Soligenix Announces Top-line Results of the Phase 2a Study of SGX302 (Synthetic Hypericin) in Patients with Mild-to-Moderate Psoriasis

Rhea-AI Summary

Soligenix (Nasdaq: SNGX) reported topline extended results from the Phase 2a exploratory extension (Cohort 3) of SGX302 (synthetic hypericin) for mild-to-moderate psoriasis on Dec 17, 2025.

Cohort 3 enrolled four patients treated 18 weeks with an optimized topical gel formulation. Three evaluable patients showed improvements across IGA, PASI, simplified psoriasis index, DLQI and Skindex-29. One patient reached IGA “Almost Clear” with PASI improvement exceeding 50%. SGX302 gel was well tolerated with no drug-related adverse events reported. Company said results are similar or improved versus the prior ointment and supports further development while advancing the HyBryte Phase 3 program for CTCL with topline results expected in H2 2026.

Positive

• Optimized SGX302 gel achieved comparable or improved results versus ointment
• One patient reached IGA “Almost Clear” with PASI >50%
• No drug-related adverse events reported in Cohort 3

Negative

• Only three evaluable patients in Cohort 3, limiting statistical robustness
• One patient discontinued for personal reasons during the 18-week treatment

Key Figures

Cohort 3 patients 4 patients Phase 2a SGX302 psoriasis gel extension cohort

Treatment duration 18 weeks Treatment period for Cohorts 1–3 in Phase 2a psoriasis study

Evaluable patients 3 patients Three evaluable out of four in Cohort 3, one discontinued

PASI improvement >50% Substantial PASI improvement for patient achieving 'Almost Clear' IGA

Psoriasis prevalence 60–125 million Estimated people worldwide living with psoriasis

Psoriasis market 2020 $15 billion Global psoriasis treatment market value in 2020

Psoriasis market 2027 $40 billion Projected global psoriasis treatment market by 2027

Phase 3 HyBryte topline H2 2026 Expected timing of confirmatory Phase 3 CTCL trial topline results

Market Reality Check

$1.23 Last Close

Volume Volume 260,940 vs 20-day avg 317,126 (relative volume 0.82x) ahead of the release. normal

Technical Shares at $1.52, trading below 200-day MA of $1.96 and 75.6% under 52-week high.

Peers on Argus

Peers in Biotechnology showed mixed moves: LPTX up 238.84%, MBRX up 4.92%, SNSE up 1.64%, while MBIO and XTLB fell 6.14% and 3.71%. No coordinated sector move is indicated.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Dec 05	Rare-disease editorial	Positive	-2.4%	Editorial spotlighting HyBryte and rare-disease positioning as pivotal opportunity.
Dec 03	CTCL platform editorial	Positive	-1.9%	Editorial on HyBryte as innovative CTCL therapy in final confirmatory study.
Nov 19	Phase 3 CTCL update	Positive	-3.6%	FLASH2 enrollment milestone with blinded response rate above anticipated level.
Nov 07	Q3 2025 earnings	Positive	+7.0%	Q3 results showing cash of $10.5M, equity $7.6M, and CTCL trial progress.
Oct 14	Advisory board update	Positive	-5.2%	Refresh of U.S. medical advisory board to guide FLASH2 CTCL strategy.

Pattern Detected

Recent fundamentally positive or strategic updates often coincided with negative or muted next-day price moves, with only the Q3 2025 results showing a clear positive alignment.

Recent Company History

Over the last few months, Soligenix highlighted late-stage development of HyBryte for cutaneous T-cell lymphoma, including completion of 50 of 80 patients for an interim Phase 3 analysis and editorials positioning the company at a pivotal rare-disease crossroads. Q3 2025 filings showed no revenue, a quarterly net loss of $2.5M, but strengthened cash of about $10.5M and stockholders’ equity of $7.6M. Advisory board updates and regulatory filings underscored efforts to support the Phase 3 program. Today’s psoriasis Phase 2a data extends this synthetic hypericin story into a broader dermatology setting.

Market Pulse Summary

The stock dropped -19.1% in the session following this news. A negative reaction despite encouraging Phase 2a psoriasis results would fit a recent pattern where favorable HyBryte or strategic updates still saw next-day declines in 4 of the last 5 events. The company reported continued net losses in 2025 and has relied on offerings and warrant-related registration statements, so dilution and funding considerations could overshadow early-stage data as investors reassess risk-reward following the announcement.

