The board of directors of ARYA Sciences Acquisition Corp IV, a Cayman Islands exempted company (“ARYA”), has approved the transactions (collectively, the “Business Combination”) contemplated by that certain Business Combination Agreement, dated February 13, 2024 (as may be amended, supplemented or otherwise modified from time to time, the “Business Combination Agreement”), by and among Aja HoldCo, Inc., a Delaware corporation and, prior to the ARYA Merger Effective Time (as defined below), a wholly owned subsidiary of ARYA (“ListCo”), ARYA, Aja Merger Sub 1, a Cayman Islands exempted company and, prior to the ARYA Merger Effective Time, a wholly owned subsidiary of ListCo (“ARYA Merger Sub”), Aja Merger Sub 2, Inc., a Delaware corporation and, prior to the Adagio Merger Effective Time (as defined below), a wholly owned subsidiary of ListCo (“Company Merger Sub”), and Adagio Medical, Inc., a Delaware corporation (“Adagio”), a copy of which is attached to this proxy statement/prospectus as Annex A and pursuant to which, among other things, ARYA Merger Sub will merge with and into ARYA (the “ARYA Merger”) and Company Merger Sub will merge with and into Adagio (the “Adagio Merger” and, together with the ARYA Merger, the “Mergers”), with ARYA and Adagio surviving the Mergers and, after giving effect to such Mergers, each of ARYA and Adagio becoming a wholly owned subsidiary of ListCo, on the terms and subject to the conditions in the Business Combination Agreement (the time that the ARYA Merger becomes effective being referred to as the “ARYA Merger Effective Time,” the time that the Adagio Merger becomes effective being referred to as the “Adagio Merger Effective Time” and the time after which both Mergers become effective being referred to as the “Closing”). Following such Mergers, shareholders of ARYA will become stockholders of ListCo. As described in this proxy statement/prospectus, ARYA’s shareholders are being asked to consider a vote upon the Business Combination, among other items. As used in this proxy statement/prospectus, “New Adagio” refers to ListCo after giving effect to the consummation of the transactions contemplated by the Business Combination Agreement. At least two business days prior to the date on which Closing occurs (the “Closing Date”), Adagio shall cause its name to be changed to such other name mutually agreed to by ARYA and Adagio. The Business Combination Agreement is subject to the satisfaction or waiver of certain closing conditions as described in the accompanying proxy statement/prospectus. There can be no assurance that the parties to the Business Combination Agreement would waive any such provision of the Business Combination Agreement if the closing conditions are not met.

On the Closing Date, immediately prior to the Adagio Merger Effective Time and in accordance with the terms and subject to the conditions of the Business Combination Agreement, the applicable Bridge Financing Notes (as defined below) and the Subscription Agreement (as defined below) executed by Perceptive Life Sciences Master Fund, Ltd, a Cayman Islands exempted company (the “Perceptive PIPE Investor”), the Perceptive PIPE Investor will contribute (i) the $15,000,000 convertible promissory notes of Adagio, which it purchased from Adagio pursuant to that certain Note Purchase Agreement, dated as of April 4, 2023 (the “April 2023 Notes”), (ii) the $8,000,000 convertible promissory notes of Adagio, which it purchased from Adagio pursuant to that certain Note Purchase Agreement, dated as of November 28, 2023 (the “November 2023 Notes” and, together with the April 2023 Notes, the “Bridge Financing Notes”), (iii) any interest that has been accruing and will remain unpaid through Closing on the Bridge Financing Notes, and (iv) an additional cash investment of approximately $8,070,575 (which amount may be reduced by up to approximately $1,070,575 subject to Additional Financing (as defined below) being raised prior to Closing) to ListCo in exchange for (or to otherwise be converted into) shares of common stock, par value $0.0001 per share, of New Adagio (the “New Adagio Common Stock”) and/or warrants exercisable for shares of New Adagio Common Stock at $10.00 per share, subject to adjustment (the “Base Warrants”), based on the purchase price in the PIPE Financing (as defined below), in each case, on the terms and subject to the conditions set forth in the applicable Bridge Financing Note and the applicable Subscription Agreement.

On the Closing Date, immediately prior to the Adagio Merger Effective Time, Adagio will also cause (A) each warrant of Adagio to be either (x) terminated, or (y) “net” exercised in exchange for shares of common stock, par value $0.001 per share, of Adagio (“Adagio Common Stock”), determined in accordance with the terms of the applicable warrant agreement; (B) all issued and outstanding unsecured convertible promissory notes of Adagio (excluding the Bridge Financing Notes) (the “Adagio Convertible Notes”), including any accrued and unpaid interest thereon, to be automatically and fully converted into shares of Adagio Common Stock in accordance with the terms of such Adagio Convertible Notes (the “Adagio Convertible Note Conversion”), and such Adagio Convertible Notes shall be canceled, satisfied, extinguished, discharged and retired in connection with such conversion; and (C) each share of preferred stock, par value $0.001 per share, of Adagio (“Adagio Preferred Stock”) that is issued and outstanding immediately prior to the Adagio Merger Effective Time to be automatically converted into shares of Adagio Common Stock (the “Adagio Preferred Stock Conversion”). Following such conversions into Adagio Common Stock, at the Adagio Merger Effective Time and in accordance with the terms and subject to the conditions of the Business Combination Agreement (A) all issued and outstanding shares of Adagio Common Stock (other than treasury shares and shares with respect to which appraisal rights under the Delaware General Corporation Law are properly exercised and not withdrawn) shall be automatically cancelled, extinguished and converted into the right to receive shares of New Adagio Common Stock based on the exchange ratio set forth in the Business Combination Agreement, (B) each issued, outstanding and unexercised option to purchase Adagio Common Stock (“Adagio Option”) that is vested as of such time or will vest in connection with, or after taking into account the effect of, the consummation of the transactions contemplated by the Business Combination Agreement (whether at the Adagio Merger Effective Time or otherwise) (the “Vested Adagio Options”) with an aggregate value that exceeds the aggregate exercise price of such Adagio Option (each an “In-the-Money Adagio Option”) shall be cancelled and extinguished in exchange for options to purchase shares of New Adagio Common Stock, and (C) each issued and outstanding Adagio equity award (other than the In-the-Money Adagio Options) shall no longer be outstanding and shall automatically be canceled and extinguished for no consideration and each holder thereof shall cease to have any rights with respect thereto.

