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Exhibit 1.1

January 10, 2014

Mr. Gil Van Bokkelen

Chief Executive Officer

Athersys, Inc.

3201 Carnegie Avenue

Cleveland, OH 44115-2634

Dear Gil:

This letter (the “Agreement”) constitutes the agreement between Maxim Group LLC (“Maxim” or the “Placement Agent”) and Athersys, Inc. (the “Company”), that Maxim shall serve as the lead placement agent for the Company, on a “reasonable best efforts” basis, in connection with the proposed placement (the “Placement”) of (i) registered shares (the “Shares”) of the Company’s common stock, par value $0.001 per share (the “Common Stock”), and (ii) warrants (the “Warrants”) to purchase shares of Common Stock (the shares of Common Stock underlying the Warrants, “Warrant Shares” and, together with the Shares and the Warrants, the “Securities”). The terms of the Placement and the Securities shall be mutually agreed upon by the Company and the purchasers (each, a “Purchaser” and collectively, the “Purchasers”) and nothing herein constitutes that Maxim would have the power or authority to bind the Company or any Purchaser or an obligation for the Company to issue any Securities or complete the Placement. This Agreement and the documents executed and delivered by the Company and the Purchasers in connection with the Placement shall be collectively referred to herein as the “Transaction Documents.” The date of the closing of the Placement shall be referred to herein as the “Closing Date.” The Company expressly acknowledges and agrees that Maxim’s obligations hereunder are on a reasonable best efforts basis only and that the execution of this Agreement does not constitute a commitment by Maxim to purchase the Securities and does not ensure the successful placement of the Securities or any portion thereof or the success of Maxim with respect to securing any other financing on behalf of the Company. The Placement Agent may retain other brokers or dealers to act as sub-agents or selected-dealers on its behalf in connection with the Placement.

SECTION 1. COMPENSATION.

The Company will pay Maxim a cash fee equal to 7% of the gross proceeds received by the Company (the “Cash Compensation”) from the sale of the Securities at the closing of the Placement (the “Closing”). Maxim will pay from the Cash Compensation any sub-agents or selected-dealers that it has retained to act on its behalf in connection with the Placement pursuant to the terms of any such agreement entered into with such sub-agent or selected-dealer.

SECTION 2. REGISTRATION STATEMENT.

The Company represents and warrants to, and agrees with, the Placement Agent that:

(A) The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement on Form S-3 (Registration No. 333-185991) under the Securities Act of 1933, as amended (the “Securities Act”), which became effective on January 22, 2013, for the registration under the Securities Act of the Securities. At the time of such filing, the Company met the requirements of Form S-3 under the Securities Act. Such registration statement meets the requirements set forth in Rule 415(a)(1)(x) under the Securities Act and complies with said Rule. The Company will file with the Commission pursuant to Rule 424(b) under the Securities Act, and the rules and regulations (the “Rules and Regulations”) of the Commission promulgated thereunder, a supplement to the form of prospectus included in such registration statement relating to the placement of the Securities and the plan of distribution thereof and has advised the Placement Agent of all further information (financial and other) with respect to the Company required to be set forth therein. Such registration statement, including the exhibits thereto, as amended at the date of this Agreement, is hereinafter called the “Registration Statement”; such prospectus in the form in which it appears in the Registration Statement is hereinafter called the “Base Prospectus”; and the supplemented form of prospectus, in the form in which it will be filed with the Commission pursuant to Rule 424(b) (including the Base Prospectus as so supplemented) is hereinafter called the “Prospectus Supplement.” Any reference in this Agreement to the Registration Statement, the Base Prospectus or the Prospectus Supplement shall be deemed to refer to and include the documents incorporated by reference therein (the “Incorporated Documents”) pursuant to Item 12 of Form S-3 which were filed under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), on or before the date of this Agreement, or the issue date of the Base Prospectus or the Prospectus Supplement, as the case may be; and any reference in this Agreement to the terms “amend,” “amendment” or “supplement” with respect to the Registration Statement, the Base Prospectus or the Prospectus Supplement shall be deemed to refer to and include the filing of any document under the Exchange Act after the date of this Agreement, or the issue date of the Base Prospectus or the Prospectus Supplement, as the case may be, deemed to be incorporated therein by reference. All references in this Agreement to financial statements and schedules and other information which is “contained,” “included,” “described,” “referenced,” “set forth” or “stated” in the Registration Statement, the Base Prospectus or the Prospectus Supplement (and all other references of like import) shall be deemed to mean and include all such financial statements and schedules and other information which is or is deemed to be incorporated by reference in the Registration Statement, the Base Prospectus or the Prospectus Supplement, as the case may be. No stop order suspending the effectiveness of the Registration Statement or the use of the Base Prospectus or the Prospectus Supplement has been issued, and no proceeding for any such purpose is pending or has been initiated or, to the Company’s knowledge, is threatened by the Commission. For purposes of this Agreement, “free writing prospectus” has the meaning set forth in Rule 405 under the Securities Act and the “Time of Sale Prospectus” means the preliminary prospectus, if any, the information set forth on Schedule 2(A), together with the free writing prospectuses, if any, used in connection with the Placement, including any documents incorporated by reference therein.

