AMAM Ambrx Biopharma Inc

As filed with the Securities and Exchange Commission on October 12, 2023

Registration No. 333-257264

Registration No. 333-264490

Registration No. 333-271005

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

Ambrx Biopharma, Inc.

(Exact name of registrant as specified in its charter)

10975 North Torrey Pines Road

La Jolla, California, 92037

(Address of Principal Executive Offices, Including Zip Code)

Second Amended and Restated 2016 Equity Incentive Plan

Amended and Restated 2021 Equity Incentive Plan

Amended and Restated 2021 Employee Share Purchase Plan

(Full title of the plan)

Daniel J. O’Connor

President and Chief Executive Officer

Ambrx Biopharma, Inc.

10975 North Torrey Pine Road

La Jolla, CA 92037

(Name and address of agent for service)

(858) 875-2400

(Telephone number, including area code, of agent for service)

Copies to:

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☒

EXPLANATORY NOTE

This Post-Effective Amendment No. 1 (this “Amendment”) to those certain Registration Statements on Form S-8 (Reg. Nos. 333-257264, 333-264490 and 333-271005) (collectively, the “Registration Statements”) is being filed pursuant to Rule 414 under the Securities Act of 1933 (the “Securities Act”) by Ambrx Biopharma, Inc. (formerly New Ambrx Biopharma Inc.), a Delaware corporation (the “Company”), as the successor registrant to Ambrx Biopharma Cayman, Inc. (formerly Ambrx Biopharma Inc.), a Cayman Islands exempted company (the “Predecessor Registrant”).

On October 11, 2023, Predecessor Registrant completed its previously announced holding company reorganization, pursuant to the Agreement and Plan of Merger, dated as of September 11, 2023 (the “Merger Agreement”), by and among the Company, Ambrx Merger Sub Inc., a Cayman Islands exempted company and newly-formed direct wholly owned subsidiary of the Company (“Merger Sub”), and the Predecessor Registrant.

The Merger Agreement provided for the merger (the “Merger”) of the Predecessor Registrant with Merger Sub, with the Predecessor Registrant surviving the Merger as a direct wholly owned subsidiary of the Company, and the automatic conversion of each ordinary share, par value $0.0001 per share, of the Predecessor Registrant (“Ordinary Shares”) issued and outstanding immediately prior to the effective time of the Merger (including Ordinary Shares underlying the outstanding American Depositary Shares (“ADSs”)), into one-seventh (1/7) of one duly issued, fully paid and non-assessable share of common stock, par value $0.0001 per share, of the Company (“Common Stock”). In addition, (1) each outstanding option to purchase or other right to acquire one Ordinary Share was automatically converted into an option to purchase or right to acquire, upon the same terms and conditions, a number of shares of Common Stock determined by dividing (x) the number of Ordinary Shares subject to the option as of immediately prior to the effective time of the Merger by (y) seven, and rounding the resulting number down to the nearest whole number of shares of Common Stock, with an adjusted exercise price determined by multiplying (x) the per share exercise price for the Ordinary Shares subject to the option as in effect immediately prior to the effective time of the Merger by (y) seven, and rounding the resulting exercise price up to the nearest whole cent; and (2) each award of restricted share units representing the right to receive an issuance of Ordinary Shares was automatically converted into an award of restricted stock units representing the right to receive, upon the same terms and conditions, a number of shares of Common Stock determined by dividing (x) the number of Ordinary Shares subject to the award of restricted share units as of immediately prior to the effective time of the Merger by (y) seven, rounded down to the nearest whole number of shares of Common Stock.

Upon completion of the Merger, the Company became the successor registrant to the Predecessor Registrant. The Company expects that its Common Stock will commence trading on the Nasdaq Global Select Market as of the open of business on October 12, 2023, under the symbol “AMAM”, which is the same symbol under which the Predecessor Registrant’s ADSs traded.

The Company and its subsidiaries continue to conduct all of the operations previously conducted by the Predecessor Registrant and its subsidiaries prior to the Merger and, as a result of the Merger, the consolidated assets and liabilities, operations and financial condition of the Company immediately after the Merger are the same as those of the Predecessor Registrant immediately prior to the Merger. Immediately prior to the Merger, the Company had no assets or liabilities other than nominal assets or liabilities. The directors and executive officers of the Company immediately following the Merger are the same individuals who were directors and executive officers, respectively, of the Predecessor Registrant immediately prior to the Merger.

In accordance with paragraph (d) of Rule 414 under the Securities Act, the Company hereby expressly adopts each of the Registration Statements as its own registration statement except as amended by this Amendment, for all purposes of the Securities Act and the Securities Exchange Act of 1934.

1

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference.