At the ARYA Merger Effective Time: (A) the issuance of shares of New Adagio Common Stock, Base Warrants and/or pre-funded warrants, each exercisable for one share of New Adagio Common Stock at $0.01 per share (the “Pre-Funded Warrants,” and together with the Base Warrants, the “PIPE Warrants”), pursuant to the terms of the PIPE Financing will occur; (B) each issued and outstanding Class A ordinary share, par value $0.0001 per share, of ARYA (the “Class A ordinary shares”) will be automatically cancelled, extinguished and converted into the right to receive one share of New Adagio Common Stock, 499,000 shares of which will be issued to ARYA Sciences Holdings IV, a Cayman Islands exempted company (the “Sponsor”) in exchange for the private placement Class A ordinary shares held by it; (C) shares of New Adagio Common Stock will be issued to the Sponsor in connection with the Sponsor’s option to contribute the ARYA Convertible Promissory Notes (as defined below) to ARYA in exchange for Class A ordinary shares; (D) each issued and outstanding Class B ordinary share, par value $0.0001 per share, of ARYA (the “Class B ordinary shares”) will be automatically cancelled, extinguished and converted into the right to receive one share of New Adagio Common Stock, other than 1,000,000 Class B ordinary shares that will be forfeited by the Sponsor and issued by ListCo to the PIPE Investors, including the Perceptive PIPE Investor, and 1,147,500 shares of New Adagio Common Stock issuable to the Sponsor will be subject to share trigger price vesting and will vest if, prior to the tenth anniversary of the Closing, the post-Closing share price of New Adagio equals or exceeds $24.00 per share for any 20 trading days within any 30 trading day period, as further described herein (the “Share Trigger Price Vesting”); (E) New Adagio will issue the New Adagio Convertible Notes (as defined below) and Convert Warrants (as defined below) pursuant to the Convertible Security Subscription Agreement (as defined below) and the 2024 Bridge Financing Note Subscription Agreement (as defined below); and (F) ARYA’s amended and restated memorandum and articles of association, as amended (the “Existing Governing Documents”) will be amended and restated in connection with ARYA becoming a subsidiary of ListCo, as described in the accompanying proxy statement/prospectus.

Prior to the ARYA Merger Effective Time, ARYA and ListCo will cause (A) ListCo to file with the Secretary of State of the State of Delaware an amended and restated certificate of incorporation of ListCo, substantially in the form attached to the accompanying proxy statement/prospectus as Annex C and (B) the board of directors of ListCo to approve and adopt amended and restated bylaws of ListCo, substantially in the form attached to the accompanying proxy statement/prospectus as Annex D. Following the Closing, ListCo’s name will be changed to “Adagio Medical, Inc.” (or such other name mutually agreed to by ARYA and Adagio).

On the Closing Date, prior to the ARYA Merger Effective Time, ARYA will cause each holder of Class A ordinary shares that has timely and validly made a redemption election to be redeemed on the terms and subject to the conditions set forth in the Existing Governing Documents and the other procedures described herein.

As described above, in connection with the execution of the Business Combination Agreement, ListCo and ARYA entered into Subscription Agreements (the “Subscription Agreements”) with the Perceptive PIPE Investor and certain other investors (the “Other PIPE Investors,” and, together with the Perceptive PIPE Investor, the “PIPE Investors”), pursuant to which the PIPE Investors committed financing valued at approximately $45,000,000, which includes (i) commitments by certain investors to subscribe for and purchase Class A ordinary shares in the open market and not to redeem such shares prior to the Closing Date, (ii) non-redemption commitments by certain investors that are shareholders of ARYA, (iii) agreements to subscribe for and purchase shares of New Adagio Common Stock, (iv) the contribution of $23,000,000 of 2023 Bridge Financing Notes to ListCo pursuant to the terms of the Subscription Agreement executed by the Perceptive PIPE Investor, and (v) an additional cash investment by the Perceptive PIPE Investor of approximately $8,070,575 (which amount may be reduced by up to approximately $1,070,575 subject to Additional Financing being raised prior to Closing) (together, the “PIPE Financing”). In connection with the PIPE Financing, the PIPE Investors will also subscribe for (i) Base Warrants or (ii) a combination of Base Warrants and Pre-Funded Warrants. As provided for in the Subscription Agreements, the number of shares of New Adagio Common Stock and Base Warrants issuable to the PIPE Investors will depend on the redemption value of the Class A ordinary shares at Closing, the average per share price of the Class A ordinary shares purchased by certain PIPE Investors in the open market and the amount of interest on the Bridge Financing Notes that will have accrued and be unpaid at Closing and be contributed to ListCo in exchange for shares of New Adagio Common Stock. The shares of New Adagio Common Stock and PIPE Warrants to be issued pursuant to the Subscription Agreements have not been registered under the Securities Act of 1933, as amended (the “Securities Act”), and will be issued in reliance upon the exemption provided in Section 4(a)(2) of the Securities Act. ListCo will grant the PIPE Investors certain registration rights in connection with the PIPE Financing. The PIPE Financing is contingent upon, among other things, the substantially concurrent closing of the Business Combination. For additional information on the calculation of the number of shares that will be issued pursuant to each Subscription Agreement, please see “Proposal 1: Business Combination Proposal—Certain Agreements Related to the Business Combination—PIPE Financing.”

Further, in connection with the execution of the Business Combination Agreement, certain investors (“Convert Investors”) executed a securities purchase agreement, dated February 13, 2024, with ListCo (the “Convertible Security Subscription Agreement”), pursuant to which ListCo will issue on the Closing Date to the Convert Investors $20,000,000 of 13% senior secured convertible notes (the “New Adagio Convertible Notes”), which will be convertible into shares of New Adagio Common Stock at a conversion price of $10.00 per share, subject to adjustment, and 1,500,000 warrants (the “Convert Warrants”), each Convert Warrant being exercisable on a cashless basis or for cash at a price of $24.00 per share, subject to adjustment (the “Base Convert Financing”). Such $20,000,000 of financing in the form of New Adagio Convertible Notes includes the Perceptive Convertible Note Commitment (as defined below) and includes the conversion of the 2024 Bridge Financing Notes into New Adagio Convertible Notes at Closing, subject in each case to Additional Financing being raised prior to Closing, as further described below. The New Adagio Convertible Notes will have a maturity of three years and nine months after Closing and interest will be payable in cash or compound as additional principal outstanding. Concurrently with the execution of the Convertible Security Subscription Agreement, the Perceptive PIPE Investor also purchased a $7,000,000 convertible promissory note of Adagio (the “2024 Bridge Financing Note”) pursuant to a note purchase agreement, dated February 13, 2024, by and among the Perceptive PIPE Investor, Adagio and ListCo (the “2024 Bridge Financing Note Subscription Agreement”). On the Closing Date, pursuant to the terms of the 2024 Bridge Financing Note and the 2024 Bridge Financing Note Subscription Agreement, the 2024 Bridge Financing Note will convert into $7,000,000 of New Adagio Convertible Notes and 525,000 Convert Warrants, and the Perceptive PIPE Investor will subscribe for an additional $5,500,000 of New Adagio Convertible Notes and 412,500 Convert Warrants, for a total of $12,500,000 of New Adagio Convertible Notes and 937,500 Convert Warrants, on the same terms as the Convert Investors executing the Convertible Security Subscription Agreement (such additional $5,500,000 commitment by the Perceptive PIPE Investor to purchase New Adagio Convertible Notes and Convert Warrants, the “Perceptive Convertible Note Commitment,” and the conversion of the 2024 Bridge Financing Note and purchase of New Adagio Convertible Notes and Convert Warrants pursuant to the Perceptive Convertible Note Commitment as part of the Base Convert Financing, the “Convertible Security Financing”). Subject to ARYA and New Adagio receiving any new financing or commitment for financing, whether in the form of equity, debt or convertible debt, before the Closing Date (any such financing, an “Additional Financing”), the Perceptive PIPE Investor may request that on the Closing Date the 2024 Bridge Financing Note is repaid, the Perceptive Convertible Note Commitment is reduced or a combination of both. The New Adagio Convertible Notes and the Convert Warrants issuable in connection with the Convertible Security Financing have not been registered under the Securities Act and will be issued in reliance upon the exemption provided in Section 4(a)(2) of the Securities Act. ListCo will grant the Convert Investors certain registration rights in connection with the Convertible Security Financing. The Convertible Security Financing is contingent upon, among other things, the substantially concurrent closing of the Business Combination. As set forth in the Convertible Security Subscription Agreement, the closing of $7,500,000 of financing by a Convert Investor in the Convertible Security Financing is conditioned on New Adagio having a certain amount of available unrestricted cash on the Closing Date.

