UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

AVISTA HEALTHCARE PUBLIC ACQUISITION CORP.
65 East 55th StreetEAST 55TH STREET, 18TH FLOOR
18th FloorNEW YORK, NEW YORK 10022
New York, New York
(212) 593-6900

PROXY STATEMENTTO BE HELD OCTOBER 4, 2018

Notice and Proxy Statement for our 2018 Annual General Meeting

May 31, 2018TO THE SHAREHOLDERS OF AVISTA HEALTHCARE PUBLIC ACQUISITION CORP.:

        This Notice and Proxy Statement is being furnishedYou are cordially invited to attend the shareholdersextraordinary general meeting (the "extraordinary general meeting") of Avista Healthcare Public Acquisition Corp. (the "Company", "we", or "us"), a Cayman Islands exempted company ("AHPAC," the "Company," "we," "us" or "our"), on October 4, 2018 at 10:00 a.m. Eastern Time at the offices of Weil, Gotshal & Manges LLP, located at 767 Fifth Avenue, New York, NY 10153, for the sole purpose of considering and voting upon (i) a proposal to amend the Company's amended and restated memorandum and articles of association (the "Articles") to extend the date by which the Company has to consummate a business combination (the "Extension") from October 14, 2018 to February 15, 2019 (the "Extended Date") (the "Extension Amendment Proposal"), (ii) a proposal to amend the Company's Investment Management Trust Agreement (the "Trust Agreement"), dated as of October 10, 2016, by and between AHPAC and Continental Stock Transfer & Trust Company (the "trustee"), to extend the date on which to commence liquidating the trust account ("trust account") established in connection with the Company's initial public offering ("IPO") in the event the Company has not consummated a business combination prior to October 14, 2018, from October 14, 2018 to the Extended Date (the "Trust Amendment Proposal") and (iii) a proposal to adjourn the extraordinary general meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies byif, based upon the Board of Directors (the "Board") for usetabulated vote at the Annual General Meetingtime of the Company.

Date, Timeextraordinary general meeting, there are not sufficient votes to approve the Extension Amendment Proposal and Place

June 28, 2018 at 10:00 A.M., local time
Avista Healthcare Public Acquisition Corp.
65 East 55th Street
18th Floor
New York, New York 10022

Matters to be Consideredthe Trust Amendment Proposal (the "Adjournment Proposal").

        Our Annual General Meeting is being held to:

1.

Elect six directors to hold office untilEach of the 2020 Annual General Meeting or until their successorsExtension Amendment Proposal, the Trust Amendment Proposal and the Adjournment Proposal are elected and qualified.



2.

Ratify the selection of Marcum LLP as independent auditors for the year ended December 31, 2018.

        If any other matters properly come before the meeting, the persons namedmore fully described in the accompanying proxy or their substitutes will vote in accordance with their best judgment on such matters.

What is included in our proxy materials?

1.

Notice of 2018 Annual General Meeting



2.

Proxy Statement



3.

2017 Annual Report on Form 10-K



4.

Proxy Card or Voting Instruction Form

Record Date; Shares Outstanding and Entitled to Votestatement.

        The Board has fixed the close of business on May 18, 2018 as the record date for the determinationpurpose of the Extension Amendment Proposal, the Trust Amendment Proposal and, if necessary, the Adjournment Proposal, is to allow the Company more time to complete its proposed business combination (the "Organogenesis Transaction") pursuant to that certain Agreement and Plan of Merger, dated as of August 17, 2018 (as it may be amended, the "Merger Agreement"), by and among the Company, Avista Healthcare Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of the Company ("Merger Sub") and Organogenesis Inc., a Delaware corporation ("Organogenesis"). Our IPO prospectus and our Articles provide that the Company has until October 14, 2018 to complete its initial business combination (the "Termination Date"). Our board of directors has determined that it is in the best interests of our shareholders to extend the Termination Date by approving the Extension Amendment Proposal and the Trust Amendment Proposal to allow additional time to consummate the Organogenesis Transaction. While we have entered into the Merger Agreement with Merger Sub and Organogenesis and have filed with the Securities and Exchange Commission a registration statement on Form S-4 including the joint proxy/consent solicitation statement/prospectus forming a part thereof (the "Registration Statement") in respect of the Organogenesis Transaction in preliminary form on August 29, 2018, our board currently believes that there will not be sufficient time before the Termination Date to hold an extraordinary general meeting at which to conduct a vote for shareholder approval of the Organogenesis Transaction and consummate the closing of the Organogenesis Transaction. Accordingly, our board of directors believes that in order to be able to consummate the Organogenesis Transaction, we will need to obtain the Extension.

        As previously reported, on August 21, 2017, the Company entered into a transaction agreement by and among the Company, Merger Sub, Avista Healthcare NewCo, LLC, a Delaware limited liability company and a direct wholly-owned subsidiary of the Company ("NewCo"), Envigo International Holdings, Inc., a Delaware corporation ("Envigo") and Jermyn Street Associates, LLC, solely in its capacity as Shareholder Representative (as defined therein), as amended by that certain Amendment No. 1, dated as of November 22, 2017, as further amended by that certain Amendment No. 2, dated as

of December 22, 2017, as further amended by that certain Amendment No. 3, dated as of January 21, 2018 and as further amended by that certain Amendment No. 4, dated as of February 9, 2018 (the "Transaction Agreement"). On February 14, 2018, pursuant to Section 7.1(a) of the Transaction Agreement, the Company and Envigo entered into a Mutual Termination Agreement (the "Mutual Termination Agreement") and the Transaction Agreement was terminated effective as of February 14, 2018.

        The holders of ourAHPAC's Class A ordinary shares parissued in the Company's IPO (the "public shares"), regardless of whether they vote for or against the Extension Amendment Proposal, may elect to redeem their public shares in exchange for their pro rata portion of the funds held in the trust account if the Extension is implemented (the "Redemption"). For illustrative purposes, based on the fair market value $0.0001of marketable securities held in the trust account of approximately $315,791,565 as of September 12, 2018, the estimated per share (the "Classredemption price would have been approximately $10.19. The Company estimates that the per share pro rata portion of the trust account will be approximately $10.19 at the time of the extraordinary general meeting. The closing price of the public shares on September 12, 2018 was $10.10. Accordingly, if the market price were to remain the same until the date of the extraordinary general meeting, exercising redemption rights would result in a public shareholder receiving approximately $0.09 more than if the stock was sold in the open market. The Company cannot assure shareholders that they will be able to sell their public shares in the open market, even if the market price per share is higher than the redemption price stated above, as there may not be sufficient liquidity in its securities when such shareholders wish to sell their shares. The Company believes that such redemption right enables the Company's public shareholders to determine not to sustain their investments for an additional period if the Company does not complete the Organogenesis Transaction in the timeframe contemplated by the terms of its Articles. If the Extension Amendment Proposal and Trust Amendment Proposal are approved by the requisite vote of shareholders, the remaining holders of public shares will retain their right to convert their public shares for their pro rata portion of the funds available in the trust account at the time when the Organogenesis Transaction is submitted to shareholders for approval and adoption.

        If the Extension Amendment Proposal and the Trust Amendment Proposal are not approved, and the Organogenesis Transaction is not completed before October 14, 2018, then as contemplated by our IPO prospectus and in accordance with our Articles, we will: (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem 100% of the issued and outstanding public shares with the aggregate amount then on deposit in the trust account and (iii) thereafter seek to dissolve and liquidate as described in more detail in this proxy statement.

        A ordinary shares")special resolution, being the affirmative vote of holders of at least two-thirds of the public shares and the Company's Class B ordinary shares, par value $0.0001 per share (the "Class B ordinary shares,"shares" and, together with the Class A ordinarypublic shares, the "ordinary shares""Ordinary Shares") entitled to notice of and to vote at the meeting. Each shareholder will be entitled to one vote for each ordinary share held on all matters for which such shareholder is eligible to vote and that come before the meeting. Shareholders may voterepresented in person or by proxy and entitled to vote thereon at the extraordinary general meeting (voting together as a single class) will be required to approve the Extension Amendment Proposal. The affirmative vote of holders of sixty five percent (65%) of the issued and outstanding Ordinary Shares will be required to approve the Trust Amendment Proposal.

        The approval of both the Extension Amendment Proposal and the Trust Amendment Proposal are essential to the implementation of our board's plan to extend the date by completingwhich we must consummate our initial business combination. Therefore, our board will abandon and not implement either amendment unless our shareholders approve both the enclosed proxy cardExtension Amendment Proposal and returning itthe Trust Amendment Proposal. This means that if one proposal is approved by the shareholders and the other proposal is not, neither proposal will take effect. Notwithstanding shareholder approval of the Extension Amendment Proposal and the Trust Amendment Proposal, our board will retain the right to abandon and not implement the Extension Amendment Proposal and the Trust Amendment Proposal at any time without any further action by our shareholders.

        Approval of the Adjournment Proposal requires the affirmative vote of holders of a majority of the Ordinary Shares represented in the enclosed postage prepaid envelope or, as indicated on the proxy card, by voting on the Internetperson or by voting byproxy at the extraordinary general meeting. The Adjournment Proposal will only be put forth for a vote if the Extension Amendment Proposal and Trust Amendment Proposal are not approved at the extraordinary general meeting.

telephone. At        The Company's board of directors has fixed the close of business on May 18,September 12, 2018 (the "Record Date") as the date for determining the Company's shareholders entitled to receive notice of and vote at the extraordinary general meeting and any adjournment thereof. Only holders of record of Ordinary Shares on that date are entitled to have their votes counted at the extraordinary general meeting or any adjournment thereof.

        After careful consideration of all relevant factors, the Company's board of directors has determined that the Extension Amendment Proposal, the Trust Amendment Proposal and the Adjournment Proposal are fair to and in the best interests of the Company and its shareholders, has declared it advisable and recommends that you vote or give instruction to vote"FOR" such proposals.

        Enclosed is the proxy statement containing detailed information concerning the Extension Amendment Proposal, the Trust Amendment Proposal, the Adjournment Proposal and the extraordinary general meeting. Whether or not you plan to attend the extraordinary general meeting, we urge you to read this material carefully and vote your shares.

