Exhibit 10.1

SUBSCRIPTION AGREEMENT

XOMA Corporation

2910 Seventh Street

Berkeley, California 94710

Ladies and Gentlemen:

The undersigned (the “Investor”) hereby confirms its agreement with you as follows:

1. This Subscription Agreement, including the Terms and Conditions For Purchase of Units attached hereto as Annex I (collectively, this “Agreement”) is made as of the date set forth below between XOMA Corporation, a Delaware corporation (the “Company”), and the Investor.

2. The Company has authorized the sale and issuance to certain investors of up to an aggregate of [                    ] units (the “Units”), with each Unit consisting of (i) one share (the “Share,” collectively, the “Shares”) of its common stock, par value $0.0075 per share (the “Common Stock”), and (ii) one warrant (the “Warrant,” collectively, the “Warrants”) to purchase one share of Common Stock, in substantially the form attached hereto as Exhibit B, for a purchase price of $[        ] per Unit (the “Purchase Price”). Units will not be issued or certificated. The Shares and Warrants are immediately separable and will be issued separately. The shares of Common Stock issuable upon exercise of the Warrants are referred to herein as the “Warrant Shares” and, together with the Units, the Shares and the Warrants, are referred to herein as the “Securities”).

3. The offering and sale of the Units (the “Offering”) are being made pursuant to (1) an effective Registration Statement on Form S-3 (File No. 333-191078) (including the Prospectus contained therein (the “Base Prospectus”), the “Registration Statement”) filed by the Company with the Securities and Exchange Commission (the “Commission”), (2) if applicable, the “free writing prospectus” (as that term is defined in Rule 405 under the Securities Act of 1933, as amended (the “Act”)), that have or will be filed with the Commission and delivered to the Investor on or prior to the date hereof (the “Issuer Free Writing Prospectus”), and (3) a Prospectus Supplement (the “Prospectus Supplement” and together with the Base Prospectus, the “Prospectus”) containing certain supplemental information regarding the Securities, the terms of the Offering the terms of the Offering and information that may be material to the Company and its securities that will be filed with the Commission and delivered to the Investor (or made available to the Investor by the filing by the Company of an electronic version thereof with the Commission).

4. The Company and the Investor agree that the Investor will purchase from the Company and the Company will issue and sell to the Investor the Units set forth below for the aggregate purchase price set forth below. The Units shall be purchased pursuant to the Terms and Conditions for Purchase of Units attached hereto as Annex I and incorporated herein by this reference as if fully set forth herein. The Investor acknowledges that the Offering is not being underwritten by the placement agents (the “Placement Agents”) named in the Prospectus Supplement and that there is no minimum offering amount.

5. The manner of settlement of the Shares included in the Units purchased by the Investor shall be as follows:

Delivery versus payment (“DVP”) through DTC (i.e., the Company shall deliver Shares registered in the Investor’s name and address as set forth below and released by the Transfer Agent to the Investor through DTC at the Closing directly to the account(s) at Cowen & Company, LLC (“Cowen”) identified by the Investor and simultaneously therewith payment shall be made by Cowen by wire transfer to the Company). NO LATER THAN ONE (1) BUSINESS DAY AFTER THE EXECUTION OF THIS AGREEMENT BY THE INVESTOR AND THE COMPANY, THE INVESTOR SHALL:

IT IS THE INVESTOR’S RESPONSIBILITY TO (A) MAKE THE NECESSARY WIRE TRANSFER OR CONFIRM THE PROPER ACCOUNT BALANCE IN A TIMELY MANNER AND (B) ARRANGE FOR SETTLEMENT BY WAY OF DWAC OR DVP IN A TIMELY MANNER. IF THE INVESTOR DOES NOT DELIVER THE AGGREGATE PURCHASE PRICE FOR THE UNITS OR DOES NOT MAKE PROPER ARRANGEMENTS FOR SETTLEMENT IN A TIMELY MANNER, THE UNITS MAY NOT BE DELIVERED AT CLOSING TO THE INVESTOR OR THE INVESTOR MAY BE EXCLUDED FROM THE OFFERING ALTOGETHER.

6. The executed Warrant included in the Units purchased by the Investor shall be delivered in accordance with the terms thereof.