In connection with the Closing and immediately prior to the ARYA Merger Effective Time, the Sponsor may elect to contribute the unsecured convertible promissory note, dated as of November 7, 2022, by and between the Sponsor and ARYA (the “First Convertible Promissory Note”), the unsecured convertible promissory note, dated as of February 28, 2023, by and between the Sponsor and ARYA (as amended on February 13, 2024, the “Second Convertible Promissory Note”), the amended and restated unsecured convertible promissory note, dated as of February 13, 2024, by and between the Sponsor and ARYA (the “A&R Third Promissory Note”) and the unsecured convertible promissory note, dated as of February 8, 2024, by and between the Sponsor and ARYA (the “Fourth Convertible Promissory Note,” and, together with the First Convertible Promissory Note, the Second Convertible Promissory Note and the A&R Third Promissory Note, the “ARYA Convertible Promissory Notes”) to ARYA in exchange for Class A ordinary shares, par value $0.0001 per share, of ARYA (the “Working Capital Shares”) at a conversion price of $10.00 per Class A ordinary share.

This prospectus covers 9,306,516 shares of New Adagio Common Stock. The number of shares of New Adagio Common Stock that this prospectus covers represents the maximum number of shares that may be issued to holders of shares of Adagio in connection with the Business Combination (as more fully described in this proxy statement/prospectus), together with the shares issued or issuable to the existing shareholders of ARYA in connection with the Business Combination, including the Share Trigger Price Vesting contemplated thereby.

ARYA’s Class A ordinary shares are currently listed on the Nasdaq Capital Market (“Nasdaq”) under the symbol “ARYD.” ListCo will apply for listing, to be effective at the time of the Business Combination, of the New Adagio Common Stock on Nasdaq under the proposed symbol “ADGM.” It is a condition of the consummation of the Business Combination that ARYA receive confirmation from Nasdaq that New Adagio has been conditionally approved for listing on Nasdaq, but there can be no assurance that such listing condition will be met or that ARYA will obtain such confirmation from Nasdaq. If such listing condition is not met or if such confirmation is not obtained, the Business Combination will not be consummated unless the Nasdaq condition set forth in the Business Combination Agreement is waived by the applicable parties.

The accompanying proxy statement/prospectus provides shareholders of ARYA with detailed information about the Business Combination and other matters to be considered at the annual general meeting of ARYA. We encourage you to read the entire accompanying proxy statement/prospectus, including the Annexes and other documents referred to therein, carefully and in their entirety. You should also carefully consider the risk factors described in “Risk Factors” beginning on page 35 of the accompanying proxy statement/prospectus.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF THE BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

You are cordially invited to attend the annual general meeting (the “General Meeting”) of ARYA Sciences Acquisition Corp IV, a Cayman Islands exempted company (“ARYA”), at [•] [a.m./p.m.], Eastern Time, on [•], 2024, at the offices of Kirkland & Ellis LLP located at 601 Lexington Avenue, New York, New York 10022, and via a virtual meeting, or at such other time, on such other date and at such other place to which the meeting may be adjourned.

The General Meeting will be conducted via live webcast, but the physical location of the General Meeting will remain at the location specified above for the purposes of our amended and restated memorandum and articles of association, as amended (the “Existing Governing Documents”). If you wish to attend the General Meeting in person, you must reserve your attendance at least two business days in advance of the General Meeting by contacting ARYA’s Secretary at ARYA4@perceptivelife.com by 9:30 a.m., Eastern Time, on [•], 2024. You will be able to attend the General Meeting online, vote and submit your questions during the General Meeting by visiting https://www.cstproxy.com/[•].

At the General Meeting, ARYA shareholders will, among others, be asked to consider and vote upon a proposal, which is referred to herein as the “Business Combination Proposal” to approve and adopt the Business Combination Agreement, dated February 13, 2024 (as may be amended, supplemented or otherwise modified from time to time, the “Business Combination Agreement”), by and among Aja HoldCo, Inc., a Delaware corporation and, prior to the ARYA Merger Effective Time (as defined below), a wholly owned subsidiary of ARYA (“ListCo”), ARYA, Aja Merger Sub 1, a Cayman Islands exempted company and, prior to the ARYA Merger Effective Time, a wholly owned subsidiary of ListCo (“ARYA Merger Sub”), Aja Merger Sub 2, Inc., a Delaware corporation and, prior to the Adagio Merger Effective Time (as defined below), a wholly owned subsidiary of ListCo (“Company Merger Sub”) and Adagio Medical, Inc., a Delaware corporation (“Adagio”). The Business Combination Agreement and the transactions contemplated thereby (the “Business Combination”) were approved by the boards of directors of ARYA (the “ARYA Board”) and Adagio. The Business Combination Agreement is subject to the satisfaction or waiver of certain other closing conditions as described in the accompanying proxy statement/prospectus. There can be no assurance that the parties to the Business Combination Agreement would waive any such provision of the Business Combination Agreement if the closing conditions are not met.

Pursuant to the Business Combination Agreement, ARYA Merger Sub will merge with and into ARYA (the “ARYA Merger”) and Company Merger Sub will merge with and into Adagio (the “Adagio Merger” and, together with the ARYA Merger, the “Mergers”), with ARYA and Adagio surviving the Mergers and, after giving effect to such Mergers, each of ARYA and Adagio becoming a wholly owned subsidiary of ListCo, on the terms and subject to the conditions in the Business Combination Agreement (the time that the ARYA Merger becomes effective being referred to as the “ARYA Merger Effective Time,” the time that the Adagio Merger becomes effective being referred to as the “Adagio Merger Effective Time,” and the time after which both Mergers become effective being referred to as the “Closing”). As used herein or in the accompanying proxy statement/prospectus, “New Adagio” refers to ListCo after giving effect to the consummation of the transactions contemplated by the Business Combination Agreement.