        I look forward to seeing you at the extraordinary general meeting.

September 12, 2018		By Order of the Board of Directors
		Executive Chairman of the Board of Directors

Your vote is very important. Whether or not you plan to attend the extraordinary general meeting, please vote as soon as possible by following the instructions in this proxy statement to make sure that your shares are represented at the extraordinary general meeting. The approval of the Extension Amendment Proposal requires a special resolution, being the affirmative vote of holders of at least two-thirds of the Ordinary Shares represented in person or by proxy and entitled to vote thereon at the extraordinary general meeting. Accordingly, if you fail to vote by proxy or to vote in person at the extraordinary general meeting, your shares will not be counted in connection with the determination of whether a valid quorum is established, however, if a valid quorum is otherwise established, such failure to vote will have no effect on the outcome of any vote on the Extension Amendment Proposal. The approval of the Trust Amendment Proposal requires the affirmative vote of holders of sixty five percent (65%) of the issued and outstanding Ordinary Shares. Accordingly, if you fail to vote by proxy or to vote in person at the extraordinary general meeting, such failure to vote will affect the outcome of any vote on the Trust Amendment Proposal as it will be the equivalent of a vote against the Trust Amendment Proposal. Approval of the Adjournment Proposal will require the affirmative vote of the majority of the Ordinary Shares represented in person or by proxy and entitled to vote thereon at the extraordinary general meeting. Accordingly, if you fail to vote by proxy or to vote in person at the extraordinary general meeting, your shares will not be counted in connection with the determination of whether a valid quorum is established, however, if a valid quorum is otherwise established, such failure to vote will have no effect on the outcome of any vote on the Adjournment Proposal. If you hold your shares in "street name" through a bank, broker or other nominee, you will need to follow the instructions provided to you by your bank, broker or other nominee to ensure that your shares are represented and voted at the extraordinary general meeting.

AVISTA HEALTHCARE PUBLIC ACQUISITION CORP.
65 EAST 55TH STREET, 18TH FLOOR
NEW YORK, NEW YORK 10022

NOTICE OF EXTRAORDINARY GENERAL MEETING

TO BE HELD OCTOBER 4, 2018

PROXY STATEMENT

        Avista Healthcare Public Acquisition Corp., a Cayman Island exempted company ("AHPAC," the "Company," "we," "us" or "our"), is providing this proxy statement in connection with the solicitation by the Board of proxies to be voted at the Extraordinary General Meeting to be held on October 4, 2018, at 10:00 a.m. Eastern Time at the offices of Weil, Gotshal & Manges LLP, located at 767 Fifth Avenue, New York, NY 10153 (the "extraordinary general meeting").

        At the extraordinary general meeting, proposals (i) to amend the Company's amended and restated articles of association (the "Articles") to extend the date by which the Company has to consummate a business combination (the "Extension") from October 14, 2018 to February 15, 2019 (the "Extended Date") (the "Extension Amendment Proposal"), (ii) to amend the Company's Investment Management Trust Agreement (the "Trust Agreement"), dated as of October 10, 2016, by and between AHPAC and Continental Stock Transfer & Trust Company (the "trustee"), to extend the date on which to commence liquidating the trust account ("trust account") established in connection with the Company's initial public offering ("IPO") in the event the Company has not consummated a business combination prior to October 14, 2018, from October 14, 2018 to the Extended Date (the "Trust Amendment Proposal") and (iii) a proposal to adjourn the extraordinary general meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies if, based upon the tabulated vote at the time of the extraordinary general meeting, there were 31,000,000are not sufficient votes to approve the Extension Amendment Proposal and the Trust Amendment Proposal (the "Adjournment Proposal"), will be considered and voted upon.

        The purpose of the Extension Amendment Proposal, the Trust Amendment Proposal and, if necessary, the Adjournment Proposal, is to allow the Company more time to complete its proposed business combination (the "Organogenesis Transaction") pursuant to that certain Agreement and Plan of Merger, dated as of August 17, 2018 (as it may be amended, the "Merger Agreement"), by and among the Company, Avista Healthcare Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of the Company ("Merger Sub") and Organogenesis Inc., a Delaware corporation ("Organogenesis") which contemplates the domestication of AHPAC as a Delaware corporation in accordance with Section 388 of the Delaware General Corporation Law and the Cayman Islands Companies Law (2018 Revision) (the "domestication"), the merger of Merger Sub with and into Organogenesis, with Organogenesis surviving the merger as a wholly owned direct subsidiary of AHPAC (the "merger") and the other transactions contemplated by the Merger Agreement. Our IPO prospectus and our Articles provide that the Company has until October 14, 2018 to complete its initial business combination (the "Termination Date"). Our board of directors has determined that it is in the best interests of our shareholders to extend the Termination Date by approving the Extension Amendment Proposal and the Trust Amendment Proposal. While we have entered into the Merger Agreement with Merger Sub and Organogenesis and have filed with the Securities and Exchange Commission a registration statement on Form S-4 including the joint proxy/consent solicitation statement/prospectus forming a part thereof (the "Registration Statement") in respect of the Organogenesis Transaction in preliminary form on August 29, 2018, our board currently believes that there will not be sufficient time before the Termination Date to hold an extraordinary general meeting at which to conduct a vote for shareholder approval of the Organogenesis Transaction and consummate

the closing of the Organogenesis Transaction. Accordingly, our board of directors believes that in order to be able to consummate the Organogenesis Transaction, we will need to obtain the Extension.

        As previously reported, on August 21, 2017, the Company entered into a transaction agreement by and among the Company, Merger Sub, Avista Healthcare NewCo, LLC, a Delaware limited liability company and a direct wholly owned subsidiary of the Company ("NewCo"), Envigo International Holdings, Inc., a Delaware corporation ("Envigo") and Jermyn Street Associates, LLC, solely in its capacity as Shareholder Representative (as defined therein), as amended by that certain Amendment No. 1, dated as of November 22, 2017, as further amended by that certain Amendment No. 2, dated as of December 22, 2017, as further amended by that certain Amendment No. 3, dated as of January 21, 2018 and as further amended by that certain Amendment No. 4, dated as of February 9, 2018 (the "Transaction Agreement"). On February 14, 2018, pursuant to Section 7.1(a) of the Transaction Agreement, the Company and Envigo entered into a Mutual Termination Agreement (the "Mutual Termination Agreement") and the Transaction Agreement was terminated effective as of February 14, 2018.

        The holders of AHPAC's Class A ordinary shares issued in the Company's IPO (the "public shares"), regardless of whether they vote for or against the Extension Amendment Proposal, may elect to redeem their public shares in exchange for their pro rata portion of the funds held in the trust account if the Extension is implemented (the "Redemption"). For illustrative purposes, based on the fair market value of marketable securities held in the trust account of approximately $315,791,565 as of September 12, 2018, the estimated per share redemption price would have been approximately $10.19. The Company estimates that the per share pro rata portion of the trust account will be approximately $10.19 at the time of the extraordinary general meeting. The closing price of the public shares on September 12, 2018 was $10.10. Accordingly, if the market price were to remain the same until the date of the extraordinary general meeting, exercising redemption rights would result in a public shareholder receiving approximately $0.09 more than if he sold his stock in the open market. The Company cannot assure shareholders that they will be able to sell their public shares in the open market, even if the market price per share is higher than the redemption price state above, as there may not be sufficient liquidity in its securities when such shareholders wish to sell their shares. The Company believes that such redemption right enables the Company's public shareholders to determine not to sustain their investments for an additional period if the Company does not complete the Organogenesis Transaction in the timeframe contemplated by the terms of its Articles. If the Extension Amendment Proposal and 7,750,000Trust Amendment Proposal are approved by the requisite vote of shareholders, the remaining holders of public shares will retain their right to convert their public shares for their pro rata portion of the funds available in the trust account at the time when the Organogenesis Transaction is submitted to shareholders.

        Approval of the Extension Amendment Proposal and the Trust Amendment Proposal are conditions to the implementation of the Extension.

        If the Extension Amendment Proposal and the Trust Amendment Proposal are approved, the amount remaining in the trust account following the Redemption may be only a small fraction of the approximately $315,791,565 that was in the trust account as of September 12, 2018 (the "Record Date"). Concurrently with the signing of the Merger Agreement, AHPAC entered into a subscription agreement with Avista Capital Partners IV, L.P., a Delaware limited partnership and Avista Capital Partners IV (Offshore), L.P., a limited partnership formed under the laws of Bermuda (collectively, the "PIPE Investor") for the purchase and sale, immediately following the domestication, of 9,022,741 shares of Class A common stock of AHPAC and 4,100,000 warrants to purchase one-half of one share of Class A common stock of AHPAC, for an aggregate purchase price of $46,000,000, through a private placement offered to a limited number of accredited investors (as defined by Rule 501 of Regulation D) pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended (the "PIPE"). Due to the PIPE, the Company believes there will be sufficient funds available to complete the

Organogenesis Transaction, if all other conditions to the consummation of the Organogenesis Transaction are satisfied.

        If the Extension Amendment Proposal and the Trust Amendment Proposal are not approved at the extraordinary general meeting or at any adjournment thereof, and the Organogenesis Transaction is not completed before October 14, 2018, then as contemplated by our IPO prospectus and in accordance with our Articles, we will: (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem the public shares, at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the trust account, including interest (which interest shall be net of taxes payable, and less up to $50,000 of interest to pay dissolution expenses) divided by the number of then issued and outstanding public shares, which redemption will completely extinguish public shareholders' rights as shareholders (including the right to receive further liquidation distributions, if any), subject to applicable law, and (iii) as promptly as reasonably possible following such redemption, subject to the approval of our remaining shareholders and our Board of Directors, dissolve and liquidate, subject in each case to our obligations under Cayman Islands law to provide for claims of creditors and the requirements of other applicable law.

        The Company's shareholders prior to the IPO (the "initial shareholders") have waived their rights to participate in any liquidation distribution with respect to the 5,812,500 shares acquired by them prior to the IPO and currently held by them ("the founder shares"). As a consequence of such waivers, a liquidating distribution will be made only with respect to the public shares. There will be no distribution from the trust account with respect to the Company's warrants, which will expire worthless in the event the Company dissolves and liquidates the trust account.

