STOCK PURCHASE AGREEMENT

STOCK PURCHASE AGREEMENT This Stock Purchase Agreement (this Agreement ) is made as of, 2015, by and between Histogen Inc., a Delaware corporation (the Company ), and (hereinafter referred to as the Investor ). NOW THEREFORE, for good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the Company and the Investor hereby agree as follows: 1. Purchase of Shares. 1.1 Purchase. Subject to the terms and conditions of this Agreement, the Investor hereby purchases, and the Company hereby sells and issues to the Investor, shares of the Company s Series D Preferred Stock (the Shares ) at a cash purchase price of $3.00 per share, for an aggregate purchase price of $ (the Purchase Price ). 1.2 Term Sheet. The Shares have all the rights, preferences and privileges as set forth in the Term Sheet attached hereto, and as are further described in the Company s Amended and Restated Certificate of Incorporation. 2. Closing. The issuance of the Shares shall take place at the offices of the Company, once this Agreement has been signed by both parties and the Purchase Price is paid, or at such other place and time as the Company and the Investor shall mutually agree, either orally or in writing (the Closing ). 3. Representations and Warranties of the Company. The Company hereby represents and warrants to the Investor as follows: 3.1 Organization and Standing; Articles and Bylaws. The Company is a corporation duly organized, validly existing, and in good standing under the laws of the State of Delaware, and has all requisite corporate power and authority to own and operate its properties and assets and to carry on its business as presently conducted. 3.2 Capitalization. Prior to the issuance of the Series D Preferred Shares, the Company s outstanding capital stock is as described in the attached Term Sheet. The Company is authorized to sell up to 6 million of Series D Preferred Shares. All issued and outstanding shares of the Company s capital stock have been duly authorized and validly issued and are fully paid and non-assessable. 3.3 Authorization. All corporate action on the part of the Company, its officers, directors and shareholders necessary for the authorization, execution and delivery of this Agreement, the performance of all the Company s obligations under this Agreement and for the authorization, issuance, sale and delivery of the Shares has been taken or will be taken prior to 367038-000013

the Closing. This Agreement, when executed and delivered by the Company and the Investor shall constitute a valid and legally binding obligation of the Company, enforceable in accordance with its terms, subject to laws of general application relating to bankruptcy, insolvency and the relief of debtors. 3.4 Validity of the Shares. The Shares will be validly issued, fully paid and nonassessable. 4. Representations and Warranties of the Investor. The Investor hereby represents and warrants to the Company as follows: 4.1 Authorization. The Investor has the requisite legal power and authority to enter into this Agreement and that this Agreement when executed shall constitute a valid and legally binding obligation of the Investor. 4.2 Investment Intent. The Shares are being acquired as the Investor s own property for investment for an indefinite period for his own account, not as a nominee or agent, and not with a view to the sale or distribution of any part thereof, and the Investor has no present intention of selling, granting participation in, or otherwise distributing the same. The Investor represents that the Investor does not have any contract, undertaking, agreement or arrangement with any person to sell, transfer, or grant participations, to such person or to any third person, with respect to any of the Shares. 4.3 Reliance Upon the Investor s Representations. The Investor understands (i) that the Shares are not registered under the Securities Act or qualified under any state s securities laws, and (ii) that the Shares are being issued to the Investor on the ground that the sale provided for in this Agreement and the issuance of securities hereunder is exempt from registration under the Securities Act pursuant to Section 4(2) thereof and/or Regulation D promulgated thereunder and the exemption from state law qualification, and (iii) that the Company s reliance on such exemptions is predicated on the Investor s representations set forth herein. 4.4 Restricted Securities. The Investor understands that the Shares are restricted securities under the Securities Act and may not be resold or transferred unless the Shares are first registered under the Federal securities laws or unless an exemption from such registration is available. In addition, the Investor understands that any resale or transfer must comply with applicable state securities laws. Accordingly, the Investor hereby acknowledges that the Investor is prepared to hold the Shares for an indefinite period, until resale is permitted under applicable law, including Rule 144 of the Securities and Exchange Commission issued under the Securities Act, and the Investor is aware that Rule 144 is not presently available to exempt the sale of the Shares from the registration requirements of the Securities Act. 4.5 Receipt of Information. The Investor acknowledges that the Investor has received all the information the Investor considers necessary or appropriate for deciding whether to acquire the Shares. The Investor further represents that the Investor has had an opportunity to ask questions and receive answers from the Company regarding the terms and conditions of the offering of the Shares and the business, properties, prospects, and financial condition of the Company and to obtain additional information (to the extent the Company possessed such 367038-000013 2