(B) The Registration Statement (and any further documents to be filed with the Commission) contains all exhibits and schedules as required by the Securities Act. Each of the Registration Statement and any post-effective amendment thereto, at the time it became effective, complied in all material respects with the Securities Act and the applicable Rules and Regulations and did not and, as amended or supplemented, if applicable, will not, contain any

untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading. The Base Prospectus, the Time of Sale Prospectus and the Prospectus Supplement, each as of its respective date, comply in all material respects with the Securities Act and the applicable Rules and Regulations. Each of the Base Prospectus, the Time of Sale Prospectus and the Prospectus Supplement, as amended or supplemented, did not and will not contain as of the date thereof any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The Incorporated Documents, when they were filed with the Commission, conformed in all material respects to the requirements of the Exchange Act and the applicable Rules and Regulations, and none of such documents, when they were filed with the Commission, contained any untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein (with respect to Incorporated Documents incorporated by reference in the Base Prospectus or Prospectus Supplement), in the light of the circumstances under which they were made not misleading; and any further documents so filed and incorporated by reference in the Base Prospectus, the Time of Sale Prospectus or Prospectus Supplement, when such documents are filed with the Commission, will conform in all material respects to the requirements of the Exchange Act and the applicable Rules and Regulations, as applicable, and will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading. No post-effective amendment to the Registration Statement reflecting any facts or events arising after the date thereof which represent, individually or in the aggregate, a fundamental change in the information set forth therein is required to be filed with the Commission. There are no documents required to be filed with the Commission in connection with the transaction contemplated hereby that (x) have not been filed as required pursuant to the Securities Act or (y) will not be filed within the requisite time period. There are no contracts or other documents required to be described in the Base Prospectus, the Time of Sale Prospectus or Prospectus Supplement, or to be filed as exhibits or schedules to the Registration Statement, which (x) have not been described or filed as required or (y) will not be filed within the requisite time period.

(C) The Company is eligible to use free writing prospectuses in connection with the Placement pursuant to Rules 164 and 433 under the Securities Act. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or behalf of or used by the Company complies or will comply in all material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. The Company will not, without the prior consent of the Placement Agent, prepare, use or refer to, any free writing prospectus.

(D) The Company has delivered, or will as promptly as practicable deliver, to the Placement Agent complete conformed copies of the Registration Statement and of each consent and certificate of experts, as applicable, filed as a part thereof, and conformed copies of the Registration Statement (without exhibits), the Base Prospectus, the Time of Sale Prospectus and the Prospectus Supplement, as amended or supplemented, in such quantities and at such places as the Placement Agent reasonably requests. Placement Agent acknowledges that all such materials

as exist on the date of this letter are available on EDGAR. Neither the Company nor any of its directors and officers has distributed and none of them will distribute, prior to the Closing Date, any offering material in connection with the offering and sale of the Shares pursuant to the Placement other than the Base Prospectus, the Time of Sale Prospectus, the Prospectus Supplement, the Registration Statement, copies of the documents incorporated by reference therein and any other materials permitted by the Securities Act.

