Theriva Biologics, Inc.

Disclosure of Material Event

The information set forth below is included herein for purposes of providing disclosures under Items 1.01 and 5.02 of Form 8-K.

Shallcross Amended and Restated Employment Agreement

Mr. Shallcross has served as our Chief Financial Officer since June 1, 2015, initially pursuant to the terms of a two year employment agreement that we entered with him on April 28, 2015, which was replaced by an employment agreement we entered into with him on December 6, 2018 when he became our Chief Executive Officer, which was replaced by a three year employment agreement we entered into with him on January 3, 2022 which expired on January 3, 2025 (the “2022 Shallcross Employment Agreement”). On March 3, 2025, we entered into a new employment agreement with Mr. Shallcross (the “2025 Shallcross Employment Agreement”) for a term of two years, pursuant to which he continued to serve as our Chief Executive Officer and Chief Financial Officer. On August 10, 2026, we entered into an Amended and Restated Employment Agreement with Mr. Shallcross (the “Amended and Restated Shallcross Employment Agreement”), which replaced and superseded the 2025 Shallcross Employment Agreement in its entirety. The Amended and Restated Shallcross Employment Agreement has a stated term of two years from the date of execution of such agreement (the “Employment Term”) and provides for Mr. Shallcross to serve as our President, Chief Executive Officer and Chief Financial Officer. Mr. Shallcross does not receive additional compensation for service as our director.

Pursuant to the Amended and Restated Shallcross Employment Agreement, Mr. Shallcross is entitled to an annual base salary of $687,562, subject to review and adjustment from time to time by the Board (or a committee thereof) in its sole discretion, but which may not be decreased. Mr. Shallcross is also eligible to receive an annual cash performance bonus of up to fifty percent (50%) of his annual base salary and payable based upon the Board's assessment of Mr. Shallcross’ performance and the Company's attainment of targeted goals as set by the Board in its sole discretion, as well as discretionary annual equity awards pursuant to the Company’s incentive equity plans.

The Amended and Restated Shallcross Employment Agreement contains confidentiality obligations and invention assignments by Mr. Shallcross, which are governed by the Proprietary Information, Inventions, Non-Solicitation and Non-Competition Agreement, dated February 27, 2017, which remains in full force and effect. The Amended and Restated Shallcross Employment Agreement also contains non-competition and non-solicitation provisions applicable during the Employment Term and for the one-year period thereafter.

The Amended and Restated Shallcross Employment Agreement provides that if Mr. Shallcross’ employment is terminated for any reason, he or his estate as the case may be, will be entitled to receive the unpaid base salary through the date of termination and accrued vacation, any unpaid annual bonus earned with respect to any calendar year ending on or preceding the date of termination, reimbursement for any unreimbursed expenses incurred through the date of termination, and all other payments and benefits to which Mr. Shallcross may be entitled under the terms of any applicable compensation arrangement or benefit, equity or perquisite plan or program or grant (the “Accrued Amounts”). Upon termination due to Disability (as such term is defined in the Amended and Restated Shallcross Employment Agreement) or death, Mr. Shallcross or his estate shall be entitled to exercise any vested equity awards for a period equal to the shorter of: (i) six (6) months after termination, or (ii) the remaining term of the awards. If Mr. Shallcross’ employment is terminated by us for Cause (as such term is defined in the Amended and Restated Shallcross Employment Agreement) or by Mr. Shallcross without Good Reason, Mr. Shallcross shall be entitled to receive any Accrued Amounts only.

If Mr. Shallcross’ employment is terminated by us without Cause (and not due to Disability or death) or by Mr. Shallcross for Good Reason (as such term is defined in the Amended and Restated Shallcross Employment Agreement), then, subject to him executing a general release in form acceptable to us that becomes effective, in addition to paying the Accrued Amounts, (a) we will continue to pay his then current base salary for a period of twelve (12) months following the termination date, (b) if Mr. Shallcross timely elects continued coverage under COBRA, we will pay the COBRA premiums necessary to continue health insurance coverage for Mr. Shallcross and his covered dependents until the earliest of twelve (12) months following the termination date, the date Mr. Shallcross becomes eligible for substantially equivalent health insurance coverage in connection with new employment or self-employment, or the date Mr. Shallcross ceases to be eligible for COBRA continuation coverage for any reason, and (c) all unvested stock options and other equity awards shall immediately vest and he shall be entitled to exercise any such vested equity awards for a period equal to the shorter of: (1) eighteen (18) months after termination, or (2) the remaining term of the awards. In addition, Mr. Shallcross will be eligible to receive a pro-rata portion of his annual bonus, as determined by the Board of Directors, for the performance year in which the termination occurs.

