Document:

Amendment to Rights Agreement

 Exhibit 4.1 
 AMENDMENT TO RIGHTS AGREEMENT 
 This Amendment to Rights Agreement (this
“Amendment”), dated as of November 9, 2006, between Tanox, Inc., a Delaware corporation (the “Company”), and American Stock Transfer & Trust Company, a New York corporation, as Rights
Agent (the “Rights Agent”), amends that certain Rights Agreement, dated as of July 27, 2001 (the “Rights Agreement”). 
 The Company and the Rights Agent have heretofore executed and entered into the Rights Agreement. Pursuant to Section 27 of the Rights Agreement, the Company and the Rights Agent may from time to time
supplement or amend the Rights Agreement in accordance with the provisions of Section 27 thereof and the Company desires and directs the Rights Agent to so amend the Rights Agreement. All acts and things necessary to make this Amendment
a valid agreement according to its terms have been done and performed, and the execution and delivery of this Amendment by the Company and the Rights Agent have been in all respects authorized by the Company and the Rights Agent. 
 In consideration of the foregoing premises and mutual agreements set forth in the Rights Agreement and this Amendment, the parties hereto agree as
follows: 
  

	1.	The definition of “Acquiring Person” as set forth in Section 1 of the Rights Agreement is hereby amended by adding as the final paragraph thereto the
following: 

 “Notwithstanding the foregoing, Genentech, Inc., a Delaware corporation
(“Genentech”), or any Affiliate or Associate thereof, including Green Acquisition Corporation, a Delaware corporation and wholly-owned subsidiary of Genentech (“Merger Sub”) (collectively with Genentech and any
Affiliate or Associate of Genentech, “Parent”), shall not become an “Acquiring Person” as a result of (i) the approval, execution or delivery of that certain Agreement and Plan of Merger dated as of November 9,
2006 (as the same may be amended from time to time, the “Merger Agreement”), by and among the Company, Genentech and Merger Sub, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of
the Merger (as such term is defined in the Merger Agreement), (iii) the acceptance for payment and purchase or exchange of Company Common Stock (as such term is defined in the Merger Agreement) pursuant to the Merger Agreement, (iv) the
announcement of the execution of the Merger Agreement or the entry into the Merger or (v) the consummation of any other transaction contemplated by the Merger Agreement.” 
  

	2.	The definition of “Distribution Date” as set forth in Section 1 of the Rights Agreement is hereby amended by adding as the final sentence thereto the
following: 

 “Notwithstanding anything in this Agreement to the contrary, no Distribution Date shall be
deemed to have occurred as a result of (i) the approval, execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of the Merger, (iii) the
acceptance for payment and purchase or exchange of Company Common Stock pursuant to the Merger Agreement, (iv) the announcement of execution of the Merger Agreement or entry into the Merger or (v) the consummation of any other transaction
contemplated by the Merger Agreement.” 

	3.	The definition of “Stock Acquisition Date” as set forth in Section 1 of the Rights Agreement is hereby amended by adding as the final sentence thereto the
following: 

 “Notwithstanding anything in the Agreement to the contrary, no Stock Acquisition Date shall
be deemed to have occurred as a result of (i) the approval, execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of the Merger, (iii) the
acceptance for payment and purchase or exchange of Company Common Stock pursuant to the Merger Agreement, (iv) the announcement of the Merger Agreement or the Merger or (v) the consummation of any other transaction contemplated by the
Merger Agreement.” 
  

	4.	The definition of “Expiration Date” as set forth in Section 1 of the Rights Agreement is hereby amended so that it reads, in its entirety, as follows:

 “Expiration Date” shall mean the earliest of (i) the Final Expiration Date, (ii) the time
at which the Rights are redeemed as provided in Section 23 hereof, (iii) the time at which the Rights expire pursuant to Section 13(d) hereof, (iv) the time at which all Rights then outstanding and exercisable are exchanged
pursuant to Section 24 hereof, and (v) immediately prior to the Effective Time (as such term is defined in the Merger Agreement). 
  

	5.	Section 11(a)(ii) of the Rights Agreement is hereby amended by adding as the final sentence thereto the following: 

 “Notwithstanding the foregoing, no “Flip-In Event” shall be deemed to have occurred as a result of (i) the approval,
execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of the Merger, (iii) the acceptance for payment and purchase or exchange of Company Common Stock
pursuant to the Merger Agreement, (iv) the announcement of the Merger Agreement or the Merger or (v) the consummation of any other transaction contemplated by the Merger Agreement.” 
  

