Cartesian Therapeutics Inc

Evaluation of Disclosure Controls and Procedures

Our management, with the participation of our Chief Executive Officer and Chief Financial Officer, evaluated, as of the end of the period covered by this Annual Report, the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act). Based on that evaluation, our Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures were not effective at the reasonable assurance level as of December 31, 2023 because of the material weakness in internal control over financial reporting discussed below.

Management’s Annual Report on Internal Control over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over our financial reporting, as such term is defined in Rule 13a-15(f) and 15d-15(f) under the Exchange Act.

Our management conducted an assessment of the effectiveness of our internal control over financial reporting based on the criteria set forth in “Internal Control - Integrated Framework (2013)” issued by the Committee of Sponsoring Organizations of the Treadway Commission.

Management’s assessment of and conclusion on the effectiveness of internal control over financial reporting did not include the internal controls of Old Cartesian, which is included in our consolidated financial statements as of and for the year ended December 31, 2023 and constituted 2% and 1% of total assets and total liabilities, respectively, as of December 31, 2023 and 0% and 1% of revenues and operating expenses, respectively, for the year then ended.

Based on this assessment, our management concluded that, as of December 31, 2023, our internal control over financial reporting was not effective.

As a result of its review, management identified a material weakness. A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that a reasonable possibility exists that a material misstatement of our annual or interim financial statements would not be prevented or detected on a timely basis. There are no material accounting errors or omissions within the consolidated financial statements as a result of this material weakness. Management concluded that it did not design and implement effective internal controls specifically related to the documentation of the assumptions supporting the valuation of the in-process intangible assets in connection with the Old Cartesian material business combination and the initial and ongoing contingent value right obligation issued at the time to legacy Selecta stockholders. This includes a lack of sufficient documentation to provide evidence of the associated management review controls.

Remediation Plans for Material Weakness in Internal Control over Financial Reporting

We are committed to maintaining a strong internal control environment. In response to the identified material weakness above, we, with the oversight of the Audit Committee, intend to take comprehensive actions to remediate the material weakness in internal control over financial reporting. We expect to re-evaluate the scope and level of precision for conducting and documenting the reviews over significant acquisitions and contingent value rights including the review of prospective financial information used in valuation reports produced by third-party specialists supporting the accounting for business combinations and contingent value rights. The remediation efforts are intended both to address the identified material weakness and to enhance our overall financial control environment.

Inherent Limitations of Internal Controls

While we believe we have a robust and efficient system of internal and disclosure controls and procedures, our management, including our Chief Executive Officer and Chief Financial Officer, recognize that it is impossible for our disclosure controls and procedures or our internal controls to prevent all errors and all fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met. Because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and instances of fraud, if any, within our company have been detected. These inherent limitations include the realities that judgments in decision-making can be faulty, and that breakdowns can occur because of a simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more people, or by management override of the control. The design of any system of controls also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Over time, controls may become inadequate because of changes in conditions, or the degree of compliance with the policies or procedures may deteriorate. Projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected.

Changes in Internal Control over Financial Reporting

Except for our identification and assessment of the material weakness described above, there have been no changes in our internal control over financial reporting as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act during the three months ended December 31, 2023 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Attestation Report of the Registered Public Accounting Firm

Ernst & Young LLP has independently assessed the effectiveness of our internal control over financial reporting as of December 31, 2023 and its report is included below.

Report of Independent Registered Public Accounting Firm

To the Stockholders and the Board of Directors of Cartesian Therapeutics, Inc.

Opinion on Internal Control over Financial Reporting

We have audited Cartesian Therapeutics, Inc.’s internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework) (the COSO criteria). In our opinion, because of the effect of the material weakness described below on the achievement of the objectives of the control criteria, Cartesian Therapeutics, Inc. (and subsidiaries) (the Company) has not maintained effective internal control over financial reporting as of December 31, 2023, based on the COSO criteria.

As indicated in the accompanying Management’s Annual Report on Internal Control Over Financial Reporting, management’s assessment of and conclusion on the effectiveness of internal control over financial reporting did not include the internal controls of Cartesian Bio, LLC, formerly known as Cartesian Therapeutics, Inc. (Old Cartesian), which is included in the 2023 consolidated financial statements of the Company and constituted 2% and 1% of total assets and total liabilities, respectively, as of December 31, 2023 and 0% and 1% of revenues and operating expenses, respectively, for the year then ended. Our audit of internal control over financial reporting of the Company also did not include an evaluation of the internal control over financial reporting of Old Cartesian.

A material weakness is a deficiency, or combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of the company’s annual or interim financial statements will not be prevented or detected on a timely basis. The following material weakness has been identified and included in management’s assessment. Management has identified a material weakness in the design and operation of controls related to the valuation of the in-process intangible assets acquired as part of the Old Cartesian business combination and the Selecta Biosciences, Inc. contingent value right obligation.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated balance sheet of the Company as of December 31, 2023 and 2022, the related consolidated statements of operations and comprehensive income (loss), changes in convertible preferred stock and stockholders’ equity (deficit) and cash flows for each of the three years in the period ended December 31, 2023, and the related notes and our report dated March 7, 2024 expressed an unqualified opinion thereon.

Basis for Opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects.

Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

/s/ Ernst & Young LLP

Boston, Massachusetts

March 7, 2024