Optionee’s death in a form acceptable to the
Administrator. If no such beneficiary has been designated by the Optionee, then such Option may be exercised by the personal representative of the Optionee’s estate or by the person(s) to whom the Option is transferred pursuant to the
Optionee’s will or in accordance with the laws of descent and distribution. If, at the time of death, the Optionee is not vested as to his or her entire Option, the Shares covered by the unvested portion of the Option shall immediately revert
to the Plan. If the Option is not so exercised within the time specified herein, the Option shall terminate, and the Shares covered by such Option shall revert to the Plan. 

(e) Leaves of Absence. 

(i) Unless the Administrator provides otherwise, vesting of Options granted hereunder to officers and Directors shall be suspended during any
unpaid leave of absence. 
 (ii) A Service Provider shall not cease to be an Employee in the case of (A) any leave of absence approved
by the Company or (B) transfers between locations of the Company or between the Company, its Parent, any Subsidiary, or any successor. 

(iii) For purposes of Incentive Stock Options, no such leave may exceed ninety (90) days, unless reemployment upon expiration of such
leave is guaranteed by statute or contract. If reemployment upon expiration of a leave of absence approved by the Company is not so guaranteed, then three (3) months following the 91st day of such leave, any Incentive Stock Option held by the
Optionee shall cease to be treated as an Incentive Stock Option and shall be treated for tax purposes as a Nonstatutory Stock Option. 
 11.
Stock Purchase Rights. 
 (a) Rights to Purchase. Stock Purchase Rights may be issued either alone, in addition to, or in
tandem with other awards granted under the Plan and/or cash awards made outside of the Plan. After the Administrator determines that it will offer Stock Purchase Rights under the Plan, it shall advise the offeree in writing or electronically of the
terms, conditions and restrictions related to the offer, including the number of Shares that such person shall be entitled to purchase, the price to be paid, and the time within which such person must accept such offer. The terms of the offer shall
comply in all respects with Section 260.140.42 of Title 10 of the California Code of Regulations. The offer shall be accepted by execution of a Restricted Stock Purchase Agreement in the form determined by the Administrator. 

(b) Repurchase Option. Unless the Administrator determines otherwise, the Restricted Stock Purchase Agreement shall grant the Company a
repurchase option exercisable within 90 days of the voluntary or involuntary termination of the purchaser’s service with the Company for any reason (including death or disability). Unless the Administrator provides otherwise, the purchase price
for Shares repurchased pursuant to the Restricted Stock Purchase Agreement shall be the original price paid by the purchaser and may be paid by cancellation of any 

  
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indebtedness of the purchaser to the Company. The repurchase option shall lapse at such rate as the Administrator may determine. Except with respect to Shares purchased by officers, Directors and
Consultants, the repurchase option shall in no case lapse at a rate of less than 20% per year over five (5) years from the date of purchase. 

(c) Other Provisions. The Restricted Stock Purchase Agreement shall contain such other terms, provisions and conditions not
inconsistent with the Plan as may be determined by the Administrator in its sole discretion. 
 (d) Rights as a Stockholder. Once the
Stock Purchase Right is exercised, the purchaser shall have rights equivalent to those of a stockholder and shall be a stockholder when his or her purchase is entered upon the records of the duly authorized transfer agent of the Company. No
adjustment shall be made for a dividend or other right for which the record date is prior to the date the Stock Purchase Right is exercised, except as provided in Section 13 of the Plan. 

12. Limited Transferability of Options and Stock Purchase Rights. Unless determined otherwise by
the Administrator, Options and Stock Purchase Rights may not be sold, pledged, assigned, hypothecated, transferred, or disposed of in any manner other than by will or the laws of descent and distribution, and may be exercised during the lifetime of
the Optionee, only by the Optionee. If the Administrator in its sole discretion makes an Option or Stock Purchase Right transferable, such Option or Stock Purchase Right may only be transferred (i) by will, (ii) by the laws of descent and
distribution, or (iii) to family members (within the meaning of Rule 701 of the Securities Act) through gifts or domestic relations orders, as permitted by Rule 701 of the Securities Act. 

