Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchanges Commission (“SEC”) regarding interim financial reporting. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). AlloVir and its subsidiaries’ operating results are included in the Company’s condensed consolidated financial statements from the Closing Date of the Merger. All other accompanying financial data as of December 31, 2024, and for the three and six months ended June 30, 2024, include only the accounts and disclosures of Legacy Kalaris. All intercompany transactions and balances have been eliminated upon consolidation. As all of the disclosures required by GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with Legacy Kalaris' audited financial statements as of and for the year ended December 31, 2024 filed as Exhibit 99.5 to the Company’s Current Report on Form 8-K filed with the SEC on March 18, 2025. All historical common share data and per-share amounts prior to the Merger were retrospectively recast to reflect the effect of the exchange ratio of 0.2016 per one share, which was determined in accordance with the Merger Agreement. The number of authorized shares and par value per share were not recast. The conversion ratios for each series of redeemable convertible preferred stock, which were converted into shares of common stock in connection with the closing of the Merger, were proportionally recast.
Unaudited Condensed Financial Statements	Unaudited Condensed Financial Statements The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of the Company’s financial position as of June 30, 2025 and its results of operations for the three and six months ended June 30, 2025 and 2024 and its cash flows for the six months ended June 30, 2025 and 2024. The results of operations for the three and six months ended June 30, 2025 and 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2025, or for any other future annual or interim period. The consolidated balance sheet as of December 31, 2024 included herein was derived from the audited financial statements as of that date. Certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted from these unaudited condensed consolidated financial statements.
Leases	Leases The Company accounts for leases in accordance with ASC 842, Leases (“ASC 842”). The Company determines whether an arrangement is or contains a lease at the inception of the arrangement and whether such a lease should be classified as a financing lease or operating lease at the commencement date of the lease. The Company does not have any leases classified as financing leases. Operating leases with a term greater than one year are recognized on the consolidated balance sheets as operating right-of-use asset (“ROU asset”) and operating lease liabilities. The Company elected not to recognize the ROU assets and lease liabilities for leases with lease terms of one year or less (short-term leases). Lease liabilities and their corresponding ROU assets are recorded based on the present value of lease payments over the lease term. ROU assets are further adjusted for initial direct costs, prepaid rent, or incentives received, if any. The Company considers the lease term to be the noncancelable period that it has the right to use the underlying asset, together with any periods where it is reasonably certain it will exercise an option to extend (or not terminate) the lease. As the interest rate implicit in the Company’s lease contracts is not readily determinable, the Company utilizes its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments. Operating lease cost is recognized on a straight-line basis over the lease term. The Company has elected not to separate lease and non-lease components for its real estate leases and instead accounts for each separate lease component and the non-lease components associated with that lease component as a single lease component. Variable lease payments are not included in the measurement of ROU assets and lease liabilities, but rather are recognized as incurred.
Capitalized Software Implementation Costs	Capitalized Software Implementation Costs The Company incurred costs to implement cloud computing arrangements hosted by third-party vendors. ASC 350-40, Internal-Use Software, requires hosting arrangements that are service contracts to follow the guidance of internal-use software to determine which implementation costs can be capitalized. Implementation costs incurred during the application development stage are capitalized until the software is ready for its intended use. The costs are then amortized on a straight-line basis over the term of the associated hosting arrangement and are recognized as an operating expense with the condensed consolidated statement of operations. As of June 30, 2025 the Company capitalized $0.1 million software implementation costs within other non-current assets on the condensed consolidated balance sheets.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Pronouncements Not Yet Adopted ASU 2023-09, Income Taxes (Topic 740) In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The amendments are effective for fiscal years beginning after December 15, 2024 for all public entities. Early adoption is permitted and should be applied either prospectively or retrospectively. The Company is currently evaluating the impact that the updated standard will have on its consolidated financial statement disclosures. ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40) 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 to improve financial reporting by requiring that public business entities disclose additional information about specific expense categories in the notes to financial statements at interim and annual reporting periods. The amendments in this ASU do not change or remove current expense disclosure requirements; however, the amendments affect where such information appears in the notes to the financial statements because entities are required to include certain current disclosures in the same tabular format as the other disaggregation requirements in the amendments. This ASU is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact that the updated standard will have on its consolidated financial statement disclosures and financial reporting processes.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2025

The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchanges

Commission (“SEC”) regarding interim financial reporting. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). AlloVir and its subsidiaries’ operating results are included in the Company’s condensed consolidated financial statements from the Closing Date of the Merger. All other accompanying financial data as of December 31, 2024, and for the three and six months ended June 30, 2024, include only the accounts and disclosures of Legacy Kalaris. All intercompany transactions and balances have been eliminated upon consolidation.

As all of the disclosures required by GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with Legacy Kalaris' audited financial statements as of and for the year ended December 31, 2024 filed as Exhibit 99.5 to the Company’s Current Report on Form 8-K filed with the SEC on March 18, 2025.

All historical common share data and per-share amounts prior to the Merger were retrospectively recast to reflect the effect of the exchange ratio of 0.2016 per one share, which was determined in accordance with the Merger Agreement. The number of authorized shares and par value per share were not recast. The conversion ratios for each series of redeemable convertible preferred stock, which were converted into shares of common stock in connection with the closing of the Merger, were proportionally recast.

Unaudited Condensed Financial Statements

The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of the Company’s financial position as of June 30, 2025 and its results of operations for the three and six months ended June 30, 2025 and 2024 and its cash flows for the six months ended June 30, 2025 and 2024. The results of operations for the three and six months ended June 30, 2025 and 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2025, or for any other future annual or interim period. The consolidated balance sheet as of December 31, 2024 included herein was derived from the audited financial statements as of that date. Certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted from these unaudited condensed consolidated financial statements.

Leases

The Company accounts for leases in accordance with ASC 842, Leases (“ASC 842”). The Company determines whether an arrangement is or contains a lease at the inception of the arrangement and whether such a lease should be classified as a financing lease or operating lease at the commencement date of the lease. The Company does not have any leases classified as financing leases. Operating leases with a term greater than one year are recognized on the consolidated balance sheets as operating right-of-use asset (“ROU asset”) and operating lease liabilities. The Company elected not to recognize the ROU assets and lease liabilities for leases with lease terms of one year or less (short-term leases). Lease liabilities and their corresponding ROU assets are recorded based on the present value of lease payments over the lease term. ROU assets are further adjusted for initial direct costs, prepaid rent, or incentives received, if any. The Company considers the lease term to be the noncancelable period that it has the right to use the underlying asset, together with any periods where it is reasonably certain it will exercise an option to extend (or not terminate) the lease. As the interest rate implicit in the Company’s lease contracts is not readily determinable, the Company utilizes its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments.

Operating lease cost is recognized on a straight-line basis over the lease term. The Company has elected not to separate lease and non-lease components for its real estate leases and instead accounts for each separate lease component and the non-lease components associated with that lease component as a single lease component. Variable lease payments are not included in the measurement of ROU assets and lease liabilities, but rather are recognized as incurred.

Capitalized Software Implementation Costs

The Company incurred costs to implement cloud computing arrangements hosted by third-party vendors. ASC 350-40, Internal-Use Software, requires hosting arrangements that are service contracts to follow the guidance of internal-use software to determine which implementation costs can be capitalized. Implementation costs incurred during the application development stage are capitalized until the software is ready for its intended use. The costs are then amortized on a straight-line basis over the term of the associated hosting arrangement and are recognized as an operating expense with the condensed consolidated statement of operations. As of June 30, 2025 the Company capitalized $0.1 million software implementation costs within other non-current assets on the condensed consolidated balance sheets.

Recent Accounting Pronouncements

Recently Issued Accounting Pronouncements Not Yet Adopted

ASU 2023-09, Income Taxes (Topic 740)

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The amendments are effective for fiscal years beginning after December 15, 2024 for all public entities. Early adoption is permitted and should be applied either prospectively or retrospectively. The Company is currently evaluating the impact that the updated standard will have on its consolidated financial statement disclosures.

ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40)

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 to improve financial reporting by requiring that public business entities disclose additional information about specific expense categories in the notes to financial statements at interim and annual reporting periods. The amendments in this ASU do not change or remove current expense disclosure requirements; however, the amendments affect where such information appears in the notes to the financial statements because entities are required to include certain current disclosures in the same tabular format as the other disaggregation requirements in the amendments. This ASU is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact that the updated standard will have on its consolidated financial statement disclosures and financial reporting processes.