Cartesian Therapeutics, Inc.

On January 31, 2024 the Board of Directors unanimously approved and recommended that our stockholders approve an amendment to our Current Charter to effect a reverse stock split of our issued and outstanding Common Stock using a ratio in the range of 1-for-20 and 1-for-30, with the specific ratio and the implementation and timing of such reverse stock split to be determined at the discretion of the Board of Directors. If Proposal No. 2 is approved, the Board of Directors may determine to effect the reverse stock split at any time prior to the date of the 2024 annual meeting of stockholders.

The reverse stock split will not change the number of authorized shares of Common Stock, the terms of our Common Stock or the relative voting power of our stockholders. Because the number of authorized shares will not be reduced, the number of authorized but unissued shares of our Common Stock will materially increase and will be available for reissuance by the Company. The reverse stock split, if effected, would affect all of our holders of Common Stock uniformly. If effected, the reverse stock split would also adjust the ratio into which the Series A Preferred Stock converts into Common Stock at the same ratio as the underlying Common Stock is adjusted.

Upon receiving stockholder approval of a reverse stock split, the Board of Directors will have the authority, but not the obligation, to elect, in its sole discretion, without further action on the part of our stockholders and as it determines to be in our and our stockholders’ best interests, to effect the reverse stock split and, if so, to select the reverse stock split ratio from within the approved range of ratios described above, each ratio within such range having been approved by our stockholders. We believe that enabling the Board of Directors to select the ratio from within the stated range will provide us with the flexibility to implement the reverse stock split in a manner designed to maximize the anticipated benefits for our stockholders. In determining the ratio following the receipt of stockholder approval, the Board of Directors may consider, among other factors, the following:

If Proposal No. 2 is approved by the stockholders and the Board of Directors determines to implement a reverse stock split, we will file an amendment to our Current Charter (the “Amendment”) with the Delaware Secretary of State. This description of the Amendment is qualified in its entirety by reference to the complete text of the Amendment, which is attached as Annex A to this proxy statement and incorporated into this proposal by reference. You are strongly encouraged to read the actual text of the Amendment. The proposed Amendment is subject to revision for such changes as may be required by the DGCL and any other changes consistent with Proposal No. 2 that we may deem necessary or appropriate.

If Proposal No. 2 is approved by the stockholders and a reverse stock split is implemented by the Board of Directors, no less than 20 and no more than 30 shares of issued and outstanding Common Stock, as determined by the Board of Directors, will be combined into one share of Common Stock; and shares of issued and outstanding Common Stock will be combined at the same ratio. Holders will receive a cash payment, in lieu of any fractional share. See the section below titled “Proposal No. 2—Reverse Stock Split Proposal—Principal Effects of Reverse Stock Split—Fractional Shares” for more information. The Amendment, if adopted, will include only the reverse stock split ratio determined by the Board of Directors to be in the best interest of the Company and its stockholders and all of the other ratios approved by our stockholders within the proposed range will be abandoned.

The Board of Directors reserves the right to elect not to effect a reverse stock split, including any or all reverse stock split ratios within the proposed range, if it determines, in its sole discretion, that implementing a reverse stock split is not in the best interest of the Company and its stockholders.

Background and Reasons for a Reverse Stock Split

We are seeking, and the Board of Directors has recommended, approval for Proposal No. 2 primarily to provide the Board of Directors with authority to effect a reverse stock split to maintain our listing on the Nasdaq Global Market. However, we cannot provide assurance that a reverse stock split would achieve its intended or desired benefits, and we strongly encourage you to review the discussion below under “Proposal No. 2—Reverse Stock Split Proposal—Risks and Potential Disadvantages Associated with a Reverse Stock Split.”

