and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Director — R. Todd Plott, M.D.: Dr. R. Todd Plott was appointed to the Board of Directors and will serve on the Governance Committee.

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Entry into a Material Definitive Agreement. On April 8, 2026, Phio Pharmaceuticals Corp. (the “Company”) entered into an At The Market Offering Agreement (the “Sales Agreement”) with H.C. Wainwright & Co., LLC, as sales agent (the “Sales Agent”), pursuant to which the Company may offer and sell, from time to time, through the Sales Agent, shares of the Company’s common stock, par value $0.0001 per share (the “Shares”). The offering and sale of up to $6,360,000 of the Shares pursuant to the Sa…

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Entry into a Material Definitive Agreement. On November 3, 2025, Phio Pharmaceuticals Corp., a Delaware corporation (the “Company”), entered into inducement letter agreements (the “Inducement Letter Agreements”) with certain holders (the “Holders”) of certain of its existing common stock warrants to exercise such warrants for an aggregate of 5,663,182 shares of the Company’s common stock, $0.0001 par value (the “Common Stock”). These warrants were originally issued to the Holders in July 2024…

The New Warrants and the Placement Agent Warrants were issued in reliance upon exemptions from registration pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”) and Rule 506 of Regulation D promulgated thereunder. The New Warrants, the Warrant Shares, the Placement Agent Warrants and the shares of Common Stock issuable thereunder were not registered under the Securities Act or any state securities laws and may not be offered or sold absent registration…

Director — Robert Ferrara: Robert Ferrara resigned from his position as a director and Lead Independent Director of the Board.

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Entry into a Material Definitive Agreement. On July 25, 2025, Phio Pharmaceuticals Corp., a Delaware corporation (the “Company”), entered into inducement letter agreements (the “Inducement Letter Agreements”) with certain holders (the “Holders”) of certain of its existing warrants to purchase an aggregate of 928,596 shares of the Company’s common stock, $0.0001 par value (the “Common Stock”), originally issued to the Holders in December 2024 and January 2025, having exercise prices between $2…

Unregistered Sales of Equity Securities. The disclosures in

VP, Finance and Administration (principal financial officer and principal accounting officer) — Lisa Carson: Ms. Carson was promoted to VP, Finance and Administration with significant responsibilities.

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Changes in Registrant’s Certifying Accountant. The Audit Committee (the “Audit Committee”) of the Board of Directors of Phio Pharmaceuticals Corp., Inc. (the “Company”) conducted a competitive process to determine the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2025. As a result of this process, on April 17, 2025, the Audit Committee approved the dismissal of BDO USA, P.C. (“BDO”) as the Company’s independent registered public accounting fir…

and attached as Exhibit 99.1 to this Report will not be treated as “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information will not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or into another filing under the Exchange Act, unless that filing expressly incorporates this information by reference.

Director — Mr. David H. Deming: Appointment of a new director to the board with no indication of significant changes or departures.

Entry into a Material Definitive Agreement. Concurrent Registered Direct Offering and Private Placement On January 16, 2025, Phio Pharmaceuticals Corp. (the “Company”) entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain institutional and accredited investors in connection with a registered direct offering (the “Registered Direct Offering”) and concurrent private placement (the “Private Placement”). Pursuant to the Securities Purchase Agreement, the…

Other Events. On January 16, 2025 , the Company issued a press release announcing the pricing of the Registered Direct Offering and the Private Placement. The full text of the press releases is attached hereto as Exhibit 99.1 and incorporated herein by reference.

Unregistered Sales of Equity Securities. The disclosures in

Unregistered Sales of Equity Securities. The disclosures in

Entry into a Material Definitive Agreement. Concurrent Registered Direct Offering and Private Placement On January 14, 2025, Phio Pharmaceuticals Corp. (the “Company”) entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain institutional and accredited investors in connection with a registered direct offering (the “Registered Direct Offering”) and concurrent private placement (the “Private Placement”). Pursuant to the Securities Purchase Agreement, the…

Other Events. On January 15, 2025 , the Company issued a press release announcing the pricing of the Registered Direct Offering and the Private Placement. The full text of the press releases is attached hereto as Exhibit 99.1 and incorporated herein by reference.

Entry into a Material Definitive Agreement. Concurrent Registered Direct Offering and Private Placement On January 13, 2025, Phio Pharmaceuticals Corp. (the “Company”) entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain institutional and accredited investors in connection with a registered direct offering (the “Registered Direct Offering”) and concurrent private placement (the “Private Placement”). Pursuant to the Securities Purchase Agreement, the…

Other Events. On January 14, 2025 , the Company issued a press release announcing the pricing of the Registered Direct Offering and the Private Placement. The full text of the press releases is attached hereto as Exhibit 99.1 and incorporated herein by reference.