SECTION 3. REPRESENTATIONS AND WARRANTIES INCORPORATED BY REFERENCE. Each of the representations and warranties (together with any related disclosure schedules thereto) made to the Purchasers in that certain Securities Purchase Agreement dated as of January 10, 2014, between the Company and each Purchaser, is hereby incorporated herein by reference (as though fully restated herein) and is hereby made to, and in favor of, the Placement Agent.

SECTION 4. REPRESENTATIONS OF MAXIM. Maxim represents and warrants that it is (i) a member in good standing of FINRA, (ii) registered as a broker/dealer under the Securities Exchange Act of 1934 (the “Exchange Act”), and (iii) licensed as a broker/dealer under the laws of the States applicable to the offers and sales of Securities by Maxim. Maxim will immediately notify the Company in writing of any change in its status as such. Maxim covenants that it will use its reasonable best efforts to conduct the Transaction hereunder in compliance with the provisions of this Agreement and the requirements of applicable law. Except as required by law or as contemplated by this agreement, Maxim will keep confidential all material nonpublic information, including information regarding the Transaction contemplated hereunder, provided to it by the Company or its affiliates or advisors and use such information only for the purposes contemplated herein.

SECTION 5. INDEMNIFICATION. The Company agrees to the indemnification and other agreements set forth in the Indemnification Provisions (the “Indemnification”) attached hereto as Addendum A, the provisions of which are incorporated herein by reference and shall survive the termination or expiration of this Agreement.

SECTION 6. ENGAGEMENT TERM. Maxim’s engagement hereunder will be until the earlier of (i) 15 days following the date hereof and (ii) the completion of the Placement. The engagement may be terminated by either the Company or Maxim at any time upon 10 days’ written notice. Notwithstanding anything to the contrary contained herein, the provisions concerning the Company’s obligation to pay any fees actually earned and to reimburse expenses actually incurred and reimbursable pursuant to Section 1 hereof and which are permitted to be reimbursed under FINRA Rule 5110(f)(2)(D), and the confidentiality, indemnification, contribution provisions contained herein and the Company’s obligations contained in the Indemnification Provisions will survive any expiration or termination of this Agreement. Maxim agrees not to disclose or use any confidential information concerning the Company provided to it by the Company for any purposes other than those contemplated under this Agreement.

SECTION 7. MAXIM INFORMATION. The Company agrees that any information or advice rendered by Maxim in connection with this engagement is for the confidential use of the Company only in their evaluation of the Placement and, except as otherwise required by law, the Company will not disclose or otherwise refer to the advice or information in any manner without Maxim’s prior written consent.

SECTION 8. NO FIDUCIARY RELATIONSHIP. This Agreement does not create, and shall not be construed as creating rights enforceable by any person or entity not a party hereto, except those entitled hereto by virtue of the Indemnification Provisions hereof. The Company acknowledges and agrees that Maxim is not and shall not be construed as a fiduciary of the Company and shall have no duties or liabilities to the equity holders or the creditors of the Company or any other person by virtue of this Agreement or the retention of Maxim hereunder, all of which are hereby expressly waived.

SECTION 9. CLOSING. The obligations of the Placement Agent, and the closing of the sale of the Securities hereunder are subject to the accuracy, when made and on the Closing Date, of the representations and warranties on the part of the Company and its Subsidiaries contained herein, to the accuracy of the statements of the Company and its Subsidiaries made in any certificates pursuant to the provisions hereof, to the performance by the Company and its Subsidiaries of their obligations hereunder, and to each of the following additional terms and conditions:

(A) No stop order suspending the effectiveness of the Registration Statement shall have been issued and no proceedings for that purpose shall have been initiated or threatened by the Commission, and any request for additional information on the part of the Commission (to be included in the Registration Statement, the Base Prospectus or the Prospectus Supplement or otherwise) shall have been complied with to the reasonable satisfaction of the Placement Agent.