Nasdaq Continued Listing Requirements

Nasdaq Listing Rule 5450(a)(1) requires that the average closing price of a listed company’s common stock not fall below $1.00 per share over a consecutive 30 business day period. If we were to fail to satisfy this rule and regain compliance within the specified cure period, our Common Stock would be subject to delisting. If our Common Stock is delisted from the Nasdaq Global Market, or if the per-share price of our Common Stock otherwise declines, our ability to raise or access additional necessary capital through equity or debt financing, or use our shares for business development or other corporate initiatives would be significantly impaired, and the ownership dilution to stockholders caused by our issuing equity in financing or other transactions would be significantly increased.

General Investment Considerations

Additionally, we believe that a reverse stock split could make our Common Stock more attractive to a broader range of institutional and other investors. In particular, many brokerage houses, institutional investors and investment funds have internal policies and practices that may prohibit them from investing in low-priced stocks or discourage individual brokers from recommending low-priced stocks to their customers. Moreover, because brokers’ commissions on low-priced stocks generally represent a relatively high percentage of the stock price, transaction costs would represent a higher percentage of total share value, which could result in decreased trading volume and increased volatility in the trading price of our Common Stock. We believe that a reverse stock split could make our Common Stock a more attractive investment for many investors, which could enhance the liquidity of our Common Stock.

Risks and Potential Disadvantages Associated with a Reverse Stock Split

The Board of Directors believes that a reverse stock split is a potentially effective means to increase the per-share market price of our Common Stock and thus enable our compliance with Nasdaq's minimum share price requirement. However, there are a number of risks and potential disadvantages associated with a reverse stock split, including the following:

brokerage houses, institutional investors or investment funds. Further, other factors, such as our financial results, market conditions and the market perception of our business, may adversely affect the interest of new investors in the shares of our Common Stock. As a result, the trading liquidity of the shares of our Common Stock may not improve as a result of a reverse stock split and there can be no assurance that a reverse stock split, if completed, will result in the intended benefits described above.

Procedures

A reverse stock split would become effective upon the filing of the Amendment with the Delaware Secretary of State. The exact timing of the filing of the Amendment, if it is filed, would be determined by the Board of Directors based on its evaluation as to when such action would be in our and our stockholders’ best interests. In addition, the Board of Directors reserves the right, notwithstanding stockholder approval and without further action by the stockholders, to elect not to proceed with a reverse stock split if, at any time prior to filing the Amendment, the Board of Directors determines in its sole discretion that it is not in our best interest and the best interest of our stockholders to proceed with a reverse stock split. Following are descriptions of how a reverse stock split would be implemented for beneficial holders, registered book entry holders, and certificated holders.

Beneficial Holders. Upon the implementation of a reverse stock split, we intend to treat shares held bystockholders through a broker, bank or other agent in the same manner as registered stockholders whose sharesare registered in their names. Brokers, banks and other agents would be instructed to effect a reverse stock splitfor their beneficial holders holding our Common Stock in street name. However, these brokers, banks and other agents may have different procedures than registered stockholders for processing a reverse stock split. Stockholders who hold shares of our Common Stock with a broker, bank or other agent and who have anyquestions in this regard are strongly encouraged to contact their brokers, banks or other agents for more information.

Registered Book Entry Holders. Certain of our registered holders of Common Stock may hold some or all oftheir shares electronically in book-entry form with Equiniti, our transfer agent. These stockholders do not have stock certificates evidencing their ownership of the Common Stock. They are, however, provided with astatement reflecting the number of shares registered in their accounts. If a reverse stock split is implemented, stockholders who hold shares electronically in book-entry form with Equiniti would not need to take action toreceive whole shares of post-reverse split Common Stock as the exchange will be automatic.

Certificated Holders. If a reverse stock split is implemented, stockholders holding shares of our Common Stockin certificated form would be sent a letter of transmittal by Equiniti following the reverse stock split. The letterof transmittal would contain instructions on how a stockholder should surrender their certificate(s) representing shares of our Common Stock (the “Old Certificates”) to Equiniti in exchange for certificates representing theappropriate number of whole shares of post-reverse split Common Stock (the “New Certificates”). No New Certificates would be issued to a stockholder until such stockholder delivered to Equiniti all Old Certificates, together with a properly completed and executed letter of transmittal, or a notification that the Old Certificates have been lost, stolen or destroyed and the execution of an agreement satisfactory to us to indemnify us for any loss incurred by it in connection with such Old Certificates. No stockholder would be required to pay a transfer or other fee to exchange their Old Certificates. Stockholders would then receive one or more New Certificate(s) representing the number of whole shares of Common Stock they are entitled to as a result of a reverse stock split, subject to the treatment of fractional shares described below. Until surrendered, we would deem outstanding Old Certificates held by stockholders to be canceled and only to represent the number of whole shares of post-reverse split Common Stock to which these stockholders are entitled and the right to receive cash in lieu of any fractional shares as described below. Any Old Certificates submitted for exchange, whether because of a sale, transfer or other disposition of stock, would automatically be exchanged for New Certificates. If an Old Certificate has a restrictive legend on it, the New Certificate would be issued with the same restrictive legends that are on the Old Certificate. If a reverse stock split is implemented, we expect that Equiniti would act as the exchange agent for purposes of implementing the exchange of stock certificates. No service charges would be payable by holders of shares of Common Stock in connection with the exchange of certificates. We would bear all such expenses.

STOCKHOLDERS SHOULD NOT DESTROY ANY STOCK CERTIFICATES. STOCKHOLDERS SHOULD NOT SUBMIT STOCK CERTIFICATES FOR EXCHANGE UNLESS AND UNTIL REQUESTED TO DO SO, AND THEN STOCK CERTIFICATES SHOULD BE SUBMITTED ONLY IN THE MANNER INSTRUCTED. STOCK CERTIFICATES SHOULD NOT BE SUBMITTED DIRECTLY TO THE COMPANY.

Principal Effects of Reverse Stock Split

Outstanding Shares of Common Stock

Depending on the ratio for a reverse stock split determined by the Board of Directors, a minimum of 20 and a maximum of 30 shares of issued and outstanding Common Stock would be combined into one new share of Common Stock.

Our Current Charter provides that upon any reclassification or combination of outstanding shares of Common Stock, all outstanding shares of Common Stock will be concurrently and proportionately reclassified or combined in a manner that maintains the same proportionate equity ownership and voting rights among the holders of outstanding Common Stock and the holders of outstanding Common Stock on the record date for the reclassification or combination.

The actual number of shares issued after giving effect to a reverse stock split, if implemented, would depend on the reverse stock split ratio that is ultimately selected by the Board of Directors. A reverse stock split would affect all holders of our Common Stock uniformly and would not affect any stockholder’s percentage ownership interest in the Company, except that, as described below in the section titled “Proposal No. 2—Reverse Stock Split Proposal—Principal Effects of Reverse Stock Split—Fractional Shares,” stockholders of record otherwise entitled to a fractional share, as a result of a reverse stock split, would instead receive an amount in cash. In addition, a reverse stock split would not affect any stockholder’s proportionate voting power, except for adjustments that may result from the treatment of fractional shares as described below. A reverse stock split may result in some stockholders owning “odd lots” of less than 100 shares of Common Stock. Odd lot shares may be more difficult to sell, and brokerage commissions and other costs of transactions in odd lots are generally somewhat higher than the costs of transactions in “round lots” of even multiples of 100 shares.

Increase in Authorized Shares of Common Stock

By reducing the number of shares outstanding without reducing the number of shares of available but unissued Common Stock, a reverse stock split will increase the number of authorized but unissued shares of Common Stock that may be issued. We may use authorized shares in connection with the financing of future mergers or acquisitions.

Although the reverse stock split would not have any dilutive effect on our stockholders, a reverse stock split without a reduction in the number of shares authorized for issuance would reduce the proportion of shares owned by our stockholders relative to the number of shares authorized for issuance, giving the Board of Directors an effective increase in the authorized shares available for issuance, in its discretion. The Board of Directors from time to time may deem it to be in the best interests of the Company and our stockholders to enter into transactions and other ventures that may include the issuance of shares of our Common Stock. If the Board of

Directors authorizes the issuance of additional shares subsequent to the reverse stock split described above, the dilution to the ownership interest of our existing stockholders may be greater than would occur had the reverse stock split not been effected. Many stock issuances not involving equity compensation do not require stockholder approval, and the Board of Directors generally seeks approval of our stockholders in connection with a proposed issuance only if required at that time.

A reverse stock split would not have any effect on the number of authorized shares of Series A Preferred Stock, which would remain at 10,000,000 shares of Series A Preferred Stock, par value $0.0001 per share. However, if effected, the reverse stock split would also adjust the ratio into which the Series A Preferred Stock converts into Common Stock at the same ratio as the underlying Common Stock is adjusted.

Fractional Shares

We would not issue fractional shares in connection with a reverse stock split. Therefore, we would not issue certificates representing fractional shares resulting from the reverse stock split because the stockholder owns a number of shares of our Common Stock not evenly divisible by the ratio.

Equiniti will aggregate all fractional shares of Common Stock and sell them as soon as practicable after the effective time of the reverse stock split at the then-prevailing prices on the open market, on behalf of those stockholders who would otherwise be entitled to receive a fractional share of Common Stock as a result of the reverse stock split. We expect that Equiniti will conduct the sale in an orderly fashion at a reasonable pace and that it may take several days to sell all of the aggregated fractional shares of our Common Stock (the “Aggregated Fractional Shares”). After Equiniti’s completion of such sale, stockholders who would have been entitled to a fractional share of Common Stock will instead receive a cash payment from Equiniti in an amount equal to their respective pro rata shares of the total proceeds of that sale (the “Total Sale Proceeds”) and, where shares of Common Stock are held in certificated form, upon the surrender of the holder’s Old Certificates.

Holders of Common Stock would receive, in lieu of any fractional share, an amount in cash (without interest) equal to such fraction multiplied by a share price equal to the Total Sale Proceeds divided by the Aggregated Fractional Shares.

Stockholders will not be entitled to receive interest for the period of time between the effective time of the reverse stock split and the date payment is made for their fractional share interest. You should also be aware that, under the escheat laws of certain jurisdictions, sums due for fractional interests that are not timely claimed after the funds are made available may be required to be paid to the designated agent for each such jurisdiction. Thereafter, stockholders otherwise entitled to receive such funds may have to obtain the funds directly from the state to which they were paid.

Effects on Equity Compensation Plans and Awards and Warrants

If a reverse stock split is implemented, proportionate adjustments would generally be made in accordance with applicable tax laws with regard to:

In the case of options or other rights to acquire shares of our Common Stock, these adjustments would result in approximately the same aggregate price required under such options or other rights upon exercise, conversion, or settlement, and approximately the same value of shares of Common Stock being delivered upon such exercise, conversion, or settlement, immediately following a reverse stock split as was the case immediately preceding such reverse stock split.

In the case of our outstanding warrants, the number of shares issuable under the warrants will be proportionately decreased and the exercise price of each warrant proportionately increased.

The number of shares of Common Stock issuable upon exercise or vesting of outstanding equity awards, options and warrants and the per-share exercise or purchase price related thereto, if any, would be equitably adjusted in accordance with the terms of our applicable equity incentive plans, or such stock option grants or warrants, as the case may be, which may include rounding the number of shares of Common Stock issuable down to the nearest whole share or the payment of cash for fractional shares.

Exchange Act Registration; Nasdaq Listing; CUSIP

Our Common Stock is currently registered under Section 12(b) of the Exchange Act, and we are subject to periodic reporting and other requirements of the Exchange Act. The implementation of a reverse stock split would not affect the registration of our Common Stock under the Exchange Act or our reporting or other requirements under the Exchange Act.

