Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Consolidation The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the Company’s accounts and those of its former wholly owned Australian subsidiary, Kezar Life Sciences Australia Pty Ltd., a proprietary company limited by shares, which was dissolved as of September 29, 2025. All intercompany balances and transactions have been eliminated upon consolidation. The condensed consolidated balance sheet as of December 31, 2025 has been derived from the audited consolidated financial statements at that date but does not include all information and footnotes required by GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements included in the Annual Report. Unaudited Condensed Consolidated Financial Statements The accompanying financial information as of March 31, 2026 is unaudited. The condensed consolidated financial statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of our financial condition at the date of the interim balance sheet. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our Annual Report.
Consolidation	Basis of Presentation and Consolidation The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the Company’s accounts and those of its former wholly owned Australian subsidiary, Kezar Life Sciences Australia Pty Ltd., a proprietary company limited by shares, which was dissolved as of September 29, 2025. All intercompany balances and transactions have been eliminated upon consolidation. The condensed consolidated balance sheet as of December 31, 2025 has been derived from the audited consolidated financial statements at that date but does not include all information and footnotes required by GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements included in the Annual Report. Unaudited Condensed Consolidated Financial Statements The accompanying financial information as of March 31, 2026 is unaudited. The condensed consolidated financial statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of our financial condition at the date of the interim balance sheet. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our Annual Report.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant items subject to such judgments, estimates and assumptions include the valuation of marketable securities, impairment of long-lived assets, determining the fair-value of stock-based compensation, and evaluating the progress to completion of external research and development costs. Management bases its estimates on historical experience and on various other market-specific relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its judgments, estimates and assumptions or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s condensed consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2025-12 Codification Improvements (“ASU 2025-12”), which address thirty-three issues, representing amendments to Accounting Standard Codification topics that clarify, correct errors or make minor improvements. The amendments make the Codification easier to understand and apply. ASU 2025-12 is effective for the Company in its annual reporting for fiscal year 2027, and in interim periods beginning in fiscal year 2027. Early adoption and retrospective application are permitted on an issue-by-issue basis. The Company is currently evaluating the impact of the adoption of ASU 2025-12 on its financial statements. In December 2025, the FASB issued Accounting Standards Update No. 2025-11 Interim Reporting (Topic 270) – Narrow-Scope Improvements (“ASU 2025-11”), which clarifies the guidance in Topic 270 to improve the consistency of interim financial reporting. ASU 2025-11 provides a comprehensive list of required interim disclosures and introduces a disclosure principle requiring entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASU 2025-11 is effective for the Company in its annual reporting for fiscal year 2028, and in interim periods beginning in fiscal year 2028. Early adoption and retrospective application are permitted. The Company is currently evaluating the impact of the adoption of ASU 2025-11 on its financial statements. In September 2025, the FASB issued Accounting Standards Update No. 2025-06 Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Targeted Improvements to the Accounting for Internal-Use Software (“ASU 2025-06”) to clarify and modernize the accounting for costs related to internal-use software by removing all references to software development project stages and clarifying the threshold entities apply to begin capitalizing costs. ASU 2025-06 is effective for the Company in its annual reporting for fiscal year 2028 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of the adoption of ASU 2025-06 on its financial statements. In November 2024, the FASB issued Accounting Standards Update No. 2024-03 Income Statement– Reporting Comprehensive Income – Expense Disaggregation Disclosures (“ASU 2024-03”), which requires more detailed information about specified categories of expenses included in certain expense captions presented on the face of the income statement. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026 and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either prospectively to financial statements issued for reporting periods after the effective date of this ASU or retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of the adoption of ASU 2024-03 on its financial statements and related disclosures. There have been no other recent accounting pronouncements, changes in accounting pronouncements or recently adopted accounting guidance that are expected to have a material impact on the Company’s condensed consolidated financial statements upon adoption.
Fair Value Measurements	Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash equivalents, other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the condensed consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are required to be recognized or disclosed at fair value in the financial statements. The Company determines the fair value of Level 1 assets using quoted prices in active markets for identical assets. The Company reviews trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, which are obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. The Company did not have any financial assets or liabilities measured using Level 3 inputs as of March 31, 2026 or December 31, 2025.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2026

Basis of Presentation and Consolidation

The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the Company’s accounts and those of its former wholly owned Australian subsidiary, Kezar Life Sciences Australia Pty Ltd., a proprietary company limited by shares, which was dissolved as of September 29, 2025. All intercompany balances and transactions have been eliminated upon consolidation.

