Organization	12 Months Ended
Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Description of the Business IDEAYA Biosciences, Inc. (the “Company”) is a synthetic lethality-focused precision medicine oncology company committed to the discovery and development of targeted therapeutics for patient populations selected using molecular diagnostics. The Company is headquartered in South San Francisco, California and was incorporated in the State of Delaware in June 2015. To date, the Company has been primarily engaged in business planning, research, development, recruiting and raising capital. Initial Public Offering On May 22, 2019, the Company’s registration statement on Form S-1 (File No. 333-231081) relating to its initial public offering (“IPO”) of common stock became effective. The IPO closed on May 28, 2019, at which time the Company issued 5,750,000 shares of its common stock at a price of $10.00 per share, which included shares issued upon the underwriters’ exercise of their overallotment option to purchase 750,000 additional shares. In addition, upon closing the IPO, all outstanding shares of the redeemable convertible preferred stock converted into 13,139,794 shares of common stock. The Company received an aggregate of $50.2 million in cash, net of underwriting discounts and commissions of $4.0 million, and after deducting offering costs of $3.3 million. Follow-On Offering On June 22, 2020, the Company completed an underwritten public offering and sold and issued 6,666,667 shares of common stock at a price to the public of $15.00 per share for gross proceeds of $100.0 million. On July 22, 2020, the Company sold and issued an additional 500,000 shares of common stock upon the exercise of the overallotment option by the underwriters for gross proceeds of $7.5 million. The aggregate net proceeds to the Company were $100.7 million after deducting underwriting discounts and commissions and other offering costs. On July 12, 2021, the Company completed an underwritten public offering and sold and issued 5,333,333 shares of common stock, which included shares issued upon the underwriters’ exercise in full of their overallotment option to purchase 695,652 additional shares, at a price to the public of $17.25 per share for net proceeds of $86.0 million, after deducting underwriting discounts and commissions and other offering expenses. Private Placement The Company entered into a stock purchase agreement with Glaxo Group Limited, or GGL, on June 17, 2020, pursuant to which, on August 3, 2020, the Company sold 1,333,333 shares at a price of $15.00 per shares to GGL for net proceeds of $20.0 million in a private placement. At-the-Market Offering On August 12, 2020, the Company filed a prospectus supplement to the prospectus dated June 10, 2020, activating its at-the-market facility by entering into an open market sale agreement (the “August 2020 Sales Agreement) with Jefferies LLC (“Jefferies”), pursuant to which the Company could offer and sell shares of its common stock with an aggregate offering price of up to $50.0 million under an “at the market” offering program. As of January 15, 2021, the Company exhausted all sales under the August 2020 Sales Agreement. On January 20, 2021, the Company entered into a new open market sale agreement (the “January 2021 Sales Agreement”) with Jefferies, pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $90.0 million under an “at the market” offering program. For the year ended December 31, 2021, the Company sold an aggregate of 3,407,872 shares for net proceeds of $57.3 million after deducting sales commission and other expenses under the August 2020 Sales Agreement and the January 2021 Sales Agreement. As of December 31, 2021, approximately $73.8 million of common stock remained available to be sold under the January 2021 Sales Agreement. Liquidity The Company has incurred significant losses and negative cash flows from operations in all periods since inception and had an accumulated deficit of $176.7 million as of December 31, 2021. The Company has historically financed its operations primarily through the sale of convertible notes, redeemable convertible preferred stock and common stock, and payments received from its collaboration arrangement. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue from commercial products since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed under Risks and Uncertainties in Note 2. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives. As of December 31, 2021, the Company had cash, cash equivalents and marketable securities of $368.1 million. Management believes that the Company’s current cash, cash equivalents and marketable securities will be sufficient to fund its planned operations for at least 12 months from the date of the issuance of these financial statements.

Organization

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Organization

Description of the Business

IDEAYA Biosciences, Inc. (the “Company”) is a synthetic lethality-focused precision medicine oncology company committed to the discovery and development of targeted therapeutics for patient populations selected using molecular diagnostics. The Company is headquartered in South San Francisco, California and was incorporated in the State of Delaware in June 2015. To date, the Company has been primarily engaged in business planning, research, development, recruiting and raising capital.

Initial Public Offering

On May 22, 2019, the Company’s registration statement on Form S-1 (File No. 333-231081) relating to its initial public offering (“IPO”) of common stock became effective. The IPO closed on May 28, 2019, at which time the Company issued 5,750,000 shares of its common stock at a price of $10.00 per share, which included shares issued upon the underwriters’ exercise of their overallotment option to purchase 750,000 additional shares. In addition, upon closing the IPO, all outstanding shares of the redeemable convertible preferred stock converted into 13,139,794 shares of common stock. The Company received an aggregate of $50.2 million in cash, net of underwriting discounts and commissions of $4.0 million, and after deducting offering costs of $3.3 million.

Follow-On Offering

On June 22, 2020, the Company completed an underwritten public offering and sold and issued 6,666,667 shares of common stock at a price to the public of $15.00 per share for gross proceeds of $100.0 million. On July 22, 2020, the Company sold and issued an additional 500,000 shares of common stock upon the exercise of the overallotment option by the underwriters for gross proceeds of $7.5 million. The aggregate net proceeds to the Company were $100.7 million after deducting underwriting discounts and commissions and other offering costs.

On July 12, 2021, the Company completed an underwritten public offering and sold and issued 5,333,333 shares of common stock, which included shares issued upon the underwriters’ exercise in full of their overallotment option to purchase 695,652 additional shares, at a price to the public of $17.25 per share for net proceeds of $86.0 million, after deducting underwriting discounts and commissions and other offering expenses.

Private Placement

The Company entered into a stock purchase agreement with Glaxo Group Limited, or GGL, on June 17, 2020, pursuant to which, on August 3, 2020, the Company sold 1,333,333 shares at a price of $15.00 per shares to GGL for net proceeds of $20.0 million in a private placement.

At-the-Market Offering

On August 12, 2020, the Company filed a prospectus supplement to the prospectus dated June 10, 2020, activating its at-the-market facility by entering into an open market sale agreement (the “August 2020 Sales Agreement) with Jefferies LLC (“Jefferies”), pursuant to which the Company could offer and sell shares of its common stock with an aggregate offering price of up to $50.0 million under an “at the market” offering program. As of January 15, 2021, the Company exhausted all sales under the August 2020 Sales Agreement. On January 20, 2021, the Company entered into a new open market sale agreement (the “January 2021 Sales Agreement”) with Jefferies, pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $90.0 million under an “at the market” offering program. For the year ended December 31, 2021, the Company sold an aggregate of 3,407,872 shares for net proceeds of $57.3 million after deducting sales commission and other expenses under the August 2020 Sales Agreement and the January 2021 Sales Agreement.

As of December 31, 2021, approximately $73.8 million of common stock remained available to be sold under the January 2021 Sales Agreement.

Liquidity

The Company has incurred significant losses and negative cash flows from operations in all periods since inception and had an accumulated deficit of $176.7 million as of December 31, 2021. The Company has historically financed its operations primarily through the sale of convertible notes, redeemable convertible preferred stock and common stock, and payments

received from its collaboration arrangement. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue from commercial products since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed under Risks and Uncertainties in Note 2. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives.

As of December 31, 2021, the Company had cash, cash equivalents and marketable securities of $368.1 million. Management believes that the Company’s current cash, cash equivalents and marketable securities will be sufficient to fund its planned operations for at least 12 months from the date of the issuance of these financial statements.