Key Terms

phase 2a medical

"extended results of its ongoing Phase 2a trial of SGX302"

Phase 2a is an early stage in testing a new medical treatment or drug, where the main goal is to assess its safety and find the right dosage. For investors, this stage indicates whether the treatment shows initial promise before moving on to larger, more definitive studies; progress here can influence expectations for future development and potential success.

investigator global assessment medical

"improvements in the Investigator Global Assessment (IGA), the Psoriasis Activity"

A clinician’s overall rating of a patient’s disease severity or improvement in a medical study, recorded on a standard numerical or descriptive scale. It serves as a key measure of whether a treatment appears to work; for investors, strong or weak results on this score can sway trial outcomes, regulatory approval chances and a drug’s commercial prospects, like a referee’s score influencing the final result of a contest.

psoriasis activity and severity index medical

"the Investigator Global Assessment (IGA), the Psoriasis Activity and Severity Index (PASI)"

A psoriasis activity and severity index is a clinical score that measures how much of the skin is affected by psoriasis and how severe the lesions are, combining area and intensity into a single number used in medical studies. Investors care because changes in this score are a primary way regulators and doctors judge whether a drug or therapy works — like watching a weather map to see if a storm is truly weakening — which directly affects a treatment’s market potential.

dermatology life quality index medical

"the simplified psoriasis index, the dermatology life quality index and the Skindex-29"

A Dermatology Life Quality Index (DLQI) is a short, patient-completed questionnaire that measures how much a skin condition affects a person’s daily life, similar to a customer satisfaction score for health. Investors watch DLQI results because they show whether a treatment meaningfully improves patients’ day-to-day well-being, which can influence regulatory decisions, market demand, pricing, and insurance coverage — all drivers of a therapy’s commercial value.

skindex-29 medical

"the dermatology life quality index and the Skindex-29 questionnaire."

Skindex-29 is a 29-question patient-reported survey that measures how skin conditions affect a person’s emotions, symptoms, and daily functioning. As a standardized measure used in clinical studies and product evaluations, it provides evidence of a treatment’s real-world benefit beyond clinical tests — like consumer reviews showing whether a product improves everyday life — and can influence regulatory decisions, labeling, reimbursement, and market acceptance.

cutaneous t-cell lymphoma medical

"HyBryte™ in targeting malignant T-cells during cutaneous T-cell lymphoma (CTCL) clinical trials"

Cutaneous T-cell lymphoma is a rare type of skin cancer that develops when certain immune system cells grow uncontrollably, causing skin patches, rashes, or tumors. While it primarily affects health, its rarity and complexity can influence medical research funding and pharmaceutical development, which may impact investment opportunities in healthcare and biotech sectors. Understanding such diseases helps investors gauge potential risks and innovations in medical treatments.

photodynamic therapies medical

"consistent with the general success of photodynamic therapies in psoriasis"

Photodynamic therapies use a light-activated drug that becomes toxic to targeted cells only after exposure to a specific wavelength of light; think of a harmless paint that turns into a spot cleaner when you shine a lamp on it. Investors care because these treatments offer potentially precise, less invasive options for cancers and certain eye or skin conditions, which can drive demand, affect reimbursement decisions, and influence the commercial value of companies developing or licensing the technology.

AI-generated analysis. Not financial advice.

Optimized Gel Formulation Demonstrates Clinical Success in Third Cohort of Patients

PRINCETON, N.J., Dec. 17, 2025 /PRNewswire/ -- Soligenix, Inc. (Nasdaq: SNGX) (Soligenix or the Company), a late-stage biopharmaceutical company focused on developing and commercializing products to treat rare diseases where there is an unmet medical need, announced today extended results of its ongoing Phase 2a trial of SGX302 (synthetic hypericin) for the treatment of mild-to-moderate psoriasis. In this extension (Cohort 3) of the exploratory phase of the study, an additional four patients were enrolled and treated with an improved topical gel formulation of synthetic hypericin.