        If the Extension Amendment Proposal and the Trust Amendment Proposal are approved, the Company will (i) remove from the trust account an amount (the "Withdrawal Amount") equal to the aggregate pro rata portion of funds available in the trust account relating to any redeemed public shares and (ii) deliver to the holders of such redeemed public shares their pro rata portion of the Withdrawal Amount. The remainder of such funds shall remain in the trust account and be available for use by the Company to complete the Organogenesis Transaction on or before the Extended Date. The remaining non-redeeming holders of public shares will retain their right to convert their public shares for their pro rata portion of the funds available in the trust account when the Organogenesis Transaction is submitted to shareholders.

        Holders of record of the public shares and of the Company's Class B ordinary shares, par value $0.0001 per share (the "Class B ordinary shares" and, collectively with the public shares, the "Ordinary Shares") at the close of business on the Record Date are entitled to vote.

Mailingvote or have their votes cast at the extraordinary general meeting. On the Record Date, there were 36,812,500 issued and outstanding Ordinary Shares, including 31,000,000 issued and outstanding public shares. The Company's warrants do not have voting rights.

        This proxy statement contains important information about the extraordinary general meeting and the accompanying form ofExtension Amendment Proposal, the Trust Amendment Proposal and the Adjournment Proposal. Please read it carefully and vote your shares.

        This proxy arestatement is dated September 12, 2018, and is first being sentmailed to holders of the ordinary sharesshareholders on or about May 31, 2018.that date.

Broker Non-Votes
QUESTIONS AND ANSWERS ABOUT THE EXTRAORDINARY GENERAL MEETING

        A "broker non-vote" occurs when a brokerage firm or other nominee holding shares for a beneficial owner does not vote on a particular proposal because the nominee does not have authority to vote on that particular proposal without receiving voting instructions from the beneficial owner. Under applicable stock exchange rules, brokers may not vote on "non-routine" proposals unless they have received voting instructions from the beneficial owner,These Questions and to the extent that they have not received voting instructions, brokers report such number of shares as "non-votes." The election of directors is considered a "non-routine" item, which means that brokerage firms may not vote in their discretion regarding these items on behalf of beneficial owners who have not furnished voting instructions. The proposal to ratify the selection of independent auditors, however, is considered a "routine" item, which means that brokerage firms may vote in their discretion regarding the selection of independent auditors on behalf of beneficial owners who have not furnished voting instructions. Because at least one routine item is to be voted upon at the meeting, broker non-votes will be counted for purposes of determining the presence or absence of a quorum for the transaction of business at the 2018 Annual General Meeting.

Required Votes for Each Proposal and RecommendationAnswers are only summaries of the Boardmatters they discuss. They do not contain all of Directorsthe information that may be important to you. You should read carefully the entire document, including the annexes to this proxy statement.

        Abstentions or withhold votes, as applicable, and broker non-votes will have no effect on the election of directors. Abstentions will have no effect on the ratification of independent auditors.

Voting and Revocation of Proxies

        Shareholders are requested to vote by proxy in one of three ways:

•

Use the toll-free telephone number shown on your proxy card;



•

Visit the Internet website at www.voteproxy.com and follow the on-screen instructions; or



•

Mail, date, sign and promptly return your proxy card in the enclosed postage prepaid envelope.

        Ordinary shares represented by properly executed proxies received by us or proxies submitted by telephone or via the Internet, which are not revoked, will be voted at the meeting in accordance with the instructions contained therein. Subject to the broker non-vote rules discussed above under "Required Votes for Each Proposal," if instructions are not given, proxies will be votedfor the election of each nominee for director named andfor ratification of the selection of our independent auditors.

        Voting instructions (including instructions for both telephonic and Internet voting) are provided on the proxy card. The Internet and telephone voting procedures are designed to authenticate shareholder

identities, to allow shareholders to give voting instructions and to confirm that shareholders' instructions have been recorded properly. A control number, located on the proxy card, will identify shareholders and allow them to vote or submit their proxies and confirm that their voting instructions have been properly recorded. Costs associated with electronic access, such as usage charges from Internet access providers and telephone companies, must be borne by the shareholder. If you vote or submit your proxy by Internet or telephone, it will not be necessary to return your proxy card.

        If your shares are held in the name of a bank or broker, follow the voting instructions on the form you receive from your record holder. The availability of Internet and telephone voting will depend on their voting procedures.

        If a shareholder does not return a signed proxy card or submit a proxy by the Internet or by telephone, and does not attend the meeting and vote in person, his or her shares will not be voted.

        Any proxy signed and returned by a shareholder or submitted by telephone or via the Internet may be revoked at any time before it is exercised by giving written notice of revocation to the General Counsel and Secretary of the Company, at our address set forth herein, by executing and delivering a later-dated proxy (either in writing, by telephone or via the Internet) or by voting in person at the meeting. Attendance at the meeting will not in and of itself constitute revocation of a proxy. If your shares are held in a brokerage, bank, or other institutional account, you must obtain a proxy from that entity showing that you were the record holder as of the close of business on May 18, 2018, in order to vote your shares at the meeting.

Electronic Delivery of Annual Report and Proxy Materials

        This proxy statement and the accompanying Annual Report are available at: www.proxyvote.com.

"Householding" of Annual Report and Proxy Materials

        We have adopted a procedure approved by the Securities and Exchange Commission (the "SEC") called "householding." Under this procedure, shareholders of record who have the same address and last name will receive only one copy of our Annual Report and proxy statement unless one or more of these shareholders notifies us that they wish to continue receiving individual copies. This procedure will reduce our printing costs and postage fees. Shareholders who participate in householding will continue to receive separate proxy cards. Also, householding will not in any way affect dividend check mailings, if any.

        If you are eligible for householding, but you and other shareholders of record with whom you share an address currently receive multiple copies of the Annual Report and/or the proxy statement, or if you hold shares in more than one account, and in either case you wish to receive only a single copy of each of these documents for your household, please contact Broadridge Financial Solutions, Inc. at (866) 540-7095 or write to: Householding Department, 51 Mercedes Way, Edgewood, New York 11717. If you do not wish to participate in householding and prefer to receive separate copies of these documents in the future, please contact Continental Stock Transfer and Trust Company as indicated above and we will deliver promptly a separate copy of the Annual Report and proxy statement to you.

        Beneficial shareholders can request information about householding from their banks, brokers or other holders of record.

Proxy Solicitation

        We will bear the costs of solicitation of proxies for the Annual General Meeting. In addition to solicitation by mail, directors and officers may solicit proxies from shareholders by telephone, in person or otherwise. These directors and officers will not receive additional compensation, but may be reimbursed for out-of-pocket expenses in connection with this solicitation. Solicitation will be conducted

by our directors and officers and we will bear all costs associated with such solicitation. Brokers, nominees, fiduciaries and other custodians have been requested to forward soliciting material to the beneficial owners of our ordinary shares held of record by them, and such custodians will be reimbursed for their reasonable expenses.

Independent Auditors

        We have been advised that representatives of Marcum LLP, our independent auditors for 2017, will not attend the 2018 Annual General Meeting, and therefore will not have an opportunity to make a statement or respond to questions.

PROPOSAL NO. 1: ELECTION OF DIRECTORS

        At the meeting, six directors are to be elected to serve until the 2020 Annual General Meeting or until their successors are elected and qualified. All of the following nominees are currently serving as directors. The persons named in the enclosed form of proxy have advised that, unless contrary instructions are received, they intend to vote for the six nominees named by the Board and listed on the following table. The Board expects that each of the nominees will be available for election as a director. However, if by reason of an unexpected occurrence one or more of the nominees is not available for election, the persons named in the form of proxy have advised that they will vote for such substitute nominees as the Board may propose. The following information is as of May 18, 2018.

        Each of the biographies of the nominees for election as directors below contains information regarding the person's service as a director, business experience, director positions with other public companies held currently or at any time during the past five years, and the experience, qualifications, attributes and skills that caused the Board to determine that the person should be nominated as a director of the Company at our 2018 Annual General Meeting.

THE EXTENSION AMENDMENT PROPOSAL

The BoardExtension Amendment Proposal

        The Company is proposing to amend its Articles to extend the date by which the Company has to consummate a business combination to the Extended Date so as to give the Company more time to complete an initial business combination. A copy of Directors recommendsthe proposed amendment to the Articles of the Company is attached to the proxy statement asAnnex A.

        The Organogenesis Transaction qualifies as a "business combination" under the Company's Articles, but the board of directors of AHPAC believes that there will not be sufficient time before the Termination Date to hold an extraordinary general meeting at which to conduct a vote for shareholder approval of the Organogenesis Transaction and consummate the closing of the Organogenesis Transaction. Accordingly, our board of directors believes that in order to be able to consummate the Organogenesis Transaction, we will need to obtain the Extension. The Company believes that given the Company's expenditure of time, effort and money on the Organogenesis Transaction, circumstances warrant providing public shareholders an opportunity to consider the Organogenesis Transaction.

        All holders of the Company's public shares, whether they vote for or against the Extension Amendment Proposal, are entitled to redeem all or a portion of their public shares in exchange for their pro rata portion of the trust account in connection with the extraordinary general meeting. For illustrative purposes, based on the fair market value of marketable securities held in the trust account of approximately $315,791,565 as of September 12, 2018, the estimated per share redemption price would have been approximately $10.19. The Company estimates that the per share pro rata portion of the trust account will be approximately $10.19 at the time of the extraordinary general meeting. The closing price of the public shares on September 12, 2018 was $10.10. Accordingly, if the market price were to remain the same until the date of the extraordinary general meeting, exercising redemption rights would result in a public shareholder receiving approximately $0.09 more than if he sold his stock in the open market. The Company cannot assure shareholders that they will be able to sell their public shares in the open market, even if the market price per share is higher than the redemption price stated above, as there may not be sufficient liquidity in its securities when such shareholders wish to sell their shares. The Company believes that such redemption right enables the Company's public shareholders to determine not to sustain their investments for an additional period if the Company does not complete the Organogenesis Transaction in the timeframe contemplated by the terms of its Articles. If the Extension Amendment Proposal and Trust Amendment Proposal are approved by the requisite vote of shareholders, the remaining holders of public shares will retain their right to convert their public shares for their pro rata portion of the funds available in the trust account when the Organogenesis Transaction is submitted to shareholders.