13. Adjustments; Dissolution or Liquidation; Merger or Change in Control. 

(a) Adjustments. In the event that any dividend or other distribution (whether in the form of cash, Shares, other securities, or other
property), recapitalization, stock split, reverse stock split, reorganization, merger, consolidation, split-up, spin-off, combination, repurchase, or exchange of Shares
or other securities of the Company, or other change in the corporate structure of the Company affecting the Shares occurs, the Administrator, in order to prevent diminution or enlargement of the benefits or potential benefits intended to be made
available under the Plan, may (in its sole discretion) adjust the number and class of Shares that may be delivered under the Plan and/or the number, class, and price of Shares covered by each outstanding Option or Stock Purchase Right; provided,
however, that the Administrator shall make such adjustments to the extent required by Section 25102(o) of the California Corporations Code. 

(b) Dissolution or Liquidation. In the event of the proposed dissolution or liquidation of the Company, the Administrator shall notify
each Optionee as soon as practicable prior to the effective date of such proposed transaction. To the extent it has not been previously exercised, an Option or Stock Purchase Right will terminate immediately prior to the consummation of such
proposed action. 
 (c) Merger or Change in Control. In the event of a merger of the Company with or into another corporation, or a
Change in Control, each outstanding Option and Stock Purchase Right shall be assumed or an equivalent option substituted by the successor corporation or a Parent 

  
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or Subsidiary of the successor corporation. In the event that the successor corporation in a merger or Change in Control refuses to assume or substitute for the Option or Stock Purchase Right,
then the Optionee shall fully vest in and have the right to exercise the Option or Stock Purchase Right as to all of the Optioned Stock, including Shares as to which it would not otherwise be vested or exercisable. If an Option or Stock Purchase
Right becomes fully vested and exercisable in lieu of assumption or substitution in the event of a merger or Change in Control, the Administrator shall notify the Optionee in writing or electronically that the Option or Stock Purchase Right shall be
fully exercisable for a period of time as determined by the Administrator, and the Option or Stock Purchase Right shall terminate upon expiration of such period. For the purposes of this paragraph and for the sake of clarity, a “successor
corporation” shall be deemed to include any “person” (as such term is used in Sections 13(d) and 14(d) of the Exchange Act) that becomes the “beneficial owner” (as defined in Rule
13d-3 of the Exchange Act), directly or indirectly, of securities of the Company representing fifty percent (50%) or more of the total voting power represented by the Company’s then outstanding voting
securities as a result of a Change in Control of the type described in Section 2(d)(i) hereof. 
 14.
Time of Granting Options and Stock Purchase Rights. The date of grant of an Option or Stock Purchase Right shall, for all purposes, be the date on which the Administrator makes the
determination granting such Option or Stock Purchase Right, or such later date as is determined by the Administrator. Notice of the determination shall be given to each Service Provider to whom an Option or Stock Purchase Right is so granted within
a reasonable time after the date of such grant. 
 15.
Amendment and Termination of the Plan. 

(a) Amendment and Termination. The Board may at any time amend, alter, suspend or terminate the Plan. 

(b) Stockholder Approval. The Board shall obtain stockholder approval of any Plan amendment to the extent necessary and desirable to
comply with Applicable Laws. 
 (c)
Effect of Amendment or Termination. No amendment, alteration, suspension or termination of the Plan shall impair the rights of any Optionee, unless mutually agreed
otherwise between the Optionee and the Administrator, which agreement must be in writing and signed by the Optionee and the Company. Termination of the Plan shall not affect the Administrator’s ability to exercise the powers granted to it
hereunder with respect to Options granted under the Plan prior to the date of such termination. 
 16.
Conditions Upon Issuance of Shares. 
 (a) Legal
Compliance. Shares shall not be issued pursuant to the exercise of an Option or Stock Purchase Right unless the exercise of such Option or Stock Purchase Right and the issuance and delivery of such Shares shall comply with Applicable Laws and
shall be further subject to the approval of counsel for the Company with respect to such compliance. 
 (b) Investment
Representations. As a condition to the exercise of an Option or Stock Purchase Right, the Administrator may require the person exercising such Option or Stock Purchase Right to represent and warrant at the time of any such exercise that the
Shares are being purchased only for investment and without any present intention to sell or distribute such Shares if, in the opinion of counsel for the Company, such a representation is required. 

  
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 17. Inability to Obtain Authority. The inability of the Company to obtain authority from
any regulatory body having jurisdiction, which authority is deemed by the Company’s counsel to be necessary to the lawful issuance and sale of any Shares hereunder, shall relieve the Company of any liability in respect of the failure to issue
or sell such Shares as to which such requisite authority shall not have been obtained. 
 18.
Reservation of Shares. The Company, during the term of this Plan, shall at all times reserve and keep available such number of Shares as shall be sufficient to satisfy the requirements of the Plan. 

