IDEAYA Biosciences, Inc. New Standards Disclosure

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) under its accounting standard codifications (“ASC”) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below.

New Accounting Pronouncements Adopted

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) under its accounting standard codifications (“ASC”) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below.

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which amends the guidance in ASC 740, Income Taxes. The ASU is intended to improve the transparency of income tax disclosures by requiring (1) consistent categories and greater disaggregation of information in the rate reconciliation and (2) income taxes paid disaggregated by jurisdiction. It also includes certain other amendments to improve the effectiveness of income tax disclosures. The ASU’s amendments are effective for public business entities for annual periods beginning after December 15, 2024. The Company adopted this ASU on a retrospective basis for the annual report for the fiscal year beginning January 1, 2025, and evaluated the impact of the adoption of the ASU. This ASU resulted in expanded disclosures in the Income Taxes footnote in this Form 10-K. See Note 7. Income Taxes.

New Accounting Pronouncements, Not yet Adopted

In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative, which modifies the disclosure or presentation requirements related to a variety of FASB Accounting Standard Codification topics. The effective date for each amendment will be the date on which the SEC’s removal of that related disclosure from Regulation S-X or Regulation S-K is effective. If by June 30, 2027, the SEC has not removed the applicable requirement from Regulation S-X or Regulation S-K, the pending content of the

associated amendment will be removed from the Codification and will not become effective for any entities. The Company is currently evaluating the effect of adopting this ASU.

In November 2024, the FASB issued ASU 2024-03 - Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The ASU requires more detailed disclosures about the types of expenses in commonly presented expense captions such as cost of sales, selling, general and administrative expenses and research and development expenses. This includes separate footnote disclosure for expenses such as purchases of inventory, employee compensation, depreciation, and intangible asset amortization. Public business entities are required to apply the guidance prospectively and may apply it retrospectively. The FASB additionally issued ASU 2025-01 to clarify that the ASU's amendments are effective for public business entities for annual periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Public business entities are required to apply the guidance prospectively and may apply it retrospectively. The Company is currently evaluating the effect of adopting this ASU.

In July 2025, the FASB issued ASU 2025-05 - Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets to simplify the estimation of credit losses on current accounts receivable and current contract assets arising from transactions accounted for under ASC 606. The amendments allow all entities to apply a practical expedient and entities other than public business entities to make an accounting policy election to simplify the estimation of credit losses on these assets. The amendments in this ASU are effective for all entities for annual reporting periods beginning after 15 December 2025, and interim reporting periods within those annual reporting periods. Early adoption is permitted in an interim or annual reporting period in which financial statements have not yet been issued (or made available for issuance). The Company is currently evaluating the impact of the ASU, but does not expect any material impact upon adoption.

In September 2025, the FASB issued ASU 2025-06 — Intangibles — Goodwill and Other — Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software to clarify and modernize the accounting for costs related to internal-use software. The ASU removes all references to project stages in ASC 350-40 and clarifies the threshold entities apply to begin capitalizing costs. The ASU specifies that the property, plant and equipment disclosure requirements under ASC 360-10 apply to capitalized software costs accounted for under ASC 350-40, regardless of how those costs are presented in the financial statements. The amendments in this ASU are effective for all entities for annual reporting periods beginning after 15 December 2027, and interim reporting periods within those annual reporting periods. Early adoption is permitted in an interim or annual reporting period in which financial statements have not yet been issued. The Company is currently evaluating the effect of adopting this ASU.

In December 2025, the FASB issued ASU 2025-11 — Interim Reporting (Topic 270): Narrow-Scope Improvements to clarify interim disclosure requirements, the applicability of ASC 270 and the form and content of interim financial statements in accordance with US GAAP. The guidance creates a comprehensive list of interim disclosures required under US GAAP and incorporates a disclosure principle that requires disclosures at interim periods when an event or change that has a material effect on an entity has occurred since the previous year end. For public business entities, the amendments in this ASU are effective for interim reporting periods within annual reporting periods beginning after 15 December 2027. Early adoption is permitted in an interim or annual reporting period in which financial statements have not yet been issued. The Company is currently evaluating the effect of adopting this ASU.

In December 2025, the FASB issued ASU 2025-12 — Codification Improvements to clarify, correct errors in or make other minor improvements to a broad range of topics in the Accounting Standards Codification (ASC) that is intended to make it easier to understand and apply, including ASC 260, Earnings Per Share, ASC 325, Investments – Other, and ASC 958, Not-for-Profit Entities. The amendments in this ASU are effective for all entities for annual reporting periods beginning after 15 December 2026, and interim reporting periods within those annual reporting periods. Early adoption is permitted in an interim or annual reporting period in which financial statements have not yet been issued. The Company is currently evaluating the effect of adopting this ASU.