Reasons for the Extension Amendment Proposal

        The Company's IPO prospectus and Articles provide that the Company has until October 14, 2018 to complete a business combination. The Company and its officers and directors agreed that it would not seek to amend the Company's Articles to allow for a longer period of time to complete a business combination unless it provided dissenting holders of public shares with the right to seek redemption of their public shares in connection therewith. Because the board of directors of the Company has determined in its reasonable judgment that it will not be able to complete the Organogenesis Transaction, or any other initial business combination, by October 14, 2018, the Company has determined to seek shareholder approval to extend the time for closing a business combination beyond October 14, 2018 to the Extended Date.

        The Extension Amendment Proposal is essential to allowing the Company more time to obtain approval for the Organogenesis Transaction at an extraordinary general meeting and to consummate the closing of the Organogenesis Transaction prior to the Extended Date. Approval of the Extension

Amendment Proposal and the Trust Amendment Proposal are conditions to the implementation of the Extension.

If the Extension Amendment Proposal Is Not Approved

        If the Extension Amendment Proposal is not approved, we will, unless we complete the Organogenesis Transaction, or another business combination, prior to October 14, 2018: (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem the public shares, at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the trust account, including interest (which interest shall be net of taxes payable, and less up to $50,000 of interest to pay dissolution expenses) divided by the number of then issued and outstanding public shares, which redemption will completely extinguish public shareholders' rights as shareholders (including the right to receive further liquidation distributions, if any), subject to applicable law, and (iii) as promptly as reasonably possible following such redemption, subject to the approval of our remaining shareholders and our board of directors, dissolve and liquidate, subject in each case to our obligations under Cayman Islands law to provide for claims of creditors and the requirements of other applicable law.

        The Company's initial shareholders have waived their rights to participate in any liquidation distribution with respect to their founder shares. There will be no distribution from the trust account with respect to the Company's warrants which will expire worthless in the event the Company dissolves and liquidates the trust account. The Company will pay the costs of liquidation from its remaining assets outside of the trust account.

If the Extension Amendment Proposal is Approved

        If the Extension Amendment Proposal and the Trust Amendment Proposal are approved, the Company will file an amendment to the Articles with the Cayman Islands in the form ofFORAnnex A hereto to extend the time it has to complete a business combination until the Extended Date. The Company will then continue to attempt to consummate a business combination until the Extended Date. The Company will remain a reporting company under the Securities Exchange Act of 1934 and its units, common stock and warrants will remain publicly traded during this time. The terms of the warrants will continue in accordance with their terms, with the warrants becoming exercisable upon the consummation of any business combination on or prior to the Extended Date.

You are not being asked to vote on any business combination at this time. If the Extension is implemented and you do not elect to redeem your public shares, you will retain the right to vote on the Organogenesis Transaction, or any other proposed business combination, when and if it is submitted to shareholders and the right to redeem your public shares into a pro rata portion of the trust account in the event the Organogenesis Transaction or any other business combination is approved and completed or the Company has not consummated a business combination by the Extended Date.

        If the Extension Amendment Proposal and the Trust Amendment Proposal are approved, and the Extension is implemented, the removal of the Withdrawal Amount from the trust account will reduce the Company's net asset value. The Company cannot predict the amount that will remain in the trust account if the Extension Amendment Proposal is approved, and the amount remaining in the trust account may be only a small fraction of the approximately $315,791,565 that was in the trust account as of the Record Date.

Redemption Rights

        If the Extension Amendment Proposal and the Trust Amendment Proposal are approved, and the Extension is implemented, each public shareholder may seek to redeem his or her public shares for a pro rata portion of the funds available in the trust account, less any income taxes owed on such funds

but not yet paid. If you exercise your redemption rights, you will be exchanging your public shares for cash and will no longer own the shares.

TO DEMAND REDEMPTION, YOU MUST CHECK THE BOX ON THE PROXY CARD PROVIDED FOR THAT PURPOSE AND RETURN THE PROXY CARD IN ACCORDANCE WITH THE INSTRUCTIONS PROVIDED OR SUBMIT A REQUEST IN WRITING THAT WE REDEEM YOUR PUBLIC SHARES FOR CASH TO CONTINENTAL STOCK TRANSFER & TRUST COMPANY AT THE ADDRESS BELOW, AND, AT THE SAME TIME, ENSURE YOUR BANK OR BROKER COMPLIES WITH THE REQUIREMENTS IDENTIFIED ELSEWHERE HEREIN, INCLUDING DELIVERING YOUR SHARES TO THE TRANSFER AGENT PRIOR TO THE VOTE ON THE EXTENSION AMENDMENT AND THE TRUST AMENDMENT.

        In connection with tendering your shares for redemption, prior to 5:00 PM Eastern time on October 2, 2018 (two business days before the extraordinary general meeting), you must elect either to physically tender your stock certificates to the Transfer Agent, at Continental Stock Transfer & Trust Company, 1 State Street—30th Floor, New York, New York 10004, Attn: Mark Zimkind, mzimkind@continentalstock.com, or to deliver your shares to the transfer agent electronically using DTC's DWAC system, which election would likely be determined based on the manner in which you hold your shares. The requirement for physical or electronic delivery prior to 5:00 PM Eastern time on October 2, 2018 (two business days before the extraordinary general meeting) ensures that a redeeming holder's election is irrevocable once the Extension Amendment Proposal and the Trust Amendment Proposal are approved. In furtherance of such irrevocable election, shareholders making the election will not be able to tender their shares after the vote at the extraordinary general meeting.

        The electronic delivery process through the DWAC system can be accomplished by the shareholder, whether or not it is a record holder or its shares are held in "street name," by contacting the Transfer Agent or its broker and requesting delivery of its shares through the DWAC system. Delivering shares physically may take significantly longer. In order to obtain a physical stock certificate, a shareholder's broker and/or clearing broker, DTC, and the Transfer Agent will need to act together to facilitate this request. There is a nominal cost associated with the above-referenced tendering process and the act of certificating the shares or delivering them through the DWAC system. The transfer agent will typically charge the tendering broker $45 and the broker would determine whether or not to pass this cost on to the redeeming holder. It is the Company's understanding that shareholders should generally allot at least two weeks to obtain physical certificates from the transfer agent. The Company does not have any control over this process or over the brokers or DTC, and it may take longer than two weeks to obtain a physical stock certificate. Such shareholders will have less time to make their investment decision than those shareholders that deliver their shares through the DWAC system. Shareholders who request physical stock certificates and wish to redeem may be unable to meet the deadline for tendering their shares before exercising their redemption rights and thus will be unable to redeem their shares.

        Certificates that have not been tendered in accordance with these procedures prior to the vote for the Extension Amendment Proposal will not be redeemed into a pro rata portion of the funds held in the trust account. In the event that a public shareholder tenders its shares and decides prior to the vote at the extraordinary general meeting that it does not want to redeem its shares, the shareholder may withdraw the tender. If you delivered your shares for redemption to our transfer agent and decide prior to the vote at the extraordinary general meeting not to redeem your shares, you may request that our transfer agent return the shares (physically or electronically). You may make such request by contacting our transfer agent at address listed above. In the event that a public shareholder tenders shares and the Extension Amendment Proposal is not approved or is abandoned, these shares will be redeemed in accordance with the terms of the Articles promptly following the extraordinary general meeting as described elsewhere herein. The Company anticipates that a public shareholder who tenders shares for redemption in connection with the vote to approve the Extension Amendment Proposal would receive

payment of the redemption price for such shares soon after the completion of the Extension Amendment Proposal. The transfer agent will hold the certificates of public shareholders that make the election until such shares are redeemed for cash or returned to such shareholders.

        If properly demanded, the Company will redeem each public share for a pro rata portion of the funds available in the trust account, less any income taxes owed on such funds but not yet paid, calculated as of two days prior to the filing of the amendment to the Articles. As of the Record Date, this would amount to approximately $10.19 per share. The closing price of the public shares on September 12, 2018 was $10.10. Accordingly, if the market price were to remain the same until the date of the extraordinary general meeting, exercising redemption rights would result in a public shareholder receiving approximately $0.09 more than if he sold his stock in the open market.

Required Vote

        The approval of Extension Amendment Proposal requires the affirmative vote of holders of two-thirds of the Ordinary Shares represented in person or by proxy and entitled to vote thereon at the extraordinary general meeting. All of the Company's directors, executive officers and their affiliates are expected to vote any Ordinary Shares owned by them in favor of the Extension Amendment Proposal. On the Record Date, directors and executive officers of the Company and their affiliates beneficially owned and were entitled to vote 5,812,500 founder shares representing approximately 15.8% of the Company's issued and outstanding Ordinary Shares.

        In addition, the Company's directors, executive officers and their affiliates may choose to buy Ordinary Shares in the open market and/or through negotiated private purchases. In the event that purchases do occur, the purchasers may seek to purchase shares from shareholders who would otherwise have voted against the Extension Amendment Proposal and elected to redeem their shares into a portion of the trust account. Any Ordinary Shares purchased by affiliates will be voted in favor of the Extension Amendment Proposal.

Recommendation of the Board

OUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT OUR SHAREHOLDERS VOTE"FOR" THE APPROVAL OF THE EXTENSION
AMENDMENT PROPOSAL

THE TRUST AMENDMENT PROPOSAL

The Trust Amendment Proposal

        The Trust Amendment Proposal would amend our existing Trust Agreement to change the date by which the trustee must commence liquidating the trust, from the 24-month anniversary of the closing of the IPO to the Extended Date, and make any other conforming amendments. The complete text of the proposed amendment is attached to this proxy statement asAnnex B. All shareholders are encouraged to read the proposed amendment in its entirety for a more complete description of its terms.