(B) The Placement Agent shall not have discovered and disclosed to the Company on or prior to the Closing Date that the Registration Statement, the Base Prospectus or the Prospectus Supplement or any amendment or supplement thereto contains an untrue statement of a fact which, in the opinion of counsel for the Placement Agent, is material or omits to state any fact which, in the opinion of such counsel, is material and is required to be stated therein or is necessary to make the statements therein not misleading.

(C) All corporate proceedings and other legal matters incident to the authorization, form, execution, delivery and validity of each of this Agreement, the Securities, the Registration Statement, the Base Prospectus and the Prospectus Supplement and all other legal matters relating to this Agreement and the transactions contemplated hereby shall be reasonably satisfactory in all material respects to counsel for the Placement Agent, and the Company shall have furnished to such counsel all documents and information that they may reasonably request to enable them to pass upon such matters.

(D) The Placement Agent shall have received from outside counsel to the Company such counsel’s written opinion, addressed to the Placement Agent and the Purchasers dated as of the Closing Date, in form and substance reasonably satisfactory to the Placement Agent, which opinion shall include a “10b-5” negative assurance from such counsel.

(E) (i) Neither the Company nor any of its Subsidiaries shall have sustained since the date of the latest audited or unaudited financial statements included or incorporated by reference in the Base Prospectus, any loss or interference with its business from fire, explosion, flood, terrorist act or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, otherwise than as set forth in or contemplated by the Base Prospectus and (ii) since such date there shall not have been any change in the capital

stock or long-term debt of the Company or any of its Subsidiaries or any change, or any development involving a prospective change, in or affecting the business, general affairs, management, financial position, stockholders’ equity, results of operations or prospects of the Company and its Subsidiaries, otherwise than as set forth in or contemplated by the Base Prospectus, the effect of which, in any such case described in clause (i) or (ii), is, in the judgment of the Placement Agent, so material and adverse as to make it impracticable or inadvisable to proceed with the sale or delivery of the Securities on the terms and in the manner contemplated by the Base Prospectus, the Time of Sale Prospectus and the Prospectus Supplement.

(F) The Common Stock is registered under the Exchange Act. The Company shall have taken no action designed to, or likely to have the effect of terminating the registration of the Common Stock under the Exchange Act, nor has the Company received any information suggesting that the Commission is contemplating terminating such registration.

(G) Subsequent to the execution and delivery of this Agreement, there shall not have occurred any of the following: (i) trading in securities generally on the New York Stock Exchange or the Nasdaq Stock Market shall have been suspended or minimum or maximum prices or maximum ranges for prices shall have been established on any such exchange or such market by the Commission, by such exchange or by any other regulatory body or governmental authority having jurisdiction, (ii) a banking moratorium shall have been declared by federal or state authorities or a material disruption has occurred in commercial banking or securities settlement or clearance services in the United States, (iii) the United States shall have become engaged in hostilities in which it is not currently engaged, the subject of an act of terrorism, there shall have been an escalation in hostilities involving the United States, or there shall have been a declaration of a national emergency or war by the United States, or (iv) there shall have occurred any other calamity or crisis or any change in general economic, political or financial conditions in the United States or elsewhere, if the effect of any such event in clause (iii) or (iv) makes it, in the sole judgment of the Placement Agent, impracticable or inadvisable to proceed with the sale or delivery of the Securities on the terms and in the manner contemplated by the Base Prospectus and the Prospectus Supplement.

(H) No action shall have been taken and no statute, rule, regulation or order shall have been enacted, adopted or issued by any governmental agency or body which would, as of the Closing Date, prevent the issuance or sale of the Securities or materially and adversely affect or potentially and adversely affect the business or operations of the Company; and no injunction, restraining order or order of any other nature by any federal or state court of competent jurisdiction shall have been issued as of the Closing Date which would prevent the issuance or sale of the Securities or materially and adversely affect or potentially and adversely affect the business or operations of the Company.

