Phio Pharmaceuticals Reports Second Quarter 2025 Financial Results and Provides Business Update Clinical trial advances for INSTASYL siRNA lead product candidate PH-762 5th cohort enrolling patients in on-going clinical

Phio Pharmaceuticals

Reports Second Quarter 2025 Financial Results and Provides Business Update

Clinical trial advances for INSTASYL siRNA lead

product candidate PH-762

5th cohort enrolling patients in on-going clinical

KING OF PRUSSIA, PA-(Newsfile Corp.-August 14, 2025) - Phio Pharmaceuticals

Corp. (NASDAQ: PHIO) is a clinical-stage biopharmaceutical company developing therapeutics using its proprietary INTASYL

siRNA gene silencing technology to eliminate cancer. Phio today reported its financial results for the quarter ended June 30, 2025 and

provided a business update.

Recent Corporate Updates

PH-762 Clinical Progress

Phio's ongoing Phase 1b dose escalation

clinical trial (NCT 06014086) is designed to evaluate the safety and tolerability of neoadjuvant use of intratumoral PH-762 in Stages

1, 2 and 4 cutaneous squamous cell carcinoma (cSCC), Stage 4 melanoma, and Stage 4 Merkel cell carcinoma. To date, a total of 15 patients

with cutaneous carcinomas have been treated across four cohorts in the Phase 1b trial. These cohorts included 13 patients with cSCC, one

patient with metastatic melanoma and one patient with metastatic Merkel cell carcinoma. There have been no dose-limiting toxicities or

clinically relevant treatment-emergent adverse effects in the patients who received intratumoral PH-762 in this trial. Moreover, PH-762

has been well tolerated in all enrolled patients in each escalating dose cohort. No patients exhibited clinical progression of disease

during the treatment phase of this trial.

The cumulative pathologic

responses in the 13 patients with cSCC include five with complete response (100% clearance), one patient with a near complete response

(>90% clearance), one with a partial response (>50% clearance) and six patients with a pathologic non-response (< 50% clearance).

The Merkel cell carcinoma

patient with stage 4 metastatic disease had a pathological partial response (>50% clearance). The melanoma patient was a non-responder

Phio is now enrolling

what is expected to be the 5th and final cohort in the Phase 1b trial.

In addition, the Company entered into a comprehensive

drug substance development services agreement with a U.S. manufacturing company. The company will provide analytical and process

development and cGMP manufacture of Phio's lead development compound PH-762.

In May 2025, Phio delivered a podium presentation

for its INTASYL self-delivering siRNA technology at the Society of Investigative Dermatology (SID). The Company presented its Phase 1b

clinical trial results to date. The Company also delivered podium presentations on its INTASYL compounds PH-762 and PH-894 in April 2025

at the 11th Annual Immunotherapy of Cancer (ITOC 11) conference in Munich, Germany. In June 2025, Phio presented interim data

on its Phase 1b clinical trial at the American Society of Clinical Oncology (ASCO) conference.

On July 25, 2025, the Company entered into warrant

inducement agreements with certain holders of the Company's existing warrants to purchase

an aggregate of 928,596 shares of common stock in connection with the exercise of common stock warrants issued between December

2024 and January 2025 with exercise prices between $2.00 and $2.485 per share. In connection with this financing, the Company raised approximately

$2.2 million after expenses.

At June 30, 2025, the Company had cash and cash

equivalents of approximately $10.8 million as compared with approximately $5.4 million at December 31, 2024.

Research and Development Expenses

Research and development expenses

for the three months ended June 30, 2025 were $1.1 million compared to $0.9 million for the same period in 2024. The increase in research

and development expenses was primarily driven by higher CRO pass-through costs associated with increased patient enrollment, as well as

higher consulting and salary-related costs.

Research and development expenses

for the six months ended June 30, 2025 were $1.9 million compared to $2.0 million for the same period in 2024. The fluctuation was immaterial

and within expected operating ranges.

General and Administrative Expenses

General and administrative

expenses for the three months ended June 30, 2025 were $1.2 million compared to $1.0 million for the same period in 2024. The increase

in general and administrative expenses was primarily driven by an increase in salary-related costs.

General and administrative

expenses for the six months ended June 30, 2025 were $2.2 million compared to $1.8 million for the same period in 2024. The increase in

general and administrative expenses was primarily driven by an increase in salary-related costs.

Net loss was $2.2 million for the three months

ended June 30, 2025 compared with $1.8 million for the same period in 2024. The increase in net loss was due to the changes in research

and development and general and administrative expenses as described above.

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 on-going 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 potential for PH-762 to present a viable non-surgical alternative for skin cancer, expectations regarding timing of enrollment, the

expectations that we have sufficient capital to complete the treatment phase of our ongoing Phase 1b clinical trial, and statements regarding

our 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, results from our preclinical and clinical activities, our

ability to execute on business strategies, the timing or likelihood of regulatory filings and approvals, 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.

Phio Pharmaceuticals Corp.

Jennifer Phillips: jphillips@phiopharma.com

PHIO PHARMACEUTICALS CORP.

CONSOLIDATED STATEMENTS OF OPERATIONS

(Amounts in thousands, except share and per

PHIO PHARMACEUTICALS CORP.

CONDENSED CONSOLIDATED BALANCE SHEETS

in thousands, except share and per share data)