Securing additional patent protection in the United States, Canada, and Japan for INTASYL Compounds

King of Prussia, Pennsylvania--(Newsfile Corp. - July 15, 2026) - Phio Pharmaceuticals Corp. (NASDAQ: PHIO) is a clinical-stage siRNA biopharmaceutical company developing therapeutics using its proprietary INTASYL^® gene silencing technology to eliminate cancer. Phio Pharmaceuticals announced today significant progress in the protection of its proprietary innovations across key international markets. The company has received multiple favorable patent actions encompassing three notices of allowance and one grant decision to further strengthen Phio's global intellectual property portfolio in the United States, Canada, and Japan, respectively. This reinforces the Company's commitment to developing and safeguarding breakthrough technologies for the INTASYL compounds.

"Strong patent protection is an important component of our strategy to advance innovative immuno-oncology therapies and maximize the long-term value of our INTASYL siRNA platform," said Robert Bitterman, President and Chief Executive Officer of Phio Pharmaceuticals. "These additional patent advancements across therapeutic areas and geographic regions will facilitate strategic partnerships, support R&D initiatives, and eventual commercialization."

The patent portfolio consists of 54 issued patents. The portfolio encompasses the INTASYL^® chemistry, specific gene targets, immuno-oncology compounds and therapeutic indications in key countries.

About Phio Pharmaceuticals Corporation

Phio Pharmaceuticals Corp. (NASDAQ: PHIO) is a clinical-stage biopharmaceutical company advancing its proprietary INTASYL^® siRNA gene silencing technology to eliminate cancer. Phio's INTASYL compounds are designed to enhance the body's immune cells to more effectively kill cancer cells. Phio's lead clinical development program is an INTASYL compound, PH-762, that silences the PD-1 gene implicated in various forms of skin cancer. The Phase 1b trial (NCT# 06014086) evaluated PH-762 for the treatment of cutaneous squamous cell carcinoma, melanoma and Merkel cell carcinoma. PH-762 is a potential non-surgical treatment for skin cancers.

For additional information, visit the Company's website, www.phiopharma.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as "intends," "believes," "anticipates," "indicates," "plans," "expects," "suggests," "may," "would," "should," "potential," "designed to," "will," "ongoing," "estimate," "forecast," "target," "predict," "could" and similar references, although not all forward-looking statements contain these words. These statements, which include statements, among other things, regarding the anticipated benefits of our INTASYL™ RNAi platform, the results from our ongoing clinical trials, our expectations that our cash runway will extend into the first half of 2027, our expectations regarding timing of FDA submissions intended to propose and seek guidance for next steps in clinical study design for PH-762, our expectations that such FDA submissions and any related FDA meetings will clarify next steps in advancing the PH-762 development program, details regarding our planned non-clinical toxicology study, and our ability to support ongoing clinical development, operational requirements and strategic initiatives with the capital we currently have on hand, are based only on our current beliefs, expectations and assumptions and are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of our control. Our actual results may differ materially from those indicated in the forward-looking statements as a result of a number of important factors, including, but not limited to, the impact of future FDA interactions on the development of our product candidates; the impact to our business and operations by inflationary pressures; recession fears; the development of our product candidates, results from our nonclinical, preclinical and clinical activities, our ability to execute on business strategies, our ability to develop our product candidates with collaboration partners, and the success of any such collaborations, the timeline and duration for advancing our product candidates into clinical development, the timing or likelihood of regulatory filings and approvals, the success of our efforts to commercialize our product candidates if approved, our ability to manufacture and supply our product candidates for clinical activities, and for commercial use if approved, the scope of protection we are able to establish and maintain for intellectual property rights covering our technology platform, our ability to obtain future financing, market and other conditions and those risks identified in our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q under the caption "Risk Factors" and in other filings the Company periodically makes with the U.S. Securities and Exchange Commission. Readers are urged to review these risk factors and to not act in reliance on any forward-looking statements, as actual results may differ from those contemplated by our forward-looking statements. Phio does not undertake to update forward-looking statements to reflect a change in its views, events or circumstances that occur after the date of this release, except as required by law.

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