19. Stockholder Approval. The Plan shall be subject to approval by the stockholders of the Company within twelve (12) months after
the date the Plan is adopted. Such stockholder approval shall be obtained in the degree and manner required under Applicable Laws. 
 20.
Information to Optionees. The Company shall provide to each Optionee and to each individual who acquires Shares pursuant to the Plan, not less frequently than annually during the period such Optionee has one or more Options or Stock Purchase
Rights outstanding, and, in the case of an individual who acquires Shares pursuant to the Plan, during the period such individual owns such Shares, copies of annual financial statements. The Company shall not be required to provide such statements
to key employees whose duties in connection with the Company assure their access to equivalent information. 

  
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 EXHIBIT B 

Form of Stock Option Agreement (as Amended) 

 SUTRO BIOPHARMA, INC. 

2004 STOCK PLAN 
 STOCK
OPTION AGREEMENT 
 Unless otherwise defined herein, the terms defined in the 2004 Stock Plan shall have the same defined meanings in
this Stock Option Agreement. 
  

	 	I.	NOTICE OF STOCK OPTION GRANT 

Name:                      
                                         
                                         
                                         
                                         
       

Address:                     
                                         
                                         
                                         
                                         
    
 The undersigned Optionee has been granted an Option to purchase Common Stock of the Company, subject to the
terms and conditions of the Plan and this Option Agreement, as follows: 
  

					
	 Date of Grant 
	  	 	  	
			
	 Vesting Commencement Date 
	  	 	  	
			
	 Exercise Price per Share
	  	$                                      
                              	  	
			
	 Total Number of Shares Granted 
	  	 	  	
			
	 Total Exercise Price
	  	$                                      
                          	  	
			
	 Type of Option: 
	  	          Incentive Stock Option	  	
			
		  	          Nonstatutory Stock Option	  	
			
	 Term/Expiration Date: 
	  	 	  	

 Vesting Schedule: 

This Option shall be exercisable, in whole or in part, according to the following vesting schedule: 

[25% of the Shares subject to the Option shall vest on the one year anniversary of the Vesting Commencement Date, and 1/48th of the Shares subject to the Option shall vest each month thereafter on the same day of the month as the Vesting Commencement Date, subject to Optionee continuing to be a Service Provider through
each such date.] 

 Termination Period: 

This Option shall be exercisable for three (3) months after Optionee ceases to be a Service Provider. Upon Optionee’s death or
Disability, this Option may be exercised for one (1) year after Optionee ceases to be a Service Provider. In no event may Optionee exercise this Option after the Term/Expiration Date as provided above. 

Code Section 409A: 

Under Code Section 409A, an option that vests after December 31, 2004 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 of Common Stock on the date of grant (a “discount option”) is considered “deferred compensation”. An option that is
a “discount option” may result in (i) income recognition by the Optionee prior to the exercise of the option (when the option vests), (ii) an additional twenty percent (20%) income tax, and (iii) potential interest charges.
Optionee acknowledges that the Company cannot guarantee and has not guaranteed that the IRS will determine that the per share exercise price of this Option equals or exceeds the fair market value of a Share of Common Stock on the date of grant.
Optionee agrees that if the IRS determines that the Option was granted with a per share exercise price that was less than the fair market value of a Share of Common Stock on the date of grant, Optionee will be solely responsible for any costs
related to such a determination. 
  

	 	II.	AGREEMENT 

 1. Grant of Option. The Plan Administrator of the Company
hereby grants to the Optionee named in the Notice of Grant (the “Optionee”), an option (the “Option”) to purchase the number of Shares set forth in the Notice of Grant, at the exercise price per Share set forth in the Notice of
Grant (the “Exercise Price”), and subject to the terms and conditions of the Plan, which is incorporated herein by reference. Subject to Section 15(c) of the Plan, in the event of a conflict between the terms and conditions of the
Plan and this Option Agreement, the terms and conditions of the Plan shall prevail. 
 If designated in the Notice of Grant as an Incentive
Stock Option (“ISO”), this Option is intended to qualify as an Incentive Stock Option as defined in Section 422 of the Code. Nevertheless, to the extent that it exceeds the $100,000 rule of Code Section 422(d), this Option shall
be treated as a Nonstatutory Stock Option (“NSO”). 
 2. Exercise of Option. 