information or could acquire it without unreasonable effort or expense) necessary to verify the accuracy or any information furnished to it or to which it had access. 4.6 Speculative Investment. The Investor acknowledges and understands that an investment in the Shares is a speculative investment, involving a high degree of risk. The Company is at its initial, start-up stage, so the Company is subject to the uncertainties and risks associated with any new, start-up business that has not yet developed marketable products or services and has not yet generated any operating revenues. The Company expects to incur substantial and increasing operating losses through its initial stages of development, and these losses can be recovered and the Company can generate profits if, and only if, the Company is able to successfully develop, make and market products or services. The ultimate success of the Company will be dependent, among other things, upon the market acceptance of the Company s products or services, the ability of the Company to make and market products or services at favorable prices, the ability of the Company to meet competition, the ability of the Company to successfully develop and obtain regulatory approval for its products, the ability of the Company to obtain and defend its intellectual property, the ability of the Company to attract and retain key personnel, and the ability of the Company to raise additional capital in the future as the Company s needs require (in amounts and at prices which will dilute the Investor s ownership in the Company). The Investor acknowledges and understands that there is no assurance that the Company will be successful in these matters. 4.7 Investment Experience. In connection with the investment representations made herein, the Investor represents that the Investor has such knowledge and experience in financial and business matters as to be capable of evaluating the merits and risks of the Investor s investment, has the ability to bear the economic risks of the Investor s investment and has been furnished with and has had access to all of the information the Investor considers necessary or appropriate to evaluate the risks and merits of an investment in the Shares, and has had an opportunity to discuss the Company s business, management and financial affairs with the Company s management. 4.8 Limitations on Disposition. The Investor agrees that the Investor will not make any disposition of any of the Shares, unless and until (a) the Investor shall have notified the Company of the proposed disposition and shall have furnished the Company with a statement of the circumstances surrounding the proposed disposition, and (b) the Investor shall have furnished the Company with an opinion of legal counsel acceptable to the Company stating that (i) such disposition will not require registration of such Shares under the Securities Act, or (ii) appropriate action necessary for compliance with the Securities Act has been taken, or (c) the Company shall have waived, expressly and in writing, its rights under clauses (a) and (b) of this subparagraph. The legal opinion shall also indicate that the disposition is exempt from, in compliance with, or qualified under any applicable state securities laws. 4.9 Legends. All certificates representing the Shares are subject to the provisions of this Agreement and shall have endorsed thereon customary legends regarding: (a) Restrictions on transfer under the Federal Securities Act of 1933. (b) Market Stand-Off Agreement pursuant to Section 6 hereof. 367038-000013 3

