Nature of the Business and Basis of Presentation	12 Months Ended
Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	Note 1. Nature of the business C4 Therapeutics, Inc., or, together with its subsidiary, the Company, is a clinical-stage biopharmaceutical company dedicated to advancing targeted protein degradation science to develop a new generation of small-molecule medicines to transform how disease is treated. C4T leverages its proprietary technology platform, TORPEDO (Target ORiented ProtEin Degrader Optimizer), to efficiently design and optimize small-molecule medicines that harness the body’s natural protein recycling system to rapidly degrade disease-causing protein, offering the potential to overcome drug resistance, drug undruggable targets and improve patient outcomes. C4T uses the TORPEDO platform to advance multiple targeted oncology programs to the clinic while expanding the platform to deliver the next wave of medicines for difficult-to-treat diseases. The Company was incorporated in Delaware on October 7, 2015 and has its principal office in Watertown, Massachusetts. Liquidity and capital resources Since its inception, the Company’s primary activities have been focused on research and development activities, building the Company’s intellectual property, recruiting personnel and raising capital to support these activities. To date, the Company has funded its operations primarily with proceeds received from the sales of redeemable convertible preferred stock, public offerings of the Company’s common stock, through its collaboration agreements, and debt financing. The Company has incurred recurring losses since its inception, including net losses of $83.9 million, $66.3 million, and 34.1 million, for the years ended December 31, 2021, 2020, and 2019, respectively. In addition, as of December 31, 2021, the Company had an accumulated deficit of $267.7 million. To date, the Company has not generated any revenue from product sales as none of its product candidates has been approved for commercialization. The Company expects to continue to generate operating losses for the foreseeable future. As further discussed in Note 10, Stockholders’ equity, on October 6, 2020, the Company completed its initial public offering, or the IPO. The net proceeds to the Company from the IPO were $191.2 million, after deducting expenses and underwriting discounts and commissions. Upon the closing of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock automatically converted into 30,355,379 shares of common stock. In June 2021, the Company completed a follow-on public offering. The net proceeds to the Company from the follow-on public offering were $169.5 million, after deducting expenses and underwriting discounts and commissions. The Company expects that its cash, cash equivalents and marketable securities of $451.5 million as of December 31, 2021 will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these consolidated financial statements. Accordingly, the consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. Reverse stock split On September 25, 2020, the Company effected a one-for-8.4335 reverse stock split of its issued and outstanding common stock and stock options, and a proportional adjustment to the existing conversion ratios for the Company’s redeemable convertible preferred stock. Accordingly, all issued and outstanding common stock, options to purchase common stock and per share amounts contained in the consolidated financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented, except as otherwise stated. Risks and uncertainties The Company is subject to risks common to other life science companies in the early development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology and intellectual property, ability to raise additional financing and compliance with the Food and Drug Administration, or the FDA, and other government regulations. If the Company does not successfully advance its programs into and through human clinical trials and commercialize any of its product candidates either directly or through collaborations with other companies, the Company may be unable to produce product revenue or achieve profitability. There can be no assurance that the Company’s research and development efforts will be successful, adequate protection for the Company’s intellectual property will be obtained, any products developed will obtain necessary government regulatory approval, or any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies.

Nature of the Business and Basis of Presentation

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of the Business and Basis of Presentation

Note 1. Nature of the business

C4 Therapeutics, Inc., or, together with its subsidiary, the Company, is a clinical-stage biopharmaceutical company dedicated to advancing targeted protein degradation science to develop a new generation of small-molecule medicines to transform how disease is treated. C4T leverages its proprietary technology platform, TORPEDO (Target ORiented ProtEin Degrader Optimizer), to efficiently design and optimize small-molecule medicines that harness the body’s natural protein recycling system to rapidly degrade disease-causing protein, offering the potential to overcome drug resistance, drug undruggable targets and improve patient outcomes. C4T uses the TORPEDO platform to advance multiple targeted oncology programs to the clinic while expanding the platform to deliver the next wave of medicines for difficult-to-treat diseases. The Company was incorporated in Delaware on October 7, 2015 and has its principal office in Watertown, Massachusetts.

Liquidity and capital resources

Since its inception, the Company’s primary activities have been focused on research and development activities, building the Company’s intellectual property, recruiting personnel and raising capital to support these activities. To date, the Company has funded its operations primarily with proceeds received from the sales of redeemable convertible preferred stock, public offerings of the Company’s common stock, through its collaboration agreements, and debt financing.

The Company has incurred recurring losses since its inception, including net losses of $83.9 million, $66.3 million, and 34.1 million, for the years ended December 31, 2021, 2020, and 2019, respectively. In addition, as of December 31, 2021, the Company had an accumulated deficit of $267.7 million. To date, the Company has not generated any revenue from product sales as none of its product candidates has been approved for commercialization. The Company expects to continue to generate operating losses for the foreseeable future.

As further discussed in Note 10, Stockholders’ equity, on October 6, 2020, the Company completed its initial public offering, or the IPO. The net proceeds to the Company from the IPO were $191.2 million, after deducting expenses and underwriting discounts and commissions. Upon the closing of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock automatically converted into 30,355,379 shares of common stock. In June 2021, the Company completed a follow-on public offering. The net proceeds to the Company from the follow-on public offering were $169.5 million, after deducting expenses and underwriting discounts and commissions.

The Company expects that its cash, cash equivalents and marketable securities of $451.5 million as of December 31, 2021 will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these consolidated financial statements. Accordingly, the consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business.

Reverse stock split

On September 25, 2020, the Company effected a one-for-8.4335 reverse stock split of its issued and outstanding common stock and stock options, and a proportional adjustment to the existing conversion ratios for the Company’s redeemable convertible preferred stock. Accordingly, all issued and outstanding common stock, options to purchase common stock and per share amounts contained in the consolidated financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented, except as otherwise stated.

Risks and uncertainties

The Company is subject to risks common to other life science companies in the early development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology and intellectual property, ability to raise additional financing and compliance with the Food and Drug Administration, or the FDA, and other government regulations. If the Company does not successfully advance its programs into and through human clinical trials and commercialize any of its product candidates either directly or through collaborations with other companies, the Company may be unable to produce product revenue or achieve profitability. There can be no assurance that the Company’s research and development efforts will be successful, adequate protection for the Company’s intellectual property will be obtained, any products developed will obtain necessary government regulatory approval, or any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product

sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies.