Organization and Principal Activities	9 Months Ended
Sep. 30, 2023
Disclosure Text Block [Abstract]
Organization and Principal Activities	1. Organization and Principal Activities Description of Business Sutro Biopharma, Inc. (the “Company”), is a clinical-stage oncology company developing site-specific and novel-format antibody drug conjugates, or ADCs. The Company was incorporated on April 21, 2003 and is headquartered in South San Francisco, California. The Company operates in one business segment, the development of biopharmaceutical products. At-The-Market Sales During the three and nine months ended September 30, 2023, the Company sold zero shares and 1,857,410 shares, respectively, of its common stock through its At-the-Market Facility (“ATM Facility”) pursuant to its Open Market Sales AgreementSM dated April 2, 2021 with Jefferies LLC (“Jefferies”), as sales agent (the “Sales Agreement”). During the three and nine months ended September 30, 2023, the gross proceeds from these sales were approximately zero and $12.4 million, respectively, before deducting fees of approximately zero and $0.4 million, respectively, resulting in net proceeds of approximately zero and $12.0 million, respectively, to the Company. Liquidity The Company has incurred significant losses and has negative cash flows from operations. As of September 30, 2023, the Company had an accumulated deficit of $590.5 million. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development and other operational activities. As of September 30, 2023, the Company had unrestricted cash, cash equivalents, and marketable securities of $321.1 million and equity securities of $34.0 million, consisting solely of common stock of Vaxcyte, which are available to fund future operations. The Company will need to raise additional capital to support the completion of its research and development activities and to support its operations. The Company believes that its unrestricted cash, cash equivalents, marketable securities and equity securities as of September 30, 2023, will enable the Company to maintain its operations for a period of at least 12 months following the filing date of its condensed financial statements.

Organization and Principal Activities

9 Months Ended

Sep. 30, 2023

1. Organization and Principal Activities

Description of Business

Sutro Biopharma, Inc. (the “Company”), is a clinical-stage oncology company developing site-specific and novel-format antibody drug conjugates, or ADCs. The Company was incorporated on April 21, 2003 and is headquartered in South San Francisco, California.

The Company operates in one business segment, the development of biopharmaceutical products.

At-The-Market Sales

During the three and nine months ended September 30, 2023, the Company sold zero shares and 1,857,410 shares, respectively, of its common stock through its At-the-Market Facility (“ATM Facility”) pursuant to its Open Market Sales AgreementSM dated April 2, 2021 with Jefferies LLC (“Jefferies”), as sales agent (the “Sales Agreement”).

During the three and nine months ended September 30, 2023, the gross proceeds from these sales were approximately zero and $12.4 million, respectively, before deducting fees of approximately zero and $0.4 million, respectively, resulting in net proceeds of approximately zero and $12.0 million, respectively, to the Company.

Liquidity

The Company has incurred significant losses and has negative cash flows from operations. As of September 30, 2023, the Company had an accumulated deficit of $590.5 million. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development and other operational activities.

As of September 30, 2023, the Company had unrestricted cash, cash equivalents, and marketable securities of $321.1 million and equity securities of $34.0 million, consisting solely of common stock of Vaxcyte, which are available to fund future operations. The Company will need to raise additional capital to support the completion of its research and development activities and to support its operations.

The Company believes that its unrestricted cash, cash equivalents, marketable securities and equity securities as of September 30, 2023, will enable the Company to maintain its operations for a period of at least 12 months following the filing date of its condensed financial statements.