EX-4

The following description of the capital stock of Sensei Biotherapeutics, Inc. (the “Company,” “we,” “us” or “our”) is a summary and does not purport to be complete. This summary is qualified in its entirety by reference to the provisions of the Delaware General Corporation Law (the “DGCL”), and the complete text of our amended and restated certificate of incorporation (our “certificate of incorporation”), our amended and restated bylaws (our “bylaws”) and the stockholder rights agreement, dated March 7, 2023, between the Company and American Stock Transfer & Trust Company, LLC (the “rights agreement”), which are incorporated by reference as Exhibits 3.1, 3.2 and 4.4, respectively, of the Company’s Annual Report on Form 10-K to which this description is also an exhibit. The Company encourages you to read that law and those documents carefully.

Under our certificate of incorporation, our authorized capital stock consists of 250,000,000 shares of common stock, $0.0001 par value per share (“common stock”), and 10,000,000 shares of preferred stock, $0.0001 par value per share (“preferred stock”), all of which shares of preferred stock are undesignated. Our board of directors may establish the rights and preferences of the preferred stock from time to time.

Holders of our common stock are entitled to one vote per share of common stock. Our common stock does not have cumulative voting rights. Accordingly, the holders of a majority of the outstanding shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they so choose, other than any directors that holders of any preferred stock we may issue may be entitled to elect.

Subject to preferences that may be applicable to any then outstanding preferred stock, holders of our common stock are entitled to receive ratably those dividends, if any, as may be declared by our board of directors out of legally available funds.

In the event of our liquidation, dissolution or winding up, the holders of our common stock will be entitled to share ratably in the assets legally available for distribution to stockholders after the payment of or provision for all of our debts and other liabilities, subject to the prior rights of any preferred stock then outstanding.

Holders of our common stock have no preemptive rights or other subscription rights and there are no redemption or sinking funds provisions applicable to our common stock. All outstanding shares of our common stock are duly authorized, validly issued, fully paid and nonassessable. The rights, preferences and privileges of holders of our common stock are subject to and may be adversely affected by the rights of the holders of shares of any series of preferred stock that we may designate and issue in the future.

Under the terms of our certificate of incorporation, our board of directors has the authority, without further action by our stockholders, to issue up to 10,000,000 shares of preferred stock in one or more series, to establish from time to time the number of shares to be included in each such series, to fix the dividend, voting and other rights, preferences and privileges of the shares of each wholly unissued series and any qualifications, limitations or restrictions thereon, and to increase or decrease the number of shares of any such series, but not below the number of shares of such series then outstanding.

Our board of directors may authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of the common stock. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring or preventing a change in our control and may adversely affect the market price of the common stock and the voting and other rights of the holders of common stock. We have no current plans to issue any shares of preferred stock.

On March 7, 2023, a special committee of our board of directors adopted the rights agreement and declared a dividend distribution of one preferred stock purchase right (a “Right”) for each outstanding share of common stock, to stockholders of record at the close of business on March 17, 2023 (the “Record Date”). In addition, one Right will automatically attach to each share of common stock issued between the Record Date and the earlier of the Distribution Date (as defined below) and the Expiration Date (as defined below). Each Right entitles the registered holder thereof to purchase from us a unit consisting of one ten-thousandth of a share (a “Unit”) of our Series A Junior Participating Cumulative Preferred Stock, par value $0.0001 per share (the “Series A preferred stock”) at a cash exercise price of $10.00 per Unit (the “Exercise Price”), subject to adjustment, under certain conditions specified in the rights agreement and summarized below.

Initially, the Rights are not exercisable and are attached to and trade with all shares of common stock outstanding as of, and issued subsequent to, the Record Date. The Rights will separate from the common stock and will become exercisable upon the earlier of (i) the close of business on the tenth calendar day following the first public announcement that a person or group of affiliated or associated persons (an “Acquiring Person”) has acquired beneficial ownership of 10% (or 20% in the case of certain investors filing on Schedule 13G) or more of the outstanding shares of common stock, other than as a result of repurchases of stock by us or certain inadvertent actions by a stockholder (the date of such announcement being referred to as the “Stock Acquisition Date”), or (ii) the close of business on the tenth business day (or such later date as our board of directors may determine) following the commencement of a tender offer or exchange offer that could result upon its consummation in a person or group becoming an Acquiring Person (the earlier of such dates being herein referred to as the “Distribution Date”). A person or group who beneficially owned 10% (or 20% in the case of certain investors filing on Schedule 13G) or more of our common stock prior to the first public announcement by us of the adoption of the rights agreement will not trigger the rights agreement so long as they do not increase their beneficial ownership of shares of then-outstanding common stock at a time when they still beneficially own 10% (or 20% in the case of certain investors filing on Schedule 13G) or more of our outstanding common stock, subject to certain exceptions as set forth in the rights agreement.

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the Company or any subsidiary of the Company, as such term is defined in the Rights Agreement;

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any employee benefit plan or compensation arrangement of the Company or any subsidiary of the Company;

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any person holding shares of common stock of the Company organized, appointed or established by the Company or any subsidiary of the Company for or pursuant to the terms of any such employee benefit plan or compensation arrangement;

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any person which, together with all affiliates and associates of such person, beneficially owns shares of common stock of the Company representing less than 20% of the shares of Common Stock of the Company then outstanding, and which is entitled to file, and files, or has filed, a statement on Schedule 13G pursuant to Rule 13d-1(b) or Rule 13d-1(c) of the General Rules and Regulations under the Securities Exchange Act of 1934, as amended; or

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any person who our board of directors determines has become an “Acquiring Person” for purposes of the rights agreement who has become such without intending to and who divests as promptly as practicable a sufficient number of shares of common stock.

For purposes of the rights agreement, beneficial ownership is defined to include ownership of securities that are subject to a derivative transaction and acquired derivative securities. Swaps dealers unassociated with any control intent or intent to evade the purposes of the rights agreement are excepted from such imputed beneficial ownership. In addition, for purposes of the rights agreement, a person or group is deemed to beneficially own shares of any other person(s) or group(s) with which such person or group is “acting in concert” (as defined in the rights agreement).

Until the Distribution Date (or earlier redemption, exchange or expiration of the Rights), (i) the Rights will be evidenced by the common stock certificates (or, with respect to any uncertificated shares of common stock registered in book entry form (“Book Entry Shares”), by notation in book entry) and will be transferred with and only with such shares of common stock, (ii) new common stock certificates or Book Entry Shares issued after the Record Date will contain a notation incorporating the rights agreement by reference, and (iii) the surrender for transfer of any certificates for common stock or Book Entry Shares will also constitute the transfer of the Rights associated with the common stock represented thereby.

As soon as practicable after the Distribution Date, one or more certificates evidencing Rights (the “Right Certificates”) will be mailed to holders of record of common stock as of the close of business on the Distribution Date and, thereafter, the separate Right Certificates alone will represent the Rights. Except as otherwise determined by our board of directors, only shares of common stock or Series A preferred stock issued prior to the Distribution Date will be issued with Rights.

In the event that a Stock Acquisition Date occurs, proper provision will be made so that each holder of a Right (other than an Acquiring Person or its associates or affiliates, whose Rights shall become null and void) will thereafter have the right to receive upon exercise, in lieu of a number of shares of Series A preferred stock, that number of shares of common stock (or, in certain circumstances, including if there are insufficient shares of common stock to permit the exercise in full of the Rights, Units of Series A preferred stock, other securities, cash or property, or any combination of the foregoing) having a market value of two times the Exercise Price of the Right (such right being referred to as the “Subscription Right”). In the event that, at any time following the Stock Acquisition Date, (i) we consolidate with, or merges with and into, any other person, and we are not the continuing or surviving corporation, (ii) any person consolidates with us, or merges with and into us and we are the continuing or surviving corporation of such merger and, in connection with such merger, all or part of the shares of common stock are changed into or exchanged for stock or other securities of any other person or cash or any other property, or (iii) 50% or more of our assets or earning power is sold, mortgaged or otherwise transferred, each holder of a Right (other than an Acquiring Person or its associates or affiliates, whose Rights shall become null and void) will thereafter have the right to receive, upon exercise, common stock of the acquiring company having a market value equal to two times the Exercise Price of the Right (such right being referred to as the “Merger Right”). The holder of a Right will continue to have the Merger Right whether or not such holder has exercised the Subscription Right. Rights that are or were beneficially owned by an Acquiring Person may (under certain circumstances specified in the Rights Agreement) become null and void.

At any time after a person becomes an Acquiring Person, our board of directors may, at its option, exchange all or any part of the then outstanding and exercisable Rights for shares of common stock at an exchange ratio of one share of common stock for each Right, subject to adjustment as specified in the rights agreement. Notwithstanding the foregoing, our board of directors generally will not be empowered to effect such exchange at any time after any person becomes the beneficial owner of 50% or more of our common stock.

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will entitle the holder thereof to quarterly dividend payments equal to the greater of (a) $1.00 per share or (b), subject to adjustment, 10,000 times the aggregate per share amount of all cash dividends, and 10,000 times the aggregate per share amount (payable in kind) of all non-cash dividends or other distributions other than a dividend payable in shares of common stock or a subdivision of the outstanding shares of common stock;

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if shares of common stock are exchanged via merger, consolidation or a similar transaction, will entitle the holder thereof to a per share payment equal to the payment made on 10,000 shares of common stock, plus accrued and unpaid dividends, if any; and

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upon liquidation, dissolution or winding up of the Company, will entitle the holder thereof to receive the greater of (a) $10,000.00 per share or (b) an aggregate amount per share, subject to the provision for adjustment hereinafter set forth, equal to 10,000 times the aggregate amount of all cash or other property to be distributed per share to holders of common stock.

The Exercise Price payable, and the number of shares of common stock or other securities or property issuable, upon exercise of the Rights are subject to adjustment from time to time to prevent dilution (i) in the event of a stock dividend on, or a subdivision, combination or reclassification of, the Series A preferred stock, (ii) if holders of the Series A preferred stock are granted certain rights or warrants to subscribe for Series A preferred stock or convertible securities at less than the current market price of the Series A preferred stock, or (iii) upon the distribution to holders of the Series A preferred stock of evidences of indebtedness or assets (excluding regular quarterly cash dividends) or of subscription rights or warrants (other than those referred to above).

With certain exceptions, no adjustment in the Exercise Price will be required until cumulative adjustments amount to at least 1% of the Exercise Price. We are not obligated to issue fractional shares. If we elect not to issue fractional shares, in lieu thereof an adjustment in cash will be made based on the fair market value of the Series A preferred stock on the last trading date prior to the date of exercise.

The Rights may be redeemed in whole, but not in part, at a price of $0.0001 per Right (payable in cash, common stock or other consideration deemed appropriate by our board of directors) by our board of directors only until the earlier of (i) the time at which any person becomes an Acquiring Person or (ii) the Expiration Date. Immediately upon the action of our board of directors ordering redemption of the Rights, the Rights will terminate and thereafter the only right of the holders of Rights will be to receive the redemption price.

The rights agreement may be amended by our board of directors in its sole discretion at any time prior to the time at which any person becomes an Acquiring Person. After such time our board of directors may, subject to certain limitations set forth in the rights agreement, amend the rights agreement only to cure any ambiguity, defect or inconsistency, to shorten or lengthen any time period, or to make changes that do not adversely affect the interests of Rights holders (excluding the interests of an Acquiring Person or its associates or affiliates).

The Rights are not exercisable until the Distribution Date and will expire on March 7, 2024 (the “Expiration Date”).

Anti-Takeover Effects of Delaware Law and Our Certificate of Incorporation and Bylaws

Some provisions of Delaware law, our certificate of incorporation and our bylaws contain provisions that could make the following transactions more difficult: an acquisition of us by means of a tender offer; an acquisition

of us by means of a proxy contest or otherwise; or the removal of our incumbent officers and directors. It is possible that these provisions could make it more difficult to accomplish or could deter transactions that stockholders may otherwise consider to be in their best interest or in our best interests, including transactions which provide for payment of a premium over the market price for our shares.

These provisions, summarized below, are intended to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors. We believe that the benefits of the increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us outweigh the disadvantages of discouraging these proposals because negotiation of these proposals could result in an improvement of their terms.

Our bylaws provide that a special meeting of stockholders may be called only by our chairman of the board, chief executive officer or president, or by a resolution adopted by a majority of our board of directors.

Our bylaws establish advance notice procedures with respect to stockholder proposals to be brought before a stockholder meeting and the nomination of candidates for election as directors, other than nominations made by or at the direction of the board of directors or a committee of the board of directors.

Our certificate of incorporation and bylaws eliminate the right of stockholders to act by written consent without a meeting.

Our board of directors is divided into three classes. The directors in each class serve for a three-year term, one class being elected each year by our stockholders. This system of electing and removing directors may tend to discourage a third-party from making a tender offer or otherwise attempting to obtain control of us, because it generally makes it more difficult for stockholders to replace a majority of the directors.

Our certificate of incorporation provides that no member of our board of directors may be removed from office by our stockholders except for cause and, in addition to any other vote required by law, upon the approval of not less than two thirds of the total voting power of all of our outstanding voting stock then entitled to vote in the election of directors.

Our certificate of incorporation does not permit stockholders to cumulate their votes in the election of directors. Accordingly, the holders of a majority of the outstanding shares of our common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they choose, other than any directors that holders of our convertible preferred stock may be entitled to elect.

We are subject to Section 203 of the DGCL, which prohibits persons deemed to be “interested stockholders” from engaging in a “business combination” with a publicly held Delaware corporation for three years following the date these persons become interested stockholders unless the business combination is, or the transaction in which the person became an interested stockholder was, approved in a prescribed manner or another prescribed exception applies. Generally, an “interested stockholder” is a person who, together with affiliates and associates, owns, or within three years prior to the determination of interested stockholder status did own, 15% or more of a corporation’s voting stock. Generally, a “business combination” includes a merger, asset or stock sale, or other

transaction resulting in a financial benefit to the interested stockholder. The existence of this provision may have an anti-takeover effect with respect to transactions not approved in advance by the board of directors.

Our certificate of incorporation provides that the Court of Chancery of the State of Delaware (or, if and only if the Court of Chancery of the State of Delaware lacks subject matter jurisdiction, any state court located within the State of Delaware or, if and only if all such state courts lack subject matter jurisdiction, the federal district court for the District of Delaware) and any appellate court therefrom is the sole and exclusive forum for the following claims or causes of action under the Delaware statutory or common law: (i) any derivative claim or cause of action brought on our behalf; (ii) any claim or cause of action for a breach of fiduciary duty owed by any of our current or former directors, officers, or other employees to us or our stockholders; (iii) any claim or cause of action against us or any of our current or former directors, officers or other employees arising out of or pursuant to any provision of the DGCL, our certificate of incorporation, or our bylaws (as each may be amended from time to time); (iv) any claim or cause of action seeking to interpret, apply, enforce or determine the validity of our certificate of incorporation or our bylaws (as each may be amended from time to time, including any right, obligation, or remedy thereunder); (v) any claim or cause of action as to which the DGCL confers jurisdiction to the Court of Chancery of the State of Delaware; and (vi) any claim or cause of action against us or any of our current or former directors, officers, or other employees governed by the internal-affairs doctrine, in all cases to the fullest extent permitted by law and subject to the court’s having personal jurisdiction over the indispensable parties named as defendants. This choice of forum provision would not apply to claims or causes of action brought to enforce a duty or liability created by the Securities Act, the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction, or the Securities Act. Our certificate of incorporation provides that the federal district courts of the United States of America will be the exclusive forum for resolving any complaint asserting a cause of action arising under the Securities Act. Additionally, our certificate of incorporation provides that any person or entity holding, owning or otherwise acquiring any interest in any of our securities shall be deemed to have notice of and consented to these provisions.

The amendment of any of the above provisions, except for the provision making it possible for our board of directors to issue convertible preferred stock, would require approval by holders of at least two thirds of the total voting power of all of our outstanding voting stock.

The provisions of Delaware law, our certificate of incorporation and our bylaws could have the effect of discouraging others from attempting hostile takeovers and, as a consequence, they may also inhibit temporary fluctuations in the market price of our common stock that often result from actual or rumored hostile takeover attempts. These provisions may also have the effect of preventing changes in the composition of our board of directors and management. It is possible that these provisions could make it more difficult to accomplish transactions that stockholders may otherwise deem to be in their best interests.

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company, LLC. The transfer agent’s address is 6201 15th Avenue, Brooklyn, New York 11219.

Our common stock is listed on the Nasdaq Global Market under the symbol “SNSE”.