Our Common Stock is currently listed on the Nasdaq Global Market under the trading symbol “RNAC.” If our Common Stock remains listed on the Nasdaq Global Market up to the time of a reverse stock split, then immediately following the reverse stock split our Common Stock would continue to be listed on the Nasdaq Global Market under the same symbol.

Following a reverse stock split, our Common Stock would have a new Committee on Uniform Securities Identification Procedures (“CUSIP”) number, which is a number used to identify our equity securities, and stock certificates with the older CUSIP number will need to be exchanged for stock certificates with the new CUSIP number by following the procedures described above.

Accounting Matters

The implementation of a reverse stock split would not affect the per-share par value of our Common Stock, which will remain $0.0001, or the total capital attributable to Common Stock plus the additional paid-in capital account on our balance sheet. However, the capital attributable specifically to our Common Stock would be reduced proportionally depending on the reverse stock split ratio, and the additional paid-in capital account would be increased by an equal and offsetting amount. Also, if a reverse stock split is implemented, reported per-share net income or loss would be higher because there will be fewer shares of our Common Stock outstanding. A reverse stock split would be reflected retroactively for all periods presented in our financial statements. We do not anticipate that any other material accounting consequences, including changes to the amount of stock-based compensation expense to be recognized in any period, would arise as a result of a reverse stock split.

Certain Federal Income Tax Consequences of a Reverse Stock Split

The following describes certain material U.S. federal income tax considerations of a reverse stock split expected to apply generally to U.S. Holders of our Common Stock. This description is based upon current provisions of the Code, existing Treasury Regulations under the Code and current administrative rulings and court decisions, all of which are subject to change or different interpretation. Any change, which may or may not be retroactive, could alter the tax consequences to us or our stockholders as described in this section. No ruling from the IRS has been or will be requested in connection with a reverse stock split.

No attempt has been made to comment on all U.S. federal income tax consequences of a reverse stock split that may be relevant to particular U.S. Holders, including holders: (i) that are subject to special tax rules such as dealers, brokers and traders in securities, mutual funds, regulated investment companies, real estate investment trusts, insurance companies, banks or other financial institutions or tax-exempt entities; (ii) that hold their shares as a hedge or as part of a hedging, straddle, “conversion transaction,” “synthetic security,” integrated investment or any risk reduction strategy; (iii) that are partnerships, S corporations, or other pass-through entities or arrangements treated as partnerships for U.S. federal income tax purposes or investors in such pass-through entities; or (iv) that do not hold their shares as capital assets for U.S. federal income tax purposes (generally, property held for investment within the meaning of Section 1221 of the Code).

In addition, the following discussion does not address the tax consequences of a reverse stock split under state, local and non-U.S. tax laws. The discussion assumes that for U.S. federal income tax purposes, a reverse stock split will not be integrated, or otherwise treated as part of a unified transaction, with any other transaction. Furthermore, the following discussion does not address the tax consequences of transactions effectuated before, after or at the same time as a reverse stock split, whether or not they are in connection with a reverse stock split.

HOLDERS OF OUR COMMON STOCK ARE ADVISED TO CONSULT THEIR OWN TAX ADVISORS REGARDING THE U.S. FEDERAL INCOME TAX CONSEQUENCES OF A REVERSE STOCK SPLIT IN LIGHT OF THEIR PERSONAL CIRCUMSTANCES AND THE CONSEQUENCES OF A REVERSE STOCK SPLIT UNDER OTHER FEDERAL, STATE, LOCAL AND FOREIGN TAX LAWS.

Based on the assumptions above, a reverse stock split will be treated as a tax-free recapitalization for U.S. federal income tax purposes. Accordingly, if a reverse stock split is adopted:

The affirmative vote of the holders of shares of Common Stock representing a majority of the votes cast on the matter is required for the approval of Proposal No. 2.

THE BOARD OF DIRECTORS RECOMMENDS THAT OUR STOCKHOLDERS VOTE “FOR” THE APPROVAL OF PROPOSAL NO. 2.