(c) (d) Right of First Refusal upon any resale of the Shares, pursuant to the Company s Bylaws and Section 5 hereof. Bring Along Commitment pursuant to Section 7 hereof. 4.10 Confidentiality. The Investor hereby covenants and agrees to maintain the confidentiality of any and all of the confidential information of the Company which may be disclosed to the Investor from time to time. Further, the Investor agrees to not disclose or use any of the Company s confidential information, without the prior written consent from the Company. For the purposes hereof, all information provided by the Company shall be deemed to be confidential information, as will the results of any clinical studies of the Company s products or drug candidates conducted by the Investor. The confidentiality covenant shall not be applicable to any information which becomes part of the public domain through no fault of a party which has a confidentiality obligation to the Company. 5. Company Right of First Refusal. Any resale of the Shares shall be subject to the Right of First Refusal provisions set forth in Article VIII of the Company s Bylaws. 6. Market Stand-off Agreement. 6.1 In connection with any underwritten public offering by the Company of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company s initial public offering, the Investor shall not sell, make any short sale of, loan, hypothecate, pledge, grant any option for the acquire of, or otherwise dispose or transfer for value or otherwise agree to engage in any of the foregoing transactions with respect to the Shares without the prior written consent of the Company or its underwriters. Such limitations shall be in effect for one hundred eighty (180) days from and after the effective date of such registration statement or such longer time as may be required by the Company s underwriters. The limitations of this Section 6 shall not be applicable to any public offering which is made more than two years following the effective date of the Company s initial public offering. 6.2 In the event any stock dividend, stock split, recapitalization or other change affecting the Company s outstanding Common Shares is effected without receipt of consideration, then any new, substituted or additional securities distributed with respect to the Shares shall be immediately subject to the provisions of this Section 6 to the same extent the Shares are at such time covered by such provisions. 6.3 In order to enforce the limitations of this Section 6, the Company may impose stop-transfer instructions with respect to the Shares until the end of the applicable stand-off period. 6.4 The obligation in this Section 6 shall not apply to a registration relating solely to employee benefit plan shares or to a Rule 145 transaction registered on Form S-4. 7. Bring Along Commitment. In the event that a majority in interest of the Company s shareholders (voting on an as converted to common shares basis) decide to sell the Company, the Investor hereby agrees to sell the Shares on the same basis as the other shareholders sell their shares, giving effect to the liquidation preference rights and conversion rights for the Preferred 367038-000013 4

Stock as specified in the Company s Certificate of Incorporation. Without limiting the generality of the foregoing, the foregoing includes the Investor agreeing to vote the Shares for such a sale of the Company, and the Investor selling the Shares. 8. Miscellaneous. 8.1 Further Instruments and Actions. The parties agree to execute such further instruments and to take such further action as may reasonably be necessary to carry out the intent of this Agreement. 8.2 Notices. Any notice required or permitted hereunder shall be given in writing and shall be deemed effectively given upon personal delivery or upon deposit in the United States Post Office, by regular mail with postage and fees prepaid, addressed to the other party hereto at his address hereinafter shown below his signature or at such other address as such party may designate by advance written notice to the other party hereto. 8.3 Governing Law. The parties hereto agree that all questions pertaining to the validity and interpretation of this Agreement shall be determined in accordance with the laws of the State of California. 8.4 Successors and Assigns. Except as otherwise provided herein, the terms and conditions of this Agreement shall inure to the benefit of the successors and assigns of the Company and, subject to the restrictions on transfer herein set forth, be binding upon the Investor, and the Investor s heirs, executors, administrators, guardians, successors and assigns. 8.5 Amendments and Waivers. This Agreement represents the entire understanding of the parties with respect to the subject matter hereof and supersedes all previous understandings, written or oral. This Agreement may only be amended with the written consent of the parties hereto, or the successors or assigns of the foregoing, and no oral waiver or amendment shall be effective under any circumstances whatsoever. IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the day and year first above written, for the purchase by Investor of shares of Series D Preferred Stock, at $3.00 per share, for a total Purchase Price of $. COMPANY: Histogen Inc., a Delaware corporation INVESTOR: Name: By: Name: Gail Naughton, Ph.D. Chief Executive Officer (signature) If Spousal Consent is required please see exhibit A. 367038-000013 5

Histogen EXHIBIT Inc. A STOCK PURCHASE SPOUSAL CONSENT AGREEMENT The undersigned certifies as follows: 1. I am the spouse of. 2. I have received, read and approved the provisions of the foregoing Stock Purchase Agreement between the CORPORATION and my spouse, to which this CONSENT is attached. 3. I agree to be bound by and accept the provisions of the Stock Purchase Agreement, as it may be amended from time to time insofar as those provisions may affect any interest I may have in the CORPORATION, whether the interest is community property or otherwise. I further agree that amendment of the Stock Purchase Agreement shall not require my consent. 4. My spouse shall have full power of management of the shares purchased pursuant to this Stock Purchase Agreement, including any portion of those interests that are our community property; and my spouse has the full right, without my further approval, to exercise my spouse's voting rights as a shareholder in the CORPORATION, and to sell, transfer, encumber, and deal in any manner with such shares. Executed effective as of, Signature of spouse: Printed name: 367038-000013