Organization	12 Months Ended
Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Description of the Business RAPT Therapeutics, Inc. (“RAPT” or the “Company”) is a clinical-stage, immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in inflammatory diseases and oncology. Utilizing its proprietary drug discovery and development engine, the Company develops highly selective small molecules that are designed to modulate the critical immune responses underlying these diseases. The Company is located in South San Francisco, California. Equity Financings In June 2021, pursuant to the shelf registration statement on Form S-3 that was declared effective by the Securities and Exchange Commission (“SEC”) on November 16, 2020, the Company completed an underwritten public offering (“2021 Public Offering”) of 4,356,060 shares of common stock, including 568,181 shares of common stock issued in connection with the exercise of the over-allotment option by the underwriters, at a public offering price of $33.00 per share. The Company received approximately $134.8 million in net proceeds from the 2021 Public Offering, after deducting underwriting discounts and other offering-related costs. In February 2020, the Company completed an underwritten follow-on public offering (“Follow‑on Offering”) of 2,500,000 shares of its common stock issued at an offering price of $30.00 per share. The Follow-on Offering generated approximately $69.8 million in net proceeds after deducting underwriting discounts and other offering related costs. In November 2020, the Company filed a shelf registration statement on Form S-3 with the SEC covering (a) up to $350 million of the Company’s securities, including up to $100 million of shares of common stock that may be offered and sold from time to time in one or more “at-the-market” offerings pursuant to a Controlled Equity Offering^SM Sales Agreement (“ATM Sales Agreement”) with Cantor Fitzgerald & Co. and Stifel, Nicolaus & Company, Incorporated, and (b) up to an aggregate of 1,000,000 shares of common stock that certain selling stockholders may offer and sell from time to time. During the year ended December 31, 2021, the Company sold 214,971 shares under the ATM Sales Agreement resulting in net proceeds of $4.7 million after deducting underwriting discounts and commissions and other offering related costs. During the year ended December 31, 2020, the Company sold 188,700 shares under the ATM Sales Agreement resulting in net proceeds of $3.8 million after deducting underwriting discounts and commissions and other offering related costs. As of December 31, 2021, there was up to $90.9 million of shares of common stock available for future issuance under the ATM Sales Agreement. Liquidity and Management Plans The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. Since inception, the Company has incurred net losses and negative cash flows from operations. During the year ended December 31, 2021, the Company incurred a net loss of $69.2 million and used $61.0 million of cash in operations. At December 31, 2021, the Company had cash and cash equivalents and marketable securities of $189.7 million and working capital of $183.4 million. Management plans to continue to incur substantial costs in order to conduct research and development activities and additional capital will be needed to undertake these activities. The Company intends to raise such capital through the issuance of additional equity, borrowings and strategic alliances with other companies. However, if such arrangements are not available at adequate levels or on acceptable terms, the Company would be required to significantly reduce operating expenses and delay or reduce the scope of or eliminate some of its development programs. Management believes that the Company’s current cash and cash equivalents and marketable securities will provide sufficient funds to enable the Company to meet its obligations for at least 12 months from the filing date of this report.

Organization

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Organization

Description of the Business

RAPT Therapeutics, Inc. (“RAPT” or the “Company”) is a clinical-stage, immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in inflammatory diseases and oncology. Utilizing its proprietary drug discovery and development engine, the Company develops highly selective small molecules that are designed to modulate the critical immune responses underlying these diseases. The Company is located in South San Francisco, California.

Equity Financings

In June 2021, pursuant to the shelf registration statement on Form S-3 that was declared effective by the Securities and Exchange Commission (“SEC”) on November 16, 2020, the Company completed an underwritten public offering (“2021 Public Offering”) of 4,356,060 shares of common stock, including 568,181 shares of common stock issued in connection with the exercise of the over-allotment option by the underwriters, at a public offering price of $33.00 per share. The Company received approximately $134.8 million in net proceeds from the 2021 Public Offering, after deducting underwriting discounts and other offering-related costs.

In February 2020, the Company completed an underwritten follow-on public offering (“Follow‑on Offering”) of 2,500,000 shares of its common stock issued at an offering price of $30.00 per share. The Follow-on Offering generated approximately $69.8 million in net proceeds after deducting underwriting discounts and other offering related costs.

In November 2020, the Company filed a shelf registration statement on Form S-3 with the SEC covering (a) up to $350 million of the Company’s securities, including up to $100 million of shares of common stock that may be offered and sold from time to time in one or more “at-the-market” offerings pursuant to a Controlled Equity Offering^SM Sales Agreement (“ATM Sales Agreement”) with Cantor Fitzgerald & Co. and Stifel, Nicolaus & Company, Incorporated, and (b) up to an aggregate of 1,000,000 shares of common stock that certain selling stockholders may offer and sell from time to time. During the year ended December 31, 2021, the Company sold 214,971 shares under the ATM Sales Agreement resulting in net proceeds of $4.7 million after deducting underwriting discounts and commissions and other offering related costs. During the year ended December 31, 2020, the Company sold 188,700 shares under the ATM Sales Agreement resulting in net proceeds of $3.8 million after deducting underwriting discounts and commissions and other offering related costs. As of December 31, 2021, there was up to $90.9 million of shares of common stock available for future issuance under the ATM Sales Agreement.

Liquidity and Management Plans

The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. Since inception, the Company has incurred net losses and negative cash flows from operations. During the year ended December 31, 2021, the Company incurred a net loss of $69.2 million and used $61.0 million of cash in operations. At December 31, 2021, the Company had cash and cash equivalents and marketable securities of $189.7 million and working capital of $183.4 million.

Management plans to continue to incur substantial costs in order to conduct research and development activities and additional capital will be needed to undertake these activities. The Company intends to raise such capital through the issuance of additional equity, borrowings and strategic alliances with other companies. However, if such arrangements are not available at adequate levels or on acceptable terms, the Company would be required to significantly reduce operating expenses and delay or reduce the scope of or eliminate some of its development programs. Management believes that the Company’s current cash and cash equivalents and marketable securities

will provide sufficient funds to enable the Company to meet its obligations for at least 12 months from the filing date of this report.