Organization and Basis of Presentation	12 Months Ended
Dec. 31, 2021
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, pegozafermin (previously BIO89-100), a specifically engineered glycoPEGylated analog of fibroblast growth factor 21, is currently being developed for the treatment of nonalcoholic steatohepatitis and for the treatment of severe hypertriglyceridemia. 89bio, Inc. was formed as a Delaware corporation in June 2019 to carry on the business of 89Bio Ltd., which was incorporated in Israel in January 2018. Public Offerings In July 2020, the Company completed an underwritten public offering of 3,047,040 shares of its common stock at the public offering price of $27.50 per share. The Company raised a total of $78.2 million in net proceeds after deducting underwriting discounts and commissions of $5.0 million and offering costs of $0.6 million. In September 2020, the Company completed an underwritten public offering of 3,025,000 shares of its common stock, at a public offering price of $28.00 per share. The Company raised a total of $79.5 million in net proceeds after deducting underwriting discounts and commissions of $4.6 million and offering costs of $0.6 million. In March 2021, the Company entered into a sales agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (the “Sales Agents”) pursuant to which it may offer and sell up to $75.0 million of shares of the Company’s common stock, from time to time, in “at-the-market” offerings (the “ATM Facility”). The Sales Agents are entitled to compensation at a commission equal to 3.0% of the aggregate gross sales price per share sold under the Sales Agreement. During the fourth quarter of 2021, the Company received proceeds of $3.3 million, net of commissions and offering expenses from sales of 186,546 shares of its common stock at a weighted-average price of $17.97 per share pursuant to the ATM Facility. Liquidity The accompanying 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 and short-term available-for-sale securities of $150.7 million as of December 31, 2021. The Company expects that its cash and cash equivalents and short-term available-for-sale securities as of December 31, 2021, together with proceeds available from the Company’s term loan (see Note 6) and its ATM Facility, will be sufficient to fund operating expenses and capital expenditure requirements for a period of at least one year from the date these audited consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2021

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, pegozafermin (previously BIO89-100), a specifically engineered glycoPEGylated analog of fibroblast growth factor 21, is currently being developed for the treatment of nonalcoholic steatohepatitis and for the treatment of severe hypertriglyceridemia.

89bio, Inc. was formed as a Delaware corporation in June 2019 to carry on the business of 89Bio Ltd., which was incorporated in Israel in January 2018.

Public Offerings

In July 2020, the Company completed an underwritten public offering of 3,047,040 shares of its common stock at the public offering price of $27.50 per share. The Company raised a total of $78.2 million in net proceeds after deducting underwriting discounts and commissions of $5.0 million and offering costs of $0.6 million.

In September 2020, the Company completed an underwritten public offering of 3,025,000 shares of its common stock, at a public offering price of $28.00 per share. The Company raised a total of $79.5 million in net proceeds after deducting underwriting discounts and commissions of $4.6 million and offering costs of $0.6 million.

In March 2021, the Company entered into a sales agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (the “Sales Agents”) pursuant to which it may offer and sell up to $75.0 million of shares of the Company’s common stock, from time to time, in “at-the-market” offerings (the “ATM Facility”). The Sales Agents are entitled to compensation at a commission equal to 3.0% of the aggregate gross sales price per share sold under the Sales Agreement. During the fourth quarter of 2021, the Company received proceeds of $3.3 million, net of commissions and offering expenses from sales of 186,546 shares of its common stock at a weighted-average price of $17.97 per share pursuant to the ATM Facility.

Liquidity

The accompanying 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 and short-term available-for-sale securities of $150.7 million as of December 31, 2021.

The Company expects that its cash and cash equivalents and short-term available-for-sale securities as of December 31, 2021, together with proceeds available from the Company’s term loan (see Note 6) and its ATM Facility, will be sufficient to fund operating expenses and capital expenditure requirements for a period of at least one year from the date these audited consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).