Reasons for the Trust Amendment Proposal

        The Company's IPO prospectus and Articles provide that the Company has until October 14, 2018 to complete a business combination. The Company and its officers and directors agreed that it would not seek to amend the Company's Articles to allow for a longer period of time to complete a business combination unless it provided dissenting holders of public shares with the right to seek redemption of their public shares in connection therewith. Because the Company has determined in its reasonable judgment that it will not be able to complete the Organogenesis Transaction, or any other initial business combination, by October 14, 2018, the Company has determined to seek shareholder approval to extend the time for closing a business combination beyond October 14, 2018 to the Extended Date.

        The Company is proposing to amend its Trust Agreement to extend the date on which the Trustee must commence liquidating the trust account in the event the Company has not consummated a business combination from October 14, 2018 to the Extended Date.

        The Trust Amendment Proposal is essential to allowing the Company more time to obtain approval for the Organogenesis Transaction at an extraordinary general meeting and consummate the closing of the Organogenesis Transaction prior to the Extended Date. Approval of the Trust Amendment Proposal is a condition to the implementation of the Extension. Approval of the Extension Amendment Proposal and the Trust Amendment Proposal are conditions to the implementation of the Extension.

        If the Trust Amendment Proposal is not approved and we have not consummated the Organogenesis Transaction, or another business combination, by October 14, 2018, we will (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem 100% of the issued and outstanding public shares with the aggregate amount then on deposit in the trust account and (iii) thereafter seek to dissolve and liquidate as described in more detail in this proxy statement. There will be no distribution from the trust account with respect to our warrants which will expire worthless in the event we wind up.

Required Vote

        Approval of the amendment to the Trust Agreement requires the affirmative vote of holders of sixty five percent (65%) of the issued and outstanding Ordinary Shares. All of the Company's directors, executive officers and their affiliates are expected to vote any Ordinary Shares owned by them in favor of the Trust Amendment Proposal. On the Record Date, directors and executive officers of the Company and their affiliates beneficially owned and were entitled to vote 5,812,501 founder shares representing approximately 15.8% of the issued and outstanding Ordinary Shares.

        In addition, the Company's directors, executive officers and their affiliates may choose to buy Ordinary Shares in the open market and/or through negotiated private purchases. In the event that purchases do occur, the purchasers may seek to purchase shares from shareholders who would otherwise have voted against the Trust Amendment Proposal and elected to redeem their shares into a portion of the trust account. Any Ordinary Shares purchased by affiliates prior to the Record Date will be voted in favor of the Trust Amendment Proposal.

Recommendation of the Board

OUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT OUR SHAREHOLDERS VOTE"FOR" THE APPROVAL OF THE TRUST AMENDMENT PROPOSAL

THE ADJOURNMENT PROPOSAL

The Adjournment Proposal

        The Adjournment Proposal, if adopted, will allow our board of directors to adjourn the extraordinary general meeting to a later date or dates to permit further solicitation of proxies. The Adjournment Proposal will only be presented to our shareholders in the event, based on the tabulated votes, there are not sufficient votes at the time of the extraordinary general meeting to approve the Extension Amendment Proposal and the Trust Amendment Proposal.

Consequences if the Adjournment Proposal is Not Approved

        If the Adjournment Proposal is not approved by our shareholders, our board of directors may not be able to adjourn the extraordinary general meeting to a later date in the event, based on the tabulated votes, there are not sufficient votes at the time of the extraordinary general meeting to approve the Extension Amendment Proposal and the Trust Amendment Proposal.

Required Vote

        Adoption of the Adjournment Proposal requires the affirmative vote of a majority of the Ordinary Shares represented in person or by proxy and entitled to vote thereon at the extraordinary general meeting. All of the Company's directors, executive officers and their affiliates are expected to vote any Ordinary Shares owned by them in favor of the Adjournment Proposal. On the Record Date, directors and executive officers of the Company and their affiliates beneficially owned and were entitled to vote 5,812,500 founder shares representing approximately 15.8% of the Company's issued and outstanding Ordinary Shares.

        In addition, the Company's directors, executive officers and their affiliates may choose to buy Ordinary Shares in the open market and/or through negotiated private purchases. In the event that purchases do occur, the purchasers may seek to purchase shares from shareholders who would otherwise have voted against the Adjournment Proposal and elected to redeem their shares into a portion of the trust account. Any Ordinary Shares purchased by affiliates prior to the Record Date will be voted in favor of the Adjournment Proposal.

Recommendation of the Board

OUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT OUR SHAREHOLDERS VOTE"FOR" THE APPROVAL OF THE ADJOURNMENT PROPOSAL

THE EXTRAORDINARY GENERAL MEETING

        Date, Time and Place.    The extraordinary general meeting of the Company will be held at 10:00 a.m., Eastern Time on October 4, 2018, at the offices of Weil, Gotshal & Manges LLP, located at 767 Fifth Avenue, New York, NY 10153.

        Voting Power; Record Date.    You will be entitled to vote or direct votes to be cast at the extraordinary general meeting, if you owned Ordinary Shares at the close of business on September 12, 2018, the Record Date for the extraordinary general meeting. At the close of business on the Record Date, there were 36,812,500 issued and outstanding Ordinary Shares each of which entitles its holder to cast one vote per proposal. Company warrants do not carry voting rights.

        Proxies; Board Solicitation.    Your proxy is being solicited by the above-named nominees.Company's board of directors on the Extension Amendment Proposal, the Trust Amendment Proposal and the Adjournment Proposal being presented to shareholders at the extraordinary general meeting. No recommendation is being made as to whether you should elect to redeem your shares. Proxies may be solicited in person or by telephone. If you grant a proxy, you may still revoke your proxy and vote your shares in person at the extraordinary general meeting.

        The Company has hired MacKenzie Partners, Inc. to assist in the proxy solicitation process for this extraordinary general meeting and for the meeting the Company will hold in connection with the Organogenesis Transaction, or any other proposed business combination. The Company will pay that firm a fee of approximately $6,500 plus disbursements for its services for this extraordinary general meeting.

Interests of the Company's Directors and Officers

        When you consider the recommendation of the Company's board of directors, you should keep in mind that the Company's executive officers and members of the Company's board of directors have interests that may be different from, or in addition to, your interests as a shareholder. These interests include, among other things:

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if the Extension Amendment Proposal and the Trust Amendment Proposal are not approved and we do not consummate a business combination by October 14, 2018 as contemplated by our IPO prospectus and in accordance with our Articles, the 5,812,500 founder shares held by the Company's officers, directors and affiliates and their permitted transferees, which were acquired prior to the IPO for an aggregate purchase price of $25,000, will be worthless (as the holders have waived liquidation rights with respect to such shares), as will the 16,400,000 private placement warrants that were acquired simultaneously with the IPO for an aggregate purchase price of $8,200,000 (as they will expire). Such founder shares had an aggregate market value of approximately $58,706,250 based on the last sale price of $10.10 of the public shares on Nasdaq on September 12, 2018;



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the fact that the initial shareholders have agreed not to redeem any of the founder shares in connection with a shareholder vote to approve a proposed initial business combination;



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the fact that AHPAC issued to the sponsor on August 11, 2017, as amended and restated on May 3, 2018, an unsecured promissory note pursuant to which AHPAC is permitted to borrow up to $600,000 in aggregate principal amount;



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the fact that the initial shareholders have agreed to waive their rights to liquidating distributions from the trust account with respect to their founder shares if AHPAC fails to complete an initial business combination by October 14, 2018;



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the fact that if AHPAC consummates a business combination, any amounts outstanding under any loan made by the sponsor to AHPAC will be repayable in cash or at the option of the

sponsor, an aggregate amount up to $1,500,000 may be converted into warrants with identical terms as the private placement warrants, at the price of $0.50 per warrant, and if AHPAC fails to complete a business combination there may be insufficient assets outside the trust account to satisfy such loans;

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the fact that if AHPAC consummates the Organogenesis Transaction, the initial shareholders will surrender to AHPAC an additional 4,421,507 founder shares and 16,400,000 private placement warrants;



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if the trust account is liquidated in the event AHPAC is unable to complete an initial business combination within the required time period, the sponsor has agreed to indemnify AHPAC to ensure that the proceeds in the trust account are not reduced below $10.00 per public share, or such lesser amount per public share held in the trust account as of the date of the liquidation of the trust account due to reductions in the value of the trust assets, in each case net of the interest which may be withdrawn to pay taxes, except as to any claims by a third party who executed a waiver of any and all rights to seek access to the trust account and except as to any claims under our indemnity of the underwriters of this offering against certain liabilities, including liabilities under the Securities Act;



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the anticipated election of Mr. Joshua Tamaroff as a director of AHPAC in the Organogenesis Transaction;



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the continued indemnification of AHPAC's existing directors and officers and the continuation of AHPAC's directors' and officers' liability insurance after the Organogenesis Transaction;



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the fact that the sponsor, officers and directors may not participate in the formation of, or become a director or officer of, any other blank check company until AHPAC (i) has entered into a definitive agreement regarding an initial business combination or (ii) fails to complete an initial business combination by October 14, 2018; and



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the fact that the sponsor, officers and directors will not be reimbursed for any out-of-pocket expenses if an initial business combination is not consummated by October 14, 2018.

        Additionally, if the Extension Amendment Proposal and the Trust Amendment Proposal are approved and the Company consummates an initial business combination, the officers and directors may have additional interests that would be described in the proxy statement for such transaction.

Board Recommendation

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE"FOR" THE EXTENSION AMENDMENT PROPOSAL AND "FOR" THE TRUST AMENDMENT PROPOSAL. THE BOARD OF DIRECTORS EXPRESSES NO OPINION AS TO WHETHER YOU SHOULD REDEEM YOUR PUBLIC SHARES.

INFORMATION CONCERNING
THE BOARD OF DIRECTORS AND BOARD COMMITTEESABOUT AHPAC

        We areAHPAC is a blank check company incorporated on December 4, 2015 as a Cayman Islands exemptedexempt company and formed for the purpose of effecting a merger, share exchange, asset acquisition, stock purchase, reorganization or similar business combination with one or more businesses, ("which we refer to as a "business combination." Prior to entering into the Merger Agreement, AHPAC's acquisition and value creation strategy was to identify, acquire and, after an initial business combination").combination, build a company in the healthcare sector in public markets that complements the experience of AHPAC's management team and can benefit from AHPAC's management's operational expertise. AHPAC's acquisition selection process has leveraged its management team's network of potential transaction sources, ranging from healthcare industry executives, board members, private equity investors, wealthy families, commercial banks, investment bankers, advisors, attorneys, accountants and other transaction intermediaries. AHPAC has neither engaged in any operations nor generated any revenue to date. Based on AHPAC's business activities, we are a "shell company" as defined under the Exchange Act because AHPAC has no operations and nominal assets consisting almost entirely of cash.