As further described in the accompanying proxy statement/prospectus, at the ARYA Merger Effective Time, (A) each issued and outstanding Class A ordinary share, par value $0.0001 per share, of ARYA (the “Class A ordinary shares”) will be automatically cancelled, extinguished and converted into the right to receive one share of common stock, par value $0.0001 per share, of New Adagio (the “New Adagio Common Stock”); and (B) each issued and outstanding Class B ordinary share, par value $0.0001 per share, of ARYA (the “Class B ordinary shares”) will be automatically cancelled, extinguished and converted into the right to receive one share of New Adagio Common Stock, other than 1,000,000 Class B ordinary shares that will be forfeited by ARYA Sciences Holdings IV (the “Sponsor”) and issued by ListCo to the PIPE Investors (as defined in the accompanying proxy statement/prospectus), and 1,147,500 shares of New Adagio Common Stock that will be issuable to the Sponsor will be subject to Share Trigger Price Vesting (as defined in the accompanying proxy statement/prospectus). In connection with the consummation of the transactions contemplated by the Business Combination Agreement and as described in more details in the accompanying proxy statement/prospectus, at Closing, ListCo will, among others, change its name to “Adagio Medical, Inc.” (or such other name mutually agreed to by ARYA and Adagio) and will

be issuing (i) shares of New Adagio Common Stock to holders of Adagio Common Stock, Adagio Preferred Stock (as defined in the accompanying proxy statement/prospectus) and Adagio Convertible Notes (as defined in the accompanying proxy statement/prospectus), (ii) options to purchase shares of New Adagio Common Stock to holders of In-the-Money Adagio Options (as defined in the accompanying proxy statement/prospectus), (iii) shares of New Adagio Common Stock and PIPE Warrants (as defined in the accompanying proxy statement/prospectus) in the PIPE Financing (as defined in the accompanying proxy statement/prospectus), (iv) New Adagio Convertible Notes (as defined in the accompanying proxy statement/prospectus) and Convert Warrants (as defined in the accompanying proxy statement/prospectus), and (v) issue shares of New Adagio Common Stock upon conversion of the ARYA Convertible Promissory Notes.

Certain related agreements were entered into in connection with the signing of the Business Combination Agreement or will be executed in connection with consummation of the transactions contemplated by the Business Combination Agreement, including the Subscription Agreements, the Base Warrant Agreement, the Pre-Funded Warrant Agreement, the Convertible Security Subscription Agreement, the Convert Warrant Agreement, the Convert Guaranty, the Convert Security Document, the Convert Registration Rights Agreement, the 2024 Bridge Financing Note Subscription Agreement, the Investor Rights Agreement, the Sponsor Letter Agreement and the Adagio Stockholder Transaction Support Agreements (each as defined and further described in the accompanying proxy statement/prospectus). See the section entitled “Proposal 1: Business Combination Proposal—Certain Agreements Related to the Business Combination” in the accompanying proxy statement/prospectus for more information.

If the Business Combination is approved, ARYA will cause any Public Shares (as defined below) that have been validly tendered or delivered for redemption on the Closing Date, as described in the accompanying proxy statement/prospectus, to be redeemed prior to the ARYA Merger Effective Time. Notwithstanding the foregoing, holders of Public Shares, together with any affiliate of his, her, its or any other person with whom he, she or it is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act of 1934, as amended) will be restricted from seeking redemption rights with respect to more than 15% of the Public Shares. Accordingly, any holders of Public Shares or “group” in excess of such 15% cap will not be redeemed by ARYA. Any outstanding Class B ordinary shares or private placement shares of ARYA will be excluded from the pro rata calculation used to determine the per share redemption price applicable to Public Shares that are redeemed.

You will also be asked to consider and vote upon (A) a proposal to (i) authorize the ARYA Merger and approve the plan of merger in the form attached to the accompanying proxy statement/prospectus as Annex E, subject to such amendments as may be approved by any director of ARYA (the “Plan of Merger”), and (ii) authorize the entry by ARYA into the Plan of Merger and approve the amendment and restatement of the Existing Governing Documents (the “ARYA Merger Proposal”), (B) a proposal to re-elect Leslie Trigg as a Class I director to serve for a term of three years or until her successor is duly elected or appointed and qualified (the “Director Election Proposal”), and (C) a proposal to adjourn the General Meeting to a later date or dates to the extent necessary (the “Adjournment Proposal”). The Adjournment Proposal provides for a vote to adjourn the General Meeting to a later date or dates, if necessary or convenient, (i) to permit further solicitation and vote of proxies for the purpose of obtaining approval of the Condition Precedent Proposals, (ii) to allow reasonable additional time for filing or mailing of any legally required supplement or amendment to the accompanying proxy statement/prospectus, or (iii) if the public holders of Class A ordinary shares, issued in ARYA’s initial public offering (the “Public Shares”), have elected to redeem such number of shares that New Adagio would not be approved for listing on a U.S. stock exchange.

Only holders of record of the Class A ordinary shares and Class B ordinary shares (collectively, the “ARYA Shares”) at the close of business on [•], 2024 are entitled to notice of the General Meeting and to vote and have their votes counted at the General Meeting and any adjournments of the General Meeting. Only holders of Class B ordinary shares may vote on the appointment of directors. The accompanying proxy statement/prospectus and proxy card is being provided to ARYA’s shareholders in connection with the solicitation of proxies to be voted at the General Meeting and at any adjournment of the General Meeting. Information about the General Meeting, the Business Combination and other related business to be considered by ARYA’s shareholders at the General Meeting is included in the accompanying proxy statement/prospectus. Whether or not you plan to attend the General

Meeting, all of ARYA’s shareholders are urged to read the accompanying proxy statement/prospectus, including the Annexes and the documents referred to therein carefully and in their entirety. You should also carefully consider the risk factors described in “Risk Factors” beginning on page 35 of the accompanying proxy statement/prospectus.

After careful consideration, the board of directors of ARYA (the “ARYA Board”) has approved the Business Combination Agreement and the transactions contemplated thereby, including the Mergers, and recommends that the ARYA shareholders vote “FOR” the Business Combination Proposal, “FOR” the ARYA Merger Proposal, “FOR” the Director Election Proposal (in the case of the holders of the Class B ordinary shares) and “FOR” the Adjournment Proposal in each case, if presented to the ARYA shareholders at the General Meeting. When you consider the ARYA Board’s recommendation of these proposals, you should keep in mind that directors and officers of ARYA have interests in the Business Combination that may conflict with your interests as a shareholder. See the section entitled “Proposal 1: Business Combination Proposal—Interests of Certain Persons in the Business Combination” in the accompanying proxy statement/prospectus.

The approval of each of the Business Combination Proposal and the Adjournment Proposal requires an ordinary resolution under Cayman Islands law, being a resolution passed by a simple majority of the votes cast by, or on behalf of, the holders of the issued ARYA Shares present in person or represented by proxy at the General Meeting and entitled to vote on such matter.

The approval of the ARYA Merger Proposal requires a special resolution under Cayman Islands law, being the affirmative vote of at least a two-thirds (2/3) majority of the votes cast by the holders of the issued ARYA Shares present in person or represented by proxy at the General Meeting and entitled to vote on such matter. Under the terms of the Existing Governing Documents, the proposed amendments to the provisions of the Existing Governing Documents governing the appointment or removal of directors prior to ARYA’s initial business combination may only be amended by a special resolution passed by holders representing at least two-thirds (2/3) of the outstanding Class B ordinary shares who attend and vote in person or represented by proxy at the General Meeting.

The approval of the Director Election Proposal requires an ordinary resolution of the holders of the Class B ordinary shares. Only holders of Class B ordinary shares may vote on the appointment of directors and our initial shareholders hold all issued and outstanding Class B ordinary shares.

Please note that as further described in the accompanying proxy statement/prospectus, the Sponsor and the officers and directors of ARYA have agreed to (a) vote any of their ARYA Shares in favor of the Business Combination and (b) waive their redemption rights with respect to any ARYA Shares they own in connection with the consummation of the Business Combination. As of the date of the accompanying proxy statement/prospectus, the Sponsor and directors and officers of ARYA own approximately 56.2% of the issued and outstanding ARYA Shares in the aggregate. Assuming that all shareholders who are entitled to do so attend the General Meeting and vote, the approval of each of the Business Combination Proposal and the Adjournment Proposal would not require the affirmative vote of any Public Shareholder in addition to the affirmative vote of the initial shareholders. Assuming that all shareholders who are entitled to do so attend the General Meeting and vote, the affirmative vote of 787,845 of the Public Shares, in addition to the affirmative vote of the initial shareholders, would be required to approve the ARYA Merger Proposal.

To ensure your representation at the General Meeting, you are urged to complete, sign, date and return the proxy card accompanying the proxy statement/prospectus as soon as possible. If your shares are held in an account at a brokerage firm or bank, you must instruct your broker or bank on how to vote your shares or, if you wish to attend the General Meeting and vote electronically, obtain a proxy from your broker or bank.

Your vote is important regardless of the number of shares you own. Whether you plan to attend the General Meeting or not, please complete, sign, date and return the enclosed proxy card as soon as possible in the envelope provided. Your proxy card must be received by ARYA not less than 48 hours before the scheduled time of the General Meeting or any adjournment thereof at which the person named in the proxy card proposes to vote. Proxy cards received after this time will not be counted. If your shares are held in “street name” or are in a margin or similar account, you should contact your broker to ensure that votes related to the shares you beneficially own are properly counted.

If you sign, date and return your proxy card without indicating how you wish to vote, your proxy will be voted FOR each of the proposals presented at the General Meeting. If you fail to return your proxy card or fail to instruct

your bank, broker or other nominee how to vote, and do not attend the General Meeting in person, the effect will be, among other things, that your shares will not be counted for purposes of determining whether a quorum is present at the General Meeting. If you are a shareholder of record and you attend the General Meeting and wish to vote in person, you may withdraw your proxy and vote in person.

TO EXERCISE YOUR REDEMPTION RIGHTS, YOU MUST DEMAND IN WRITING THAT YOUR PUBLIC SHARES ARE REDEEMED FOR A PRO RATA PORTION OF THE FUNDS HELD IN THE TRUST ACCOUNT AND TENDER YOUR SHARES TO ARYA’S TRANSFER AGENT AT LEAST TWO BUSINESS DAYS PRIOR TO THE INITIALLY SCHEDULED VOTE AT THE GENERAL MEETING. IN ORDER TO EXERCISE YOUR REDEMPTION RIGHT, YOU NEED TO IDENTIFY YOURSELF AS A BENEFICIAL HOLDER AND PROVIDE YOUR LEGAL NAME, PHONE NUMBER AND ADDRESS IN YOUR WRITTEN DEMAND. YOU MAY TENDER YOUR SHARES BY EITHER TENDERING OR DELIVERING YOUR PUBLIC SHARES (AND CERTIFICATES, IF ANY) AND OTHER REDEMPTION FORMS TO THE TRANSFER AGENT OR BY TENDERING OR DELIVERING YOUR PUBLIC SHARES (AND CERTIFICATES, IF ANY) AND OTHER REDEMPTION FORMS ELECTRONICALLY USING THE DEPOSITORY TRUST COMPANY’S DWAC (DEPOSIT WITHDRAWAL AT CUSTODIAN) SYSTEM. IF THE BUSINESS COMBINATION IS NOT COMPLETED, THEN THESE SHARES WILL BE RETURNED TO YOU OR YOUR ACCOUNT. IF YOU HOLD THE SHARES IN STREET NAME, YOU WILL NEED TO INSTRUCT THE ACCOUNT EXECUTIVE AT YOUR BANK OR BROKER TO WITHDRAW THE SHARES FROM YOUR ACCOUNT IN ORDER TO EXERCISE YOUR REDEMPTION RIGHTS.

On behalf of ARYA’s board of directors, I would like to thank you for your support and look forward to the successful completion of the Business Combination.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF THE BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

The accompanying proxy statement/prospectus is dated [•], 2024 and is first being mailed to shareholders on or about [•], 2024.

NOTICE IS HEREBY GIVEN that the annual general meeting of the shareholders (the “General Meeting”) of ARYA Sciences Acquisition Corp IV, a Cayman Islands exempted company (“ARYA”), will be held at [•] [a.m./p.m.], Eastern Time, on [•], 2024, at the offices of Kirkland & Ellis LLP located at 601 Lexington Avenue, New York, New York 10022, and via virtual meeting, or at such other time, on such other date and at such other place to which the meeting may be adjourned.

The General Meeting will be conducted via live webcast, but the physical location of the General Meeting will remain at the location specified above for the purposes of our amended and restated memorandum and articles of association, as amended (the “Existing Governing Documents”). If you wish to attend the General Meeting in person, you must reserve your attendance at least two business days in advance of the General Meeting by contacting ARYA’s Secretary at ARYA4@perceptivelife.com by 9:30 a.m., Eastern Time, on [•], 2024. You will be able to attend the General Meeting online, vote and submit your questions during the General Meeting by visiting https://www.cstproxy.com/[•].

You are cordially invited to attend the General Meeting, which will be held for the purpose of considering and, if thought fit, passing each of the following resolutions that is put to the shareholders for a vote:

Each of the Business Combination Proposal and the ARYA Merger Proposal (the “Condition Precedent Proposals”) is conditioned upon the approval and adoption of the other Condition Precedent Proposal. Neither the Director Election Proposal and the Adjournment Proposal is conditioned on any other proposal.

These items of business are described in the accompanying proxy statement/prospectus, which we encourage you to read carefully and in its entirety before voting.

Only holders of record of the ARYA Shares at the close of business on [•], 2024 (the “Record Date”) are entitled to notice of the General Meeting and to vote and have their votes counted at the General Meeting and any adjournments of the General Meeting. Only holders of Class B ordinary shares may vote on the appointment of directors. The accompanying proxy statement/prospectus and accompanying proxy card is being provided to ARYA’s shareholders in connection with the solicitation of proxies to be voted at the General Meeting and at any adjournment of the General Meeting. Whether or not you plan to attend the General Meeting, all of ARYA’s shareholders are urged to read the accompanying proxy statement/prospectus, including the Annexes and the documents referred to therein carefully and in their entirety. You should also carefully consider the risk factors described in “Risk Factors” beginning on page [•] of the accompanying proxy statement/prospectus.

After careful consideration, the board of directors of ARYA (the “ARYA Board”) has approved the Business Combination Agreement and the transactions contemplated thereby, including the Mergers, and recommends that the ARYA shareholders vote “FOR” the Business Combination Proposal, “FOR” the ARYA Merger Proposal, “FOR” the Director Election Proposal (in the case of the holders of the Class B ordinary shares) and “FOR” the Adjournment Proposal, in each case, if presented to the ARYA shareholders at the General Meeting. When you consider the ARYA Board’s recommendation of these proposals, you should keep in mind that directors and officers of ARYA have interests in the Business Combination that may conflict with your interests as a shareholder. See the section entitled “Proposal 1: Business Combination Proposal—Interests of Certain Persons in the Business Combination” in the accompanying proxy statement/prospectus.

Pursuant to the Existing Organizational Documents, a public holder of the Class A ordinary shares sold in ARYA’s initial public offering (whether they were purchased in ARYA’s initial public offering or thereafter in the open market) (a “Public Shareholder,” and, such shares, the “Public Shares”) may request that ARYA redeems all or a portion of its Public Shares for cash if the Business Combination is consummated. If the Business Combination is approved, ARYA will cause any Public Shares that have been validly tendered or delivered for redemption on the date for which the closing of the Business Combination occurs (the “Closing Date”), to be redeemed prior to the ARYA Merger Effective Time. As a holder of Public Shares, you will be entitled to receive cash for any Public Shares to be redeemed only if you:

The redemption rights include the requirement that a holder must identify itself in writing as a beneficial holder and provide its legal name, phone number and address to Continental in order to validly redeem its shares. Public Shareholders may seek to have their Public Shares redeemed by ARYA, regardless of whether they vote for or against the Business Combination Proposal or any other proposal and whether they held ARYA Shares as of the Record Date or acquired them after the Record Date. Any Public Shareholder who holds ARYA Shares on or before [•], 2024 (two business days prior to the initially scheduled vote at the General Meeting) will have the right to demand that his, her or its shares be redeemed for a pro rata portion of the aggregate amount then on deposit in the trust account established at the consummation of ARYA’s initial public offering (the “Trust Account”), calculated as of two business days prior to the consummation of the Business Combination and including interest earned on the funds

held in the Trust Account, less any taxes then due but not yet paid. For illustrative purposes, based on funds in the Trust Account of approximately $37,543,644 on May 9, 2024, the estimated per share redemption price is expected to be approximately $11.37. A Public Shareholder who has properly tendered or delivered his, her or its Public Shares for redemption will be entitled to receive his, her or its pro rata portion of the aggregate amount then on deposit in the Trust Account in cash for such shares only if the Business Combination is completed. If the Business Combination is not completed, the redemptions will be canceled and the tendered shares will be returned to the relevant Public Shareholders as appropriate. If a Public Shareholder exercises its redemption rights in full, then it will be electing to exchange its Public Shares for cash and will no longer own any shares. See “Annual General Meeting of ARYA Shareholders—Redemption Rights” in the accompanying proxy statement/prospectus for a detailed description of the procedures to be followed if you wish to redeem your Public Shares for cash.

Public Shareholders who seek to redeem their Public Shares must demand redemption no later than 5:00 p.m., Eastern Time, on [•], 2024 (two business days prior to the initially scheduled vote at the General Meeting) by (a) submitting a written request to the Transfer Agent that ARYA redeem such holder’s Public Shares for cash, (b) affirmatively certifying in such request to the Transfer Agent for redemption if such holder is acting in concert or as a “group” (as defined in Section 13d-3 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) with any other shareholder with respect to ARYA Shares and (c) tendering or delivering their ARYA Shares, either physically or electronically using DTC’s deposit/withdrawal at custodian system (“DWAC”), at the holder’s option, to the Transfer Agent prior to the General Meeting. If you hold the shares in street name, you will have to coordinate with your broker to have your shares certificated or delivered electronically. Certificates that have not been tendered or delivered to the Transfer Agent (either physically or electronically) in accordance with these procedures will not be redeemed for cash. There is a nominal cost associated with this 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 a nominal fee and it would be up to the broker whether or not to pass this cost on to the redeeming shareholder. In the event the Business Combination is not completed, this may result in an additional cost to shareholders for the return of their shares.

Notwithstanding the foregoing, a Public Shareholder, together with any affiliate of his, her, its or any other person with whom he, she or it is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act) will be restricted from seeking redemption rights with respect to more than 15% of the Public Shares. Accordingly, any shares held by a Public Shareholder or “group” in excess of such 15% cap will not be redeemed by ARYA.

Pursuant to that certain letter agreement, dated as of February 25, 2021 (the “SPAC Sponsor Letter Agreement”), the Sponsor, officers and directors of ARYA have waived all of their redemption rights and will not have redemption rights with respect to any ARYA Shares owned by them, directly or indirectly. As of the date of the accompanying proxy statement/prospectus, the initial shareholders own approximately 56.2% of the issued and outstanding ARYA Shares. Such shares will be excluded from the pro rata calculation used to determine the per-share redemption price. Concurrently with the execution of the Business Combination Agreement, ARYA, the Sponsor, each of Messrs. Wider and Henderson and Ms. Trigg (collectively, the “Other Class B Shareholders” and with the Sponsor, the “initial shareholders”), each of Joseph Edelman, Adam Stone, Michael Altman and Konstantin Poukalov (with the initial shareholders, the “Insiders”), ListCo and Adagio entered into the Sponsor Letter Agreement (the “Sponsor Letter Agreement”) pursuant to which, among other things, (i) each initial shareholder agreed to vote in favor of each of the transaction proposals to be voted upon at the meeting of ARYA shareholders, including approval of the Business Combination Agreement and the transactions contemplated thereby, (ii) each initial shareholder agreed to waive any adjustment to the conversion ratio set forth in the governing documents of ARYA or any other anti-dilution or similar protection with respect to the Class B ordinary shares (whether resulting from the transactions contemplated by the Subscription Agreements (as defined in the accompanying proxy statement/prospectus) or otherwise), (iii) each of the Insiders and ARYA agreed to terminate the lock-up provisions contained in the SPAC Sponsor Letter Agreement (as defined in the accompanying proxy statement/prospectus) and to replace such lock-up provisions with the transfer restrictions included in the Investor Rights Agreement, (iv) each initial shareholder agreed to be bound by certain transfer restrictions with respect to his, her or its shares in ARYA prior to the Closing, (v) the Sponsor agreed that 1,147,500 shares of New Adagio Common Stock issued to the Sponsor will be subject to Share Trigger Price Vesting, and (vi) the Sponsor has agreed to irrevocably forfeit, surrender and transfer to ARYA for no consideration 1,000,000 Class B ordinary shares, which will be issued by ListCo to PIPE Investors, including the Perceptive PIPE Investor, as Incentive Shares. Pursuant to the Investor Rights Agreement and subject to customary exceptions set forth therein, the shares of New Adagio Common Stock

