Organization and Basis of Presentation	3 Months Ended
Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Description of Business 89bio, Inc. (“89bio” or the “Company”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of liver and cardio-metabolic diseases. The Company’s lead product candidate, BIO89-100, a specifically engineered glycoPEGylated analog of fibroblast growth factor 21, is currently being developed for the treatment of nonalcoholic steatohepatitis. 89bio, Inc. was formed as a Delaware corporation on June 28, 2019, for the purpose of completing an initial public offering (“IPO”) and related transactions in order to carry on the business of 89Bio Ltd., which was incorporated in Israel in January 2018. The Company completed an internal reorganization transaction in September 2019, pursuant to which 89Bio Ltd. became a wholly owned subsidiary of 89bio, Inc. (the “Reorganization”). As part of the Reorganization, all of the equity holders of 89Bio Ltd. exchanged 100% of the equity of 89Bio Ltd. for 100% of the equity of 89bio, Inc. The Reorganization was considered a transaction between entities under common control. Initial Public Offering On November 13, 2019, 89bio, Inc. completed the IPO, pursuant to which it issued and sold an aggregate of 6,100,390 shares of common stock (inclusive of 795,703 shares pursuant to the underwriters’ option to purchase additional shares) at the IPO price of $16.00 per share, resulting in net proceeds of $87.7 million after deducting underwriting discounts and commissions of $6.8 million and other offering expenses of $3.1 million. Upon the closing of the IPO, the Company’s outstanding convertible preferred stock automatically converted into 7,077,366 shares of common stock of 89bio, Inc. based on a proportional adjustment to the conversion ratio of the convertible preferred stock on a 1-for-6.217 basis. Liquidity The accompanying condensed consolidated financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and liquidation of liabilities in the normal course of business. To date, the Company has not generated revenues from its activities and has incurred substantial operating losses. Management expects the Company to continue to generate substantial operating losses for the foreseeable future until it completes development of its products and seeks regulatory approvals to market such products. The Company had cash and cash equivalents of $85.5 million as of March 31, 2020. Management expects to continue to fund its operations primarily through utilization of its current financial resources and through additional raises of capital. The Company intends to raise such capital through the issuance of additional equity financing and/or debt financing. However, if such financing is not available at adequate levels, the Company will need to reevaluate its operating plan and may be required to delay the development of its products. The Company expects that its cash and cash equivalents as of March 31, 2020 will be sufficient to fund operating expenses and capital expenditure requirements for a period of at least one year from the date these unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Organization and Basis of Presentation

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Organization and Basis of Presentation

Description of Business

89bio, Inc. (“89bio” or the “Company”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of liver and cardio-metabolic diseases. The Company’s lead product candidate, BIO89-100, a specifically engineered glycoPEGylated analog of fibroblast growth factor 21, is currently being developed for the treatment of nonalcoholic steatohepatitis.

89bio, Inc. was formed as a Delaware corporation on June 28, 2019, for the purpose of completing an initial public offering (“IPO”) and related transactions in order to carry on the business of 89Bio Ltd., which was incorporated in Israel in January 2018.

The Company completed an internal reorganization transaction in September 2019, pursuant to which 89Bio Ltd. became a wholly owned subsidiary of 89bio, Inc. (the “Reorganization”). As part of the Reorganization, all of the equity holders of 89Bio Ltd. exchanged 100% of the equity of 89Bio Ltd. for 100% of the equity of 89bio, Inc. The Reorganization was considered a transaction between entities under common control.

Initial Public Offering

On November 13, 2019, 89bio, Inc. completed the IPO, pursuant to which it issued and sold an aggregate of 6,100,390 shares of common stock (inclusive of 795,703 shares pursuant to the underwriters’ option to purchase additional shares) at the IPO price of $16.00 per share, resulting in net proceeds of $87.7 million after deducting underwriting discounts and commissions of $6.8 million and other offering expenses of $3.1 million. Upon the closing of the IPO, the Company’s outstanding convertible preferred stock automatically converted into 7,077,366 shares of common stock of 89bio, Inc. based on a proportional adjustment to the conversion ratio of the convertible preferred stock on a 1-for-6.217 basis.

Liquidity

The accompanying condensed consolidated financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and liquidation of liabilities in the normal course of business. To date, the Company has not generated revenues from its activities and has incurred substantial operating losses. Management expects the Company to continue to generate substantial operating losses for the foreseeable future until it completes development of its products and seeks regulatory approvals to market such products. The Company had cash and cash equivalents of $85.5 million as of March 31, 2020. Management expects to continue to fund its operations primarily through utilization of its current financial resources and through additional raises of capital.

The Company intends to raise such capital through the issuance of additional equity financing and/or debt financing. However, if such financing is not available at adequate levels, the Company will need to reevaluate its operating plan and may be required to delay the development of its products. The Company expects that its cash and cash equivalents as of March 31, 2020 will be sufficient to fund operating expenses and capital expenditure requirements for a period of at least one year from the date these unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).