Phio Pharmaceuticals Announces Significant Step Forward in its Drug Development Program for PH-762

Rhea-AI Summary

Phio Pharmaceuticals (NASDAQ: PHIO) announced FDA acceptance of a nonclinical protocol for its INTASYL candidate PH-762 and said a required toxicology study will commence in Q1 2026. The company also said initiatives to produce commercially viable drug product under cGMP are ongoing and targeted for later in 2026, with part of recent financing directed to these efforts.

Interim Phase 1b results reported from 18 treated patients: among 16 cutaneous squamous cell carcinoma (cSCC) patients, there were 6 complete responses, 2 near-complete responses, and 2 partial responses; six cSCC and one metastatic melanoma showed pathologic non-response. No dose-limiting toxicities or clinically relevant treatment-emergent adverse effects were observed to date.

Positive

• FDA accepted nonclinical protocol for PH-762
• Toxicology study to start in Q1 2026
• 6 complete responses among 16 cSCC patients
• No dose-limiting toxicities reported to date
• cGMP drug production initiative on target for late 2026
• Portion of recent financing directed to PH-762 development

Negative

• Dataset limited to 18 patients overall
• Six cSCC and one metastatic melanoma showed pathologic non-response

Key Figures

Patients treated 18 patients Phase 1b dose-escalation trial for PH-762 in skin cancers

Complete responses 6 patients Among 16 cSCC patients in Phase 1b trial (100% clearance)

Near-complete responses 2 patients (>90% clearance) Among 16 cSCC patients in Phase 1b trial

Partial responses 2 cSCC + 1 MCC (>50% clearance) Phase 1b PH-762 skin cancer trial responses

Dose-limiting toxicities 0 observed Safety profile in Phase 1b intratumoral PH-762 trial

Registered warrant shares 11,763,800 shares Shares covered by S-3 resale registration for warrant exercises

Potential warrant proceeds $24.5 million Maximum cash to company on full exercise of registered warrants

Q3 2025 net loss $2.392 million Net loss reported in Q3 2025 10-Q filing

Market Reality Check

$1.05 Last Close

Volume Volume 396,289 vs 20-day average 351,643 (relative volume 1.13x). normal

Technical Price $1.10 is trading below the 200-day MA at $1.94 and far below the 52-week high of $9.79.

Peers on Argus 1 Down

Peer moves are mixed: PHGE up 3.3%, APLM up 8.76%, BCDA up 1.57%, BCTX up 7.51% but flagged separately in momentum scanner as down 18.91%, and ADAP down 17.57%. This pattern suggests today’s PHIO setup is more stock-specific than broad sector-driven.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Nov 25	Clinical milestone	Positive	+3.5%	Completion of enrollment and positive interim PH-762 Phase 1b data.
Nov 17	Conference presentation	Positive	+1.5%	Upcoming podium presentation on INTASYL siRNA technology and PH-762.
Nov 13	Earnings update	Negative	-9.5%	Q3 2025 net loss and financing-related developments alongside PH-762 progress.
Nov 07	Clinical data update	Positive	+5.4%	Planned SITC presentation of recent PH-762 skin cancer trial results.
Nov 07	Award recognition	Positive	+5.4%	PH-762 named Immunomodulatory Solution of the Year by award program.

Pattern Detected

Recent PHIO news has generally been clinical or platform-positive and has most often aligned with same-day positive price reactions, with earnings-related financing news drawing the only notable pullback.

Recent Company History

Over the last two months, PHIO has focused on advancing its INTASYL siRNA lead PH-762 for cutaneous carcinomas. Clinical updates on November 3 and 25, 2025 highlighted favorable safety and response data in a Phase 1b trial, while conference and award announcements on November 7 and a podium talk on November 18 reinforced visibility of the platform. An earnings update on November 13, 2025 combined ongoing clinical progress with financing to extend runway. Today’s FDA-accepted nonclinical protocol and planned toxicology work continue that PH-762 development trajectory.

