As filed with the Securities and Exchange Commission on December 18, 2019

Registration No. 333-                

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

89bio, Inc.

(Exact name of registrant as specified in its charter)

535 Mission Street, 14^th Floor

San Francisco, CA 94105

(Address of Principal Executive Offices, Zip Code)

Amended and Restated 89bio, Inc. 2019 Equity Incentive Plan

89bio, Inc. 2019 Employee Stock Purchase Plan

(Full title of the plans)

Rohan Palekar

Chief Executive Officer

89bio, Inc.

535 Mission Street, 14^th Floor

San Francisco, CA 94105

(Name and address of agent for service)

(415) 500-4614

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

Copies to:

Ryan A. Murr

Branden C. Berns

Gibson, Dunn & Crutcher, LLP

555 Mission Street

San Francisco, CA 94105

(415) 393-8373

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.  ☐

CALCULATION OF REGISTRATION FEE

EXPLANATORY NOTE

This Registration Statement on Form S-8 is filed by 89bio, Inc. (the “Registrant”), relating to 1,540,034 shares of its common stock, par value $0.001 per share (the “Common Stock”), available for issuance pursuant to future awards to eligible persons under the Amended and Restated 89bio, Inc. 2019 Equity Incentive Plan (the “2019 Plan”), 1,304,159 shares of Common Stock issuable pursuant to outstanding options under the 2019 Plan and 225,188 shares of Common Stock issuable to eligible persons under the 89bio, Inc. 2019 Employee Stock Purchase Plan (the “ESPP” and, together with the 2019 Plan, the “Plans”).

PART I

INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

The information required by this Part I has been omitted from this Registration Statement pursuant to the Note to Part I of Form S-8.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

The following documents filed by the Registrant with the Securities and Exchange Commission (the “Commission”), are incorporated by reference herein and shall be deemed to be a part hereof:

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In addition, all documents filed by the Registrant pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date hereof, but prior to the filing of a post-effective amendment to this Registration Statement that indicates that all securities offered hereby have been sold or that deregisters all such securities then remaining unsold, shall be deemed to be incorporated by reference in this Registration Statement and to be a part hereof from the date of filing of such documents. Notwithstanding the foregoing, unless specifically stated to the contrary in such filing, none of the information that the Registrant discloses under Items 2.02 or 7.01 of any Current Report on Form 8-K that it may from time to time furnish to the Commission will be incorporated by reference into, or otherwise be included in or deemed to be a part of, this Registration Statement.

For purposes of this Registration Statement, any document or any statement contained in a document incorporated or deemed to be incorporated herein by reference shall be deemed to be modified or superseded to the extent that a subsequently filed document or a statement contained herein or in any other subsequently filed document that also is or is deemed to be incorporated herein by reference modifies or supersedes such document or such statement in such document. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Registration Statement. Subject to the foregoing, all information in this Registration Statement is so qualified in its entirety by the information appearing in the documents incorporated herein by reference.

Not applicable.

Not applicable.

Registrant is a Delaware corporation. Section 145(a) of the Delaware General Corporation Law (the “DGCL”) provides that a Delaware corporation may indemnify any person who was or is 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 the right of the corporation, by reason of the fact that such person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe his or her conduct was unlawful.

Section 145(b) of the DGCL provides that a Delaware corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or

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completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that such person acted in any of the capacities set forth above, against expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit if the person acted in good faith and in a manner the person reasonably believed to be in, or not opposed to, the best interests of the corporation, except that no indemnification shall be made in respect of 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 the court in which such action or suit was brought shall determine, upon application, that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the court shall deem proper.

Further subsections of DGCL Section 145 provide that:

As used in this Item 6, the term “proceeding” means any threatened, pending, or completed action, suit, or proceeding, whether or not by or in the right of Registrant, and whether civil, criminal, administrative, investigative or otherwise.

Section 145 of the DGCL makes provision for the indemnification of officers and directors in terms sufficiently broad to indemnify officers and directors of the company under certain circumstances from liabilities (including reimbursement for expenses incurred) arising under the Securities Act. The Company’s Second Amended and Restated Certificate of Incorporation and Second Amended and Restated Bylaws provide, in effect, that, to the fullest extent and under the circumstances permitted by Section 145 of the DGCL, the Company will indemnify any and all of its officers and directors. The Company has entered into

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indemnification agreements with its officers and directors. The Company may, in its discretion, similarly indemnify its employees and agents. The Company’s Second Amended and Restated Certificate of Incorporation also relieves the Company’s directors from monetary damages to the Company or its shareholders for breach of such director’s fiduciary duty as a director to the fullest extent permitted by the DGCL. Under Section 102(b)(7) of the DGCL, a corporation may relieve its directors from personal liability to such corporation or its shareholders for monetary damages for any breach of their fiduciary duty as directors except (i) for a breach of the duty of loyalty, (ii) for failure to act in good faith,(iii) for intentional misconduct or knowing violation of law, (iv) for willful or negligent violations of certain provisions in the DGCL imposing certain requirements with respect to stock repurchases, redemptions and dividends or (v) for any transactions from which the director derived an improper personal benefit.

The Company has purchased insurance policies that, within the limits and subject to the terms and conditions thereof, cover certain expenses and liabilities that may be incurred by directors and officers in connection with proceedings that may be brought against them as a result of an act or omission committed or suffered while acting as a director or officer of the Company.

Not applicable.

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(a) The undersigned Registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this Registration Statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the Registration Statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the Registration Statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the Registration Statement or any material change to such information in the Registration Statement;

provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the Registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the Registration Statement;

(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof; and

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

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(b) The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the Registration Statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

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SIGNATURES

Pursuant to the requirements of the Securities Act, 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 San Francisco, State of California, on December 18, 2019.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Rohan Palekar, Ram Waisbourd and Ryan Martins, and each of them, his or her true and lawful attorneys-in-fact and agents, each with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments, including post-effective amendments, to this Registration Statement, and any registration statement relating to the offering covered by this Registration Statement and filed pursuant to Rule 462 under the Securities Act, and to file the same, with exhibits thereto and other documents in connection therewith, with the Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that each of said attorneys-in-fact and agents or their substitute or substitutes may lawfully so or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, the following persons have signed this Registration Statement in the capacities and on the date(s) indicated.

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Exhibit 5.1

December 18, 2019

89bio, Inc.

535 Mission Street, 14^th Floor

San Francisco, California 94105

Re: 2019 Equity Incentive Plan and 2019 Employee Stock Purchase Plan

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8, (the “Registration Statement”) of 8bio, Inc., a Delaware corporation (the “Company”), to be filed with the Securities and Exchange Commission (the “Commission”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), in connection with the offering by the Company of up to 3,069,381 shares of the Company’s Common Stock, par value $0.001 per share (the “Shares”). 1,540,034 of the Shares subject to the Registration Statement are reserved for issuance pursuant to future awards under the Amended and Restated 89bio, Inc. 2019 Equity Incentive Plan (the “2019 Plan”), 1,304,159 of the Shares subject to the Registration Statement are to be issued with respect to outstanding options under the 2019 Plan and 225,188 of the Shares subject to the Registration Statement are reserved for issuance under the 89bio, Inc. 2019 Employee Stock Purchase Plan (the “ESPP” and, together with the 2019 Plan, the “Plans”).

We have examined the originals, or photostatic or certified copies, of such records of the Company and certificates of officers of the Company and of public officials and such other documents as we have deemed relevant and necessary as the basis for the opinions set forth below. In our examination, we have assumed the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as copies. We have also assumed that there are no agreements or understandings between or among the Company and any participants in the Plans that would expand, modify or otherwise affect the terms of the Plans or the respective rights or obligations of the participants thereunder. Finally, we have assumed the accuracy of all other information provided to us by the Company during the course of our investigations, on which we have relied in issuing the opinion expressed below.

Based upon the foregoing examination and in reliance thereon, and subject to the qualifications, assumptions and limitations stated herein and in reliance on the statements of fact contained in the documents that we have examined, we are of the opinion that the Shares, when issued and sold in accordance with the terms set forth in the Plans and against payment therefor, and when the Registration Statement has become effective under the Securities Act, will be validly issued, fully paid and non-assessable.

We render no opinion herein as to matters involving the laws of any jurisdiction other than the Delaware General Corporation Law (the “DGCL”). We are not admitted to practice in the State of Delaware; however, we are generally familiar with the DGCL as currently in effect and have made such inquiries as we consider necessary to render the opinions above. This opinion is limited to the effect of the current state of the DGCL and the facts as they currently exist. We assume no obligation to revise or supplement this opinion in the event of future changes in such law or the interpretations thereof or such facts.

We consent to the filing of this opinion as an exhibit to the Registration Statement, and we further consent to the use of our name under the caption “Legal Matters” in the Registration Statement and the prospectus that forms a part thereof. In giving these consents, 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 Rules and Regulations of the Commission.

Very truly yours,

/s/ Gibson, Dunn & Crutcher LLP

Exhibit 23.1

CONSENT OF INDEPENDENT

REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-8 pertaining to the 2019 Equity Incentive Plan and 2019 Employee Stock Purchase Plan of 89bio, Inc. (the “Company”) of our report dated September 19, 2019 (October 28, 2019 as to the retroactive effect of the reverse stock split and the Reorganization as described in Note 2 and Note 4, respectively) on our audit of the financial statement of 89bio, Inc. as of June 28, 2019, appearing in this Registration Statement.

/s/ Brightman Almagor Zohar & Co.

A Firm in the Deloitte Global Network

Tel Aviv, Israel

December 18, 2019

Exhibit 23.2

CONSENT OF INDEPENDENT

REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-8 pertaining to the 2019 Equity Incentive Plan and 2019 Employee Stock Purchase Plan of 89bio, Inc. (the “Company”) of our report dated August 15, 2019 (October 28, 2019 as to the retroactive effect of the reverse stock split and the Reorganization as described in Note 2 and Note 13, respectively) on our audit of the consolidated financial statements of 89Bio Ltd. as of December 31, 2018, and the related statements of operations and comprehensive loss, change in convertible preferred shares and shareholders’ deficit and cash flows from inception January 18, 2018 through December 31, 2018 (which report expresses an unqualified opinion and includes an explanatory paragraph regarding the Company’s ability to continue as a going concern), appearing in this Registration Statement.

/s/ Brightman Almagor Zohar & Co.

A Firm in the Deloitte Global Network

Tel Aviv, Israel

December 18, 2019