(a) Right to Exercise. This Option shall be exercisable during its term in accordance with the Vesting Schedule set out in the Notice
of Grant and with the applicable provisions of the Plan and this Option Agreement. 
 (b) Method of Exercise. This Option shall be
exercisable by delivery of an exercise notice in the form attached as Exhibit A (the “Exercise Notice”) which shall state the election to exercise the Option, the number of Shares with respect to which the Option
is being exercised, and such other representations and agreements as may be required by the Company. The Exercise Notice shall be accompanied by payment of the aggregate Exercise Price as to all Exercised Shares. This Option shall be deemed to be
exercised upon receipt by the Company of such fully executed Exercise Notice accompanied by the aggregate Exercise Price. 

  
 -2- 

 No Shares shall be issued pursuant to the exercise of an Option unless such issuance and such
exercise complies with Applicable Laws. Assuming such compliance, for income tax purposes the Shares shall be considered transferred to the Optionee on the date on which the Option is exercised with respect to such Shares. 

3. Optionee’s Representations. In the event the Shares have not been registered under the Securities Act of 1933, as amended, at
the time this Option is exercised, the Optionee shall, if required by the Company, concurrently with the exercise of all or any portion of this Option, deliver to the Company his or her Investment Representation Statement in the form attached hereto
as Exhibit B. 
 4. Lock-Up Period. Optionee hereby agrees that
Optionee shall not offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or
indirectly, any Common Stock (or other securities) of the Company or enter into any swap, hedging or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any Common Stock (or other
securities) of the Company held by Optionee (other than those included in the registration) for a period specified by the representative of the underwriters of Common Stock (or other securities) of the Company not to exceed one hundred eighty
(180) days following the effective date of any registration statement of the Company filed under the Securities Act. 
 Optionee agrees
to execute and deliver such other agreements as may be reasonably requested by the Company or the underwriter which are consistent with the foregoing or which are necessary to give further effect thereto. In addition, if requested by the Company or
the representative of the underwriters of Common Stock (or other securities) of the Company, Optionee shall provide, within ten (10) days of such request, such information as may be required by the Company or such representative in connection
with the completion of any public offering of the Company’s securities pursuant to a registration statement filed under the Securities Act. 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 Commission Rule 145 transaction on
Form S-4 or similar forms that may be promulgated in the future. The Company may impose stop-transfer instructions with respect to the shares of Common Stock (or other securities) subject to the foregoing
restriction until the end of said one hundred eighty (180) day period. Optionee agrees that any transferee of the Option or shares acquired pursuant to the Option shall be bound by this Section. 

5. Method of Payment. Payment of the aggregate Exercise Price shall be by any of the following, or a combination thereof, at the
election of the Optionee: 
 (a) cash or check; 

(b) consideration received by the Company under a formal cashless exercise program adopted by the Company in connection with the Plan; or 

  
 -3- 

 (c) surrender of other Shares which, (i) in the case of Shares acquired from the Company,
either directly or indirectly, have been owned by the Optionee, and not subject to a substantial risk of forfeiture, for more than six (6) months on the date of surrender, and (ii) have a Fair Market Value on the date of surrender equal to
the aggregate Exercise Price of the Exercised Shares. 
 6. Restrictions on Exercise. This Option may not be exercised until such
time as the Plan has been approved by the shareholders of the Company, or if the issuance of such Shares upon such exercise or the method of payment of consideration for such shares would constitute a violation of any Applicable Law. 

7. Non-Transferability of Option. This Option may not be transferred in any manner otherwise
than by will or by the laws of descent or distribution and may be exercised during the lifetime of Optionee only by Optionee. The terms of the Plan and this Option Agreement shall be binding upon the executors, administrators, heirs, successors and
assigns of the Optionee. 
 8. Term of Option. This Option may be exercised only within the term set out in the Notice of Grant, and
may be exercised during such term only in accordance with the Plan and the terms of this Option. 
 9. Tax Obligations. 