7. The Investor represents that, except as set forth below, (a) it has had no position, office or other material relationship within the past three years with the Company or persons known to it to be affiliates of the Company, (b) it is not a FINRA member or an Associated Person (as such term is defined under the FINRA Membership and Registration Rules Section 1011) as of the Closing, and (c) neither the Investor nor any group of Investors (as identified in a public filing made with the Commission) of which the Investor is a part in connection with the Offering, acquired, or obtained the right to acquire, 20% or more of the Common Stock (or securities convertible into or exercisable for Common Stock) or the voting power of the Company on a post-transaction basis. Exceptions:

8. The Investor represents that it has received (or otherwise had made available to it by the filing by the Company of an electronic version thereof with the Commission) the Base Prospectus, dated September 20, 2013, which is a part of the Company’s Registration Statement, the documents incorporated by reference therein and the Issuer Free Writing Prospectus (collectively, the “Disclosure Package”), which includes pricing and other information regarding the Offering (the “Offering Information”), prior to or in connection with the receipt of this Agreement. Such information may be provided to the Investor by any means permitted under the Act, including the Preliminary Prospectus Supplement, Prospectus Supplement, a free writing prospectus and oral communications.

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9. No offer by the Investor to buy Units will be accepted and no part of the Purchase Price will be delivered to the Company until the Investor has received the Disclosure Package including the Offering Information and the Company has accepted such offer by countersigning a copy of this Agreement, and any such offer may be withdrawn or revoked, without obligation or commitment of any kind, at any time prior to the Company (or a Placement Agent on behalf of the Company) sending (orally, in writing or by electronic mail) notice of its acceptance of such offer. An indication of interest will involve no obligation or commitment of any kind until the Investor has been delivered the Disclosure Package including the Offering Information and this Agreement is accepted and countersigned by or on behalf of the Company.

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Please confirm that the foregoing correctly sets forth the agreement between us by signing in the space provided below for that purpose.

Agreed and Accepted

this [    ] day of December, 2014:

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ANNEX I

TERMS AND CONDITIONS FOR PURCHASE OF UNITS

1. Authorization and Sale of the Units. Subject to the terms and conditions of this Agreement, the Company has authorized the sale of the Units.

2. Agreement to Sell and Purchase the Units; Placement Agents.

2.1 At the Closing (as defined in Section 3.1), the Company will sell to the Investor, and the Investor will purchase from the Company, upon the terms and conditions set forth herein, the number of Units set forth on the last page of the Agreement to which these Terms and Conditions for Purchase of Units are attached as Annex I (the “Signature Page”) for the aggregate purchase price therefor set forth on the Signature Page.

2.2 The Company proposes to enter into substantially this same form of Subscription Agreement with certain other investors (the “Other Investors”) and expects to complete sales of Units to them. The Investor and the Other Investors are hereinafter sometimes collectively referred to as the “Investors,” and this Agreement and the Subscription Agreements executed by the Other Investors are hereinafter sometimes collectively referred to as the “Agreements.”

2.3 Investor acknowledges that the Company has agreed to pay Cowen & Company, LLC (“Cowen” or the “Placement Agents”) a fee (the “Placement Fee”) in respect of the sale of Units to the Investor.

2.4 The Company has entered into a Placement Agent Agreement, dated December [    ], 2014 (the “Placement Agreement”), with the Placement Agents that contains certain representations, warranties, covenants and agreements of the Company that may be relied upon by the Investor, which shall be a third party beneficiary thereof. The Company confirms that neither it nor any other Person (as defined below) acting on its behalf has provided the Investor or their agents or counsel with any information that constitutes or could reasonably be expected to constitute material, nonpublic information, except as will be disclosed in the Form 8-K filing (as defined below) that will be filed with the Commission in connection with the Offering. The Company understands and confirms that the Investor will rely on the foregoing representations in effecting transactions in securities of the Company. “Person” means an individual, a limited liability company, a partnership, a joint venture, a corporation, a trust, an unincorporated organization, any other entity and a government or any department or agency thereof.

3. Closings and Delivery of the Units and Funds.

3.1 Closing. The completion of the purchase and sale of the Units (the “Closing”) shall occur at a place and time (the “Closing Date”) to be specified by the Company and Cowen, and of which the Investors will be notified in advance by Cowen, in accordance with Rule 15c6-1 promulgated under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). At the Closing, (a) the Company shall cause the Transfer Agent to deliver to the Investor the number of Shares set forth on the Signature Page registered in the name of the Investor or, if so indicated on the Investor Questionnaire attached hereto as Exhibit A, in the name of a nominee designated by the Investor, (b) the Company shall cause to be delivered to the Investor a Warrant to purchase a number of whole Warrant Shares equal to the number of Shares set forth on the signature page and (c) the aggregate purchase price for the Units being purchased by the Investor will be delivered by or on behalf of the Investor to the Company.

