UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant  ☒

Filed by a Party other than the Registrant  ☐

Check the appropriate box:

ZIOPHARM Oncology,Alaunos Therapeutics, Inc.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):

8030 El Rio Street

One First Avenue, Parris Building 34, Navy Yard Plaza, Third Floor

Boston, Massachusetts 02129Houston, TX 77054

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To be Held on May 19, 2021June 13, 2022

April 27, 2022

To the stockholders of Ziopharm Oncology,Alaunos Therapeutics, Inc.:

NOTICE IS HEREBY GIVEN thatWe cordially invite you to the 20212022 annual meeting of stockholders (the “annual meeting”“Annual Meeting”) of Ziopharm Oncology,Alaunos Therapeutics, Inc. (the(“we,” “Alaunos” or the “Company”), which due to the public health concerns regarding the ongoing coronavirus pandemic (COVID-19), will be held virtually and exclusively online via live audio-only webcast, on Wednesday, May 19, 2021,June 13, 2022, at 9:00 a.m. Eastern time,Time, for the following purposes:

These items of business are more fully described in the Proxy Statementproxy statement accompanying this Notice.notice. The proxy statement accompanying this notice is being issued in connection with the solicitation by the Board of a proxy on the enclosed form of proxy card for use at the Annual Meeting.

You will be able to attend and participate in the annual meetingAnnual Meeting online, submit your questions during the annual meetingAnnual Meeting and vote your shares electronically during the meeting by visiting www.virtualshareholdermeeting.com/ZIOP2021.TCRT2022. Because the annual meetingAnnual Meeting is being held electronically, you will not be able to attend the annual meetingAnnual Meeting in person.

The record date for the annual meetingAnnual Meeting is MarchApril 22, 2021.2022. Only stockholders of record at the close of business on that date may vote at the annual meetingAnnual Meeting or any adjournment or postponement thereof. To participate in and vote at the annual meeting,Annual Meeting, stockholders will need the unique 16-digit control number (printed in the box marked by the arrow) in their Notice of Internet Availability of Proxy Materials or proxy card (if you requested a printed copy of the proxy materials).

Table of Contents

Ziopharm Oncology,Alaunos Therapeutics, Inc.

One First Avenue, Parris Building 34, Navy Yard Plaza, Third Floor8030 El Rio Street,

Boston, Massachusetts 02129Houston, TX 77054

PROXY STATEMENT

FOR THE ANNUAL MEETING OF STOCKHOLDERS

To Be Held On May 19, 2021June 13, 2022

QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING

Who is soliciting my vote?

We are providing you with these proxy materials because the board of directors (the “board”“Board”) of Ziopharm Oncology,Alaunos Therapeutics, Inc. (sometimes referred to as( “we,” “us,” “our”“Alaunos” or the “Company”) is soliciting your proxy to vote at the 20212022 annual meeting of stockholders (the “annual meeting”“Annual Meeting”), including at any adjournments or postponements thereof. The annual meetingAnnual Meeting will be held on May 19, 2021June 13, 2022 at 9:00 a.m., Eastern Time virtually and exclusively online via live audio-only webcast at www.virtualshareholdermeeting.com/ZIOP2021.TCRT2022.

Why did I receive a notice regarding the availability of proxy materials through the internet?

Pursuant to rules adopted by the Securities and Exchange Commission or the SEC,(the “SEC”), we have elected to provide access to our proxy materials over the internet. Accordingly, we have sent you a Notice of Internet Availability of Proxy Materials (the “Notice”) because the boardBoard is soliciting your proxy to vote at the annual meeting,Annual Meeting, including at any adjournments or postponements thereof. All stockholders will have the ability to access the proxy materials through the website referred to in the Notice or to request a printed set of the proxy materials. Instructions on how to access the proxy materials over the internet or to request a printed set of the proxy materials may be found in the Notice.

We intend to mail the Notice on or about , 2021April 27, 2022 to all stockholders of record entitled to vote at the annual meeting.Annual Meeting.

Why are you holding a virtual annual meeting?

As part of our effort to maintain a safe and healthy environment for our directors, members of management and stockholders who wish to attend the annual meeting,Annual Meeting, in light of the ongoing coronavirus disease, COVID-19, pandemic we believe that hosting a virtual meeting is in the best interest of the Company and its stockholders and enables increased stockholder attendance and participation because stockholders can participate from any location around the world. Stockholders will have the same rights and opportunities to participate as they would have at an in-person meeting.

Will I receive any other proxy materials by mail?

We may send you a proxy card, along with a second Notice, on or after , 2021.April 27, 2022.

How do I attend the annual meeting?Annual Meeting?

You cannot attend the annual meetingAnnual Meeting physically. You can attend the annual meetingAnnual Meeting by visiting www.virtualshareholdermeeting.com/ZIOP2021,TCRT2022, where you will be able to listen to the annual meetingAnnual Meeting live, submit questions and vote online.

The annual meetingAnnual Meeting will start at 9:00 a.m. Eastern Time on May 19, 2021.June 13, 2022. We encourage you to access the annual meetingAnnual Meeting prior to the start time to allow time for online check-in. We have worked to offer the same

participation opportunities as would be provided at an in-person meeting while further enhancing the online experience available to all stockholders regardless of their location. However, please be aware that you must bear any costs associated with your internet access, such as usage charges from internet access providers and telephone companies. If you experience technical difficulties during the annual meeting,Annual Meeting, you should call the technical support phone number provided when you log in to the annual meeting.Annual Meeting.

In order to enter the annual meetingAnnual Meeting virtually, you will need the unique 16-digit control number, which is included in the Notice or on your proxy card if you are a stockholder of record of the shares, or included with your voting instruction card and voting instructions received from your broker, bank, trustee, or nominee if you are the beneficial owner of the shares held in “street name.”

What if I cannot virtually attend the annual meeting?Annual Meeting?

You may vote your shares electronically before the meeting by internet, by proxy or by telephone as described below. You do not need to access the annual meetingAnnual Meeting audio-only webcast to vote if you submitted your vote via proxy, by internet or by telephone in advance of the annual meeting.Annual Meeting.

Who can vote at the annual meeting?Annual Meeting?

Only stockholders of record at the close of business on MarchApril 22, 20212022 (the “Record Date”) will be entitled to vote at the annual meeting.Annual Meeting. On the record date,Record Date, there were 215,205,173215,950,561 shares of common stock outstanding and entitled to vote. A list of such holders will be open to the examination of any stockholder for any purpose germane to the annual meetingAnnual Meeting at Ziopharm Oncology, One First Avenue, Parris Building 34, Navy Yard Plaza, Boston, MassachusettsAlaunos Therapeutics, Inc., 8030 El Rio Street, Houston, TX 77054 for a period of ten (10)10 days prior to the annual meeting.Annual Meeting. Please contact the Secretary of the Company to make arrangements to inspect the list.

Stockholder of Record — Record—Shares Registered in Your Name: If on MarchApril 22, 2021,2022, your shares were registered directly in your name with our transfer agent, American Stock Transfer & Trust Company, LLC (“AST”), then you are a stockholder of record. As a stockholder of record, you may vote at the annual meetingAnnual Meeting virtually or vote by proxy prior to the annual meeting.Annual Meeting. Whether or not you plan to attend the annual meeting,Annual Meeting, we urge you to vote by proxy through the internet, by telephone or using a proxy card that you may request as instructed below, to ensure your vote is counted.

