Engagement Letter, dated June 12, 2017, between the Registrant and H.C. Wainwright & Co., LLC

Cash Fee.  The Company shall pay to Wainwright a cash fee, or as to an underwritten Offering an underwriter discount, equal to 6.5% of the aggregate gross proceeds raised in the Offering; provided, that, in no event shall any cash fee be paid to Wainwright in connection with sales of Securities to jVen Capital, LLC, Merck & Co., Inc., any Chinese party introduced to the Company by M.S.Q. Ventures Inc., International Finance Corporation, or any of their respective affiliates.

Warrant Coverage.  The Company shall issue to Wainwright or its designees at each Closing, warrants (the “Wainwright Warrants”) to purchase that number of shares of common stock of the Company equal to 5.0% of the aggregate number of shares of common stock placed in the Offering (and if the Offering includes a “greenshoe” or “additional investment” option component, such number of shares of common stock underlying such additional option component, with the Wainwright Warrants issuable upon the exercise of such option).  If the Securities included in the Offering are convertible, the Wainwright Warrants shall be determined by dividing the gross proceeds raised in such Offering divided by the Offering Price (as defined hereunder).  The Wainwright Warrants shall have the same terms as the warrants issued to investors in the applicable Offering, except that such Wainwright Warrants shall have an exercise price equal to 125% of the offering price per share (or unit, if applicable) in the applicable Offering and if such offering price is not available, the market price of the common stock on the date the Offering is commenced (such price, the “Offering Price”).  If no warrants are issued to investors in the Offering, the Wainwright Warrants shall be in a customary form reasonably acceptable to Wainwright, have a term of five (5) years and an exercise price equal to 125% of the Offering Price.

Expense Allowance.  Out of the proceeds of each Closing, the Company also agrees to pay Wainwright (a) a management fee equal to 1.0% of the gross proceeds raised in the Offering provided, that, in no event shall any management fee be paid to Wainwright in connection with sales of Securities to jVen Capital, LLC, Merck & Co., Inc., any Chinese party introduced to the Company by M.S.Q. Ventures Inc., International Finance Corporation, or any of their respective affiliates; (b) $50,000 for non-accountable expenses; (c) up to $100,000 for fees and expenses of legal counsel; plus the additional reimbursable amount payable by the Company pursuant to Paragraph D.3 hereunder; provided, however, that such reimbursement amount in no way limits or impairs the indemnification and contribution provisions of this Agreement.

[Reserved.]

Right of First Refusal.  If, from the date hereof until the 12-month anniversary following consummation of the Offering, the Company or any of its subsidiaries (a) decides to finance or refinance any indebtedness using a manager or agent, Wainwright (or any affiliate designated by Wainwright) shall have the right to act as a joint book-runner, a manager, a placement agent or an agent with respect to such financing or refinancing for the same economics as the other joint book-runner, manager, placement agents or agent; provided, that Wainwright shall be entitled to at least 33% of the economics of such financing (to be increased to 50% of the economics of such financing if neither Cowen nor Leerink participates in such financings); or (b) decides to raise funds by means of a public offering or a private placement of equity or debt securities using an underwriter or placement agent in each case other than through (i) its existing “at the market” program; (ii) any transaction with a Chinese party introduced to the Company by M.S.Q. Ventures Inc.; or (iii) any transaction with the International Finance Corporation, Wainwright (or any affiliate designated by Wainwright) shall have the right to act as a joint book-running manager or a placement agent for such financing, for the same economics as the other joint bookrunning manager or placement agents; provided, that Wainwright shall be entitled to at least 33% of the economics of such financing (to be increased to 50% of the economics of such financing if neither Cowen nor Leerink participates in such financings). The Company and Wainwright will enter into a new engagement letter with respect to such financing having terms customary for transactions of similar type and size.  For the avoidance of doubt, in no event shall Wainwright be entitled to any right of first refusal under the terms of this Agreement in the event that the Offering is not consummated during the Term (as defined below).  If Wainwright or one of its affiliates decides to accept any such engagement, the agreement governing such engagement will contain, among other things, provisions for customary fees for transactions of similar size and nature and the provisions of this Agreement, including indemnification, which are appropriate to such a transaction.  Wainwright hereby acknowledges that (i) the Company has a pre-existing obligation pursuant to (i) a letter agreement, dated February 26, 2016 as amended by letter dated May 10, 2016 (the “Cowen Engagement Letter”), between the Company and Cowen, and (ii) letter agreement, dated as of March 3, 2016, as amended by letter dated May 10, 2016 (the “Leerink Engagement Letter”), by and between Leerink Partners LLC (“Leerink”) and the Company, to provide each of Cowen and Leerink with a right of first refusal to serve as the Company’s joint bookrunning managing underwriter underwriter in connection with any public offering conducted by the Company (other than an “at the market” offering) until February 26, 2018 in the case of Cowen and March 3, 2018 in the case of Leerink and (ii) the Company will seek a waiver of the right of first refusal from each of Cowen and Leerink pursuant to each respective engagement letter, prior to filing of a registration statement on Form S-1 in connection with the Offering. Notwithstanding anything in this Section to the contrary, the Company’s obligation to offer a right of first refusal to Wainwright is in addition to the Company’s obligation to offer each of Cowen and Leerink the right of first refusal provided in the Cowen Engagement Letter and the Leerink Engagement Letter, respectively. Notwithstanding anything herein to the contrary, Wainwright shall not be entitled to receive a tail fee as provided under clause (4) above with respect to any investor that participates in an offering in connection with which Wainwright serves as a joint book-running manager or placement agent pursuant to the right of first refusal provided in this clause (5).