The following documents filed by Company or the Predecessor Registrant with the Securities and Exchange Commission (the “SEC”) are hereby incorporated by reference in this registration statement:

All reports and other documents subsequently filed by the Company pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 (the “Exchange Act”) (other than Current Reports or portions thereof furnished under Item 2.02 or Item 7.01 or any related Item 9.01 of Form 8-K and exhibits filed on such form that are related to such items and other portions of documents that are furnished, but not filed, pursuant to applicable rules promulgated by the SEC) after the date hereof, and prior to the filing of a post-effective amendment that indicates that all the securities offered hereby have been sold or that deregisters the securities offered hereby then remaining unsold, shall also be deemed to be incorporated by reference into this registration statement and to be a part hereof from the date of filing of such documents.

Any statement contained in this registration statement or in a document incorporated or deemed to be incorporated by reference in this registration statement will be deemed to be modified or superseded to the extent that a statement contained herein or in any other subsequently filed document which also is or is deemed to be incorporated by reference in this registration statement modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this registration statement.

Item 6. Indemnification of Directors and Officers.

The Company is subject to the laws of Delaware on corporate matters, including its indemnification provisions. Section 102 of the Delaware General Corporate Law (“DGCL”) permits a corporation to eliminate the personal liability of directors of a corporation to the corporation or its stockholders for monetary damages for a breach of fiduciary duty as a director, except where the director breached such director’s duty of loyalty, failed to act in good faith, engaged in intentional misconduct or knowingly violated a law, authorized the payment of a dividend or approved a stock repurchase in violation of Delaware corporate law or obtained an improper personal benefit.

Section 145 of the DGCL provides that a corporation has the power to indemnify a director, officer, employee, or agent of the corporation, or a person serving at the request of the corporation for another corporation, partnership, joint venture, trust or other enterprise in related capacities against expenses, including attorneys’ fees, judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with an action, suit or proceeding to which such person was or is a party or is threatened to be made a party to any threatened, ending or completed action, suit or proceeding by reason of such position, if such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interests of the corporation, and, in any criminal action or proceeding, had no reasonable cause to believe such person’s conduct was unlawful, except that, in the case of actions brought by or in the right of the corporation, no indemnification shall be made with respect to any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or other adjudicating court determines that, despite the adjudication of liability but in view of all of the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery or such other court shall deem proper. The statute provides that indemnification pursuant to these provisions is not exclusive of other rights of indemnification to which a person may be entitled under any bylaw, agreement, vote of stockholders or disinterested directors or otherwise.

2

The Company’s certificate of incorporation states that to the fullest extent permitted by the DGCL, a director of the corporation shall not be liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director.

Under Article VIII of the Company’s bylaws, any person who was or is made a party or is threatened to be made a party to any threatened, pending or completed action suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in right of the Company), by reason of the fact that such person is or was a director of the Company, or is or was serving at the Company’s request as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorney’s fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding if such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interest of the Company, and, with respect to any criminal action or proceeding, had no reasonable cause to believe such person’s conduct was unlawful. The indemnification provided in the Company’s bylaws is not exclusive of any other rights to which those seeking indemnification may otherwise be entitled.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to the Company directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, the Company has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

Item 8. Exhibits.

3

Item 9. Undertakings.

(a) The undersigned registrant hereby undertakes:

4

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of La Jolla, State of California on October 12, 2023.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

5

Exhibit 5.1

October 12, 2023

Ambrx Biopharma, Inc.

10975 North Torrey Pines Road

La Jolla, California, 92037

Ladies and Gentlemen:

We have acted as special United States counsel to Ambrx Biopharma, Inc., a Delaware corporation (the “Company”), in connection with the Post-Effective Amendments No. 1 (the “Post-Effective Amendments”) to the registration statements on Form S-8 (File Nos. 333-257263, 333-257264 and 333-271005) (collectively, the “Registration Statements”) to be filed on the date hereof by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933 (the “Securities Act”). The Post-Effective Amendments relate to the adoption by the Company of the Second Amended and Restated 2016 Equity Incentive Plan (the “2016 Plan”), the Amended and Restated 2021 Equity Incentive Plan (the “2021 Plan”) and the Amended and Restated 2021 Employee Share Purchase Plan (the “2021 ESPP” and collectively with the 2016 Plan and the 2021 Plan, the “Plans”), respectively, pursuant to Rule 414 under the Securities Act as the successor registrant to Ambrx Biopharma Inc., a Cayman Islands exempted company, and the shares (the “Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”), issuable pursuant to such Plans.

Ambrx Biopharma, Inc.