Beneficial Owner — Owner—Shares Registered in the Name of a Broker or Bank: If on MarchApril 22, 2021,2022, your shares were not registered in your name, but instead are held in an account at a brokerage firm, bank, dealer or similar organization, then you are the beneficial owner of shares held in “street name” and the Notice is being forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the annual meeting.Annual Meeting. As a beneficial owner, you have the right to direct your broker, bank or other agent regarding how to vote the shares in your account. You are also invited to attend the annual meeting.Annual Meeting. Since you are not the stockholder of record, however, you may not vote your shares at the annual meetingAnnual Meeting even if you participate virtually unless you request and obtain a valid proxy from your broker, bank or other agent.

What am I voting on?

There are foursix matters scheduled for a vote:

your vote is counted. You may still attend the annual meetingAnnual Meeting virtually and vote electronically at the annual meetingAnnual Meeting even if you have already voted by proxy. You may vote as follows:

Beneficial Owner — Owner—Shares Registered in the Name of a Broker or Bank: If you are a beneficial owner of shares registered in the name of your broker, bank or other agent, you should have received a Notice containing voting instructions from that organization rather than from us. Simply follow the voting instructions in the Notice to ensure that your vote is counted. To vote electronically at the annual meeting,Annual Meeting, you must obtain a valid proxy from your broker, bank or other agent. Follow the instructions from your broker, bank or bankother agent included with these proxy materials, or contact your broker, bank or bankother agent to request a proxy form.

We provide Internet proxy voting to allow you to vote your shares online, with procedures designed to ensure the authenticity and correctness of your proxy vote instructions. However, please be aware that you must bear any costs associated with your internet access, such as usage charges from internet access providers and telephone companies.

If I am a beneficial owner of shares held in street name and I do not provide my broker or bank with voting instructions, what happens?

If you are a beneficial owner of shares held in street name and you do not instruct your broker, bank or other agent how to vote your shares, your broker, bank or other agent may still be able to vote your shares in its discretion.discretion on certain “routine” proposals. Under the rules of the New York Stock Exchange or NYSE,(“NYSE”), brokers, banks and other securities intermediaries that are subject to NYSE rules may use their discretion to vote your “uninstructed” shares with respect to matters considered to be “routine” under NYSE rules, but not with respect to “non-routine” matters. Proposals 1 and 3 are considered to be “non-routine” under NYSE rules, meaning that your broker, bank or other agent may not vote your shares on those proposals in the absence of your voting instructions. However, ProposalsProposal 2, the Reverse Stock Split Proposal, the Authorized Stock Increase Proposal and 4the Adjournment Proposal are considered to be “routine” matters under NYSE rules, meaning that if you do not return voting instructions to your broker, bank or other agent by its deadline, your shares may be voted by your broker, bank or other agent in its discretion on ProposalsProposal 2, the Reverse Stock Split Proposal, the Authorized Stock Increase Proposal and 4.the Adjournment Proposal. Accordingly, if you own shares through a nominee, such as a broker, bank or other agent, please be sure to instruct your nominee how to vote to ensure that your vote is counted on all of the proposals.proposals

If you are a beneficial owner of shares held in street name, in order to ensure your shares are voted in the way you would prefer, you must provide voting instructions to your broker, bank or other agent by the deadline provided in the materials you receive from your broker, bank or other agent.

How are proxies solicited for the Annual Meeting?

At this time we have not engaged a proxy solicitation firm, but we may decide to retain the services of a proxy solicitation firm in the future if we believe it is appropriate under the circumstances. If we do engage a proxy solicitor, weWe will pay for the entire cost of soliciting proxies. In additionWe have retained Alliance Advisors, LLC, on customary terms, to these proxy materials, ouraid in the solicitation of proxies for an estimated fee of $15,000, plus reimbursement of out-of-pocket expenses. Our directors and employees may also solicit proxies in person, by telephone, or by other means of communication. Directors and employees will not be paid any additional compensation for soliciting proxies. We may also reimburse brokerage firms, banks and other agents for the cost of forwarding proxy materials to beneficial owners.

If you have any questions or require any assistance in voting your shares, please contact:

Alliance Advisors

200 Broadacres Drive, 3^rd Floor

Bloomfield, NJ 07003

Toll-Free: 833-757-0787

E-mail: TCRT@allianceadvisors.com

What does it mean if I receive more than one Notice?

If you receive more than one Notice, your shares may be registered in more than one name or in different accounts. Please follow the voting instructions on each Notice to ensure that all of your shares are voted.

Your most current proxy card, telephone proxy or internet proxy is the one that is counted.

Beneficial Owner: Shares Registered in the Name of Broker, Bank or BankOther Agent

If your shares are held by your broker, bank or bankother agent as a nominee, or agent, you should follow the instructions provided by yoursuch broker, bank or bank.other agent.

How are votes counted?

Votes will be counted by the inspector of election appointed for the annual meeting,Annual Meeting, who will separately count, for the proposal to elect directors (Proposal 1), votes “For,” “Withhold” and broker non-votes; and with respect to all other proposals, votes “For” and “Against,” abstentions and, if applicable, broker non-votes. Abstentions will have the same effect as “Against” votes on ProposalsProposal 2, Proposal 3, the Reverse Stock Split Proposal, the Authorized Stock Increase Proposal and 4,the Adjournment Proposal, and will have no effect on Proposal 1. Broker non-votes on Proposals 1 and 3 will have no effect and will not be counted towards the vote total for anyeither of those proposals.

What are “broker non-votes”?

As discussed above, when a beneficial owner of shares held in street name does not give voting instructions to his or her broker, bank or other securities intermediaryagent holding his or her shares as to how to vote on matters

deemed to be “non-routine”non-routine,” under the NYSE rules, the broker, bank or other such agent cannot vote the shares. These un-voted shares are counted as “broker non-votes.” Proposals 1 and 3 are considered to be “non-routine” under the NYSE rules and therefore we expect broker non-votes to exist in connection with those proposals. Broker non-votes will have no effect on those proposals.

As a reminder, if you are a beneficial owner of shares held in street name, in order to ensure your shares are voted in the way you would prefer, you must provide voting instructions to your broker, bank or other agent by the deadline provided in the materials you receive from your broker, bank or other agent.

What is the quorum requirement?

A quorum of stockholders is necessary to hold a valid meeting. A quorum will be present if stockholders holding at least a majority in voting power of the outstanding shares entitled to vote are deemed present at the annual meetingAnnual Meeting in person or represented by proxy. On the record date,Record Date, there were 215,205,173215,950,561 shares outstanding and entitled to vote. Thus, the holders of 107,602,587107,975,281 shares must be deemed present in person or represented by proxy at the annual meetingAnnual Meeting to have a quorum.

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee)agent) or if you vote electronically at the annual meeting.Annual Meeting. Abstentions and broker non-votes will be counted towards the quorum requirement. If there is no quorum, the holders of a majority of shares deemed present at the annual meetingAnnual Meeting in person or represented by proxy may adjourn the annual meetingAnnual Meeting to another date.

Who will serve as inspector of elections?

A representative of Broadridge Financial Solutions (“Broadridge”) will serve as inspector of elections and Broadridge will tabulate votes.