The condensed consolidated balance sheet as of December 31, 2025 has been derived from the audited consolidated financial statements at that date but does not include all information and footnotes required by GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements included in the Annual Report.

Unaudited Condensed Consolidated Financial Statements

The accompanying financial information as of March 31, 2026 is unaudited. The condensed consolidated financial statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of our financial condition at the date of the interim balance sheet. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our Annual Report.

Consolidation

Basis of Presentation and Consolidation

Unaudited Condensed Consolidated Financial Statements

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant items subject to such judgments, estimates and assumptions include the valuation of marketable securities, impairment of long-lived assets, determining the fair-value of stock-based compensation, and evaluating the progress to completion of external research and development costs. Management bases its estimates on historical experience and on various other market-specific relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates.

Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its judgments, estimates and assumptions or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s condensed consolidated financial statements.

Recently Issued Accounting Pronouncements

In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2025-12 Codification Improvements (“ASU 2025-12”), which address thirty-three issues, representing amendments to Accounting Standard Codification topics that clarify, correct errors or make minor improvements. The amendments make

the Codification easier to understand and apply. ASU 2025-12 is effective for the Company in its annual reporting for fiscal year 2027, and in interim periods beginning in fiscal year 2027. Early adoption and retrospective application are permitted on an issue-by-issue basis. The Company is currently evaluating the impact of the adoption of ASU 2025-12 on its financial statements.

In December 2025, the FASB issued Accounting Standards Update No. 2025-11 Interim Reporting (Topic 270) – Narrow-Scope Improvements (“ASU 2025-11”), which clarifies the guidance in Topic 270 to improve the consistency of interim financial reporting. ASU 2025-11 provides a comprehensive list of required interim disclosures and introduces a disclosure principle requiring entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASU 2025-11 is effective for the Company in its annual reporting for fiscal year 2028, and in interim periods beginning in fiscal year 2028. Early adoption and retrospective application are permitted. The Company is currently evaluating the impact of the adoption of ASU 2025-11 on its financial statements.

In September 2025, the FASB issued Accounting Standards Update No. 2025-06 Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Targeted Improvements to the Accounting for Internal-Use Software (“ASU 2025-06”) to clarify and modernize the accounting for costs related to internal-use software by removing all references to software development project stages and clarifying the threshold entities apply to begin capitalizing costs. ASU 2025-06 is effective for the Company in its annual reporting for fiscal year 2028 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of the adoption of ASU 2025-06 on its financial statements.

In November 2024, the FASB issued Accounting Standards Update No. 2024-03 Income Statement– Reporting Comprehensive Income – Expense Disaggregation Disclosures (“ASU 2024-03”), which requires more detailed information about specified categories of expenses included in certain expense captions presented on the face of the income statement. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026 and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either prospectively to financial statements issued for reporting periods after the effective date of this ASU or retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of the adoption of ASU 2024-03 on its financial statements and related disclosures.

There have been no other recent accounting pronouncements, changes in accounting pronouncements or recently adopted accounting guidance that are expected to have a material impact on the Company’s condensed consolidated financial statements upon adoption.

Fair Value Measurements

Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash equivalents, other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the condensed consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability.

The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are required to be recognized or disclosed at fair value in the financial statements. The Company determines the fair value

of Level 1 assets using quoted prices in active markets for identical assets. The Company reviews trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, which are obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data.

In certain cases, where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. The Company did not have any financial assets or liabilities measured using Level 3 inputs as of March 31, 2026 or December 31, 2025.