	6.	Section 11(a)(iii) of the Rights Agreement is hereby amended by adding as the final sentence thereto the following: 

 “Notwithstanding the foregoing, no “Flip-In Trigger Date” shall be deemed to have occurred as a result of (i) the
approval, execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of the Merger, (iii) the acceptance for payment and purchase or exchange of Company
Common Stock pursuant to the Merger Agreement, (iv) the announcement of the Merger Agreement or the Merger or (v) the consummation of any other transaction contemplated by the Merger Agreement.” 
  

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	7.	Section 13(a) of the Rights Agreement is hereby amended by adding as the final sentence thereto the following: 

 “Notwithstanding anything in this Agreement to the contrary, none of the events described in clauses (x) through
(z) of the first sentence of Section 13(a) shall be deemed to have occurred as a result of (i) the approval, execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments
thereto, (ii) the consummation of the Merger, (iii) the acceptance for payment and purchase or exchange of Company Common Stock pursuant to the Merger Agreement, (iv) the announcement of the Merger Agreement or the Merger or
(v) the consummation of any other transaction contemplated by the Merger Agreement.” 
  

	8.	Section 13(b) of the Rights Agreement is hereby amended by adding as the final sentence thereto the following: 

 “Notwithstanding anything in this Agreement to the contrary, Genentech, or any Affiliate or Associate thereof, including Merger Sub,
shall not become a “Principal Party” as a result of (i) the approval, execution or delivery of the Merger Agreement, including the approval, execution and delivery of any amendments thereto, (ii) the consummation of the Merger,
(iii) the acceptance for payment and purchase or exchange of Company Common Stock pursuant to the Merger Agreement, (iv) the announcement of the Merger Agreement or the Merger or (v) the consummation of any other transaction
contemplated by the Merger Agreement.” 
  

	9.	A new Section 35 shall be added and shall read as follows: 

 “Section 35. TERMINATION. Immediately prior to the Effective Time (as such term is defined in the Merger Agreement), this Agreement shall terminate and all outstanding Rights shall expire.”

  

	10.	Except as expressly amended hereby, the Rights Agreement remains in full force and effect in accordance with its terms. 

  

	11.	This Amendment to the Rights Agreement shall be governed by and construed in accordance with the laws of the State of Delaware. 

  

	12.	This Amendment may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed an original, and all such counterparts shall together
constitute but one and the same instrument. 

  

	13.	Except as expressly set forth herein, this Amendment shall not by implication or otherwise alter, modify, amend or in any way affect any of the terms, conditions, obligations,
covenants or agreements contained in the Rights Agreement, all of which are ratified and affirmed in all respects and shall continue in full force and effect. 

  

	14.	Capitalized terms used herein but not defined shall have the meanings given to them in the Rights Agreement or in the Merger Agreement, as the case may be. 

 

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 IN WITNESS WHEREOF, the parties hereto have caused this Amendment to the Rights Agreement to be duly
executed as of the day and year first above written. 
  

			
	TANOX, INC.
		
	By:	 	 /s/ Gregory Guidroz

	Name:	 	 Gregory Guidroz

	Title:	 	 V. P. – Finance

	
	 AMERICAN STOCK TRANSFER & TRUST
 COMPANY, as Rights Agent

		
	By:	 	 /s/ Herbert J. Lemmer

	Name:	 	Herbert J. Lemmer
	Title:	 	Vice President

  