(a) Withholding Taxes. Optionee agrees to make appropriate arrangements with the Company (or the Parent or Subsidiary employing or
retaining Optionee) for the satisfaction of all Federal, state, local and foreign income and employment tax withholding requirements applicable to the Option exercise. Optionee acknowledges and agrees that the Company may refuse to honor the
exercise and refuse to deliver Shares if such withholding amounts are not delivered at the time of exercise. 
 (b) Notice of
Disqualifying Disposition of ISO Shares. If the Option granted to Optionee herein is an ISO, and if Optionee sells or otherwise disposes of any of the Shares acquired pursuant to the ISO on or before the later of (1) the date two years
after the Date of Grant, or (2) the date one year after the date of exercise, the Optionee shall immediately notify the Company in writing of such disposition. Optionee agrees that Optionee may be subject to income tax withholding by the
Company on the compensation income recognized by the Optionee. 
 10. Adoption Agreement. Upon execution of this Option Agreement and
as a condition to receiving the Option, Optionee shall have executed and delivered to the Company the Adoption Agreement in the form attached hereto as Exhibit C (the “Adoption Agreement”), pursuant to which Optionee shall be bound
by all provisions of the Agreement (as defined in the Adoption Agreement) in the capacity of Common Holder and/or Stockholder (each as defined in the Adoption Agreement), as applicable. 

11. Entire Agreement; Governing Law. The Plan is incorporated herein by reference. The Plan and this Option Agreement constitute the
entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and Optionee with respect to the subject matter hereof, and may not be modified adversely
to the Optionee’s interest except by means of a writing signed by the Company and Optionee. This agreement is governed by the internal substantive laws but not the choice of law rules of California. 

  
 -4- 

 12. No Guarantee of Continued Service. OPTIONEE ACKNOWLEDGES AND AGREES THAT THE VESTING
OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (NOT THROUGH THE ACT OF BEING HIRED, BEING GRANTED THIS OPTION OR ACQUIRING SHARES HEREUNDER). OPTIONEE FURTHER
ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A SERVICE PROVIDER FOR THE VESTING PERIOD, FOR
ANY PERIOD, OR AT ALL, AND SHALL NOT INTERFERE IN ANY WAY WITH OPTIONEE’S RIGHT OR THE COMPANY’S RIGHT TO TERMINATE OPTIONEE’S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR WITHOUT CAUSE. 

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

									
	OPTIONEE	 		 	SUTRO BIOPHARMA, INC.
			
	 	 		 	 
	Signature	 		 	By
			
	 	 		 	 
	Print Name	 		 	Title
			
	 	 		 	
	 	 		 	
	Residence Address	 		 	

  
 -5- 

 EXHIBIT A 

2004 STOCK PLAN 
 EXERCISE
NOTICE 
 Sutro Biopharma, Inc. 
 Address:_______________

 Attention: _______________ 
 1. Exercise
of Option. Effective as of today, _____________, _____, the undersigned (“Optionee”) hereby elects to exercise Optionee’s option to purchase _________ shares of the Common Stock (the “Shares”) of Sutro Biopharma, Inc.
(the “Company”) under and pursuant to the 2004 Stock Plan (the “Plan”) and the Stock Option Agreement dated _____________, _____ (the “Option Agreement”). 

2. Delivery of Payment. Optionee herewith delivers to the Company the full purchase price of the Shares, as set forth in the Option
Agreement, and any and all withholding taxes due in connection with the exercise of the Option. 
 3. Representations of Optionee.
Optionee acknowledges that Optionee has received, read and understood the Plan and the Option Agreement and agrees to abide by and be bound by their terms and conditions. 

4. Rights as Shareholder. Until the issuance of the Shares (as evidenced by the appropriate entry on the books of the Company or of a
duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a shareholder shall exist with respect to the Optioned Stock, notwithstanding the exercise of the Option. The Shares shall be issued to the
Optionee as soon as practicable after the Option is exercised in accordance with the Option Agreement. No adjustment shall be made for a dividend or other right for which the record date is prior to the date of issuance except as provided in
Section 13 of the Plan. 
 5. Company’s Right of First Refusal. Before any Shares held by Optionee or any transferee
(either being sometimes referred to herein as the “Holder”) 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”). 
 (a) Notice of Proposed Transfer. The
Holder of the Shares shall deliver to the Company a written notice (the “Notice”) stating: (i) the Holder’s bona fide intention to sell or otherwise transfer such Shares; (ii) the name of each proposed purchaser or other
transferee (“Proposed Transferee”); (iii) the number of Shares to be transferred to each Proposed Transferee; and (iv) 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). 

 (b) 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 (c) below. 
 (c) 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. 

(d) 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. 
 (e) 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. 

(f) 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 Optionee’s lifetime or on the Optionee’s death by will or intestacy to the Optionee’s immediate family or a trust for the benefit of the Optionee’s immediate family shall be exempt from the 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. 

(g) Termination of Right of First Refusal. The Right of First Refusal shall terminate as to any Shares upon the earlier of (i) the
first sale of Common Stock of the Company to the general public, or (ii) a Change in Control in which the successor corporation has equity securities that are publicly traded. 

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

  
 -2- 

 7. Restrictive Legends and Stop-Transfer Orders. 

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

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) AND MAY NOT BE OFFERED, SOLD
OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE
THEREWITH. 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN RESTRICTIONS ON TRANSFER AND A RIGHT OF FIRST REFUSAL HELD BY
THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER. SUCH 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 TRANSFER FOR
A PERIOD NOT TO EXCEED 180 DAYS FOLLOWING THE EFFECTIVE DATE OF THE UNDERWRITTEN PUBLIC OFFERING OF THE COMPANY’S SECURITIES AND MAY NOT BE SOLD OR OTHERWISE DISPOSED OF BY THE HOLDER WITHOUT THE CONSENT OF THE COMPANY OR THE MANAGING
UNDERWRITER. 
 (b) Stop-Transfer Notices. Optionee agrees that, in order to ensure compliance with the restrictions referred to
herein, the Company may issue appropriate “stop transfer” instructions to its transfer agent, if any, and that, if the Company transfers its own securities, it may make appropriate notations to the same effect in its own records. 

(c) Refusal to Transfer. The Company shall not be required (i) to transfer on its books any Shares that have been sold or
otherwise transferred in violation of any of the provisions of this Exercise Notice or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any purchaser or other transferee to whom such Shares shall have
been so transferred. 
 8. Successors and Assigns. The Company may assign any of its rights under this Exercise Notice to single or
multiple assignees, and this Exercise Notice shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Exercise Notice shall be binding upon Optionee and his or her heirs,
executors, administrators, successors and assigns. 

  
 -3- 

 9. Interpretation. Any dispute regarding the interpretation of this Exercise Notice shall
be submitted by Optionee or by the Company forthwith to the Administrator which shall review such dispute at its next regular meeting. The resolution of such a dispute by the Administrator shall be final and binding on all parties. 

10. Governing Law; Severability. This Exercise Notice is governed by the internal substantive laws but not the choice of law rules, of
California. In the event that any provision hereof becomes or is declared by a court of competent jurisdiction to be illegal, unenforceable or void, this Exercise Notice will continue in full force and effect. 

11. Entire Agreement. The Plan and Option Agreement are incorporated herein by reference. This Exercise Notice, the Plan, the Option
Agreement and the Investment Representation Statement constitute the entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the Optionee’s interest except by means of a writing signed by the Company and Optionee. 
  

					
	Submitted by:	  		  	Accepted by:
			
	OPTIONEE	  		  	SUTRO BIOPHARMA, INC.
			
	 	  		  	 
	Signature	  		  	By
			
	 	  		  	 
	Print Name	  		  	Title
			
	Address:	  		  	Address:
			
	 	  		  	 
			
	 	  		  	 
			
	 	  		  	
		  		  	
			
		  		  	 
		  		  	Date Received

  
 -4- 

 EXHIBIT B 

INVESTMENT REPRESENTATION STATEMENT 
  

					
	OPTIONEE:	  	 	  	
			
	COMPANY:	  	 SUTRO BIOPHARMA, INC.
	  	
			
	SECURITY:	  	 COMMON STOCK
	  	
			
	AMOUNT:	  	 	  	
			
	DATE:	  	 	  	