beneficially owned or owned of record by the Sponsor, the Perceptive PIPE Investor, certain officers and directors of ARYA and New Adagio (including any PIPE Shares or shares of New Adagio Common Stock issued pursuant to the Business Combination Agreement) will be subject to a lock-up period beginning on the Closing Date until the date that is the earlier of (i) 365 days following the Closing Date (or six months after the Closing Date, in the case of Olav Bergheim, John Dahldorf, Hakon Bergheim, Todd Wider, Michael Henderson and Leslie Trigg) or (ii) the first date subsequent to the Closing Date with respect to which the closing price of the shares of New Adagio Common Stock equals or exceeds $12.00 per share for any 20 trading days within any 30-trading day period commencing at least 150 days after the Closing Date. See “Proposal 1: Business Combination Proposal—Certain Agreements Related to the Business Combination—Investor Rights Agreement” and “Proposal 1: Business Combination Proposal—Certain Agreements Related to the Business Combination—Sponsor Letter Agreement” in the accompanying proxy statement/prospectus for more information related to the Sponsor Letter Agreement and the Investor Rights Agreement.

The Business Combination Agreement is subject to the satisfaction or waiver of certain other closing conditions as described in the accompanying proxy statement/prospectus. There can be no assurance that the parties to the Business Combination Agreement would waive any such provision of the Business Combination Agreement.

The approval of each of the Business Combination Proposal and the Adjournment Proposal requires an ordinary resolution under Cayman Islands law, being a resolution passed by a simple majority of the votes cast by, or on behalf of, the holders of the issued ARYA Shares present in person or represented by proxy at the General Meeting and entitled to vote on such matter.

The approval of the ARYA Merger Proposal requires a special resolution under Cayman Islands law, being the affirmative vote of at least a two-thirds (2/3) majority of the votes cast by the holders of the issued ARYA Shares present in person or represented by proxy at the General Meeting and entitled to vote on such matter. Under the terms of the Existing Governing Documents, the proposed amendments to the provisions of the Existing Governing Documents governing the appointment or removal of directors prior to ARYA’s initial business combination may only be amended by a special resolution passed by holders representing at least two-thirds (2/3) of the outstanding Class B ordinary shares who attend and vote in person or represented by proxy at the General Meeting.

The approval of the Director Election Proposal requires an ordinary resolution of the holders of the Class B ordinary shares. Only holders of Class B ordinary shares may vote on the appointment of directors and our initial shareholders hold all issued and outstanding Class B ordinary shares. Assuming that all shareholders who are entitled to do so attend the General Meeting and vote, the approval of each of the Business Combination Proposal and the Adjournment Proposal would not require the affirmative vote of any Public Shareholder in addition to the affirmative vote of the initial shareholders. Assuming that all shareholders who are entitled to do so attend the General Meeting and vote, the affirmative vote of 787,845 of the Public Shares, in addition to the affirmative vote of the initial shareholders, would be required to approve the ARYA Merger Proposal. To ensure your representation at the General Meeting, you are urged to complete, sign, date and return the proxy card accompanying the proxy statement/prospectus as soon as possible. If your shares are held in an account at a brokerage firm or bank, you must instruct your broker or bank on how to vote your shares or, if you wish to attend the General Meeting and vote electronically, obtain a proxy from your broker or bank.

Your vote is important regardless of the number of shares you own. Whether you plan to attend the General Meeting or not, please complete, sign, date and return the enclosed proxy card as soon as possible in the envelope provided. Your proxy card must be received by ARYA not less than 48 hours before the scheduled time of the General Meeting or any adjournment thereof at which the person named in the proxy card proposes to vote. Proxy cards received after this time will not be counted. If your shares are held in “street name” or are in a margin or similar account, you should contact your broker to ensure that votes related to the shares you beneficially own are properly counted.

An ARYA shareholder who is entitled to attend and vote at the General Meeting is entitled to appoint one or more proxies to attend and vote instead of that shareholder. A proxyholder need not be an ARYA shareholder.

If you sign, date and return your proxy card without indicating how you wish to vote, your proxy will be voted FOR each of the proposals presented at the General Meeting. If you fail to return your proxy card or fail to instruct your bank, broker or other nominee how to vote, and do not attend the General Meeting in person, the effect will be,

among other things, that your shares will not be counted for purposes of determining whether a quorum is present at the General Meeting. If you are a shareholder of record and you attend the General Meeting and wish to vote in person, you may withdraw your proxy and vote in person.

Your attention is directed to the remainder of the accompanying proxy statement/prospectus (including the Annexes and other documents referred to therein) for a more complete description of the proposed Business Combination and related transactions and each of the proposals. You are encouraged to read the accompanying proxy statement/prospectus carefully and in its entirety, including the Annexes and other documents referred to therein. If you have any questions or need assistance voting your ARYA Shares, please contact Morrow Sodali LLC, our proxy solicitor, by calling (800) 662-5200, or banks and brokers can call collect at (203) 658-9400, or by emailing ARYD.info@investor.morrowsodali.com.

Thank you for your participation. We look forward to your continued support.

TO EXERCISE YOUR REDEMPTION RIGHTS, YOU MUST DEMAND IN WRITING THAT YOUR PUBLIC SHARES ARE REDEEMED FOR A PRO RATA PORTION OF THE FUNDS HELD IN THE TRUST ACCOUNT AND TENDER YOUR SHARES TO ARYA’S TRANSFER AGENT AT LEAST TWO BUSINESS DAYS PRIOR TO THE INITIALLY SCHEDULED VOTE AT THE GENERAL MEETING. IN ORDER TO EXERCISE YOUR REDEMPTION RIGHT, YOU NEED TO IDENTIFY YOURSELF AS A BENEFICIAL HOLDER AND PROVIDE YOUR LEGAL NAME, PHONE NUMBER AND ADDRESS IN YOUR WRITTEN DEMAND. YOU MAY TENDER YOUR SHARES BY EITHER TENDERING OR DELIVERING YOUR PUBLIC SHARES (AND CERTIFICATES, IF ANY) AND OTHER REDEMPTION FORMS TO THE TRANSFER AGENT OR BY TENDERING OR DELIVERING YOUR PUBLIC SHARES (AND CERTIFICATES, IF ANY) AND OTHER REDEMPTION FORMS ELECTRONICALLY USING THE DEPOSITORY TRUST COMPANY’S DWAC (DEPOSIT WITHDRAWAL AT CUSTODIAN) SYSTEM. IF THE BUSINESS COMBINATION IS NOT COMPLETED, THEN THESE SHARES WILL BE RETURNED TO YOU OR YOUR ACCOUNT. IF YOU HOLD THE SHARES IN STREET NAME, YOU WILL NEED TO INSTRUCT THE ACCOUNT EXECUTIVE AT YOUR BANK OR BROKER TO WITHDRAW THE SHARES FROM YOUR ACCOUNT IN ORDER TO EXERCISE YOUR REDEMPTION RIGHTS.

You may request copies of this proxy statement/prospectus and any other publicly available information concerning ARYA, without charge, by written request to ARYA Sciences Acquisition Corp IV, 51 Astor Place, 10^th Floor, New York, New York 10003, or by telephone request at (212) 284-2300; or Morrow Sodali LLC, our proxy solicitor, by calling (800) 662-5200, or banks and brokers can call collect at (203) 658-9400, or by emailing ARYD.info@investor.morrowsodali.com or from the SEC through the SEC website at http://www.sec.gov.

In order for ARYA’s shareholders to receive timely delivery of the documents in advance of the General Meeting to be held on [•], 2024, you must request the information no later than five business days prior to the date of the General Meeting, i.e., by [•], 2024.

This document, which forms part of a registration statement on Form S-4 filed with the U.S. Securities and Exchange Commission (the “SEC”) by ListCo (File No. 333-278811), constitutes a prospectus of ListCo under Section 5 of the U.S. Securities Act of 1933, as amended (the “Securities Act”), with respect to the New Adagio Securities to be issued to ARYA shareholders, if the business combination described below is consummated. This document also constitutes a notice of meeting and a proxy statement under Section 14(a) of the U.S. Securities Exchange Act of 1934, as amended (the “Exchange Act”), with respect to the General Meeting of ARYA shareholders at which ARYA shareholders will be asked to consider and vote upon a proposal to adopt the Business Combination Agreement and approve the Business Combination by the approval and adoption of the Business Combination Proposal, among other matters.

Adagio and its subsidiaries own or have rights to trademarks, trade names and service marks that they use in connection with the operation of their business. In addition, Adagio’s name, logo and website name and address are its trademarks or service marks. This document also contains references to other trademarks, trade names and service marks belonging to other entities. Solely for convenience, trademarks, trade names and service marks referred to in this proxy statement/prospectus may appear without the ® or TM symbols, but such references are not intended to indicate, in any way, that the applicable licensor will not assert, to the fullest extent under applicable law, its rights to these trademarks and trade names. We do not intend our use or display of other companies’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

This proxy statement/prospectus includes market and industry data and forecasts that Adagio has derived from publicly available information, industry publications and surveys, reports from government agencies, reports by market research firms or other independent sources and Adagio’s internal data and estimates based on its management’s knowledge of and experience in the market sectors in which it competes.

Certain monetary amounts, percentages and other figures included in this proxy statement/prospectus have been subject to rounding adjustments. Accordingly, figures shown as totals in certain tables or charts may not be the arithmetic aggregation of the figures that precede them, and figures expressed as percentages in the text may not total 100% or, as applicable, when aggregated may not be the arithmetic aggregation of the percentages that precede them.

The industry and market position information that appears in this proxy statement/prospectus involves a number of assumptions and limitations, and you are cautioned not to give undue weight to these estimates. Although Adagio has not independently verified the accuracy or completeness of any third-party information, Adagio believes the industry and market position information included in this proxy statement/prospectus is reliable.

Such information is supplemented where necessary with Adagio’s internal estimates and Adagio’s management’s judgment where information is not publicly available.

Industry reports, publications, research, studies and forecasts generally state that the information they contain has been obtained from sources believed to be reliable, but that the accuracy and completeness of such information is not guaranteed. In some cases, Adagio does not expressly refer to the sources from which this data is derived. While

Adagio has compiled, extracted, and reproduced industry data from these sources, Adagio has not independently verified any third-party information. Forecasts and other forward-looking information obtained from these sources are subject to the same qualifications and uncertainties as the other forward-looking statements in this proxy statement/prospectus. These forecasts and forward-looking information are subject to uncertainty and risk due to a variety of factors, including those described under the headings “Risk Factors,” “Cautionary Note Regarding Forward-Looking Statements” and “Adagio’s Management’s Discussion and Analysis of Financial Condition and Results of Operations.” These and other factors could cause results to differ materially from those expressed in any forecasts or estimates.

The industry in which Adagio operates is subject to a high degree of uncertainty and risk. As a result, the estimates and market and industry information provided in this proxy statement/prospectus are subject to significant uncertainty and may prove to be incorrect based on various factors, including those described in the section entitled “Risk Factors–Risks Related to Adagio’s Business” and elsewhere in this proxy statement/prospectus.

In this proxy statement/prospectus, unless otherwise specified, all monetary amounts are in U.S. dollars and all references to “$” mean U.S. dollars. Certain monetary amounts described herein have been expressed in U.S. dollars for convenience only and, when expressed in U.S. dollars in the future, such amounts may be different from those set forth herein due to intervening exchange rate fluctuations.

The historical financial statements of ARYA were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and are denominated in U.S. dollars.

ListCo was incorporated on December 19, 2023 for the purpose of effectuating the Business Combination described herein. ListCo has no material assets or liabilities and does not operate any businesses. Accordingly, no financial statements of ListCo have been included in this proxy statement/prospectus.

This proxy statement/prospectus contains:

The historical results and pro forma financial information presented below are not necessarily indicative of the results to be expected for any future period. You should carefully read the following selected financial information in conjunction with the section entitled “Adagio’s Management’s Discussion and Analysis of Financial Condition and Results of Operations” and Adagio’s financial statements and the related notes appearing elsewhere in this proxy statement/prospectus.

Unless indicated otherwise, financial data presented in this proxy statement/prospectus has been taken from the audited financial statements of Adagio included in this proxy statement/prospectus. Unless otherwise indicated, financial information of Adagio have been prepared in accordance with GAAP and are denominated in U.S. dollars.

We have made rounding adjustments to some of the figures included in this proxy statement/prospectus. Accordingly, numerical figures shown as totals in some tables may not be an arithmetic aggregation of the figures that preceded them.

Unless otherwise stated in this proxy statement/prospectus or the context otherwise requires, references to:

The questions and answers below highlight only selected information from this document and only briefly address some commonly asked questions about the proposals to be presented at the General Meeting, including with respect to the proposed Business Combination. The following questions and answers do not include all the information that is important to ARYA’s shareholders. We urge shareholders to read this proxy statement/prospectus, including the Annexes and the other documents referred to herein, carefully and in their entirety to fully understand the proposed Business Combination and the voting procedures for the General Meeting, which will be held at [•] [a.m./p.m.], Eastern Time, on [•], 2024, at the offices of Kirkland & Ellis LLP located at 601 Lexington Avenue, New York, New York 10022 and via a virtual meeting, or at such other time, on such other date and at such other place to which the meeting may be adjourned.

Historical market price information regarding shares of ListCo is not provided because there is no public market for shares of ListCo.

ListCo has not paid any cash dividends on its capital stock to date and does not intend to pay cash dividends prior to the consummation of the Business Combination.

On February 26, 2021, the Public Shares began trading on Nasdaq under the symbol “ARYD.” Upon the consummation of the Business Combination and by operation of the Business Combination, the Public Shares will be delisted and holders that elect not to redeem their Public Shares in connection with the Business Combination will receive shares of New Adagio Common Stock, which are expected to be listed on Nasdaq.

The following table sets forth, for the calendar quarter indicated, the high and low sales prices per Public Share, as reported on Nasdaq for the periods presented: