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. Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Chief Executive Officer, the Company’s chief operating decision maker, in deciding how to allocate resources and assessing performance. The Company operates and manages its business as one operating segment. The Company’s Chief Executive Officer reviews financial information on an aggregate basis for the purposes of allocating and evaluating financial performance.

All of the Company’s long-lived assets are maintained in the United States.

At-The-Market Sales

During the year ended December 31, 2023, the Company sold an aggregate of 1,857,410 shares 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 year ended December 31, 2023, the gross proceeds from these sales were approximately $12.4 million, before deducting fees of approximately $0.4 million, resulting in net proceeds of approximately $12.0 million, to the Company.

Liquidity

The Company has incurred significant losses and has negative cash flows from operations. As of December 31, 2023, there was an accumulated deficit of $559.4 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 December 31, 2023, the Company had unrestricted cash, cash equivalents and marketable securities of $333.7 million and equity securities of $41.9 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 investments in equity securities as of December 31, 2023 will enable the Company to maintain its operations for a period of at least 12 months following the filing date of these financial statements.