(I) The Company shall have prepared and filed with the Commission a Current Report on Form 8-K with respect to the Placement, including as an exhibit thereto this Agreement.

(J) The Company shall have entered into purchase agreements with each of the Purchasers and such agreements shall be in full force and effect and shall contain representations, warranties and covenants of the Company as agreed between the Company and the Purchasers.

(K) FINRA shall have raised no objection to the fairness and reasonableness of the terms and arrangements of this Agreement. In addition, the Company shall, if requested by the Placement Agent, make or authorize Placement Agent’s counsel to make on the Company’s behalf, an Issuer Filing with FINRA pursuant to FINRA Rule 5110 with respect to the Registration Statement and pay all filing fees required in connection therewith.

(L) Prior to the Closing Date, the Company shall have furnished to the Placement Agent such further information, certificates and documents as the Placement Agent may reasonably request.

(M) The Company and the Placement Agent shall have entered into an escrow agreement with a commercial bank or trust company reasonably satisfactory to both parties pursuant to which the Purchasers shall deposit their subscription funds in an escrow account and the Company and the Placement Agent shall jointly authorize the disbursement of the funds from the escrow account. The Company shall pay the reasonable fees of the escrow agent.

All opinions, letters, evidence and certificates mentioned above or elsewhere in this Agreement shall be deemed to be in compliance with the provisions hereof only if they are in form and substance reasonably satisfactory to counsel for the Placement Agent.

SECTION 10. DELIVERY OF COLD COMFORT LETTER. Within fourteen (14) calendar days from the Closing Date, Placement Agent shall have received a letter, addressed to the Placement Agent and in form and substance satisfactory in all respects to the Placement Agent from Ernst & Young LLP.

SECTION 11. GOVERNING LAW. This Agreement will be governed by, and construed in accordance with, the laws of the State of New York applicable to agreements made and to be performed entirely in such State. This Agreement may not be assigned by either party without the prior written consent of the other party. This Agreement shall be binding upon and inure to the benefit of the parties hereto, and their respective successors and permitted assigns. Any right to trial by jury with respect to any dispute arising under this Agreement or any transaction or conduct in connection herewith is waived. Each of the Placement Agent and the Company: (i) agrees that any legal suit, action or proceeding arising out of or relating to this Agreement and/or the transactions contemplated hereby shall be instituted exclusively in New York Supreme Court, County of New York, or in the United States District Court for the Southern District of New York, (ii) waives any objection which it may have or hereafter to the venue of any such suit, action or proceeding, and (iii) irrevocably consents to the jurisdiction of the New York Supreme Court, County of New York, and the United States District Court for the Southern District of New York in any such suit, action or proceeding. Each of the Placement Agent and the Company further agrees to accept and acknowledge service of any and all process which may be served in any such suit, action or proceeding in the New York Supreme Court, County of New York, or in the United States District Court for the Southern District of New York and agrees that service of process upon the Company mailed by certified mail to the Company’s address shall be deemed in every respect effective service of process upon the Company, in any such suit, action or proceeding, and service of process upon the Placement Agent mailed by certified mail to the Placement Agent’s address shall be deemed in every respect effective service process upon the Placement Agent, in any such suit, action or proceeding. Nothing contained herein

shall be deemed to limit in any way any right to serve process in any manner permitted by law. If either party shall commence an action or proceeding to enforce any provisions of a Transaction Document, then the prevailing party in such action or proceeding shall be reimbursed by the other party for its attorneys fees and other costs and expenses incurred with the investigation, preparation and prosecution of such action or proceeding.