The Cohort 3 patients were treated for the same 18-week period as Cohorts 1 and 2, but utilized an optimized gel formulation of synthetic hypericin. The gel formulation was specifically designed to improve ease of application to larger areas of the skin. SGX302 gel therapy was well tolerated by all patients with no drug related adverse events identified.  On average over the three evaluable patients (one patient discontinued for personal reasons), there were improvements in the Investigator Global Assessment (IGA), the Psoriasis Activity and Severity Index (PASI), the simplified psoriasis index, the dermatology life quality index and the Skindex-29 questionnaire. One patient achieved a disease status of "Almost Clear" using the IGA, which is considered a standard clinical measure for treatment success in psoriasis, with a substantial improvement in their PASI score, exceeding 50%. These outcomes were very similar to or improved relative to those obtained with the previous ointment formulation, as expected given the comparable release characteristics of the two formulations and the enhanced ease of application of the gel. In totality, the initial exploratory phase of the study has confirmed that SGX302 improves psoriasis lesions, consistent with the general success of photodynamic therapies in psoriasis, and is well tolerated, potentially providing a non-carcinogenic, non-mutagenic treatment for the thicker lesions found in psoriasis.

"We are pleased with the preliminary findings from our ongoing Phase 2a trial," stated Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix. "The optimized gel formulation was designed to improve the patient experience, with both easier dispensation and skin application. The expansion of this psoriasis study continues our evaluation of synthetic hypericin into other disease indications, including non-orphan indications, where there remains an unmet medical need. Current estimates show as many as 60-125 million people worldwide living with the condition, with a global treatment market valued at approximately $15 billion in 2020 and projected to reach as much as $40 billion by 2027. The success of HyBryte™ in targeting malignant T-cells during cutaneous T-cell lymphoma (CTCL) clinical trials is a promising indicator of the ability of SGX302 to provide a much-needed approach for the treatment of mild-to-moderate psoriasis, also caused by dysregulated T-cells. We anticipate continuing to pursue SGX302 in psoriasis as we advance the confirmatory Phase 3 trial for HyBryte™ in the treatment of early-stage CTCL where topline results are expected in the second half of 2026."

About Synthetic Hypericin

Visible light-activated synthetic hypericin is a novel, first-in-class, photodynamic therapy (PDT) that is expected to avoid many of the long-term risks associated with other PDT treatments. Synthetic hypericin is a potent photosensitizer that is topically applied to skin lesions and absorbed by cutaneous T-cells. With subsequent activation by safe, visible light, T-cell apoptosis is induced, addressing the root cause of psoriasis lesions. Other PDTs have shown efficacy in psoriasis with a similar apoptotic mechanism, albeit using ultraviolet (UV) light associated with more severe potential long-term safety concerns. The use of visible light in the red-yellow spectrum has the advantage of deeper penetration into the skin (much more than UV light) potentially treating deeper skin disease and thicker plaques and lesions, similar to what was observed in the positive Phase 3 FLASH (Fluorescent Light Activated Synthetic Hypericin) study in CTCL. Synthetic hypericin or HyBryte™ (tradename used in CTCL) was demonstrated in this study to be equally effective in treating both plaque (42% treatment response rate after 12 weeks treatment, p<0.0001 relative to placebo treatment) and patch (37%, p=0.0009) lesions in this orphan disease caused by malignant T-cells. In a published Phase 1/2 proof of concept clinical study using synthetic hypericin, efficacy was demonstrated in patients with CTCL (58.3% response, p=0.04) as well as psoriasis (80% response, p<0.02).

In an ongoing Phase 2a study in mild-to-moderate psoriasis, patients enrolled in the initial portion of the trial (Part A) have completed treatment. In Cohort 1, the initial five patients enrolled received twice weekly treatment for 18 weeks with 0.25% hypericin ointment, followed by light activation approximately 24 hours later. Light doses were increased by up to 1 J/cm² on subsequent visits until mild erythema was observed in the treated lesions. Light doses for all patients were still being intermittently increased when the scheduled treatments ended, and light doses were generally safe and well tolerated. Evaluation of the initial cohort of five patients demonstrated a clear biological signal, with the majority of patients recording an improvement in the PASI (psoriasis area and severity index) score, providing evidence of biological improvement, but no patient met the definition of treatment success (IGA score of 0 or 1) at the 18-week treatment timepoint. The second cohort of five patients were enrolled once the Cohort 1 patients had completed all treatment visits. Given how well-tolerated light treatments were in the first Cohort, it was determined that the second cohort of patients could safely receive an accelerated light treatment with increases in the light dose by up to 2 J/cm² at each visit and allowing the maximum light dose (25 J/cm²) to be reached earlier by approximately week 14, allowing more treatments at the maximum light dose to be completed in the 18-week treatment schedule. Two of the four evaluable patients achieved a clinical success score at some point during the 18-week treatment period and all evaluable patients improved, yielding an average reduction of approximately 50% in the PASI score. One patient in Cohort 2 dropped out of the study for personal reasons unrelated to the study. The third cohort of the study enrolled four patients, and one of the three evaluable patients achieved a clinical success score, and all evaluable patients improved in multiple indices, including PASI, simplified psoriasis index, and dermatology Life Quality Index. One patient in Cohort 3 discontinued the study for personal reasons and was considered not evaluable. The third cohort specifically assessed the use of an improved formulation of SGX302, designed as a gel as opposed to the previous ointment format. The gel formulation was designed for ease of application and for use in squeezable tubes, instead of jars.