Underwritten Offering.  If an Offering is an underwritten Offering, the Company and Wainwright shall enter into a customary underwriting agreement in form and substance satisfactory to Wainwright and its counsel.

Best Efforts Offering.  If the Offering is on a best efforts basis, the sale of Securities to the investors in the Offering will be evidenced by a purchase agreement (“Purchase Agreement”) between the Company and such investors in a form reasonably satisfactory to the Company and Wainwright.  Wainwright shall be a third party beneficiary with respect to the representations and warranties included in the Purchase Agreement. Prior to the signing of any Purchase Agreement, officers of the Company with responsibility for financial affairs will be available to answer inquiries from prospective investors.

Escrow and Settlement.  In respect of the Offering, the Company and Wainwright shall enter into an escrow agreement with a third party escrow agent, which may also be Wainwright’s clearing agent, pursuant to which Wainwright’s compensation and expenses shall be paid from the gross proceeds of the Securities sold.  If the Offering is settled in whole or in part via delivery versus payment (“DVP”), Wainwright shall arrange for its clearing agent to provide the funds to facilitate such settlement. The Company shall bear the cost of the escrow agent and shall reimburse Wainwright for the actual out-of-pocket cost of such clearing agent settlement and financing, if any, which cost shall not exceed $10,000.

FINRA Amendments.  Notwithstanding anything herein to the contrary, in the event that Wainwright determines that any of the terms provided for hereunder shall not comply with a FINRA rule, including but not limited to FINRA Rule 5110, then the Company shall agree to amend this Agreement (or include such revisions in the final underwriting agreement) in writing upon the request of Wainwright to comply with any such rules; provided that any such amendments shall not provide for terms that are less favorable to the Company than are reflected in this Agreement.

In connection with the Company’s engagement of Wainwright as Offering agent, the Company hereby agrees to indemnify and hold harmless Wainwright and its affiliates, and the respective controlling persons, directors, officers, members, shareholders, agents and employees of any of the foregoing (collectively the “Indemnified Persons”), from and against any and all claims, actions, suits, proceedings (including those of shareholders), damages, liabilities and expenses incurred by any of them (including the reasonable fees and expenses of counsel), as incurred, (collectively a “Claim”), that are (A) related to or arise out of (i) any actions taken or omitted to be taken (including any untrue statements made or any statements omitted to be made) by the Company, or (ii) any actions taken or omitted to be taken by any Indemnified Person in connection with the Company’s engagement of Wainwright, or (B) otherwise relate to or arise out of Wainwright’s activities on the Company’s behalf under Wainwright’s engagement, and the Company shall reimburse any Indemnified Person for all expenses (including the reasonable fees and expenses of counsel) as incurred by such Indemnified Person in connection with investigating, preparing or defending any such claim, action, suit or proceeding, whether or not in connection with pending or threatened litigation in which any Indemnified Person is a party; provided, that the Company has received a written undertaking of such Indemnified Person to repay to the Company the amount so advanced if it shall be determined by a court of competent jurisdiction in a final judgment that has become non-appealable that such Indemnified Person was not entitled to indemnification hereunder.  The Company will not, however, be responsible for any Claim that is finally judicially determined to have resulted from the fraud, gross negligence or willful misconduct by any person seeking indemnification for such Claim.  The Company further agrees that no Indemnified Person shall have any liability to the Company for or in connection with the Company’s engagement of Wainwright except for any Claim incurred by the Company as a result of such Indemnified Person’s fraud, gross negligence or willful misconduct.

The Company further agrees that it will not, without the prior written consent of Wainwright, settle, compromise or consent to the entry of any judgment in any pending or threatened Claim in respect of which indemnification may be sought hereunder (whether or not any Indemnified Person is an actual or potential party to such Claim), unless such settlement, compromise or consent includes an unconditional, irrevocable release of each Indemnified Person from any and all liability arising out of such Claim.

Promptly upon receipt by an Indemnified Person of notice of any complaint or the assertion or institution of any Claim with respect to which indemnification is being sought hereunder, such Indemnified Person shall notify the Company in writing of such complaint or of such assertion or institution but failure to so notify the Company shall not relieve the Company from any obligation it may have hereunder, except and only to the extent such failure results in the forfeiture by the Company of substantial rights and defenses.  If the Company so elects or is requested by such Indemnified Person, the Company will assume the defense of such Claim, including the employment of counsel reasonably satisfactory to such Indemnified Person and the payment of the fees and expenses of such counsel.  In the event, however, that legal counsel to such Indemnified Person reasonably determines that having common counsel would present such counsel with a conflict of interest or if the defendant in, or target of, any such Claim, includes an Indemnified Person and the Company, and legal counsel to such Indemnified Person reasonably concludes that there may be legal defenses available to it or other Indemnified Persons different from or in addition to those available to the Company, then such Indemnified Person may employ its own separate counsel to represent or defend him, her or it in any such Claim and the Company shall pay the reasonable fees and expenses of such counsel.  Notwithstanding anything herein to the contrary, if the Company fails timely or diligently to defend, contest, or otherwise protect against any Claim, the relevant Indemnified Party shall have the right, but not the obligation, to defend, contest, compromise, settle, assert crossclaims, or counterclaims or otherwise protect against the same, and shall be fully indemnified by the Company therefor, including without limitation, for the reasonable fees and expenses of its counsel and all amounts paid as a result of such Claim or the compromise or settlement thereof.  In addition, with respect to any Claim in which the Company assumes the defense, the Indemnified Person shall have the right to participate in such Claim and to retain his, her or its own counsel therefor at his, her or its own expense.

The Company agrees that if any indemnity sought by an Indemnified Person hereunder is held by a court to be unavailable for any reason then (whether or not Wainwright is the Indemnified Person), the Company and Wainwright shall contribute to the Claim for which such indemnity is held unavailable in such proportion as is appropriate to reflect the relative benefits to the Company, on the one hand, and Wainwright on the other, in connection with Wainwright’s engagement referred to above, subject to the limitation that in no event shall the amount of Wainwright’s contribution to such Claim exceed the amount of fees actually received by Wainwright from the Company pursuant to Wainwright’s engagement.  The Company hereby agrees that the relative benefits to the Company, on the one hand, and Wainwright on the other, with respect to Wainwright’s engagement shall be deemed to be in the same proportion as (a) the total value paid or proposed to be paid or received by the Company pursuant to the applicable Offering (whether or not consummated) for which Wainwright is engaged to render services bears to (b) the fee paid or proposed to be paid to Wainwright in connection with such engagement.  Notwithstanding the provisions of this paragraph F.4., no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) if the Securities Act of 1933, as amended) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

The Company’s indemnity, reimbursement and contribution obligations under this Agreement (a) shall be in addition to, and shall in no way limit or otherwise adversely affect any rights that any Indemnified Party may have at law or at equity and (b) shall be effective whether or not the Company is at fault in any way.