As filed with the Securities and Exchange Commission on March 18, 2020

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)

142 Sansome Street, Second Floor

San Francisco, CA 94104

(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.

142 Sansome Street, Second Floor

San Francisco, CA 94104

(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 additional shares of its common stock, par value $0.001 per share (the “Common Stock”), available for issuance pursuant to the Amended and Restated 89bio, Inc. 2019 Equity Incentive Plan (the “2019 Plan”) and the 89bio, Inc. 2019 Employee Stock Purchase Plan (the “ESPP” and, together with the 2019 Plan, the “Plans”). The information contained in the Registrant’s registration statement on Form S-8 (SEC File No. 333-235577), together with all exhibits filed therewith or incorporated therein by reference, is hereby incorporated by reference pursuant to General Instruction E to Form S-8.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

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 March 18, 2020.

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 Securities and Exchange 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.

Exhibit 5.1

March 18, 2020

89bio, Inc.

142 Sansome Street, Second Floor

San Francisco, California 94104

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 689,449 shares of the Company’s Common Stock, par value $0.001 per share (the “Shares”). 551,559 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”) and 137,890 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.

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 of our report dated March 18, 2020, relating to the financial statements of 89bio Inc. appearing in the Annual Report on Form 10-K of 89bio, Inc. for the year ended December 31, 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 of our report dated August 15, 2019, except for the retroactive effect of both the 1-for-6.217 reverse stock split and the reorganization, as described in Note 1, as to which the date is October 28, 2019 relating to the financial statements of 89bio, Inc. (operating as 89Bio, Ltd. prior to the reorganization described in Note 1), appearing in the Annual Report on Form 10-K of 89bio, Inc. for the year ended December 31, 2019.

/s/ Brightman Almagor Zohar & Co.

A Firm in the Deloitte Global Network

Tel Aviv, Israel

March 18, 2020