For purposes of the Amended and Restated Shallcross Employment Agreement, a “Change in Control” includes: (i) the acquisition by any person or entity of beneficial ownership of securities representing 50% or more of our voting power; (ii) a merger or consolidation in which our stockholders immediately prior to the transaction do not retain a majority of the voting power of the surviving entity; (iii) the sale of substantially all of our assets or our liquidation or dissolution; or (iv) the execution of a definitive agreement providing for a transaction involving us and a non-listed private operating company, including a reverse merger, sign and close reverse merger, forward merger, share exchange, asset acquisition, recapitalization or similar transaction, that is intended to ultimately result in a change of the majority of the board of directors or a shift in majority voting power from our pre-transaction stockholders after consummation of all of the transactions contemplated by the relevant transaction documents, included the conversion of securities issued as merger consideration. In the case of a Change in Control, Mr. Shallcross’ 180-day period for providing notice of Good Cause will not begin until all conditions necessary to effect the employee’s change in title or position have occurred and any required stockholder approvals relating to the resulting ownership changes have been obtained.

The Amended and Restated Shallcross Employment Agreement provides that upon the occurrence of a Change in Control, all unvested stock options and other equity awards shall immediately vest (and any equity awards subject to the satisfaction of performance goals shall be deemed earned at not less than target performance) and the time period that Mr. Shallcross will have to exercise all vested stock options and other awards shall be equal to the shorter of: (i) twenty-four (24) months after termination, or (ii) the remaining term of the awards.

If within eighteen (18) months after the occurrence of a Change in Control, Mr. Shallcross terminates his employment for Good Reason or we terminate Mr. Shallcross’ employment without Cause, Mr. Shallcross will be entitled to receive: (i) the portion of his base salary for periods prior to the effective date of termination accrued but unpaid (if any); (ii) all unreimbursed expenses (if any); (iii) an aggregate amount (the “Change in Control Severance Amount”) equal to two (2) times the sum of his base salary plus an amount equal to the bonus that would be payable if the target level performance were achieved under our annual bonus plan (if any) in respect of the fiscal year during which the termination occurs (or the prior fiscal year if bonus levels have not yet been established for the year of termination); and (iv) a payment equal to twenty-four (24) times the monthly COBRA premium for Mr. Shallcross and his eligible dependents (at the rate in effect for Mr. Shallcross’ coverage at the time of his termination), subject to him executing a general release in form acceptable to us that becomes effective. An amount equal to $500,000 shall be allocated from the Change in Control Severance Amount as, and deemed, a payment to Mr. Shallcross in exchange for Mr. Shallcross’ covenant not to compete.

Upon the termination of employment for Good Reason by Mr. Shallcross or upon the involuntary termination of employment by the Company for any reason other than death, Disability or Cause, in either case within eighteen (18) months after the occurrence of a

Change in Control, the Company shall also provide, for the period of two (2) consecutive years commencing on the date of such termination of employment, medical, dental, life and disability insurance coverage for Mr. Shallcross and the members of his family that are not less favorable to Mr. Shallcross than the group medical, dental, life and disability insurance coverage carried by the Company for Mr. Shallcross and the members of his family at the time of termination, subject to him executing a general release in form acceptable to the Company that becomes effective. The Change in Control Severance Amount is to be paid in a lump sum if the Change in Control event constitutes a “change in the ownership” or a “change in the effective control” of the Company or a “change in the ownership of a substantial portion of a corporation's assets” (each within the meaning of Section 409A of the Internal Revenue Code (“Section 409A”)), or in 48 substantially equal payments, if the Change in Control event does not so comply with Section 409A.

The foregoing description of the material terms of the Amended and Restated Shallcross Employment Agreement is not complete and is qualified in its entirety by reference to the full text thereof, a copy of which is filed as Exhibit 10.1 to this Quarterly Report on Form 10-Q and is incorporated herein by reference.

Insider Trading Arrangements

During the three months ended June 30, 2026, no director orofficer of the Company adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K.