        Prior to our IPO, on December 14, 2015, our sponsor purchased 8,625,000 Class B ordinary shares, for an aggregate purchase price of $25,000, or approximately $0.003 per share. In October 2016, our sponsor transferred 50,000 Class B ordinary shares to each of our independent directors at their original per share purchase price. In addition, at such time, each of our independent directors purchased an additional 421,250 Class B ordinary shares from our sponsor at their original purchase price.

        On October 14, 2016, we completed an initial public offeringconsummated our IPO of our30,000,000 units which are comprisedat a price of $10.00 per unit generating gross proceeds of $300,000,000 before underwriting discounts and expenses. Each unit ("unit") consists of one Class A ordinaryOrdinary Share, par value $0.0001 per share and one warrant to purchase one-half of one Class A ordinary share. Our publicly tradedOrdinary Share where two warrants must be exercised for one whole Ordinary Share at an exercise price of $11.50 per whole share (each, a "public warrant"). Simultaneously with the closing of our IPO, AHPAC completed the private sale of an aggregate of 16,000,000 private placement warrants (each, a "private placement warrant"), at a purchase price of $0.50 per private placement warrant, to the initial shareholders, generating gross proceeds to AHPAC of $8,000,000.

        On November 28, 2016, we completed the sale of an additional 1,000,000 units to the underwriters of the IPO at the public offering price of $10.00 per unit pursuant to the partial exercise of the Over-allotment Option. On November 28, 2016, we sold an additional 400,000 private placement warrants for an aggregate purchase price of $200,000 in connection with the exercise of the Over-allotment Option. Following the partial exercise of the Over-allotment Option, 875,000 Class B ordinary shares were forfeited in order to maintain the ownership of the initial shareholders at 20% of the issued and outstanding ordinary shares. On November 28, 2016, our sponsor sold 161,180 Class B ordinary shares and 350,114 private placement warrants to one of our independent directors at their original purchase price. On July 5, 2017, our sponsor sold 186,320 Class B ordinary shares and 404,723 private placement warrants to one of our independent directors at their original per share purchase price.

        We received gross proceeds from the IPO, including the partial exercise of the Over-allotment Option, and the sale of the private placement warrants of $310,000,000 and $8,200,000, respectively, for an aggregate of $318,200,000. Of such amount, $310,000,000 was deposited into the trust account by trustee. The remaining $8,200,000 was held outside of the trust account, of which $6,200,000 was used to pay underwriting discounts, with the balance used to repay a note to our sponsor and to pay accrued offering and formation costs, and the remainder was reserved for business, legal and accounting due diligence on prospective acquisitions and continuing general and administrative expenses. In the future,

a portion of interest income on the funds held in the trust account may be released to us to pay tax obligations. At June 30, 2018, funds held in the trust account consisted solely of cash.

        On November 28, 2016, we announced that, commencing November 29, 2016, holders of the 31,000,000 units sold in the IPO may elect to separately trade the public shares and public warrants are currently listedincluded in the units. Those Units not separated will continue to trade on the NASDAQ Capital Marketunder the symbol "AHPAU," and the public shares and warrants that are separated will trade on the NASDAQ under the symbols "AHPA," "AHPAU""AHPA" and "AHPAW," respectively.

        Based on our business activities,On August 21, 2017, the Company, isMerger Sub, NewCo, Envigo, and Jermyn Street Associates, LLC, entered into the Transaction Agreement (as amended) providing for a "shell company"proposed business combination. On February 14, 2018, we executed and entered into the Mutual Termination Agreement pursuant to Section 7.1(a) of the Transaction Agreement, with NewCo, Envigo, and Jermyn Street Associates, LLC, solely in its capacity as defined undershareholder representative, for the Exchange Actpurpose of 1934mutually terminating the Transaction Agreement, and all proposed transactions relating to the merger. The Transaction Agreement was terminated effective as of February 14, 2018.

        On January 4, 2018, we received a letter from the staff of the Listing Qualifications Department of NASDAQ (the "Exchange Act""Notification Letter") notifying us that we no longer comply with NASDAQ Listing Rules 5620(a) and 5810(c)(2)(G) (the "Rules") because we have no operations and nominal assets consisting almost entirely of cash. We also have neither engaged in any operations nor generated any revenue to date. We have reviewed, and continue to review, a number of opportunities to enter into a business combination with an operating business, but we are not able to determine at this time whether we will complete a business combination with any of the target businesses that we have reviewed or with any other target. Our efforts to identify a prospective target business have not been limited to a particular industry or geographic region, although we have focused our search on targeted North American or European healthcare related business.

Corporate Governance and Number and Terms of Office of Directors

        Our Board consists of six members, four of whom are independent under NASDAQ Listing Standards. An "independent director" is defined generally as a person other than an officer or employee of the company or its subsidiaries or any other individual having a relationship which in the opinion of the Board, would interfere with the director's exercise of independent judgment in carrying out the responsibilities of a director.

        This general meeting will be the Company's first Annual General Meeting. Our amended and restated memorandum and articles of association (our "articles") require that we hold director elections at the first such meeting. Commencing at this Annual General Meeting and at each annual general meeting thereafter, each of our directors will hold office for a two-year term.

        In addition, under our articles, only holders of our Class B ordinary shares initially purchased by Avista Acquisition Corp., a Cayman Islands exempted company (the "Sponsor") and certain other accredited investors (the "Founder Shares") have the right to elect directors prior to the consummation of a business combination. Accordingly, holders of our Class A ordinary shares will not have the right to vote on the election of directors at this Annual General Meeting. These provisions of our articles may only be amended by a special resolution passed by a majority of at least 90% of our ordinary shares voting in a general meeting. Subject to any other special rights applicable to the shareholders, any vacancies on our Board may be filled by the affirmative vote of a majority of the directors present and voting at the meeting of our board or by a majority of the holders of our Founder Shares.

Director Independence

        The Board has determined that Messrs. Björklund, Harwood, Markison and O'Neil are "independent directors" as defined in Rule 10A-3 of the Exchange Act and the rules of the NASDAQ. Our independent directors have regularly scheduled meetings at which only independent directors are present.

Committee Membership, Board and Committee Meetings and Attendance

        The Board has two standing committees: an Audit Committee and a Compensation Committee. Each of the Audit Committee and Compensation Committee is composed solely of independent directors.

        From December 4, 2015 (inception) through December 31, 2016, the end of the Company's fiscal year, the Company's Audit Committee held one meeting, at which all members of the Audit Committee were present. The Board or a committee thereof acted by way of unanimous written resolution six times in fiscal year 2016. The Company's Compensation Committee did not hold meetings in fiscal year 2016.

        From December 31, 2016 through December 31, 2017, the Company's Audit Committee held three meetings, at which all members of the Audit Committee were present. The Board or a committee thereof acted by way of unanimous written resolution nine times in fiscal year 2017. The Company's Compensation Committee did not hold meetings in fiscal year 2017 because none of our officers or directors were compensated in 2017 (See "Executive Compensation" below).

Audit Committee

        The members of our Audit Committee are Messrs. Harwood, Markison and O'Neil. Mr. Harwood serves as Chairman of the Audit Committee.

        Each member of the Audit Committee is financially literate and the Board has determined that Mr. Harwood qualifies as an "Audit Committee financial expert" as defined in applicable SEC rules.

        We have adopted an Audit Committee charter, which details the principal functions of the Audit Committee, including:

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the appointment, compensation, retention, replacement, and oversight of the work of the independent auditors and any other independent registered public accounting firm engaged by us;



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pre-approving all audit and non-audit services to be provided by the independent auditors or any other registered public accounting firm engaged by us, and establishing pre-approval policies and procedures;



•

reviewing and discussing with the independent auditors all relationships the auditors have with us in order to evaluate their continued independence;



•

setting clear hiring policies for employees or former employees of the independent auditors;



•

setting clear policies for audit partner rotation in compliance with applicable laws and regulations;



•

obtaining and reviewing a report, at least annually, from the independent auditors describing (i) the independent auditor's internal quality-control procedures and (ii) any material issues raised by the most recent internal quality-control review, or peer review, of the audit firm, or by any inquiry or investigation by governmental or professional authorities, within, the preceding five years respecting one or more independent audits carried out by the firm and any steps taken to deal with such issues;



•

reviewing and approving any related party transaction required to be disclosed pursuant to Item 404 of Regulation S-K promulgated by the SEC prior to us entering into such transaction; and



•

reviewing with management, the independent auditors, and our legal advisors, as appropriate, any legal, regulatory or compliance matters, including any correspondence with regulators or

government agencies and any employee complaints or published reports that raise material issues regarding our financial statements or accounting policies and any significant changes in accounting standards or rules promulgated by the Financial Accounting Standards Board, the SEC or other regulatory authorities.

Compensation Committee

        The members of our Compensation Committee are Messrs. Markison and Harwood. Mr. Markison serves as Chairman of the Compensation Committee. The Company adopted a Compensation Committee Charter which details the principal functions of the Compensation Committee, including:

•

reviewing and approving on an annual basis the corporate goals and objectives relevant to the Chief Executive Officer's compensation, evaluating the Chief Executive Officer's performance in light of such goals and objectives and determining and approving the remuneration (if any) of the Chief Executive Officer's based on such evaluation;



•

reviewing and approving the compensation of all of the Company's other officers;



•

reviewing the Company's executive compensation policies and plans;



•

implementing and administering the Company's incentive compensation equity-based remuneration plans;



•

assisting management in complying with the Company's proxy statement and Annual Report disclosure requirements;



•

approving all special perquisites, special cash payments and other special compensation and benefit arrangements for the Company's officers and employees;



•

producing a report on executive compensation to be included in the Company's annual proxy statement; and



•

reviewing, evaluating and recommending changes, if appropriate, to the remuneration for directors.