How can I find out the results of the voting at the annual meeting?Annual Meeting?

Preliminary voting results will be announced at the annual meeting.Annual Meeting. In addition, final voting results will be published in a current report on Form 8-K that we expect to file within four business days after the annual meeting.Annual Meeting. If final voting results are not available to us in time to file a Form 8-K within four business days after the meeting,Annual Meeting, we intend to file a Form 8-K to publish preliminary results and, within four business days after the final results are known to us, file an additional Form 8-K to publish the final results.

What if I have questions for the Company’s transfer agent?

Please contact AST, at the phone number or address listed below, if you are a registered stockholder and have questions concerning stock certificates, transfers or ownership or other matters pertaining to your stock account.

800-937-5449

6201 15th Avenue,

Brooklyn, NY 11219

PROPOSALS

Proposal 1

Election of Directors

Our board of directorsBoard presently has eightseven directors: Christopher Bowden M.D.; Kevin Buchi; Heidi Hagen;S. Boyle, Sr.; James Huang; Robert W. Postma; Mary Thistle; Jaime Vieser; and Holger Weis. Each of Dr. Bowden, Mr. Huang, Mr. Postma, Ms. Thistle, Mr. Vieser and Ms. HagenWeis was previously elected by the stockholders. In March 2021, Mr. Buchi notified our board of directors of his intention to retireBoyle was appointed as a member our board, effective as of this annual meeting, and, as a result, our board has elected to reduce the size of our board from eightBoard effective August 30, 2021, and is standing for election to seven directors at thatour Board for the first time.

On March 22, 2021,April 15, 2022, our board of directorsBoard nominated all of our existing directors other than Mr. Buchi, for election at the annual meeting.Annual Meeting. If elected, each of our proposed nominees has consented to serve as one of our directors, to hold office until our next annual meeting of stockholders and until his or her successor has been duly elected and qualified, or, if sooner, until his or her earlier death, resignation or removal. Proxies cannot be voted for a greater number of persons than the number of nominees named in the proxy statement. If any director nominee should withdraw or otherwise become unavailable to serve, the proxies which would have otherwise been voted for that director nominee may be voted for a substitute director nominee selected by our board.Board. We are not aware of any reason that a nominee will be unable or unwilling to serve as a director.

The following table sets forth each nominee to be elected at the annual meeting,Annual Meeting, the year each nominee was first elected as a director, the position(s) currently held by each nominee with us and the year each nominee’s term will expire, if such nominee is elected at the annual meeting.Annual Meeting.

In 2016, we adopted aUnder our director resignation policy. Under this policy, any nominee in an uncontested election who does not receive a majority of the votes cast (i.e. receives a greater number of votes “withheld” from his or her election than votes “for” in such election) shall submit his or her offer of resignation for consideration by the corporate governance and nominating committee.committee of the Board (the “corporate governance and nominating committee”). The corporate governance and nominating committee shall consider all of the relevant facts and circumstances and recommend to the boardBoard the action to be taken with respect to such offer of resignation, and the boardBoard will then act on such recommendation.

Our corporate governance and nominating committee seeks to assemble a boardBoard that, as a whole, possesses the appropriate balance of professional and industry knowledge, financial expertise and management experience

None of the director nominees isare related by blood, marriage or adoption to any of our other director nominees or executive officers. Further, noneCertain of the director nominees is party to an arrangement or understanding with any person pursuant to which the nominee is to beour directors were selected or nominated for election as a director, except that certain arrangement described inpursuant to the WaterMill Settlement Agreement (as defined below). See the section entitled “Certaintitled “Certain Relationships and Related Transactions—Certain Related-Party Transactions—WaterMill Settlement Agreement”Agreement” in this proxy statement. Mr. Boyle, our Chief Executive Officer and a director, was nominated as a director pursuant to the terms of his employment agreement as described in the section titled “Executive Compensation—Narrative to the Summary Compensation Table—Employment and Change in Control Agreements—Employment Agreement with Kevin S. Boyle, Sr.”

Vote Required

Directors are elected by a plurality of the votes of the holders of shares deemed present in person or represented by proxy and entitled to vote on the election of directors. Accordingly, if a quorum is present, the seven nominees receiving the highest number of “For”“FOR” votes will be elected. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the seven nominees named above.

The boardBoard recommends that you vote “FOR” the election of each named nominee.

Proposal 2

Ratification of Selection of Independent Registered Public Accounting Firm

The audit committee of the boardBoard has selected RSM US LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2021.2022. RSM US LLP has audited our financial statements since 2010. A representative of RSM US LLP is expected to virtually attend the annual meeting.Annual Meeting. He or she will have an opportunity to make a statement if he or she so desires and will be available to respond to appropriate questions from stockholders.

We are not required by statute or our bylaws or other governing documents to obtain stockholder ratification of the appointment of RSM US LLP as our independent registered public accounting firm. The audit committee has submitted the selection of RSM US LLP to the stockholders for ratification as a matter of good corporate practice. If the stockholders do not ratify the appointment, the audit committee may reconsider its selection. Notwithstanding the proposed ratification of the selection of RSM US LLP by the stockholders, the audit committee, in its discretion, may direct the appointment of a new independent registered public accounting firm at any time during the year without notice to, or the consent of, the stockholders, if the audit committee determines that such a change would be in our best interestsinterest and the best interestsinterest of our stockholders.

Vote Required

The affirmative vote of the holders of a majority of the shares deemed present in person or represented by proxy and entitled to vote at the annual meeting will be required to ratify the selection of RSM US LLP. Abstentions will be counted toward the vote total for Proposal 2 and will have the same effect as “Against” votes.

Principal Accountant Fees and Services

The following table presents the aggregate fees billed by RSM US LLP for the years ended December 31, 20202021 and 2019.2020.

Other than as discussed above, we did not incur any fees of RSM US LLP for audit-related, tax or other services in 20202021 or 2019.2020.

All fees described above were pre-approved by the audit committee.

Vote Required

The affirmative vote of the holders of a majority of the shares deemed present in person or represented by proxy and entitled to vote at the annual meeting will be required to ratify the selection of RSM US LLP. Abstentions will be counted toward the vote total for Proposal 2 and will have the same effect as “AGAINST” votes.

The boardBoard recommends that you vote “FOR” the ratification of the selection of RSM US LLP

as our independent registered public accounting firm for our fiscal year ending December 31, 2021.2022.

Proposal 3

Advisory Vote on Executive Compensation

Under the Dodd-Frank Wall Street Reform and Consumer Protection Act or the Dodd-Frank Act, and Section 14A of the Securities Exchange Act of 1934, as amended or the Exchange Act,(the “Exchange Act”), our stockholders are entitled to vote to approve, on an advisory basis, the compensation of our named executive officers as disclosed in this proxy statement in accordance with the SECSEC’s rules. At the 2017 annual meeting of stockholders, our stockholders indicated their preference that we solicit a non-binding advisory vote on the compensation of the named executive officers, commonly referred to as a “say-on-pay vote,” every year. The boardBoard has adopted a policy that is consistent with that preference indicated by our stockholders. Accordingly, this year we are again asking the stockholders to approve, on an advisory basis, the compensation of our named executive officers as disclosed in this proxy statement.