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3.2 Conditions to the Company’s Obligations.

(a) The Company’s obligation to issue and sell the Units to the Investor shall be subject to: (i) the receipt by the Company of the purchase price for the Units being purchased hereunder as set forth on the Signature Page and (ii) the accuracy of the representations and warranties made by the Investor and the fulfillment of those undertakings of the Investor to be fulfilled prior to the Closing Date.

(b) Conditions to the Investor’s Obligations. The Investor’s obligation to purchase the Units will be subject to the accuracy of the representations and warranties made by the Company and the fulfillment of those undertakings of the Company to be fulfilled prior to the Closing Date, including without limitation, those contained in the Placement Agreement, and to the condition that the Placement Agents shall not have: (a) terminated the Placement Agreement pursuant to the terms thereof or (b) determined that the conditions to the closing in the Placement Agreement have not been satisfied. The Investor’s obligations are expressly not conditioned on the purchase by any or all of the Other Investors of the Units that they have agreed to purchase from the Company.

3.3 Delivery of Funds. No later than the Closing Date, the Investor shall confirm that the account or accounts at Cowen to be credited with the Units being purchased by the Investor have a minimum balance equal to the aggregate purchase price for the Units being purchased by the Investor.

3.4 Delivery of Shares. Delivery Versus Payment through The Depository Trust Company. No later than one (1) business day after the execution of this Agreement by the Investor and the Company, the Investor shall notify Cowen of the account or accounts at Cowen to be credited with the Shares being purchased by such Investor. On the Closing Date, the Company shall deliver the Shares to the Investor through DTC directly to the account(s) at Cowen identified by Investor and simultaneously therewith payment shall be made by Cowen by wire transfer to the Company.

4. Representations, Warranties and Covenants of the Investor.

The Investor acknowledges, represents and warrants to, and agrees with, the Company and the Placement Agents that:

4.1 The Investor (a) is knowledgeable, sophisticated and experienced in making, and is qualified to make decisions with respect to, investments in securities presenting an investment decision like that involved in the purchase of the Units, including investments in securities issued by the Company and investments in comparable companies, (b) has answered all questions on the Signature Page and the Investor Questionnaire and the answers thereto are true and correct as of the date hereof and will be true and correct as of the Closing Date and (c) in connection with its decision to purchase the number of Units set forth on the Signature Page, has received and is relying only upon the Disclosure Package (including the documents incorporated by reference therein).

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4.2 No action has been or will be taken in any jurisdiction outside the United States by the Company or the Placement Agents that would permit an offering of the Units, or possession or distribution of offering materials in connection with the issue of the Securities in any jurisdiction outside the United States where action for that purpose is required, (b) if the Investor is outside the United States, it will comply with all applicable laws and regulations in each foreign jurisdiction in which it purchases, offers, sells or delivers Securities or has in its possession or distributes any offering material, in all cases at its own expense and (c) the Placement Agents are not authorized to make and have not made any representation, disclosure or use of any information in connection with the issue, placement, purchase and sale of the Units, except as set forth in the Issuer Free Writing Prospectus or as set forth in or incorporated by reference in the Base Prospectus or the Prospectus Supplement.

4.3 The Investor has full right, power, authority and capacity to enter into this Agreement and to consummate the transactions contemplated hereby and has taken all necessary action to authorize the execution, delivery and performance of this Agreement, and (b) this Agreement constitutes a valid and binding obligation of the Investor enforceable against the Investor in accordance with its terms, except as enforceability may be limited by applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting creditors’ and contracting parties’ rights generally and except as enforceability may be subject to general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law) and except as to the enforceability of any rights to indemnification or contribution that may be violative of the public policy underlying any law, rule or regulation (including any federal or state securities law, rule or regulation).

4.4 The Investor understands that nothing in this Agreement, the Prospectus, the Disclosure Package or any other materials presented to the Investor in connection with the purchase and sale of the Units constitutes legal, tax or investment advice. The Investor has consulted such legal, tax and investment advisors as it, in its sole discretion, has deemed necessary or appropriate in connection with its purchase of Units. The Investor also understands that there is no established public trading market for the Warrants being offered in the Offering, and that the Company does not expect such a market to develop. In addition, the Company does not intend to apply for listing the Warrants on any securities exchange. Without an active market, the liquidity of the Warrants will be limited.