        The Compensation Committee Charter also provides that the Compensation Committee may, in its sole discretion, retain or obtain the advice of a compensation consultant, legal counsel or other adviser and will be directly responsible for the appointment, compensation and oversight of the work of any such adviser. However, before engaging or receiving advice from a compensation consultant, external legal counsel or any other adviser, the Compensation Committee will consider the independence of each such adviser, including the factors required by NASDAQ and the SEC.

Certain Relationships and Related Person Transactions

Policies and Procedures with Respect to Transactions with Related Persons

        The Company has not yet adopted a formal policy for the review, approval or ratification of related party transactions.

        The Company has adopted a code of ethics requiring it to avoid, wherever possible, all conflicts of interest, except under guidelines or resolutions approved by the Board (or the appropriate committee of the Board) or as disclosed in its public filings with the SEC. Under the Company's code of ethics, conflict of interest situations include any financial transaction, arrangement or relationship (including any indebtedness or guarantee of indebtedness) involving the Company.

        In addition, the Company's Audit Committee is responsible for reviewing and approving related party transactions to the extent that the Company enters into such transactions. An affirmative vote of a majority of the members of the Audit Committee present at a meeting at which a quorum is present

is required in order to approve a related party transaction. A majority of the members of the entire Audit Committee constitutes a quorum. Without a meeting, the unanimous written resolution of all of the members of the Audit Committee is be required to approve a related party transaction. The Company also requires each of its directors and executive officers to complete a directors' and officers' questionnaire that elicits information about related party transactions. These procedures are intended to determine whether any such related party transaction impairs the independence of a director or presents a conflict of interest on the part of a director, employee or officer.

        To further minimize conflicts of interest, the Company has agreed not to consummate an initial business combination with an entity that is affiliated with any of its Sponsor, officers or directors unless the Company, or a committee of independent directors, has obtained an opinion from an independent investment banking firm which is a member of FINRA or an independent accounting firm that the Company's initial business combination is fair from a financial point of view. Furthermore, no finder's fees, reimbursements or cash payments will be made to the Sponsor, the Company's officers or directors, or its or their affiliates, for services rendered to the Company prior to or in connection with the completion of the Company's initial business combination.

        The Company's Audit Committee reviews on a quarterly basis all payments that were made to the Sponsor, the Company's officers or directors, or its or their affiliates.

Director Nomination Process

        The Company does not have a standing nominating committee. In accordance with Rule 5605(e)(2) of the NASDAQ rules, a majority of the independent directors may recommend a director nominee for selection by the Board. The Board believes that the independent directors can satisfactorily carry out the responsibility of properly selecting or approving director nominees without the formation of a standing nominating committee. In accordance with Rule 5605(e)(1)(A) of the NASDAQ rules, all such directors are independent. As there is no standing nominating committee, the Company does not have a nominating committee charter in place.

        Prior to a business combination, the Board will also consider director candidates recommended for nomination by holders of our Founder Shares during such times as they are seeking proposed nominees to stand for election at an annual general meeting (or, if applicable, an extraordinary general meeting). Prior to a business combination, holderswithin twelve months of the end of our Class A ordinary shares willfiscal year ended December 31, 2016.

        On February 21, 2018, in response to the plan we submitted to the Listing Qualifications Department of NASDAQ in response to the Notification Letter on February 20, 2018, we received a letter from the staff of the Listing Qualifications Department of NASDAQ notifying us that we have been granted an extension until June 29, 2018 to regain compliance with the Rules by holding an annual general meeting. On June 28, 2018, we held our annual general meeting.

        On August 29, 2018, we received a letter (the "August Notification Letter") from the staff of the Listing Qualifications Department of NASDAQ notifying us that we no longer comply with NASDAQ Listing Rule 5550(a)(3) because we did not maintain a minimum of 300 public holders. The August Notification Letter informed us that under the NASDAQ Listing Rules, we have 45 calendar days following the rightdate of such notice to recommend director candidates for nominationsubmit a plan to our board.

regain compliance. The Company has not formally established any specific, minimum qualificationsintends to submit such plan ahead of that must be met or skills that are necessary for directors to possess. In general, in identifying and evaluating nominees for director, the Board considers educational background, diversity of professional experience, knowledgedeadline.

        The mailing address of the Company's business, integrity, professional reputation, independence, wisdom, and the ability to represent the best interests of the Company's shareholders.

Board Leadership Structure and Risk Oversight

        The Board recognizes that the leadership structure and combination or separation of the Chief Executive Officer and Chairman rolesprincipal executive office is driven by the needs of the Company at any point in time. As a result, no policy exists requiring combination or separation of leadership roles and the Company's governing documents do not mandate a particular structure. Currently, the Company's Chief Executive Officer and Chairman roles are separately held by Messrs. Burgstahler and Dean, respectively.

        The Board oversees the Company's risk management process directly and through its committees. The Board focuses on the Company's general risk management strategy and ensures that appropriate risk mitigation strategies are implemented by management, including in light of the Company's status as a Special Purpose Acquisition Company, or "SPAC," prior to the business combination.

        Shareholders may communicate with the Board generally or a specific director at any time by writing to the Company's General Counsel and Secretary at Avista Healthcare Public Acquisition Corp., 65 East 55th Street, 18th18^th Floor, New York, New York 10022. The Company reviews all messages received,10022, and forwards any message that reasonably appears to be a communication from a shareholder about a matter of shareholder interest thatits telephone number is intended for communication to the Board.(212) 593-6900.

INFORMATION ON SHAREBENEFICIAL OWNERSHIP OF SECURITIES

Present Beneficial Ownership

        The following table sets forth information available to us at May 18,September 12, 2018 with respect to our ordinary sharesOrdinary Shares held by:

•

each person known by us to be the beneficial owner of more than 5% of our issued and outstanding ordinary shares;Ordinary Shares;



•

each of our officers and directors that beneficially own ordinary shares;Ordinary Shares; and



•

all our officers and directors as a group.

        Unless otherwise indicated, we believe that all persons named in the table have sole voting and investment power with respect to all ordinary sharesOrdinary Shares beneficially owned by them. The following table does not reflect record or beneficial ownership of the private placement warrants as they are not exercisable within 60 days of May 18,September 12, 2018.

Section 16(a) Beneficial Ownership Reporting Compliance

        Section 16(a) of the Exchange Act, as amended, requires our officers, directors and persons who beneficially own more than ten percent of our ordinary sharesOrdinary Shares to file reports of ownership and changes in ownership with the SEC. These reporting persons are also required to furnish us with copies of all Section 16(a) forms they file. Based solely upon a review of such Forms,forms, we believe that during the year ended December 31, 2017 there were no delinquent filers.

EXECUTIVE COMPENSATION
Compensation Discussion and AnalysisFUTURE SHAREHOLDER PROPOSALS

        We do not have any employees. Additionally, none of our officers or directors have received any cash compensation for services rendered to us. Commencing on October 11, 2016,If the Extension Amendment Proposal and until the earlier of the consummation of a business combination or our liquidation, we will pay an affiliate of our Sponsor a total of $10,000 per month for office space, administrative and support services. Our Sponsor, officers and directors, or any of their respective affiliates, will be reimbursed for any out of

pocket expenses incurred in connection with activities on our behalf such as identifying potential target businesses and performing due diligence on suitable business combinations. Our Audit Committee will review on a quarterly basis all payments that were made to our Sponsor, officers, directors or our or their affiliates.

        After the completion of a business combination, directors or members of our management team who remain with us may be paid consulting, management or other fees from the combined company. Directors of the post combination business will be responsible for determining officer and director compensation.

        We do not intend to take any action to ensure that members of our management team maintain their positions with us after the consummation of a business combination, although it is possible that some or all of our officers and directors may negotiate employment or consulting arrangements to remain with us after the business combination. The existence or terms of any such employment or consulting arrangements to retain their positions with us may influence our management's motivation in identifying or selecting a target business but we do not believe that the ability of our management team to remain with us after the consummation of a business combination will be a determining factor in our decision to proceed with any potential business combination. WeTrust Amendment Proposal are not party to any agreements with our officers and directors that provide for benefits upon termination of employment.

Compensation Committee Report

        I have reviewed and discussed with our management the above Compensation Discussion and Analysis ("CD&A"). Based upon my review and discussions, I have recommended to the Board of Directors that the CD&A be included in this proxy statement on Schedule 14A.

AUDIT COMMITTEE REPORT

Audit Committee Report

        The Audit Committee has reviewed and discussedapproved, the Company's audited financial statements with management, and has discussed with2019 annual general meeting will likely be held in June 2019, unless the date is changed by the Company's independent registered public accounting firm the matters required to be discussed by Public Company Accounting Oversight Board. Additionally, the Audit Committee has received the written disclosures and the letter from Marcum LLP, the Company's independent registered public accounting firm, as required by the applicable requirementsboard of the PCAOB, and has discussed with Marcum LLP, the independent registered public accounting firm's independence. The Audit Committee also concluded that Marcum LLP's provision of audit and non-audit services to the Company, as described in the proxy statement, is compatible with Marcum LLP's independence. Based upon such review and discussion, the Audit Committee recommended to the Board that the audited financial statements for the year ended December 31, 2017 be included in the Company's Annual Report on Form 10-K for the last fiscal year for filing with the SEC.

FEES AND SERVICES

        Fees for professional services provided by our independent registered public accounting firm since inception include:

Policy on Board Pre-Approval of Audit and Permissible Non-Audit Services of the Independent Auditors

        The Audit Committee is responsible for appointing, setting compensation and overseeing the work of the independent auditors. In recognition of this responsibility, the Audit Committee shall review and, in its sole discretion, pre-approve all audit and permitted non-audit services to be provided by the independent auditors as provided under the Audit Committee charter.