This vote is not intended to address any specific item of compensation, but rather the overall compensation of our named executive officers and the philosophy, policies and practices described in this proxy statement. The compensation of our named executive officers is disclosed in the section entitled “Executive Compensation”titled “Executive Compensation” below, including the tabular and narrative disclosures set forth in such section under the headings “Executive Compensation Tables” and “Compensation Discussion and Analysis.” As discussed in those disclosures, wesame heading. We believe that our compensation policies and decisions are focused on pay-for-performance principles and strongly aligned with our stockholders’ interests. Compensation of our named executive officers is designed to enable us to attract and retain talented and experienced executives, whose knowledge, skills and performance are critical to our success, and motivate these executive officers to achieve our business objectives and to lead us in a competitive environment.

We are asking our stockholders to indicate their support for the compensation of our named executive officers as described in this proxy statement by casting a non-binding advisory vote “FOR” the following resolution:

“RESOLVED, that the stockholders hereby approve the compensation of the “named executive officers” of Ziopharm Oncology,Alaunos Therapeutics, Inc., as disclosed in the section entitledtitled “Executive Compensation” in the proxy statement for the Ziopharm Oncology,Alaunos Therapeutics, Inc. 20212022 Annual Meeting of Stockholdersstockholders pursuant to the compensation disclosure rules of the Securities and Exchange Commission,SEC, including the Compensation Discussion and Analysis, compensation tables and narrative discussion.”

Vote Required

The affirmative vote of the holders of a majority of the shares deemed present in person or represented by proxy and entitled to vote at the annual meetingAnnual Meeting will be required to approve, on an advisory basis, the compensation of our named executive officers as described herein. Because the vote is advisory, it will not be binding on us, the boardBoard or ourthe Board’s compensation committee.committee (the “compensation committee”). Nevertheless, the views expressed by our stockholders, whether through this vote or otherwise, are important to us and, accordingly, the boardBoard and our compensation committee intend to consider the results of this vote in making determinations in the future regarding executive compensation arrangements. Abstentions will be counted toward the vote total for Proposal 3 and will have the same effect as “AGAINST” votes.

The boardBoard recommends that you vote “FOR” the proposal to approve the compensation of our

named executive officers, as described in this proxy statement.

Proposal 4

Approval of Certificate of Amendment of the Second Amended and Restated Certificate of Incorporation to Increase the Total Number of Authorized SharesEffect a Reverse Stock Split of Common Stock

Overview

On April 15, 2022, our Board unanimously approved and recommended that our stockholders approve the amendment and restatement of our Charter to, at the discretion of the Board, effect a reverse stock split with respect to the Company’s issued and outstanding common stock, par value $0.001 per share, including stock held by the Company as treasury shares, at any reverse stock split ratio within a range of 1-for-5 to 1-for-15, inclusive, and a proportionate decrease in the number of our total authorized capital stock and common stock, as further described below. As further described below, we are seeking approval of this Reverse Stock Split Proposal primarily to provide our Board with the authority to effect a reverse stock split if needed to maintain our listing on the Nasdaq Global Select Market. Our board of directorsBoard has accordingly determined that it is advisable and in the best interestsinterest of the Company and its stockholders for this Reverse Stock Split Proposal to be approved so that the Board has the necessary flexibility if, as we near the end of the relevant compliance period (including any granted extensions), we have not regained compliance with the Minimum Price Standard (as defined below) and the Board makes the determination that a reverse stock split provides us the best chance to regain compliance and avoid delisting.

A reverse stock split, if implemented, would be at any ratio approved by our stockholders in this proposal within the range described above and would apply equally to all outstanding shares of our common stock. Accordingly, each stockholder would hold the same percentage of common stock outstanding immediately following a reverse stock split as that stockholder held immediately prior to a reverse stock split, except for adjustments that may result from the treatment of fractional shares as described below. In addition, a reverse stock split would result in a proportionate reduction in the number of shares of common stock authorized under the Charter.

Approval of this proposal would permit, but not require, our Board to effect a reverse stock split by any ratio between 1-for-5 to 1-for-15, inclusive, with the exact ratio to be selected at a whole number within this range as determined by our Board in its sole discretion, provided that any reverse stock split is implemented within one year after the conclusion of the Annual Meeting.

Upon receiving stockholder approval of a reverse stock split, the Board 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 a 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 our Board to select the ratio from within the stated range will provide us with the flexibility to implement a 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, our Board may consider, among other factors, the following:

If this Reverse Stock Split Proposal is approved by the stockholders and the Board determines to implement a reverse stock split, we will file an amended and restated Charter (the “Second Amended and Restated Charter”), with the Delaware Secretary of State. The material changes in the proposed Second Amended and Restated Charter are described in this proposal. This description is qualified in its entirety by reference to the complete text of the Second Amended and Restated Charter, 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 Second Amended and Restated Charter. The proposed Second Amended and Restated Charter is subject to revision for such changes as may be required by the Delaware General Corporation Law and any other changes consistent with this proposal that we may deem necessary or appropriate.

If this Reverse Stock Split Proposal is approved by the stockholders and a reverse stock split is implemented by our Board, no less than 5 and no more than 15 shares of existing common stock, as determined by our Board, will be combined into one share of common stock. Holders will receive, in lieu of any fractional share, an amount in cash (without interest) equal to such fraction multiplied by the closing sales price of our common stock as reported on the Nasdaq Global Select Market on the trading day immediately preceding the effective date of the Second Amended and Restated Charter. The Second Amended and Restated Charter, if adopted, will include only the reverse stock split ratio determined by our Board to be in the best interestsinterest of the Company and its stockholders and all of the other ratios approved by our stockholders within the proposed range will be abandoned.

If this Reverse Stock Split Proposal is approved and the Board elects to implement a reverse stock split, the number of outstanding shares of our stockholderscommon stock would be reduced in proportion to amendthe ratio of the reverse stock split chosen by our amended and restated certificate of incorporation (our “charter”), to increaseBoard. If a reverse stock split is implemented, the total number of authorized shares of our common stock from 250,000,000would decrease by the same proportion as the number of shares of common stock that are outstanding at the time of the reverse stock split.

Our Board reserves the right to 350,000,000 shares. On March 22, 2021, our board of directors adopted resolutions approvingelect not to effect a reverse stock split, including any or all reverse stock split ratios within the proposed certificate of amendment of our charter (the “certificate of amendment”)range, if it determines, in substantially the form attached hereto as Appendix A. Atits sole discretion, that time, our board of directors declared the proposed certificate of amendment to be advisable andimplementing a reverse stock split is not in the best interestsinterest of the Company and its stockholders. If we regain compliance with the Minimum Price Standard (as defined below) prior to the end of the 180 calendar days we have to come into compliance with such standard, our stockholdersBoard may decide to not effect a reverse stock split. If our Board does not implement a reverse stock split on or prior to the one year anniversary of the conclusion of the Annual Meeting, stockholder approval would again be required prior to implementing any future reverse stock split.

Background and Reasons for a Reverse Stock Split

As further described below, we and our Board are seeking approval for the Reverse Stock Split Proposal primarily to provide our Board with authority to effect a reverse stock split if needed to maintain our listing on the Nasdaq Global Select 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 in the section titled “Risks and Potential Disadvantages Associated with a Reverse Stock Split.”

Nasdaq Minimum Price Standard

Nasdaq Listing Rule 5450(a)(1) requires that companies listed on the Nasdaq Global Select Market maintain a minimum closing bid price of at least $1.00 per share (the “Minimum Price Standard”). Companies are considered out of compliance with the Minimum Price Standard if the Nasdaq closing bid price is accordingly submittingbelow $1.00 per share for 30 consecutive business days. Under Nasdaq Listing Rule 5810(c)(3)(A), once out of compliance with the proposed certificateMinimum Price Standard, a company has 180 calendar days to regain compliance by meeting the Minimum Price Standard. The 180 calendar day period for regaining compliance with the Minimum Price Standard ends on September 13, 2022. The Minimum Price Standard will be met if the Company’s common stock has a minimum closing bid price of amendmentat least $1.00 per share for approvala minimum of 10 consecutive business days during the 180 calendar day period to regain compliance with the Minimum Price Standard. If we do not regain

compliance with the Minimum Price Standard by September 13, 2022, we may be eligible for an additional 180 calendar day compliance period. To qualify, we would need to transfer the listing of our stockholders.common stock to the Nasdaq Capital Market, provided that it meets the continued listing requirement for the market value of publicly held shares and all other initial listing standards, with the exception of the Minimum Price Standard. To effect such a transfer, we would also need to pay an application fee and will need to provide written notice of our intention to cure the deficiency during the additional compliance period.

As of the date of this proxy statement, we are not in compliance with the Minimum Price Standard. The equity markets have experienced and continue to experience substantial volatility due to, among other factors, the COVID-19 global pandemic and the war in Ukraine. On April 22, 2022, the reported closing price of the our common stock was $0.49 per share. Accordingly, there is a significant risk that we may be unable to gain compliance with the Minimum Price Standard without a reverse stock split.

The primary purpose of a reverse stock split would be to achieve an increase in the per share market price of our common stock as necessary to meet the Minimum Price Standard. A delisting of our common stock would materially and adversely affect a stockholder’s ability to dispose of, or to obtain accurate quotations as to the market value of, our common stock. Furthermore, any delisting may cause our common stock to be subject to “penny stock” regulations promulgated by the SEC. Under such regulations, broker-dealers are required to, among other things, comply with disclosure and special suitability determinations prior to the sale of shares of common stock. If our common stock becomes subject to these regulations, the market price of our common stock and the liquidity thereof would be materially and adversely affected. Absent other factors, we believe that reducing the number of outstanding shares of our common stock is a potentially effective means to increase the per share market price of our common stock.

If our shares of common stock are delisted from the Nasdaq Global Select Market, we believe that our shares of common stock would likely be eligible to be quoted over-the-counter on an inter-dealer electronic quotation and trading system operated by OTC Markets Group. These markets are generally considered not to be as efficient as, and not as broad as, the Nasdaq Global Select Market. Selling our shares of common stock on these markets could be more difficult because smaller quantities of shares would likely be bought and sold, and transactions could be delayed. In addition, in the event our shares of common stock are delisted, broker-dealers would have certain regulatory burdens imposed upon them with respect to our common stock, which may discourage broker-dealers from effecting transactions in our common stock, further limiting the liquidity of our common stock. These factors could result in lower prices and larger spreads in the bid and ask prices for our common stock.

A delisting from the Nasdaq Global Select Market and continued or further declines in our share price could also greatly impair our ability to raise additional necessary capital through equity or debt financing, or to use our shares for business development or other corporate initiatives, and could significantly increase the ownership dilution to stockholders approvecaused by our issuing equity in financing or other transactions. Without the ability to raise additional capital, our ability to carry on our business and advance the development of our product candidates would be significantly impaired.

Our Board believes that the proposed reverse stock split would be a potentially effective means for us to obtain and/or maintain compliance with the Minimum Price Standard and to avoid, or at least defer, the consequences of our common stock being delisted from the Nasdaq Global Select Market by producing the immediate effect of increasing the bid price of our common stock. Our Board currently intends to effect a reverse stock split only if, in its sole discretion, it deems it to be a necessary step to regain compliance with the Minimum Price Standard.

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, as we have been advised that the current market price of our common

stock may affect its acceptability to certain institutional investors and other members of the investing public. In particular, many brokerage houses and institutional investors 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 and cost effective investment for many investors, which could enhance the liquidity of our common stock.

Risks and Potential Disadvantages Associated with a Reverse Stock Split

Our Board 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 us to regain compliance with the Minimum Price Standard. However, there are a number of risks and potential disadvantages associated with a reverse stock split, including the following:

Procedures for and Effects of Implementing a Reverse Stock Split

Procedures

A reverse stock split would become effective upon the filing of the Second Amended and Restated Charter with the Secretary of State of the State of Delaware. The exact timing of the filing of the Second Amended and Restated Charter, if it is filed, would be determined by our Board based on its evaluation as to when such action would be in our and our stockholders’ best interests. In addition, our Board 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 Second Amended and Restated Charter, our Board 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. If the Second Amended and Restated Charter has not been filed with the Secretary of State of the State of Delaware within one year after the conclusion of the Annual Meeting, our Board will abandon the reverse stock split or seek stockholder reauthorization of 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 increasetreat shares held by stockholders through a broker, bank or other agent in the same manner as registered stockholders whose shares are registered in their names. Brokers, banks and other agents would be instructed to effect a reverse stock split for 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 any questions 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 of their shares electronically in book-entry form with AST. These stockholders do not have stock certificates evidencing their ownership of the common stock. They are, however, provided with a statement 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 AST would not need to take action (the exchange will be automatic) to receive whole shares of post-reverse split common stock.

Certificated Holders. If a reverse stock split is implemented, stockholders holding shares of our common stock in certificated form would be sent a letter of transmittal by AST following the reverse stock split. The letter of transmittal would contain instructions on how a stockholder should surrender their certificate(s) representing shares of our common stock (the “Old Certificates”) to AST in exchange for certificates representing the appropriate 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 all Old Certificates, together with a properly completed and executed letter of transmittal, to AST. 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 cancelled 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 AST 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 of 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.

Outstanding Shares of Common Stock

Depending on the ratio for a reverse stock split determined by our Board, a minimum of 5 and a maximum of 15 shares of existing common stock would be combined into one new share of common stock. Based on 215,950,561 shares of common stock issued and outstanding as of April 22, 2022, immediately following a reverse stock split we would have approximately 43,190,112 shares of common stock issued and outstanding (without giving effect to the treatment of fractional shares) if the ratio for a reverse stock split is 1-for-5, and 14,396,704 shares of common stock issued and outstanding (without giving effect to the treatment of fractional shares) if the ratio for a reverse stock split is 1-for-15. Any other ratio selected within such range would result in a number of shares of common stock issued and outstanding following the reverse stock split between approximately 35,991,760 and 15,425,040 shares.

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 our Board. 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 “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.

Authorized Shares of Common Stock

A reverse stock split would result in a proportionate reduction in the number of authorized shares of our common stock as soon as practicable following stockholder approval. In this regard, upon filing ofunder the certificate of amendment withCharter at the Secretary of State oftime a reverse stock split is effected. A reverse stock split would not have any effect on the State of Delaware, the first paragraph of section four of our charter would be amended as follows, with the proposed additions double-underlined and proposed deletions stricken through:

“4. Number of Shares. The total number of shares of all classes of stock that the Corporation shall have authority to issue isTwo Hundred Eighty Million (280,000,000)Three Hundred Eighty Million (380,000,000) shares consisting of:Two Hundred Fifty Million (250,000,000)Three Hundred Fifty Million (350,000,000) shares of common stock, $.001 par value per share (“Common Stock”); and Thirty Million (30,000,000)authorized shares of preferred stock, $.001which would remain at 30,000,000 shares of preferred stock, par value per share (“Preferred Stock”).”$0.001.

OfFor clarity, if the 250,000,000Authorized Stock Increase Proposal described below is approved by our stockholders and implemented by our Board, in its discretion, through the filing of a certificate of amendment to our Charter prior to the implementation of the reverse stock split, the reverse stock split would have the effect of reducing the increased number of authorized shares.

Following the effective time of a reverse stock split, any authorized shares of our common stock, if and when issued, would be part of our existing class of our common stock and would have the same rights and privileges as the shares of our common stock currently authorized,outstanding. Our stockholders do not, as of the close of business on March 12, 2021, there were 215,180,173 shares of common stock outstanding. In additionsuch, have preemptive rights or preferential rights to the 215,180,173 shares of common stock outstanding on March 12, 2021, as of March 12, 2021:

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 exercisereverse stock split because the stockholder owns a number of options outstanding, having a weighted-average exercise price of $4.08 per share pursuant to the ZIOPHARM Oncology, Inc. 2012 Equity Incentive Plan (the “2012 Plan”);

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.

We are currently listed on the Nasdaq Global Select Market under the trading symbol “TCRT.” If our common stock remains listed on the Nasdaq Global Select 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 Select Market under the TCRT symbol, although it is likely that Nasdaq would add the letter “D” to the end of the trading symbol for a period of 20 trading days after the effective date of the reverse stock split to indicate that the reverse stock split had occurred.

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 filing of the Second Amended and Restated Charter and implementation of a reverse stock split would not affect the par value of our common stock per share, which will remain $0.001. As a result, the stated capital attributable to common stock and the additional paid-in capital account on our balance sheet would not change due to a reverse stock split. However, the stated 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 credited with the amount by which the stated capital would be reduced. 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. We do not anticipate that any other accounting consequences would arise as a result of a reverse stock split.

Appraisal Rights

Our stockholders are not entitled to dissenters’ or appraisal rights under the Delaware General Corporation Law with respect to any of the proposals being voted on at the Annual Meeting and described in this proxy statement.

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 (as defined below) of our common stock. This description is based upon current provisions of the Internal Revenue Code of 1986, as amended (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 U.S. Internal Revenue Service 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

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 foreign 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.

For purposes of this discussion, a “U.S. Holder” means a beneficial owner of our common stock that is: (i) an individual who is a citizen or resident of the U.S.; (ii) a corporation (or other entity taxable as a corporation for U.S. federal income tax purposes) created or organized in the U.S. or under the laws of the U.S. or any subdivision thereof; (iii) an estate the income of which is includible in gross income for U.S. federal income tax purposes regardless of its source; or (iv) a trust (other than a grantor trust) if (A) a court within the U.S. is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have the authority to control all substantial decisions of the trust or (B) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

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:

For purposes of determining the tax basis and holding period of shares of our common stock received in a reverse stock split, U.S. Holders that acquired different blocks of shares our common stock at different times for different prices must calculate their basis and holding periods separately for each identifiable block of such stock exchanged in the reverse stock split.

Certain of our stockholders may be required to attach a statement to their tax returns for the year in which a reverse stock split is consummated that contains the information listed in applicable Treasury Regulations. All of our stockholders are advised to consult their own tax advisors with respect to the applicable reporting requirements.

Vote Required

The affirmative vote of the holders of a majority of the shares issued and outstanding and entitled to vote at the Annual Meeting is required to approve this proposal. Abstentions will be counted toward the vote total for Proposal 4 and will have the same effect as “AGAINST” votes.

The approval of this proposal is not conditioned on the approval or disapproval of Authorized Stock Increase Proposal. However, should both this proposal and the Authorized Stock Increase Proposal be approved by our stockholders, the Board would, in its discretion, choose which proposal(s) to implement, subject to its discretion to determine that neither proposal is in the best interest of the Company or its stockholders. In the event that this proposal is approved by the stockholders and the Authorized Stock Increase Proposal is not, the Board currently intends to nonetheless implement this proposal if, in its sole discretion, it deems it to be a necessary step to regain compliance with the Minimum Price Standard.

The Board recommends that you vote “FOR” the proposal to approve the Second Amended and Restated Charter to effect a reverse stock split, at our Board’s discretion.

Proposal 5

Approval of the Certificate of Amendment to our Charter to Increase our Authorized Stock

Overview

On April 15, 2022, our Board unanimously approved and recommended that our stockholders approve an amendment to our Charter to, at the discretion of the Board, increase the authorized shares of our common stock from 350,000,000 shares of common stock to 420,000,000 shares of common stock within one year after the conclusion of the Annual Meeting, representing an increase of 20%. The number of shares of preferred stock authorized for issuance will remain the same, at 30,000,000 shares of preferred stock, and will not be impacted by the increase in the authorized shares of capital stock or common stock, if approved by our stockholders. As of April 22, 2022, there were 215,950,561 shares of common stock issued and outstanding, no shares of common stock held as treasury stock, no shares of preferred stock issued or outstanding and 33,981,996 shares of our common stock reserved for future issuance in connection with the following:

As of April 22, 2022, 87,126,711 authorized shares of common stock remained available for future issuance pursuantissuance. Accordingly, our Board unanimously determined it was advisable and in the best interest of the stockholders and the Company to outstanding warrants.amend our Charter to increase the number of authorized shares of common stock (the “Share Increase”) and directed that it be submitted for approval by the stockholders at the Annual Meeting in light of the time and expense that would otherwise be required to convene a special meeting for consideration of the proposed amendment at a later time. The form of the proposed Share Increase amendment is attached to this Proxy Statement as Annex B.

or understandings to issue any authorized but unissued shares of our common stock. However, these additional authorized shares could be used in the future for various purposes without further stockholder approval, except as such approval may be harmed, perhaps severely,required in particular cases by our organizational documents, applicable law or the rules of any stock exchange or other system on which our securities may then be listed.

Notwithstanding the foregoing, authorized but unissued shares of common stock may enable our Board to render more difficult or to discourage an attempt to obtain control of the Company. One of the consequences of such an action would be to protect the continuity of or entrench our management. This may adversely affect the market price of our common stock. If, in the due exercise of its fiduciary obligations, for example, our Board were to determine that a takeover proposal were not in the best interest of the Company, such shares could be issued by the Board without stockholder approval in one or more private placements or other transactions that might prevent or render more difficult or make more costly the completion of any attempted takeover transactions by diluting voting or other rights of the proposed acquirer or insurgent stockholder group, by creating a substantial voting block in institutional or other hands that might support the position of the incumbent Board, by effecting an acquisition that might complicate or preclude the takeover, or otherwise. We have no current intention to issue shares for anti-takeover purposes.

Failure to approve this limitation.Authorized Stock Increase Proposal could have adverse results for, and effects on, the Company. Without a reasonable amount of authorized shares available to us for issuance, we may not have the ability to raise additional capital, establish strategic relationships with other companies or expand our business or product lines through acquisition. In addition, if we effect a reverse stock split as described in Proposal 4, we will have a more limited number of authorized shares available for issuance which could further exacerbate the problems described above. Furthermore, our future success depends in part onupon our continued ability to attract, retain and motivate highly qualified managementhighly-skilled scientific, commercial and clinical and scientific personnel,managerial employees, and if this Proposal 4proposal is not approved by our stockholders, the lack of sufficient unissued and unreserved authorized shares of common stock to provide future equity incentive opportunities that our compensation committee deems appropriate could adversely impact our ability to achieve these goals. In summary, if our stockholders do not approve this Proposal 4, we may not be able to accessFurthermore, given the capital markets, complete corporate collaborations or partnerships, attract, retain and motivate employees, and pursue other business opportunities integral to our growth and success, all of which could severely harm our business and our prospects.

Effects ofdecline in the Increase in Authorized Shares

The additional common stock to be authorized by stockholder approval of this Proposal 4 would have rights identical to the currently outstanding shares of our common stock. Approval of this Proposal 4 and issuance of the additional authorized shares of common stock would not affect the rights of the holders of currently outstanding sharesprice of our common stock, except for effects incidental to increasing the number of shares of our common stock outstanding, such as dilution of any earnings per share and voting rights of current holders of common stock. Thewe may need additional shares of common stock authorized by the approval of this Proposal 4 could be issued by our board of directors without further vote of our stockholders except as may be required in particular cases by our charter, applicable law, regulatory agencies or the rules of the Nasdaq. Under our charter, stockholders do not have preemptive rights to subscribe to additional securities that may be issued by us, which means that current stockholders do not have a prior right thereunder to purchase any new issue of common stock in order to maintain their proportionate ownership interests in our Company.

The proposed certificate of amendment to increase the number of authorized shares of our common stock could, under certain circumstances, have an anti-takeover effect. The additional shares of common stock that would become available for issuance if this Proposal 4 is approved could also be used by us to oppose a hostile takeover attempt or to delay or prevent changes in control or our management. For example, without further stockholder approval, the board could adopt a “poison pill” which would, under certain circumstances related to an acquisition of our securities not approved by the board, give certain holders the right to acquire additional shares of common stock at a low price, or the board could strategically sell shares of common stock in a private transaction to purchasers who would oppose a takeover or favor the current board. Although this Proposal 4 to increase the authorized common stock has been prompted by business and financial considerations and not by the threatto satisfy our capital needs.

Effectiveness of any hostile takeover attempt (nor is the board currently aware of any such attempts directed at us), nevertheless, stockholders should be aware that approval of this Proposal 4 could facilitate future efforts by us to deter or prevent changes in control, including transactions in which the stockholders might otherwise receive a premium for their shares over then current market prices.

Notwithstanding approval of these proposals by our stockholders, our Board has reserved its right to abandon, at any time, either or both of the proposed amendments if, in its sole discretion, it determines doing so is in the best interest of the Company and our boardstockholders.

Vote Required for Approval

The affirmative vote of directors determinesthe holders of a majority of the shares issued and outstanding and entitled to exercisevote at the Annual Meeting is required to approve this proposal. Abstentions will be counted toward the vote total for Proposal 5 and will have the same effect as “AGAINST” votes.

The approval of this proposal is not conditioned on the approval or disapproval of Reverse Stock Split Proposal. However, should both this proposal and the Reverse Stock Split Proposal be approved by our stockholders, the Board would, in its discretion, choose which proposal(s) to implement, subject to its discretion to determine that neither proposal is in the best interest of the Company or its stockholders.

The Board recommends that you vote “FOR” the proposal to approve the amendment to implement the Share Increase, at our Board’s discretion.

Proposal 6

Adjournment of Annual Meeting

We are asking you to vote to approve one or more adjournments of the Annual Meeting to a later date or dates if necessary or appropriate to solicit additional proxies if there are insufficient votes to approve either the Reverse Stock Split Proposal or the Authorized Stock Increase Proposal at the time of the Annual Meeting or if we do not have a quorum.

If our stockholders approve this Adjournment Proposal, we could adjourn the Annual Meeting and any reconvened session of the Annual Meeting and use the additional time to solicit additional proxies, including proxies from stockholders that have previously returned properly executed proxies voting against the approval of the Reverse Stock Split Proposal or the Authorized Stock Increase Proposal. Among other things, approval of the Adjournment Proposal could mean that, even if we had received proxies representing a sufficient number of votes against the approval of the Reverse Stock Split Proposal or the Authorized Stock Increase Proposal such discretion,that the proposal to approve any such proposal would be defeated, we will publicly disclosecould adjourn the Annual Meeting without a vote on the approval of such proposal and seek to convince the holders of those shares to change their votes to votes in favor of approval of such proposal. Additionally, we may seek to adjourn the Annual Meeting if a quorum is not present.

Our Board believes that factit is in the best interest of the Company and our boardstockholders to be able to adjourn the Annual Meeting to a later date or dates if necessary or appropriate for the purpose of directors’ reasonsoliciting additional proxies in respect of the approval of the Reverse Stock Split Proposal or reasons for its determination.the Authorized Stock Increase Proposal if there are insufficient votes to approve either or both at the time of the Annual Meeting or in the absence of a quorum.

Vote Required

The affirmative vote of the holders of a majority of the outstanding shares onof common stock present in person or represented by proxy and entitled to vote at the record date.Annual Meeting is required for approval of the Adjournment Proposal. Abstentions will be counted toward the vote total for Proposal 46 and will have the same effect as “Against”“AGAINST” votes.

The boardBoard recommends that you vote “FOR” approval of the proposaladjournment of the Annual Meeting, if necessary, to solicit additional proxies if there are insufficient votes at the time of the Annual Meeting to approve either the amendment of our charter.Reverse Stock Split Proposal or the Authorized Stock Increase Proposal.

STOCKHOLDER PROPOSALS FOR THE 20222023 ANNUAL MEETING OF STOCKHOLDERS

For a proposal to be considered for inclusion in our proxy materials for presentation at the 20222023 annual meeting of stockholders pursuant to Rule 14a-8 under the Exchange Act, the proposal must be received by our Secretary at our principal executive offices at One First Avenue, Parris Building 34, Navy Yard Plaza, Third Floor, Boston, Massachusetts 02129,8030 El Rio Street, Houston, TX 77054, by no later than ,December 28, 2022, unless the date of 20222023 annual meeting of stockholders is changed by more than 30 days from the one-year anniversary of this year’s annual meeting, in which case the deadline will be a reasonable time before we begin to distribute the proxy materials for the 20222023 annual meeting of stockholders. Due to the complexity of the respective rights of the stockholders and us in this area, any stockholder desiring to propose such an action is advised to consult with his or her legal counsel with respect to such rights. We suggest that any such proposal be submitted to us by certified mail, return receipt requested.

Rule 14a-4 under the Exchange Act governs our use of our discretionary proxy voting authority with respect to a stockholder proposal that the stockholder has not sought to include in our proxy statement. Rule 14a-4 provides that if a proponent of a proposal fails to notify us at least 45 days prior to the month andone-year anniversary of the day of mailing of the prior year’s proxy statement, management proxyholders will be allowed to use their discretionary voting authority as to whether the proposal is raised at the annual meeting, without any discussion of the matter. If a stockholder wishes to bring a matter before the stockholders at the 20222023 annual meeting of stockholders but does not notify us before , 2022March 13, 2023 (or a reasonable time before we begin to distribute the proxy materials for the 20222023 annual meeting of stockholders if the date of the 20222023 annual meeting of stockholders is changed by more than 30 days from the one-year anniversary of this year’s annual meeting), for all proxies we receive, the management proxyholders will have discretionary authority to vote on the matter, including discretionary authority to vote in opposition to the stockholder’s proposal.

Recommendations for candidates to be considered for election to the Board at the 2023 annual meeting of stockholders may be submitted to the corporate governance and nominating committee by our stockholders. In order to make such a recommendation, a stockholder must submit the recommendation in writing to the Chairperson of the corporate governance and nominating committee, in care of our Secretary at our principal executive offices at 8030 El Rio Street, Houston, TX 77054, at least 120 days prior to the mailing date of the one-year anniversary of the previous year’s annual meeting proxy statement. To enable the corporate governance and nominating committee to evaluate the candidate’s qualifications, stockholder recommendations must include the following information:

CURRENT DIRECTORS, DIRECTOR NOMINEES AND EXECUTIVE OFFICERS

Our Board of Directors

Set forth below are the names and certain information about each of our directors as of March 12, 2021.April 14, 2022. The information presented includes each director’s age, principal occupation and business experience for the past five years and the names of other public companies of which he or she has served as a director during the past five years. In addition, the table contains information about the specific and particular experience, qualifications, attributes or skills of each current director and each nominee for director at the annual meetingAnnual Meeting that led the corporate governance and nominating committee to believe that such current director was appropriate for nomination at a previous annual meeting of stockholders or otherwise and, in the case of each nominee for director at the annual meeting,Annual Meeting, that such nominee should serve on the boardBoard following election at the annual meeting.Annual Meeting.

(1) Mr. Buchi will be retiring from the board of directors and its committees at the end of his term, which expires at the annual meeting.

EXECUTIVE COMPENSATION

Summary Compensation Discussion and AnalysisTable

This Compensation Discussion and Analysis explains our executive compensation philosophy and objectives, programs and practices and the material elements of 2020 compensation for our named executive officers. There is also discussion of the 2021 compensation decisions for our new Interim Chief Executive Officer and Interim Chief Financial Officer. As discussed in Proposal 3 of this proxy statement, we are conducting our annual advisory vote on executive compensation, or “say-on-pay” vote, that requests approval of the compensation provided to our named executive officers, as described in this subsection titled “—Compensation Discussion and Analysis” and in the tables and accompanying narrative contained below under this section “Executive Compensation.” Please review our compensation philosophies, the design of our executive compensation programs in the context of this say-on-pay vote.

For 2020, our named executive officers were:

Executive Summary

Business Highlights

During 2020 and the first quarter of 2021, we evolved our focus to our cell therapy programs and, in particular, our TCR-T program. During this period, we made significant progress advancing this program and our CAR-T and Controlled IL-12 programs, which included the following achievements:

Other Significant Factors in Determining ExecutiveNarrative to the Summary Compensation Table

The biotechnology industry is characterized by a very long product development cycle,We use base salaries to recognize the experience, skills, knowledge and responsibilities required of all our employees, including a lengthy research and development period and a rigorous approval phase involving preclinical studies, clinical trials and governmental regulatory approval. As a result, many of the traditional commercial product metrics, such as product sales, revenues and profits are irrelevant for a development-stage biotechnology company like us. Instead, the specific performance factors our compensation committee considers when determining the compensation of our named executive officers include factors related to development progress, commercialization progress, and cash/expense management, whichofficers. Base salaries are typical pre-commercial drug development metrics:

These performance factors are considered by our compensation committeereviewed annually, typically in connection with our annual performance reviews described belowreview process, and are a critical component inadjusted from time to time to realign salaries with market levels after taking into account individual responsibilities, performance and experience.

Formal bonus plan goals were not set for 2021 because our CEO was not hired until August 2021. 2021 bonuses were paid out between 69% and 100% of target based on the determinationCommittee’s assessment of annual cash and equity incentive awards for our executives.

Role of our Compensation Committee, Management and Consultant

Compensation Committee

each individual’s performance. Our compensation committee is responsible for reviewing, evaluating, approving, administering and interpreting our executive compensation and benefits policies, programs and plans, including our equity compensation plans. In particular,employment arrangements with respect to the compensation of our named executive officers ourprovide that the executive may be eligible to earn an annual performance bonus of up to a target percentage of the executive’s base salary, as described further below under the section titled “Employment and Change in Control Agreements.”

compensation committee is responsible for reviewing and recommendingIn 2021, Mr. Boyle was granted an option to the outside, independent and non-employee members of the board of directors the compensation levels and performance goals relevant to the compensation of these officers, and for evaluating the officers’ performance in light of those goals and objectives. The outside, independent and non-employee members of the board of directors approved the compensation committee’s recommendations for the 2020 compensationpurchase 2,625,000 shares of our named executive officers.

Management

Our human resources, financecommon stock, which option has an exercise price of $1.64 per share, and legal departments work875,000 shares of restricted common stock in connection with his appointment as our Chief Executive OfficerOfficer. The new hire award was intended as an inducement for Mr. Boyle to designjoin the Company and develop new executive compensation programs, to recommend changes to existing compensation programs, to recommend financial and other performance targetsa similar number of equity awards is not expected to be achieved under those programs, to prepare analyses of financial data, to prepare peer group data comparisonsgranted in 2022. The options are currently underwater and other briefing materials for consideration byare not providing the compensation committee and ultimately, to implement the decisions of the compensation committee.

The Chief Executive Officer recommends to the compensation committee for its discussion and ultimately, approval, proposed corporate performance and strategic goals and their relative weighting for the upcoming fiscal year, and provides input on the level of attainment of the prior year’s strategic goals, for purposes of determining awards under the annual performance bonus plan for all our executives, including the Chief Executive Officer. For executives other than the Chief Executive Officer, the compensation committee will consider the individual performance of the executives, as assessed by the Chief Executive Officer, and the compensation recommendations submitted to the compensation committee by the Chief Executive Officer. Our Chief Executive Officer and other members of management generally attend our compensation committee meetings for a portion of the meeting. No executive officer was present or voted in the compensation committee or the board of directors’ final determinations regarding the amount of any component of his or her own 2020 compensation package.

Consultant

During 2019 and early 2020, the compensation committee engaged Haigh and Company, or Haigh, as an independent compensation consultant. Haigh was engaged by and reported directly to the compensation committee and was determined to have no conflicts of interests in a review conducted by the compensation committee.

As part of its duties, Haigh provided the compensation committee with the following services:

Beginning in March 2020, our compensation committee engaged FW Cook as its independent compensation consultant. FW Cook provided independent market findings to the compensation committee in August 2020 and has provided advice to the compensation committee as to Interim Chief Executive Officer compensation and non-employee director compensation in 2021. FW Cook was determined to be free of conflicts of interest and able to operate as an independent compensation advisor.

Peer Group, Survey Sources and Market Data

Peer Group

In November 2019, in consultation with Haigh, the compensation committee evaluated the list of companies that should be included in the peer group used as a reference point in making 2020 executive compensation decisions, which we refer to as the 2019 peer group. The selected 2019 peer group companies were chosen based upon the following selection criteria: