Organization and Basis of Presentation	6 Months Ended
Jun. 30, 2022
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 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 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. In October and November 2021, the Company received aggregate 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. For the six months ended June 30, 2022, there were no sales pursuant to the ATM Facility. In July 2022, pursuant to a shelf registration statement on Form S-3 (No. 333-254684), the Company completed an underwritten public offering of its common stock, warrants to purchase shares of its common stock and pre-funded warrants to purchase shares of its common stock. The Company sold 18,675,466 shares of its common stock with accompanying warrants to purchase up to 9,337,733 shares of its common stock at a combined public offering price of $3.55 per share. The Company also sold 7,944,252 pre-funded warrants to purchase shares of its common stock with accompanying warrants to purchase up to 3,972,126 shares of its common stock at a combined public offering price of $3.549 per pre-funded warrant. The warrants have an exercise price of $5.325 per share. The offering was completed on July 1, 2022 and the Company raised net proceeds of approximately $88.2 million, after deducting underwriting discounts and commissions of approximately $5.7 million and other offering costs of approximately $0.6 million. The Company received $28.2 million in proceeds in June 2022 prior to the closing of the offering. The proceeds are classified as a liability related to public offering on the condensed consolidated balance sheet. 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 and short-term available-for-sale securities of $139.3 million as of June 30, 2022. The Company expects that its cash and cash equivalents and short-term available-for-sale securities as of June 30, 2022, together with the proceeds received from the Company’s July 2022 offering and proceeds available from the Company’s 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 unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Organization and Basis of Presentation

6 Months Ended

Jun. 30, 2022

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 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 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. In October and November 2021, the Company received aggregate 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. For the six months ended June 30, 2022, there were no sales pursuant to the ATM Facility.

In July 2022, pursuant to a shelf registration statement on Form S-3 (No. 333-254684), the Company completed an underwritten public offering of its common stock, warrants to purchase shares of its common stock and pre-funded warrants to purchase shares of its common stock. The Company sold 18,675,466 shares of its common stock with accompanying warrants to purchase up to 9,337,733 shares of its common stock at a combined public offering price of $3.55 per share. The Company also sold 7,944,252 pre-funded warrants to purchase shares of its common stock with accompanying warrants to purchase up to 3,972,126 shares of its common stock at a combined public offering price of $3.549 per pre-funded warrant. The warrants have an exercise price of $5.325 per share. The offering was completed on July 1, 2022 and the Company raised net proceeds of approximately $88.2 million, after deducting underwriting discounts and commissions of approximately $5.7 million and other offering costs of approximately $0.6 million. The Company received $28.2 million in proceeds in June 2022 prior to the closing of the offering. The proceeds are classified as a liability related to public offering on the condensed consolidated balance sheet.

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 and short-term available-for-sale securities of $139.3 million as of June 30, 2022.

The Company expects that its cash and cash equivalents and short-term available-for-sale securities as of June 30, 2022, together with the proceeds received from the Company’s July 2022 offering and proceeds available from the Company’s 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 unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).