PROPOSAL NO. 2: RATIFICATION OF SELECTION OF INDEPENDENT AUDITORS

        The ratification of the selection of Marcum LLP as independent auditors is being submitted to shareholders because we believe that this action follows sound corporate practice and is in the best interests of the shareholders. If the shareholders do not ratify the selection by the affirmative vote of the holders of a majority of the ordinary shares voted at the meeting, the Audit Committee of the Board may reconsider the selection of independent auditors, but such a vote will not be binding on the Audit Committee. If the shareholders ratify the selection, the Audit Committee, in its discretion, may still direct the appointment of new independent auditors at any time during the year if they believe that this change would be in our and our shareholders' best interests.

        The Board recommends that the shareholders ratify the selection of Marcum LLP, an independent registered public accounting firm, as the independent auditors to audit our accounts and those of our subsidiaries for 2018. The Audit Committee approved the selection of Marcum LLP as our independent auditors for 2018. Marcum LLP are currently our independent auditors.

        Accordingly, we ask our shareholders to vote on the following resolution:

        "Resolved, that the selection of Marcum LLP as independent auditors for the year ended December 31, 2018 be ratified, approved and confirmed in all respects."

        The Board of Directors recommends a vote FOR this proposal.

ANNUAL REPORT AND COMPANY INFORMATION

A copy of our Annual Report (without exhibits) on Form 10-K, including the financial statements and financial statement schedules as required to be filed with the SEC, is being furnished to shareholders concurrently herewith and will also be available to shareholders on request without charge by writing to: General Counsel and Secretary, Avista Healthcare Public Acquisition Corp., 65 East 55th Street, 18th Floor, New York, NY 10022. Exhibits to the Annual Report will be furnished to shareholders upon payment of reasonable photocopying and shipping charges. Shareholders may request a written copy of our Audit Committee Charter and our Code of Ethics, by writing to the General Counsel and Secretary at the aforementioned address.

PROPOSALS AND NOMINATIONS BY SHAREHOLDERS
directors.

        Proposals that shareholders wish to include in our proxy statement and form of proxy for presentation at our 2019 Annual General Meeting must be received by us at 65 East 55th Street, 18th Floor, New York, NY 10022, Attention of Benjamin Silbert, General Counsel and Secretary no later than January 31, 2019. Any shareholder proposal must submitted be in accordance with the rules and regulations of the SEC. With respect to proposals or nominations submitted by a shareholder other than for inclusion in our 2019 proxy statement and related form of proxy, timely notice of any shareholder's intention to present such business must be received by us in accordance with our articles no later than January 31, 2019. Any proxies solicited

        If the Extension Amendment Proposal and the Trust Amendment Proposal are not approved, and we do not consummate the Organogenesis Transaction before October 14, 2018, there will be no annual general meeting in 2019.

DELIVERY OF DOCUMENTS TO SHAREHOLDERS

        Pursuant to the rules of the SEC, the Company and its agents that deliver communications to its shareholders are permitted to deliver to two or more shareholders sharing the same address a single copy of the Company's proxy statement. Upon written or oral request, the Company will deliver a separate copy of the proxy statement to any shareholder at a shared address who wishes to receive separate copies of such documents in the future. Shareholders receiving multiple copies of such documents may likewise request that the Company deliver single copies of such documents in the future. Shareholders may notify the Company of their requests by calling or writing the Company at the Company's principal executive offices at 65 East 55th Street, 18^th Floor, New York, New York 10022.

WHERE YOU CAN FIND MORE INFORMATION§

        The Company files reports, proxy statements and other information with the SEC as required by the Board forSecurities Exchange Act of 1934, as amended. You may read and copy reports, proxy statements and other information filed by the 2018 Annual General MeetingCompany with the SEC at its public reference room located at 100 F Street, N.E., Washington, D.C. 20549-1004. You may confer discretionary authorityobtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. You may also obtain copies of the materials described above at prescribed rates by writing to votethe SEC, Public Reference Section, 100 F Street, N.E., Washington, D.C. 20549-1004. The Company files its reports, proxy statements and other information electronically with the SEC. You may access information on any proposals noticethe Company at the SEC website containing reports, proxy statements and other information at http://www.sec.gov. This proxy statement describes the material elements of which is not timely received.relevant contracts, exhibits and other information attached as annexes to this proxy statement. Information and statements contained in this proxy statement are qualified in all respects by reference to the copy of the relevant contract or other document included as an annex to this document.

        This proxy statement contains important business and financial information about us that is not included in or delivered with this document. You may obtain this additional information, or additional copies of this proxy statement, at no cost, and you may ask any questions you may have about the Extension Amendment Proposal by contacting us at the following address, telephone number or facsimile number:

Avista Healthcare Public Acquisition Corp.
65 East 55th, 18^th Floor
New York, New York 10022
Attn: Benjamin Silbert
Telephone: (212) 591-6900

        In order to receive timely delivery of the documents in advance of the extraordinary general meeting, you must make your request for information no later than September 20, 2018.

ANNEX A

AVISTA HEALTHCARE PUBLIC ACQUISITIONS CORP.
(the "Company")
SPECIAL RESOLUTION OF THE SHAREHOLDERS OF THE COMPANY

Extension Amendment Proposal

It was resolved as a special resolution THAT, effective immediately, the Amended and Restated Memorandum and Articles of Association of the Company be amended by:

(a)

amending Article 49.4(a) by deleting the following introduction of such article:

"the Company does not consummate a Business Combination by twenty-four months after the closing of the IPO the Company shall:"

and replacing it with the following:

"the Company does not consummate a Business Combination by 15 February 2019, the Company shall"; and

(b)

amending Article 49.4(b) by deleting the words:

"within 24 months from the date of
the closing of the IPO" and

        replacing them with the words:

"by 15 February, 2019".

ANNEX B

AMENDMENT NO. 1 TO THE INVESTMENT MANAGEMENT TRUST AGREEMENT

        This Amendment No. 1 (this "Amendment") to the Investment Management Trust Agreement (as defined below) is importantmade by and between Avista Healthcare Public Acquisition Corp., a Cayman Islands exempted company (the "Company") and Continental Stock Transfer & Trust Company (the "Trustee"). Capitalized terms used herein but not specifically defined shall have the meanings ascribed to such terms in the Investment Management Trust Agreement.

        WHEREAS, the Company and the Trustee are parties to the Investment Management Trust Agreement, dated as of October 10, 2016 (the "Investment Management Trust Agreement");

        WHEREAS, Section 1(i) of the Investment Management Trust Agreement sets forth the terms that your proxygovern the liquidation of the Trust Account under circumstances described therein;

        WHEREAS, at an extraordinary general meeting of shareholders of the Company held on October 4, 2018, the Company's shareholders approved (i) a proposal (the "Extension Amendment Proposal") to amend the Company's amended and restated memorandum and articles of association (the "Articles") to extend the date by which the Company has to consummate a business combination (the "Extension") from October 14, 2018 to February 15, 2019 (the "Extended Date") and (ii) a proposal to extend the date on which to commence liquidating the Trust Account established in connection with the Company's initial public offering in the event the Company has not consummated a business combination to the Extended Date; and

        WHEREAS, on the date hereof, the Company is filing the amendment to the Company's Articles with the Cayman Islands.

        NOW, THEREFORE, IT IS AGREED:

        1.     Section 1(i) of the Investment Management Trust Agreement is hereby amended and restated in its entirety to read as follows:

"(i) Commence liquidation of the Trust Account only after and promptly after (x) receipt of, and only in accordance with, the terms of a letter from the Company ("Termination Letter") in a form substantially similar to that attached hereto as either Exhibit A or Exhibit B signed on behalf of the Company by its Chief Executive Officer, President, Chief Financial Officer, Secretary or Chairman of the board of directors (the "Board") of the Company or other authorized officer of the Company, and complete the liquidation of the Trust Account and distribute the Property in the Trust Account, including interest (which interest shall be returned promptly, whether by mail,net of any taxes payable and less up to $50,000 of interest that may be released to the Company to pay dissolution expenses, it being understood that the Trustee has no obligation to monitor or question the Company's position that an allocation has been made for taxes payable), only as directed in the Termination Letter and the other documents referred to therein; provided, that, in the case a Termination Letter in the form of Exhibit A is received, or (y) on February 15, 2019, if a Termination Letter has not been received by the Internet or by telephone. The proxyTrustee prior to such date, in which case the Trust Account shall be liquidated in accordance with the procedures set forth in the Termination Letter attached as Exhibit B and the Property in the Trust Account, including interest (which interest shall be net of any taxes payable and less up to $50,000 of interest that may be revoked at any time by you before it is exercised. If you attendreleased to the meetingCompany to pay dissolution expenses), shall be distributed to the Public Shareholders of record as of such date; provided, however, that in person, you may withdraw any proxy (including an Internet or telephonic proxy) and vote your own shares. If your shares are heldthe event the Trustee receives a Termination Letter in a brokerage, bank,form substantially similar to Exhibit B hereto, or if the Trustee begins to liquidate the Property because it has received no such Termination Letter by February 15, 2019, the Trustee shall keep the Trust Account open until

twelve (12) months following the date the Property has been distributed to the Public Shareholders;"

        2.     All other institutional account, you must obtain a proxy fromprovisions of the Investment Management Trust Agreement shall remain unaffected by the terms hereof.

        3.     This Amendment may be signed in any number of counterparts, each of which shall be an original and all of which shall be deemed to be one and the same instrument, with the same effect as if the signatures thereto and hereto were upon the same instrument. A facsimile signature shall be deemed to be an original signature for purposes of the Amendment.

        4.     This Amendment is intended to be in full compliance with the requirements for an Amendment to the Investment Management Trust Agreement as required by Section 6(c) of the Investment Management Trust Agreement, and every defect in fulfilling such requirements for an effective amendment to the Investment Management Trust Agreement is hereby ratified, intentionally waived and relinquished by all parties hereto.

        5.     This Amendment shall be governed by and construed and enforced in accordance with the laws of the State of New York, without giving effect to conflicts of law principles that entity showing that you werewould result in the record holderapplication of the substantive laws of another jurisdiction.

[The remainder of this page is intentionally left blank.]

        IN WITNESS WHEREOF, each party has caused this Amendment to be signed by its respective officer thereunto duly authorized, all as of the close of business on May 18, 2018, in orderdate first written above.

[Signature Page to vote your shares at the meeting.Amendment to Investment Management Trust Agreement]

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