Item 1.01. Entry Into a Material Definitive Agreement

On October 17, 2025, Entero Therapeutics, Inc. (the "Company") entered into a Securities Purchase Agreement (the "Purchase Agreement") with an investor ("Investor"), pursuant to which the Company may sell to the Investor in a private placement ("Offering") up to $5,000,000 in gross proceeds: (i) Promissory Notes ("Notes") and (ii) a common stock purchase warrant to purchase up to an aggregate of 1,520,000 shares of common stock (the "Warrant," and the shares issuable upon exercise of the Warrant, the "Warrant Shares," and the Notes, together with the Warrant sold under the Offering, the "Securities"). The Purchase Agreement permits subsequent Closings after the Initial Closing, for all or any portion of the remaining aggregate offering amount of the Securities not sold at the time of the Initial Closing or any subsequent Closing. The parties made customary representations and warranties, and agreed to customary covenants and indemnification provisions. The capitalized terms used herein but not otherwise defined have the meanings set forth in the Purchase Agreement.

The Company intends to use the net proceeds for general corporate purposes (which for the avoidance of doubt may include acquisitions, in the Company's discretion), including working capital. The Initial Closing took place on October 17, 2025, pursuant to which the Company sold to the Investor: (i) a Note in the principal amount of $500,000 and (ii) a Warrant to purchase up to 200,000 shares of common stock, for gross proceeds of $500,000.

Promissory Note

The Note issued to the Investor on October 17, 2025 was in the principal amount of $500,000, with a maturity date ("Maturity Date") of one year and one day after its date of issuance. The Company may extend the Maturity Date upon notice to the Investor for an unrestricted number of times; provided, however, that each time the Company exercises such extension option the Company can only extend the Maturity Date in increments of one year and one day. The Note is not convertible and does not bear interest. The Note's default events include any default in the payment of the principal amount of the Note, as and when the same shall become due and payable (whether on the Maturity Date or by acceleration or otherwise), which default is not cured within five (5) Business Days (as defined in the Note); or the Company or any Subsidiary (as defined in the Note) shall be subject to a Bankruptcy Event (as defined in the Note).

Warrant

The Warrant is exercisable on stockholder approval (such date of stockholder approval, the "Stockholder Approval Date") and expire five years from the Stockholder Approval Date. The Warrant has an exercise price of $2.50 per share, subject to adjustment as set forth in the Warrant for stock splits, stock dividends, recapitalizations and similar customary adjustments. Additionally, during such time as the Warrant is outstanding, if the aggregate amount of proceeds invested by the Investor pursuant to the Purchase Agreement increases above the amount invested on the Initial Closing Date pursuant to subsequent Closings, if any, then the number of Warrant Shares will be adjusted, pro rata, such that the aggregate number of Warrant Shares issuable under the Warrant (as adjusted for any stock splits, stock dividends or similar corporate events) equals the product of (i) the Holder's total Subscription Amount multiplied by (ii) 0.40, up to an maximum of 1,520,000 Warrant Shares.

The Investor may exercise the Warrant on a cashless basis if the shares of common stock underlying the Warrant are not then registered pursuant to an effective registration statement. The Investor agreed to restrict its ability to exercise the Warrant such that the number of shares of the Company's common stock held by the Investor and its affiliates after such exercise does not exceed a Beneficial Ownership Limitation of 4.9% of the Company's then issued and outstanding shares of common stock.

Pursuant to the Purchase Agreement, the Company agreed to hold a shareholder meeting to obtain Stockholder Approval as soon as practicable following preparation of any required financial statements for a proxy statement for a special or annual meeting. If the Company does not obtain Stockholder Approval at such meeting, the Company shall call a stockholder meeting each 90 days thereafter to seek Stockholder Approval until the earlier of the date on which Stockholder Approval is obtained or the Warrant is no longer outstanding.

Also pursuant to the Purchase Agreement, the Company agreed to file a registration statement as soon as practicable providing for the resale by the Investor of the Warrant Shares.

The foregoing descriptions of each of the Purchase Agreement, the Note, and the Warrant do not purport to be complete and are each qualified in their entirety by reference to the full text of the Purchase Agreement, the form of Note and Warrant, copies of which are filed as Exhibits 10.1, 10.2, and 10.3, respectively, to this Current Report on Form 8-K ("Form 8-K") and incorporated herein by reference.