 4Form of Voting Agreement

 Exhibit 10.1 
 EXECUTION COPY 
 FORM OF VOTING AGREEMENT 
 THIS VOTING AGREEMENT (this “Agreement”) is made and entered into as of November 9, 2006, by and between Genentech, Inc., a
Delaware corporation (“Parent”) and the undersigned stockholder (“Stockholder”) of Tanox, Inc. (the “Company”). 
 RECITALS 
 A. Concurrently with the execution of this Agreement, Parent and the Company have entered
into an Agreement and Plan of Merger (the “Merger Agreement”), which provides for the merger (the “Merger”) of a wholly-owned subsidiary of Parent with and into the Company. 
 B. Pursuant to the Merger, all of the issued and outstanding shares of capital stock and options of the Company will be canceled and converted into the
right to receive the consideration set forth in the Merger Agreement, all upon the terms and subject to the conditions set forth in the Merger Agreement. 
 C. As of the date hereof, Stockholder is the beneficial owner (as defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) of the number of shares of
outstanding capital stock of the Company (the “Shares”) and other securities convertible into, or exercisable or exchangeable for, shares of capital stock of the Company (the “Options”), all as set forth on the
signature page of this Agreement; provided that for purposes of determining beneficial ownership pursuant to this Agreement, Stockholder shall in all cases be deemed to be the beneficial owner of any securities which may be acquired by such
Stockholder pursuant to any agreement, arrangement or understanding or upon the exercise of conversion rights, exchange rights, warrants or options, or otherwise (irrespective of whether the right to acquire such securities is exercisable
immediately or only after the passage of time, including the passage of time in excess of 60 days, the satisfaction of any conditions, the occurrence of any event or any combination of the foregoing). 
 D. As a material inducement to Parent to enter into and to consummate the transactions contemplated by the Merger Agreement, Parent has required that
Stockholder agree, and Stockholder is willing to agree, to restrict the transfer or disposition of any Shares, Options and any New Shares (as defined in Section 1(b) hereof), and to vote the Shares and any New Shares as set forth in this
Agreement. 
 NOW, THEREFORE, the parties hereto hereby agree as follows: 
 1. Agreement to Retain Shares and Options. 
 (a) Transfer. Stockholder agrees that, at all times during the period beginning on the date hereof and ending at the Expiration Time, Stockholder shall not Transfer (as defined below) any of the Shares, Options and any New Shares, or
make any agreement or understanding 

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 regarding any Transfer, in each case without the prior written consent of Parent. Stockholder agrees that any Transfer in violation of this Agreement shall be void and of no force or effect. 
 As used herein, the term “Expiration Time” shall mean the earlier to occur of (i) such date and time as the Merger shall become
effective in accordance with the terms and provisions of the Merger Agreement, or (ii) the termination of the Merger Agreement in accordance with the terms thereof. As used herein, the term “Transfer” shall mean, with respect
to any security, the direct or indirect assignment, sale, transfer, tender, pledge, hypothecation, or the gift, placement in trust, or the Constructive Sale (as defined below) or other disposition of such security (excluding [exercises of Options
and]1 transfers by testamentary or intestate succession or otherwise by operation of law) or any right, title or
interest therein (including, but not limited to, any right or power to vote to which the holder thereof may be entitled, whether such right or power is granted by proxy or otherwise), or the record or beneficial ownership thereof, the offer to make
such a sale, transfer, tender, pledge, hypothecation or Constructive Sale or other disposition, and each agreement, arrangement or understanding, whether or not in writing, to effect any of the foregoing, excluding any Transfer (A) pursuant to
a court order, (B) pursuant to the Merger, (C) to any affiliate or family member of Stockholder if such transferee, prior to the Transfer, executes a binding agreement with Parent and the Company substantially in the form of this Agreement
[or (D) that is a sale (other than a Constructive Sale) in the open market through a brokers’ transaction (as defined in Rule 144(g) under the Securities Act of 1933, as amended)]2. As used herein, the term “Constructive Sale” shall mean, with respect to any security, a short sale with respect to such security, entering
into or acquiring an offsetting derivative contract with respect to such security, entering into or acquiring a futures or forward contract to deliver such security or entering into any other hedging or other derivative transaction that has the
effect of materially changing the economic benefits and risks of ownership. 
 (b) New Shares. Stockholder agrees that any shares of
capital stock of the Company that Stockholder purchases or with respect to which Stockholder otherwise acquires beneficial ownership after the date of this Agreement and prior to the Expiration Time, including, without limitation, shares issued or
issuable upon the conversion, exercise or exchange, as the case may be, of any Options held by Stockholder (“New Shares”), shall be subject to the terms and conditions of this Agreement to the same extent as if they constituted
Shares as of the date hereof. 
 2. Agreement to Vote Shares. Until the Expiration Time, at every meeting of stockholders of the
Company called with respect to any of the following, and at every adjournment or postponement thereof, and on every action or approval by written consent of stockholders of the Company with respect to any of the following, Stockholder shall vote, to
the extent not voted by the person(s) appointed under the Proxy (as defined in Section 3), the outstanding Shares and any outstanding New Shares (to the extent any such New Shares may be voted): 
  

	1	This language was included in voting agreements executed by Julia Brown, Heinz Bull, Danong
Chen, Gary Frashier, Osama Mikhail and Peter Traber, but was excluded from the voting agreements executed by Nancy Chang and Tse-Wen Chang. 

	2	This language was included in voting agreements executed by Julia Brown, Heinz Bull, Danong
Chen, Gary Frashier, Osama Mikhail and Peter Traber, but was excluded from the voting agreements executed by Nancy Chang and Tse-Wen Chang. 

  

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 (i) in favor of adoption of the Merger Agreement and in favor of any other action contemplated by the Merger Agreement or required in furtherance of the Merger and the transactions contemplated by the Merger
Agreement (including one or more adjournments necessary to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement and any such related proposals at the time of any meeting held for such purposes); 
 (ii) against approval of any proposal made in opposition to, or in competition with, consummation of the Merger and the transactions contemplated by
the Merger Agreement; 
 (iii) against any of the following actions (other than those actions contemplated by the Merger Agreement):
(A) any merger, consolidation, business combination, sale of assets, reorganization or recapitalization of the Company or any subsidiary of the Company with any party, (B) any sale, lease, license or transfer of any significant part of the
assets of the Company or any subsidiary of the Company, (C) any reorganization, recapitalization, dissolution, liquidation or winding up of the Company or any subsidiary of the Company, (D) any amendment to the certificate of incorporation
or bylaws of the Company or any subsidiary of the Company or any material change in the capitalization of the Company or any subsidiary of the Company, or the corporate structure of the Company or any subsidiary of the Company, or (E) any other
action that is intended, or could reasonably be expected to, impede, frustrate, prevent, interfere with, delay, postpone, discourage, nullify or adversely affect the Merger, the Merger Agreement or any of the other transactions contemplated by the
Merger Agreement; and 
 (iv) in favor of waiving any notice that may have been or may be required relating to any such meeting of
stockholders or written consent, the Merger, the Merger Agreement or the transactions contemplated thereby. 
 Prior to the Expiration Time,
Stockholder shall not enter into any agreement or understanding with any person to vote or give instructions in any manner inconsistent with this Section 2. Prior to the Expiration Time, to the extent not represented thereat by the
person(s) appointed under the Proxy, Stockholder shall [cause the Shares and any New Shares to be counted as present thereat for purposes of establishing quorum.]3 
 3. Irrevocable Proxy. Concurrently with
the execution of this Agreement, Stockholder agrees to deliver to Parent an irrevocable proxy in the form attached hereto as Appendix A (the “Proxy”), which shall be irrevocable to the fullest extent permitted by
applicable law, covering the total number of Shares and New Shares. 
 4. Representations, Warranties and Covenants of Stockholder.
Stockholder represents, warrants and covenants to Parent as follows: 
 (i) Stockholder is the beneficial owner of the Shares, with full power
to vote or direct the voting of the Shares and to dispose of the Shares for and on behalf of any and all beneficial owners of the Shares, with no limitations, qualifications or restrictions on such rights. 
  

	3	This language was included in voting agreements executed by Julia Brown, Heinz Bull, Danong Chen, Gary Frashier, Osama Mikhail and Peter Traber. In the voting
agreements executed by Nancy Chang and Tse-Wen Chang, the following language was substituted for the highlighted language: “appear at any meeting of stockholders of the Company and cause the Shares and any New Shares to be counted as present
thereat for purposes of establishing quorum.” 

	

  

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 (ii) As of the date hereof, the Shares are, and at all times up until the Expiration Time the Shares will be, free and clear of any rights of first refusal, co-sale rights, security interests, liens, pledges, claims,
options, charges or other encumbrances of any kind or nature, in each case that could impair Stockholder’s ability to fulfill its obligations under Section 2. The execution and delivery of this Agreement by Stockholder do not, and
Stockholder’s performance of its obligations under this Agreement will not, conflict with or violate any order, decree, judgment or Contract applicable to Stockholder or by which Stockholder or any of Stockholder’s properties or Shares is
bound. 
 (iii) Stockholder does not beneficially own any shares of capital stock of the Company, or any securities convertible into, or
exchangeable or exercisable for, shares of capital stock of the Company, other than as set forth on the signature page hereto. 
 (iv)
Stockholder has full power and authority to make, enter into and carry out the terms of this Agreement, the Proxy and any other related agreements to which Stockholder is a party. 
 (v) Stockholder shall not take any action that the Company is prohibited from authorizing or permitting any Representative (as defined in the Merger
Agreement) from taking under Section 5.4(a) of the Merger Agreement, whether or not Stockholder is or remains a Representative. 
 (vi)
Stockholder agrees that it will not bring, commence, institute, maintain, prosecute, participate in or voluntarily aid any Action before any Governmental Entity, which alleges that the execution and delivery of this Agreement by Stockholder, either
alone or together with the other Company voting agreements and proxies to be delivered in connection with the execution of the Merger Agreement, or the approval of the Merger Agreement by the board of directors of the Company, breaches any fiduciary
duty of the board of directors of the Company or any member thereof; provided, that Stockholder may defend against, contest or settle any such action, claim, suit or cause of action brought against Stockholder that relates solely to
Stockholder’s capacity as a director or officer of the Company. 
 (vii) Stockholder shall not exercise any rights (including under
Section 262 of the Delaware Law) to demand appraisal or dissenters’ rights with respect to any Shares or New Shares that may be available with respect to the Merger. 
 5. Further Assurances. Stockholder hereby covenants and agrees to take, or cause to be taken, all actions, and to do, or cause to be done, all
things reasonably necessary to fulfill such Stockholder’s obligations under this Agreement, and to execute and deliver any additional documents reasonably necessary or desirable to carry out the purpose and intent of this Agreement. 

 

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 6. Consents and Waivers. Stockholder hereby gives any consents or waivers that are reasonably required for the consummation of the Merger under the terms of any Contract or other instrument to which Stockholder
is a party or subject or in respect of any rights Stockholder may have. Stockholder further consents to the Company placing a stop transfer order on the Shares and any New Shares with its transfer agent(s) in accordance with Section 8.

 7. Termination. This Agreement and the Proxy delivered in connection herewith shall terminate automatically and shall have no
further force or effect as of the Expiration Time. 
 8. Company Covenants. The Company agrees to make a notation on its records and
give instructions to its transfer agent(s) to not permit, prior to the Expiration Time, the transfer of any Shares or New Shares, except as permitted pursuant to Section 1(a). 
 9. Miscellaneous. 
 (a) Directors
and Officers. Notwithstanding any provision of this Agreement to the contrary, Stockholder has entered into this Agreement in his or her capacity as a Stockholder of the Company, and nothing in this Agreement shall limit or restrict Stockholder
from acting in the Stockholder’s capacity as a director or officer of the Company, as applicable (it being understood that this Agreement shall apply to Stockholder solely in Stockholder’s capacity as a stockholder of the Company).

 (b) Waiver. No waiver by any party hereto of any condition or any breach of any term or provision set forth in this Agreement shall
be effective unless in writing and signed by the other party hereto. The waiver of any breach of any term or provision of this Agreement shall not operate as or be construed to be a waiver of any other previous or subsequent breach of any term or
provision of this Agreement. No delay or omission by Parent in exercising any right under this Agreement shall operate as a waiver of that right or any other right under this Agreement. 
 (c) Notices. All notices and other communications hereunder shall be in writing and shall be deemed given if delivered personally or by commercial
delivery service, or sent via telecopy (receipt confirmed) to the parties at the following addresses or telecopy numbers (or at such other address or telecopy numbers for a party as shall be specified by like notice): 
  

	 	(i)	if to Parent, to: 

 Genentech, Inc. 
 1 DNA Way 
 South San Francisco, California
94080 
 Attention: Corporate Secretary 
 Telephone No.: (650) 225-1000 
 Telecopy No.: (650) 467-9146 
  

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 EXECUTION COPY 
 with a copy to: 
 Wilson Sonsini Goodrich & Rosati 
 Professional Corporation 
 650 Page Mill
Road 
 Palo Alto, California 94304 
 Attention:     Martin W. Korman, Esq. 
       Bradley L Finkelstein, Esq.

 Telephone No.: (650) 493-9300 
 Telecopy No.: (650) 493-6811 
  

	 	(ii)	if to Stockholder: To the address for notice set forth on the signature page hereof. 

 (d) Headings. All captions and section headings used in this Agreement are for are for reference purposes only and shall not affect in any way the meaning or interpretation of this Agreement. 
 (e) Counterparts. This Agreement may be executed in one or more counterparts, all of which shall be considered the same agreement and shall become
effective when one or more counterparts have been signed by each of the parties and delivered to the other party, it being understood that all parties need not sign the same counterpart. 
 (f) Entire Agreement; Amendment. This Agreement constitutes the entire agreement among the parties with respect to the subject matter hereof and
supersedes all prior agreements and understandings, both written and oral, among the parties with respect to the subject matter hereof. This Agreement may not be changed or modified, except by an agreement in writing specifically referencing this
Agreement and executed by each of the parties hereto. 
 (g) Severability. In the event that any provision of this Agreement, or the
application thereof, becomes or is declared by a court of competent jurisdiction to be illegal, void or unenforceable, the remainder of this Agreement will continue in full force and effect and the application of such provision to other persons or
circumstances will be interpreted so as reasonably to effect the intent of the parties hereto. The parties further agree to replace such void or unenforceable provision of this Agreement with a valid and enforceable provision that will achieve, to
the extent possible, the economic, business and other purposes of such void or unenforceable provision. 
 (h) Governing Law. This
Agreement shall be governed by and construed in accordance with the laws of the State of Delaware, regardless of the laws that might otherwise govern under applicable principles of conflicts of law thereof. The parties hereto hereby irrevocably
submit to the exclusive jurisdiction of the Court of Chancery in Newcastle County in the state of Delaware (and any appellate courts therefrom), or if such jurisdiction shall be unavailable, any court in the State of Delaware and the Federal courts
of the United States of 
  

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 EXECUTION COPY 
 America, each located within Newcastle County in the State of Delaware., solely in respect of the interpretation and enforcement of the provisions of this Agreement, and in respect of the transactions contemplated hereby and thereby, and
hereby waive, and agree not to assert, as a defense in any action, suit or proceeding for the interpretation or enforcement hereof or thereof, that it is not subject thereto or that such action, suit or proceeding may not be brought or is not
maintainable in said courts or that the venue thereof may not be appropriate or that this Agreement may not be enforced in or by such courts, and the parties hereto irrevocably agree that all claims with respect to such action or proceeding shall be
heard and determined in the Court of Chancery in the State of Delaware or, if jurisdiction is not available in the Court of Chancery, any other Delaware state court or Federal court, each located in Newcastle, County Delaware. The parties hereby
consent to and grant any such court jurisdiction over the person of such parties and over the subject matter of such dispute and agree that mailing of process or other papers in connection with any such action or proceeding in the manner provided in
Section 9(c) or in such other manner as may be permitted by applicable law, shall be valid and sufficient service thereof. With respect to any particular action, suit or proceeding, venue shall lie solely in Newcastle County, Delaware.

 (i) Rules of Construction. The parties hereto agree that they have been represented by counsel during the negotiation and
execution of this Agreement and, therefore, waive the application of any law, regulation, holding or rule of construction providing that ambiguities in this Agreement will be construed against the party drafting such agreement or document. The words
“include,” “includes” and “including” when used herein shall be deemed in each case to be followed by the words “without limitation.” All capitalized terms that are used but not defined herein shall have the
meanings ascribed to them in the Merger Agreement. 
 (j) Remedies. The parties acknowledge that Parent will be irreparably harmed and
that there will be no adequate remedy at law for a violation of any of the covenants or agreements of Stockholder set forth herein. Therefore, it is agreed that, in addition to any other remedies that may be available to Parent upon any such
violation, Parent shall have the right to enforce such covenants and agreements by specific performance, injunctive relief or by any other means available to Parent at law or in equity. 
 (k) No Assignment. Unless otherwise provided for herein, Stockholder may not assign this Agreement. This Agreement shall inure to the benefit of
Parent, Company and their respective successors and assigns. 
 (l) Waiver of Jury Trial. EACH OF PARENT AND STOCKHOLDER HEREBY
IRREVOCABLY WAIVES ALL RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE ACTIONS OF PARENT OR STOCKHOLDER IN THE NEGOTIATION,
ADMINISTRATION, PERFORMANCE AND ENFORCEMENT HEREOF. 
  

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 [Remainder of Page Intentionally Left Blank] 
  

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 IN WITNESS WHEREOF, the undersigned have executed this Agreement on the date first above written. 
  

			
	GENENTECH, INC.
		
	By:	 	  

	Name:	 	  

	Title:	 	  

	
	STOCKHOLDER:
	
	  

	Signature
	  

	Print Name
	
	Shares:
	Company Common Stock: ___________________________________
	Company Options: _________________________________________
	
	Stockholder’s address for notice:
	
	  

	  

	  

 **** Signature Page to Company Voting Agreement*** 

 EXECUTION COPY 
 APPENDIX A 
 IRREVOCABLE PROXY 
 The undersigned stockholder (“Stockholder”) of Tanox, Inc., a Delaware corporation (the “Company”), hereby irrevocably
(to the fullest extent permitted by law) appoints Stephen Julesgaard and David Ebersman of Genentech, Inc., a Delaware corporation (“Parent”), and each of them, as the sole and exclusive attorneys-in-fact and proxies of the
undersigned, with full power of substitution and resubstitution, to vote and exercise all voting and related rights (to the full extent that the undersigned is entitled to do so) with respect to all Shares and New Shares (each as defined in the that
certain Voting Agreement, dated of even date herewith, by and among Parent, the Company and Stockholder (the “Voting Agreement”)), in accordance with the terms of this Proxy until the Expiration Time (as defined in the Voting
Agreement). The Shares beneficially owned by the undersigned stockholder of the Company as of the date of this Proxy are listed on the final page of this Proxy. Upon the undersigned’s execution of this Proxy, any and all prior proxies given by
the undersigned with respect to any Shares are hereby revoked and the undersigned hereby agrees not to grant any subsequent proxies with respect to the Shares or any New Shares until after the Expiration Time (as defined in the Voting Agreement).

 This Proxy is irrevocable (to the fullest extent permitted by law), is coupled with an interest, is granted pursuant to the Voting
Agreement, and is granted in consideration of Parent entering into that certain Agreement and Plan of Merger, dated as of November 9, 2006, by and among Parent, the Company and certain other parties (the “Merger Agreement”).
The Merger Agreement provides for the merger of a wholly-owned subsidiary of Parent with and into the Company in accordance with its terms (the “Merger”), and Stockholder is receiving a portion of the proceeds of the Merger.

 The attorneys-in-fact and proxies named above are hereby authorized and empowered by the undersigned, at any time prior to the Expiration
Time, to act as the undersigned’s attorney-in-fact and proxy to vote the Shares and any New Shares, and to exercise all voting, consent and similar rights of the undersigned with respect to the Shares and new Shares (including, without
limitation, the power to execute and deliver written consents), at every annual, special, adjourned or postponed meeting of stockholders of the Company and in every written consent in lieu of such meeting: 
 (i) in favor of adoption of the Merger Agreement and in favor of any other action contemplated by the Merger Agreement or required in furtherance of
the Merger and the transactions contemplated by the Merger Agreement (including one or more adjournments necessary to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement and any such related proposals at the time
of any meeting held for such purposes); 

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 (ii) against approval of any proposal made in opposition to, or in competition with, consummation of the Merger and the transactions contemplated by the Merger Agreement; 
 (iii) against any of the following actions (other than those actions contemplated by the Merger Agreement): (A) any merger, consolidation, business
combination, sale of assets, reorganization or recapitalization of the Company or any subsidiary of the Company with any party, (B) any sale, lease, license or transfer of any significant part of the assets of the Company or any subsidiary of
the Company, (C) any reorganization, recapitalization, dissolution, liquidation or winding up of the Company or any subsidiary of the Company, (D) any amendment to the certificate of incorporation or bylaws of the Company or any subsidiary
of the Company or any material change in the capitalization of the Company or any subsidiary of the Company, or the corporate structure of the Company or any subsidiary of the Company, or (E) any other action that is intended, or could
reasonably be expected to, impede, frustrate, prevent, interfere with, delay, postpone, discourage, nullify or adversely affect the Merger, the Merger Agreement or any of the other transactions contemplated by the Merger Agreement; and 

(iv) in favor of waiving any notice that may have been or may be required relating to any such meeting of stockholders or written consent, the Merger,
the Merger Agreement or the transactions contemplated thereby. 
 Any obligation of the undersigned hereunder shall be binding upon the
successors and assigns of the undersigned. 
 This Proxy shall terminate, and be of no further force and effect, automatically as of the
Expiration Time. 
 [Remainder of Page Intentionally Left Blank] 
 ***** 
  

 2 

 EXECUTION COPY 
 This Proxy shall terminate, and be of no further force and effect, automatically upon the Expiration Time (as defined in the Voting Agreement). 
 Dated: November 9, 2006 
  

	
	  

	Signature
	  

	Print Name
	  

	  

	Address
	
	Shares:
	
	Company Common Stock: ___________________________________
	
	Company Options: _________________________________________

 ****Signature Page to Proxy****

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