SECTION 12. ENTIRE AGREEMENT/MISC. This Agreement (including the attached Indemnification Provisions) embodies the entire agreement and understanding between the parties hereto, and supersedes all prior agreements and understandings, relating to the subject matter hereof. If any provision of this Agreement is determined to be invalid or unenforceable in any respect, such determination will not affect such provision in any other respect or any other provision of this Agreement, which will remain in full force and effect. This Agreement may not be amended or otherwise modified or waived except by an instrument in writing signed by both Maxim and the Company. The representations, warranties, agreements and covenants contained herein shall survive the closing of the Placement and delivery and/or exercise of the Securities, as applicable. This Agreement may be executed in two or more counterparts, all of which when taken together shall be considered one and the same agreement and shall become effective when counterparts have been signed by each party and delivered to the other party, it being understood that both parties need not sign the same counterpart. In the event that any signature is delivered by facsimile transmission or a .pdf format file, such signature shall create a valid and binding obligation of the party executing (or on whose behalf such signature is executed) with the same force and effect as if such facsimile or .pdf signature page were an original thereof. The Company agrees that the Placement Agent may rely upon, and is a third party beneficiary of, the representations and warranties, and applicable covenants set forth in any such purchase, subscription or other agreement with the Purchasers in the Placement.

SECTION 13. CONFIDENTIALITY. The Placement Agent (i) will keep the Confidential Information (as such term is defined below) confidential and will not (except as required by applicable law or stock exchange requirement, regulation or legal process), without the Company’s prior written consent, disclose to any person any Confidential Information, and (ii) will not use any Confidential Information other than in connection with its evaluation of the Transaction. The Placement Agent further agrees to disclose the Confidential Information only to its Representatives who need to know the Confidential Information for the purpose of evaluating the Transaction, and who are informed by the Placement Agent of the confidential nature of the Confidential Information. The term “Confidential Information” shall mean, all confidential, proprietary and non-public information (whether written, oral or electronic communications) furnished by the Company to the Placement Agent or its Representatives in connection with the Placement Agent’s evaluation of the Transaction, which information is (a) clearly marked as “confidential” or with a similar designation, or (b) if disclosed orally or otherwise than in writing, is identified as confidential and/or proprietary at the time of disclosure by the Company. Information communicated orally or otherwise than in writing, shall only be considered Confidential Information if such information is designated as being confidential at the time of disclosure (or promptly thereafter) and is reduced in writing and identified to the Placement Agent as being Confidential Information immediately after the initial disclosure. The term “Confidential Information” will not, however, include information which (i) is or becomes publicly available other than as a result of a disclosure by the Placement Agent or its Representatives in violation of this Agreement, (ii) is or becomes available to the Placement Agent or any of its Representatives on a nonconfidential basis from a third-party, (iii) is known

to the Placement Agent or any of its Representatives prior to disclosure by the Company or any of its Representatives, or (iv) is or has been independently developed by the Placement Agent and/or the Representatives without use of any Confidential Information furnished to it by the Company. The term “Representatives” shall mean a party’s directors, board committees, officers, employees, financial advisors, attorneys and accountants. This provision shall be in full force and effect for two years.

SECTION 14. NOTICES. Any and all notices or other communications or deliveries required or permitted to be provided hereunder shall be in writing and shall be deemed given and effective on the earliest of (a) the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number specified on the signature pages attached hereto prior to 6:30 p.m. (New York City time) on a business day, (b) the next business day after the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number on the signature pages attached hereto on a day that is not a business day or later than 6:30 p.m. (New York City time) on any business day, (c) the business day following the date of mailing, if sent by U.S. nationally recognized overnight courier service, or (d) upon actual receipt by the party to whom such notice is required to be given. The address for such notices and communications shall be as set forth on the signature pages hereto.

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Please confirm that the foregoing correctly sets forth our agreement by signing and returning to Maxim the enclosed copy of this Agreement.

Accepted and Agreed to as of

the date first written above:

ADDENDUM A

INDEMNIFICATION PROVISIONS

In connection with the engagement of Maxim Group LLC (“Maxim”) by Athersys, Inc. (the “Company”) pursuant to a letter agreement dated January 10, 2014, between the Company and Maxim, as it may be amended from time to time in writing (the “Agreement”), the Company hereby agrees as follows:

[Sig Page to Indemnification Provisions

Pursuant to Engagement Agreement

between Athersys, Inc. and Maxim Group LLC]