October 12, 2023

Page 2

This opinion is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

In rendering the opinion stated herein, we have examined and relied upon the following:

(a) the Registration Statements;

(b) the Post-Effective Amendments;

(c) the Plans;

(d) an executed copy of a certificate, dated the date hereof, of Jared Kelly, Senior Vice President, General Counsel and Corporate Secretary of the Company (the “Secretary’s Certificate”);

(e) copies of the Company’s (i) Certificate of Incorporation as in effect on August 11, 2023 and certified pursuant to the Secretary’s Certificate and (ii) Amended and Restated Certificate of Incorporation, as in effect from October 11, 2023, certified by the Secretary of State of the State of Delaware as of October 11, 2023 (the “Current Charter”), and certified pursuant to the Secretary’s Certificate;

(f) a copy of the Company’s (i) Bylaws as in effect on August 11, 2023 and certified pursuant to the Secretary’s Certificate and (ii) Amended and Restated Bylaws as in effect from October 11, 2023 and certified pursuant to the Secretary’s Certificate and as in effect as of the date hereof (the “Current Bylaws”) and certified pursuant to the Secretary’s Certificate;

(g) copies of certain resolutions of the Board of Directors of the Company, duly executed on October 2, 2023, certified pursuant to the Secretary’s Certificate;

(h) the report of the inspector of elections of the Special Meeting of the Stockholders of the Company held on October 10, 2023, reflecting approval of the Plans, certified pursuant to the Secretary’s Certificate; and

(i) the forms of award agreements under the Plans.

We have also examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company and such agreements, certificates and receipts of public officials, certificates of officers or other representatives of the Company and others, and such other documents as we have deemed necessary or appropriate as a basis for the opinion stated below, including the facts and conclusions set forth in the Secretary’s Certificate.

In our examination, we have assumed the genuineness of all signatures, including electronic signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as facsimile, electronic, certified or photocopied copies, and the authenticity of the originals of such copies. In making our examination of executed documents, we have assumed that the parties thereto, other than the Company, had the power, corporate or other, to enter into and perform all obligations thereunder and have also assumed the due authorization by all requisite action, corporate or other, and the execution and delivery by such parties of such documents and the validity and binding effect thereof on such parties. As to any facts relevant to the opinion stated herein that we did not independently establish or verify, we have relied upon statements and representations of officers and other representatives of the Company and others and of public officials, including the facts and conclusions set forth in the Secretary’s Certificate.

Ambrx Biopharma, Inc.

October 12, 2023

Page 3

In rendering the opinion stated herein, we have also assumed that (i) an appropriate account statement evidencing Shares credited to an eligible individual’s account maintained with the Company’s transfer agent has been or will be issued by the Company’s transfer agent, (ii) the issuance of Shares will be properly recorded in the books and records of the Company, (iii) each award agreement under which Purchase Rights, Incentive Stock Options, Nonstatutory Stock Options, SARs, Restricted Stock Awards, RSU Awards, Performance Awards, Options, Restricted Share awards, Restricted Share Units, Other Share or Cash-Based Awards or Other Awards (each as defined in such Plans) are granted pursuant to each of the Plans will be consistent with the Plans, and the applicable form of award agreement and will be duly authorized, executed and delivered by the parties thereto and (iv) the consideration received by the Company for each of the Shares delivered pursuant to each of the Plans shall not be less than the per share par value of the Shares.

We do not express any opinion with respect to the laws of any jurisdiction other than the General Corporation Law of the State of Delaware (the “DGCL”).

Based upon the foregoing and subject to the qualifications and assumptions stated herein, we are of the opinion that the Shares have been duly authorized by all requisite corporate action on the part of the Company under the DGCL and when the Shares are issued to the eligible individuals in accordance with the terms and conditions of each of the Plans and the applicable award agreement for consideration in an amount at least equal to the par value of such Shares, the Shares will be validly issued, fully paid and nonassessable.

In addition, in rendering the foregoing opinion we have assumed that the issuance of the Shares does not and will not constitute a violation of, or a default under, any lease, indenture, agreement or other instrument to which the Company or its property is subject (except that we do not make this assumption with respect to the Current Charter or Current Bylaws).

Ambrx Biopharma, Inc.

October 12, 2023

Page 4

We hereby consent to the reference to our firm under the heading “Legal Matters” in the prospectus forming part of the Post-Effective Amendments. We also hereby consent to the filing of this opinion with the Commission as an exhibit to the Post-Effective Amendments. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the General Rules and Regulations of the Commission promulgated under the Securities Act. This opinion is expressed as of the date hereof unless otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

Very truly yours,

/s/ Skadden, Arps, Slate, Meagher & Flom LLP

GAN

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Post-Effective Amendment No. 1 to Registration Statements Nos. 333-257264, 333-264490 and 333-271005 on Form S-8 of our report dated March 30, 2023, relating to the financial statements of Ambrx Biopharma Inc., appearing in the Annual Report on Form 10-K of Ambrx Biopharma Inc. for the year ended December 31, 2022.

/s/ Deloitte & Touche LLP

San Diego, California

October 12, 2023