Regulatory & Risk Context

Active S-3 Shelf Registration 2025-11-20

$24.5 million registered capacity

An effective S-3 resale registration has been filed covering up to 11,763,800 shares issuable upon exercise of outstanding warrants. Existing stockholders, not the company, would sell these shares. Phio would only receive cash proceeds if warrants are exercised, which at full cash exercise would total approximately $24.5 million, earmarked to support working capital and development of PH-762.

Market Pulse Summary

The stock moved -6.4% in the session following this news. A negative reaction despite clinically constructive news would contrast with most prior PH-762 announcements, which often aligned with gains of 1–5%. The update describes FDA-accepted nonclinical plans and continued manufacturing work rather than new efficacy data, which may temper enthusiasm. An active S-3 tied to 11,763,800 warrant shares and recent financings could also weigh on sentiment if investors focus on supply over the longer development timeline.

Key Terms

sirna medical

"is a clinical-stage siRNA biopharmaceutical company developing therapeutics"

Small interfering RNA (siRNA) is a short strand of genetic material that binds to and destroys the messenger RNA that carries instructions for making a specific protein, effectively switching that gene off. Investors care because siRNA is a platform for precise medicines: successful trials or approvals can create high-value drugs, while delivery challenges, manufacturing complexity, patent positions and regulatory risk can sharply affect a biotech company's prospects.

gene silencing medical

"using its proprietary INTASYL gene silencing technology to eliminate cancer"

Gene silencing is a biological process that turns down or shuts off the activity of a specific gene so it stops making its product, like dimming or muting a single light in a room instead of cutting power to the whole house. Investors care because therapies or products that intentionally silence harmful genes can become new drugs, diagnostics, or royalties, affecting a company’s future revenue, risk profile, and valuation.

toxicology study medical

"The company will begin a toxicology study, which is required by the FDA"

A toxicology study tests whether a drug, chemical, or product causes harmful effects and at what doses, usually using laboratory cells or animal models before human use. It matters to investors because the results influence regulatory approval, development costs, timelines and potential legal or market risks—think of it as a crash test that reveals safety problems early and can make or break a product’s commercial prospects.

pivotal trial medical

"required by the FDA prior to commencing a human pivotal trial"

A pivotal trial is a key test of a new medicine or treatment to see if it works and is safe enough to be approved by health authorities. It's like a final exam for a new product, and passing it is essential for bringing the treatment to the public.

current good manufacturing practices regulatory

"drug product in 2026 that meets FDA's current Good Manufacturing Practices"

Current good manufacturing practices (cGMPs) are the regulatory standards that govern how medicines, medical devices, and other regulated products must be made to ensure consistent safety, purity, and quality. Think of them as a strict recipe and kitchen rules—clean facilities, trained staff, documented steps, and quality checks—so each batch turns out the same. For investors, cGMP compliance reduces the risk of product recalls, regulatory fines, production shutdowns, and damage to long-term revenue and reputation.

phase 1b medical

"results were reported in the on-going Phase 1b dose escalation clinical trial"

"Phase 1b" is an early stage in testing a new medical treatment or vaccine, where it is given to a small group of people to evaluate its safety and determine the right dose. For investors, this phase signals progress in development, indicating the treatment is advancing through initial safety checks, which can influence expectations for future success and potential market impact.

dose-limiting toxicities medical

"there were no dose-limiting toxicities or clinically relevant treatment-emergent"

Dose-limiting toxicities are the harmful side effects seen in early clinical trials that are severe enough to stop researchers from raising a drug’s dose. Like a car’s speed limiter marking the safe top speed, DLTs define the maximum tolerable dose, and they matter to investors because they determine whether a medicine can reach effective levels, influence development timelines, costs, and regulatory chances, and thus affect a drug’s commercial prospects.

treatment-emergent adverse effects medical

"no dose-limiting toxicities or clinically relevant treatment-emergent adverse effects"

Adverse effects that first appear or worsen after a patient begins a therapy or enters a clinical study; they capture any new symptoms or health problems that are linked in time to the treatment. Investors watch these because they reveal a drug’s safety profile—like spotting warning lights on a dashboard—and can affect regulatory approval, prescribing decisions, liability risk, and ultimately a company’s revenue and stock value.

AI-generated analysis. Not financial advice.

Nonclinical protocol study design accepted by FDA

Study to commence in First Quarter 2026

King of Prussia, Pennsylvania--(Newsfile Corp. - December 23, 2025) - 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 announced today that it has taken a major step forward in its drug development program for PH-762. The company will begin a toxicology study, which is required by the FDA prior to commencing a human pivotal trial. Concurrently, initiatives are continuing to advance the delivery of commercially viable drug product in 2026 that meets FDA's current Good Manufacturing Practices. A portion of the net proceeds from Phio's recent financing is being directed to these two major initiatives.

Recently, positive interim safety and efficacy results were reported in the on-going Phase 1b dose escalation clinical trial with the INTASYL compound PH-762 for the treatment of skin cancer. To date, a total of 18 patients with cutaneous carcinomas have completed treatment across five dose escalating cohorts in the Phase 1b trial. The cumulative pathologic response in 16 patients with cSCC include six with a complete response (100% clearance), two with a near complete response (> 90% clearance) and two with a partial response (> 50% clearance). A single patient with metastatic Merkel cell carcinoma had a partial response (> 50% clearance). Six patients with cSCC and one patient with metastatic melanoma had a pathologic non-response (< 50% clearance). No patients in the study, however, exhibited clinical progression of disease. To date, there were no dose-limiting toxicities or clinically relevant treatment-emergent adverse effects in the patients receiving intratumoral PH-762 in this trial. Moreover, PH-762 has been well tolerated in all enrolled patients in each escalating dose cohort.

"The conduct of this nonclinical study is a very significant step in progressing the drug development pathway of PH-762 toward an NDA approval. Phio's communication with FDA is essential in advancing our development strategy for PH-762," stated Robert Bitterman, CEO and Chairman of Phio Pharmaceuticals. "In addition, the initiative to deliver commercially viable drug product from our US supplier is on target for later in 2026. This is another critical advancement in the drug development program of PH-762."

About Phio Pharmaceuticals Corp.

Phio Pharmaceuticals Corp. (Nasdaq: PHIO) is a clinical-stage siRNA biopharmaceutical company advancing its INTASYL^® gene silencing technology focused on immuno-oncology therapeutics. Phio's INTASYL compounds are designed to enhance the body's immune cells to more effectively kill cancer cells. Phio's lead clinical program is an INTASYL compound, PH-762, that silences the PD-1 gene implicated in various forms of skin cancer. The ongoing Phase 1b trial (NCT# 06014086) is evaluating 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. Examples of forward-looking statements contained in this press release include, among others, the possibility that our INTASYL® siRNA gene silencing technology will make the body's immune cells more effective in killing cancer cells, the timing of our studies and trials, including the planned toxicology study for PH-762, the expectation that commercially viable drug product will be available in 2026, the advancement of the drug development pathway of PH-762 toward an NDA approval, the potential for additional potential applications across the INTASYL portfolio, and statements regarding our commercial and clinical strategy, development plans and timelines and other future events.  

These statements 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 to our business and operations by inflationary pressures, rising interest rates, recession fears, the development of our product candidates, results from our 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 identified in our 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 SEC. 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.  

Contact:
Phio Pharmaceuticals Corp.
Jennifer Phillips: jphillips@phiopharma.com
Corporate Affairs

To view the source version of this press release, please visit https://www.newsfilecorp.com/release/278866

FAQ

What did Phio (PHIO) announce about PH-762 on December 23, 2025?

Phio said the FDA accepted a nonclinical protocol and a toxicology study will begin in Q1 2026.

What interim clinical results did PH-762 report in the Phase 1b trial?

Among 16 cSCC patients: 6 complete responses, 2 near-complete, 2 partial; six cSCC and one melanoma were non-responders.

Were there any safety issues reported for PH-762 in the Phase 1b trial?

No dose-limiting toxicities or clinically relevant treatment-emergent adverse effects were reported to date.

When will Phio start the nonclinical toxicology study required for PH-762?

The company plans to commence the required toxicology study in Q1 2026.

What is Phio’s timeline for producing commercially viable PH-762 drug product?

Phio expects commercially viable, cGMP-compliant drug product from its US supplier targeted for later in 2026.