4.5 Since the date on which the Placement Agents first contacted such Investor about the Offering, the Investor has not engaged in any transactions in the securities of the Company (including, without limitation, any Short Sales involving the Company’s securities). Each Investor covenants that it will not engage in any transactions in the securities of the Company (including Short Sales) or disclose any information about the Offering (other than to its advisors that are under a legal obligation of confidentiality prior to the time that the transactions contemplated by this Agreement are publicly disclosed pursuant to the Form 8-K Filing. The Investor agrees that it will not use any of the Securities acquired pursuant to this Agreement to cover any short position in the Common Stock if doing so would be in violation of applicable securities laws. For purposes hereof, “Short Sales” include, without limitation, all “short sales” as defined in Rule 200 promulgated under Regulation SHO under the Exchange Act, whether or not against the box, and all types of direct and indirect stock pledges, forward sales contracts, options, puts, calls, short sales, swaps, “put equivalent positions” (as defined in Rule 16a-1(h) under the Exchange Act) and similar arrangements (including on a total return basis), and sales and other transactions through non-US broker dealers or foreign regulated brokers.

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5. Representations, Warranties and Covenants of the Company

6.1. 5.1 The Company acknowledges and agrees that the Investor is acting solely in the capacity of an arm’s length purchaser with respect to the Securities and the transactions contemplated hereby and thereby and that the Investor is not (i) an officer or director of the Company or any of its Subsidiaries (as defined below), (ii) an “affiliate” (as defined in Rule 144) of the Company or any of its Subsidiaries or (iii) to its knowledge, a “beneficial owner” of more than 10% of the shares of Common Stock (as defined for purposes of Rule 13d-3 of the Exchange Act. The Company further acknowledges that the Investor is not acting as a financial advisor or fiduciary of the Company or any of its Subsidiaries (or in any similar capacity) with respect to the Securities and the transactions contemplated hereby and thereby, and any advice given by the Investor or any of its representatives or agents in connection with this Agreement and the transactions contemplated hereby and thereby is merely incidental to the Investor’s purchase of the Securities. The Company further represents to the Investor that the Company’s decision to enter into this Agreement has been based solely on the independent evaluation by the Company and its representatives. “Subsidiaries” means any Person in which the Company, directly or indirectly, (I) owns any of the outstanding capital stock or holds any equity or similar interest of such Person or (II) controls or operates all or any part of the business, operations or administration of such Person, and each of the foregoing, is individually referred to herein as a “Subsidiary”.

5.2 It is understood and acknowledged by the Company that (i) following the public disclosure of the transactions contemplated by this Agreement in connection with the Form 8-K Filing, in accordance with the terms thereof, the Investor has not been asked by the Company or any of its Subsidiaries to agree, nor has the Investor agreed with the Company or any of its Subsidiaries, to desist from effecting any transactions in or with respect to (including, without limitation, purchasing or selling, long and/or short) any securities of the Company, or “derivative” securities based on securities issued by the Company or to hold any of the Securities for any specified term; (ii) the Investor, and counterparties in “derivative” transactions to which any the Investor is a party, directly or indirectly, presently may have a “short” position in the Common Stock which was established prior to the Investor’s knowledge of the transactions contemplated by this Agreement; and (iii) the Investor shall not be deemed to have any affiliation with or control over any arm’s length counterparty in any “derivative” transaction. The Company further understands and acknowledges that following the public disclosure of the transactions contemplated by this Agreement pursuant to the Form 8-K Filing, the Investor may engage in hedging and/or trading activities at various times during the period that the Securities are outstanding and (b) such hedging and/or trading activities, if any, can reduce the value of the existing stockholders’ equity interest in the Company both at and after the time the hedging and/or trading activities are being conducted. The Company acknowledges that such aforementioned hedging and/or trading activities do not constitute a breach of this Agreement or the Warrants or any of the documents executed in connection herewith or therewith.

5.3 Except as disclosed in the Form 8-K Filing, the Company confirms that neither it nor any other Person acting on its behalf has provided the Investor or their agents or counsel with any information that constitutes or could reasonably be expected to constitute material, non-public information concerning the Company or any of its Subsidiaries, other than the existence of the transactions contemplated by this Agreement. The Company understands and confirms that the Investor will rely on the foregoing representations in effecting transactions in securities of the Company. All disclosure provided to the Investor regarding the Company and its Subsidiaries, their businesses and the transactions contemplated hereby, furnished by or on behalf of the Company or any

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of its Subsidiaries is true and correct and does not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements made therein, in the light of the circumstances under which they were made, not misleading. Each press release issued by the Company or any of its Subsidiaries during the twelve (12) months preceding the date of this Agreement did not at the time of release contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary in order to make the statements therein, in the light of the circumstances under which they are made, not misleading. No event or circumstance has occurred or information exists with respect to the Company or any of its Subsidiaries or its or their business, properties, liabilities, prospects, operations (including results thereof) or conditions (financial or otherwise), which, under applicable law, rule or regulation, requires public disclosure at or before the date hereof or announcement by the Company but which has not been so publicly disclosed. The Company acknowledges and agrees that the Investor does not make and has not made any representations or warranties with respect to the transactions contemplated hereby other than those specifically set forth in Section 4.

5.4. No executive officer (as defined in Rule 501(f) promulgated under the Act) or other key employee of the Company or any of its Subsidiaries has notified the Company or any such Subsidiary that such officer intends to leave the Company or any such Subsidiary or otherwise terminate such officer’s employment with the Company or any such Subsidiary.

6. Covenants.

6.1. Press Release and Form 8-K. The Company and the Investor agree that the Company shall issue a press release and file a Form 8-K announcing the Offering prior to the open of regular trading on The NASDAQ Global Market on December [    ], 2014, which such Form 8-K shall include any other material information regarding the Company that is contained in the Issuer Free Writing Prospectus, and attaching this Agreement and the Form of Warrants (the “Form 8-K Filing”), and shall be in a form reasonably acceptable to the Investor. The Company confirms that it has not provided the Investor with any information that constitutes material, nonpublic information, except as will be disclosed in the Form 8-K filing. The Company shall not, and the Company shall cause each of its Subsidiaries and each of its and their respective officers, directors, employees and agents not to, provide the Investor with any material, non-public information regarding the Company or any of its Subsidiaries from and after the Form 8-K Filing without the express prior written consent of such Buyer.

6.2 Company Lock Up.

(a) For the period specified below (the “Lock-Up Period”), the Company will not, directly or indirectly, take any of the following actions with respect to its Securities or any securities convertible into or exchangeable or exercisable for any of its Securities (“Lock-Up Securities”): (i) amend, modify or change the terms of any warrants to acquire Common Stock outstanding on the date hereof, (ii) offer, sell, issue, contract to sell, pledge or otherwise dispose of Lock-Up Securities, (iii) offer, sell, issue, contract to sell, contract to purchase or grant any option, right or warrant to purchase Lock-Up Securities, (iv) enter into any swap, hedge or any other agreement that transfers, in whole or in part, the economic consequences of ownership of Lock-Up Securities, (v) establish or increase a put equivalent position or liquidate or decrease a call equivalent position in Lock-Up Securities within the meaning of Section 16 of the Exchange Act or (vi) file with the Commission a registration statement under the Act relating to Lock-Up Securities, or publicly

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disclose the intention to take any such action, without the prior written consent of the Placement Agents, except (A) grants of awards to purchase Lock-Up Securities, or issuing Lock-Up Securities, pursuant to employee benefit plans in effect on the date hereof and described in the General Disclosure Package and the Final Prospectus, (B) issuances of Lock-Up Securities pursuant to the exercise, conversion or exchange of convertible or exchangeable securities outstanding as of the date of this Agreement provided that the exercise price or conversion price of such securities are not lowered or otherwise materially amended in any manner that adversely affects the Investor or (C) issuances of Lock-Up Securities, which in the aggregate shall not exceed 5% of the outstanding shares of the Securities as of the date of this Agreement, as consideration in connection with collaborations, acquisitions or strategic transactions approved by a majority of the disinterested directors of the Company, provided that (x) any such issuance shall only be to a person or entity (or to the equityholders of such entity) which is, itself or through its subsidiaries, an operating company or an owner of an asset in a business synergistic with the business of the Company or any of the Subsidiaries and shall provide to the Company additional benefits in addition to the investment of funds, but shall not include a transaction in which the Company is issuing securities primarily for the purpose of raising capital or to an entity whose primary business is investing in securities and (y) the recipient of any such Lock-Up Securities shall agree in writing to be bound by the terms of this Section 6.2(a).

(b) For so long as any Warrant remain outstanding, the Company and each of its Subsidiaries shall be prohibited from effecting or entering into an agreement to effect any Subsequent Placement involving a Variable Rate Transaction. “Variable Rate Transaction” means a transaction in which the Company or any subsidiary (i) issues or sells any Convertible Securities either (A) at a conversion, exercise or exchange rate or other price that is based upon and/or varies with the trading prices of or quotations for the shares of Common Stock at any time after the initial issuance of such Convertible Securities, or (B) with a conversion, exercise or exchange price that is subject to being reset at some future date after the initial issuance of such Convertible Securities or upon the occurrence of specified or contingent events directly or indirectly related to the business of the Company or the market for the Common Stock, other than pursuant to a customary “weighted average” anti-dilution provision or (ii) enters into any agreement (including, without limitation, an equity line of credit) whereby the Company or any subsidiary may sell securities at a future determined price (other than standard and customary “preemptive” or “participation” rights). The Investor shall be entitled to obtain injunctive relief against the Company and its subsidiaries to preclude any such issuance, which remedy shall be in addition to any right to collect damages.

6. Survival of Representations, Warranties and Agreements; Third Party Beneficiary. Notwithstanding any investigation made by any party to this Agreement or by the Placement Agents, all covenants, agreements, representations and warranties made by the Company and the Investor herein will survive the execution of this Agreement, the delivery to the Investor of the Units being purchased and the payment therefor. The Placement Agent shall be third party beneficiary with respect to the representations, warranties and agreements of the Investor in Section 4 hereof.

7. Notices. All notices, requests, consents and other communications hereunder will be in writing, will be mailed (a) if within the domestic United States by first-class registered or certified airmail, or nationally recognized overnight express courier, postage prepaid, or by facsimile or (b) if delivered from outside the United States, by International Federal Express or facsimile, and will be deemed given (i) if delivered by first-class registered or certified mail domestic, three business days after so mailed, (ii) if delivered by nationally recognized overnight carrier, one business day after so mailed, (iii) if delivered by International Federal Express, two business days after so mailed and (iv) if delivered by facsimile, upon electric confirmation of receipt and will be delivered and addressed as follows:

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(a) if to the Company, to:

XOMA Corporation

2910 Seventh Street

Berkeley, California 94710

Attention: Fred Kurland

Facsimile: (510) 649 0315

with copies to (which shall not constitute notice):

Cooley LLP

Five Palo Alto Square

3000 El Camino Real

Palo Alto, CA 94306

Attention: Jim Fulton and Mike Tenta

Facsimile: (650) 490-7400

(b) if to the Investor, at its address on the Signature Page hereto, or at such other address or addresses as may have been furnished to the Company in writing.

8. Changes. This Agreement may not be modified or amended except pursuant to an instrument in writing signed by the Company and the Investor.

9. Headings. The headings of the various sections of this Agreement have been inserted for convenience of reference only and will not be deemed to be part of this Agreement.

10. Severability. In case any provision contained in this Agreement should be invalid, illegal or unenforceable in any respect, the validity, legality and enforceability of the remaining provisions contained herein will not in any way be affected or impaired thereby.

11. Governing Law. This Agreement will be governed by, and construed in accordance with, the internal laws of the State of New York, without giving effect to the principles of conflicts of law that would require the application of the laws of any other jurisdiction.

12. Counterparts. This Agreement may be executed in two or more counterparts, each of which will constitute an original, but all of which, when taken together, will constitute but one instrument, and will become effective when one or more counterparts have been signed by each party hereto and delivered to the other parties. The Company and the Investor acknowledge and agree that the Company shall deliver its counterpart to the Investor along with the Prospectus Supplement (or the filing by the Company of an electronic version thereof with the Commission).

13. Confirmation of Sale. The Investor acknowledges and agrees that such Investor’s receipt of the Company’s counterpart to this Agreement, together with the Prospectus Supplement (or the filing by the Company of an electronic version thereof with the Commission), shall constitute written confirmation of the Company’s sale of Units to such Investor.

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14. Termination. In the event that the Placement Agreement is terminated by the Placement Agents pursuant to the terms thereof, this Agreement shall terminate without any further action on the part of the parties hereto.

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EXHIBIT A

XOMA CORPORATION

INVESTOR QUESTIONNAIRE

Pursuant to Section 3 of Annex I to the Agreement, please provide us with the following information:

Exhibit B

Form of Warrant

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