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

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

(c) Optionee is familiar with the provisions of Rule 701 and Rule 144, each promulgated under the Securities Act, which, in
substance, permit limited public resale of “restricted securities” acquired, directly or indirectly from the issuer thereof, in a non-public offering subject to the satisfaction of certain
conditions. Rule 701 provides that if the issuer qualifies under Rule 701 at the time of the grant of the Option to Optionee, the exercise shall be exempt from registration under the Securities Act. In the event the Company becomes subject
to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, ninety (90) days thereafter (or such 

 
longer period as any market stand-off agreement may require) the Securities exempt under Rule 701 may be resold, subject to the satisfaction of the
applicable conditions specified by Rule 144, including in the case of affiliates (1) the availability of certain public information about the Company, (2) the amount of Securities being sold during any three (3) month period not
exceeding specified limitations, (3) the resale being made in an unsolicited “broker’s transaction”, transactions directly with a “market maker” or “riskless principal transactions” (as those terms are defined
under the Securities Exchange Act of 1934) and (4) the timely filing of a Form 144, if applicable. 
 In the event that the
Company does not qualify under Rule 701 at the time of grant of the Option, then the Securities may be resold in certain limited circumstances subject to the provisions of Rule 144, which may require (i) the availability of current
public information about the Company; (ii) the resale to occur more than a specified period after the purchase and full payment (within the meaning of Rule 144) for the Securities; and (iii) in the case of the sale of Securities by an
affiliate, the satisfaction of the conditions set forth in sections (2), (3) and (4) of the paragraph immediately above. 
 (d)
Optionee further understands that in the event all of the applicable requirements of Rule 701 or 144 are not satisfied, registration under the Securities Act, compliance with Regulation A, or some other registration exemption will be required;
and that, notwithstanding the fact that Rules 144 and 701 are not exclusive, the Staff of the Securities and Exchange Commission has expressed its opinion that persons proposing to sell private placement securities other than in a registered
offering and otherwise than pursuant to Rules 144 or 701 will have a substantial burden of proof in establishing that an exemption from registration is available for such offers or sales, and that such persons and their respective brokers who
participate in such transactions do so at their own risk. Optionee understands that no assurances can be given that any such other registration exemption will be available in such event. 

 

			
	Signature of Optionee:
		
		 	 
		
		 	Date:_____________________________,_____

  
 -2- 

 EXHIBIT C 

ADOPTION AGREEMENT 
 This
Adoption Agreement (“Adoption Agreement”) is executed on _________, 20__, by the undersigned (the “Holder”) pursuant to the terms of that certain Second Amended and Restated Voting Agreement dated as of September 26,
2014, as amended (the “Agreement”), by and among the Company and certain of its Stockholders, as such Agreement may be amended or amended and restated hereafter. Capitalized terms used but not defined in this Adoption Agreement shall have
the respective meanings ascribed to such terms in the Agreement. By the execution of this Adoption Agreement, the Holder agrees as follows. 

1. Acknowledgement. Holder acknowledges that Holder is acquiring certain shares of the capital stock of the Company (the
“Stock”) or options, warrants or other rights to purchase such Stock (the “Options”), for one of the following reasons (Check the correct box): 
  

	 	☐	as a transferee of Shares from a party in such party’s capacity as an “Investor” bound by the Agreement, and after such transfer, Holder shall be considered an “Investor” and a
“Stockholder” for all purposes of the Agreement. 

  

	 	☐	as a transferee of Shares from a party in such party’s capacity as a “Common Holder” bound by the Agreement, and after such transfer, Holder shall be considered a “Common Holder” and a
“Stockholder” for all purposes of the Agreement. 

  

	 	☐	as a new Investor in accordance with Section 7.1(a) of the Agreement, in which case Holder will be an “Investor” and a “Stockholder” for all purposes of the Agreement.

  

	 	☐	in accordance with Section 7.1(b) of the Agreement, as a new party who is not a new Investor, in which case Holder will be a “Stockholder” for all purposes of the Agreement.

 2. Agreement. Holder hereby (a) agrees that the Options, and any other shares of capital stock or securities
required by the Agreement to be bound thereby, shall be bound by and subject to the terms of the Agreement and (b) adopts the Agreement with the same force and effect as if Holder were originally a party thereto. 

3. Notice. Any notice required or permitted by the Agreement shall be given to Holder at the address or facsimile number listed below
Holder’s signature hereto. 
 [Signature Page Follows] 

							
				
	HOLDER:    ______________________________________	 		 		 	ACCEPTED AND AGREED:
				
	By:    ____________________________________________	 		 		 	SUTRO BIOPHARMA, INC.
	 Name and Title of Signatory
	 		 		 	
				
	Address:  _________________________________________	 		 	By:	 	 
				
	 	 		 	Title:	 	 
		 		 		 	
	Facsimile Number:    ________________________________	 		 		 	

 [Signature Page to Adoption Agreement]

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