This treatment approach avoids the risk of secondary malignancies (including melanoma) inherent with both the frequently used DNA-damaging drugs and other phototherapies that are dependent on UV A or B exposure. The use of synthetic hypericin coupled with safe, visible light also avoids the risk of serious infections and cancer associated with the systemic immunosuppressive treatments used in psoriasis. 

About Psoriasis

Psoriasis is a chronic, non-communicable, itchy and often painful inflammatory skin condition for which there is no cure. Psoriasis has a significantly detrimental impact on patients' quality of life, and is associated with cardiovascular, arthritic, and metabolic diseases, as well as psychological conditions such as anxiety, depression and suicide. Many factors contribute to development of psoriasis including both genetic and environmental factors (e.g., skin trauma, infections, and medications). The lesions develop because of rapidly proliferating skin cells, driven by autoimmune T-cell mediated inflammation. Of the various types of psoriasis, plaque psoriasis is the most common and is characterized by dry, red raised plaques that are covered by silvery-white scales occurring most commonly on the elbows, knees, scalp, and lower back. Approximately 80% of patients have mild-to-moderate disease. Mild psoriasis is generally characterized by the involvement of less than 3% of the body surface area (BSA), while moderate psoriasis will typically involve 3-10% BSA and severe psoriasis greater than 10% BSA. Between 20% and 30% of individuals with psoriasis will go on to develop chronic, inflammatory arthritis (psoriatic arthritis) that can lead to joint deformations and disability. Studies have also associated psoriasis, and particularly severe psoriasis, with an increased relative risk of lymphoma, particularly CTCL. Although psoriasis can occur at any age, most patients present with the condition before age 35.

Treatment of psoriasis is based on its severity at the time of presentation with the goal of controlling symptoms. It varies from topical options including PDT to reduce pain and itching, and potentially reduce the inflammation driving plaque formation, to systemic treatments for more severe disease. Most common systemic treatments and even current topical photo/photodynamic therapy such as UV A and B light, carry a risk of increased skin cancer.

Psoriasis is the most common immune-mediated inflammatory skin disease. According to the World Health Organization (WHO) Global Report on Psoriasis 2016, the prevalence of psoriasis is between 1.5% and 5% in most developed countries, with some suggestions of incidence increasing with time. It is estimated, based upon review of historic published studies and reports and an interpolation of data, that psoriasis affects 3% of the U.S. population or more than 7.5 million people. Current estimates have as many as 60-125 million people worldwide living with the condition. The global psoriasis treatment market was valued at approximately $15 billion in 2020 and is projected to reach as much as $40 billion by 2027.

About Soligenix, Inc.

Soligenix is a late-stage biopharmaceutical company focused on developing and commercializing products to treat rare diseases where there is an unmet medical need. Our Specialized BioTherapeutics business segment is developing and moving toward potential commercialization of HyBryte™ (SGX301 or synthetic hypericin sodium) as a novel photodynamic therapy utilizing safe visible light for the treatment of cutaneous T-cell lymphoma (CTCL). With successful completion of the second Phase 3 study, regulatory approvals will be sought to support potential commercialization worldwide. Development programs in this business segment also include expansion of synthetic hypericin (SGX302) into psoriasis, our first-in-class innate defense regulator (IDR) technology, dusquetide (SGX942) for the treatment of inflammatory diseases, including oral mucositis in head and neck cancer, and (SGX945) in Behçet's Disease.

Our Public Health Solutions business segment includes development programs for RiVax®, our ricin toxin vaccine candidate, as well as our vaccine programs targeting filoviruses (such as Marburg and Ebola) and CiVax™, our vaccine candidate for the prevention of COVID-19 (caused by SARS-CoV-2). The development of our vaccine programs incorporates the use of our proprietary heat stabilization platform technology, known as ThermoVax®. To date, this business segment has been supported with government grant and contract funding from the National Institute of Allergy and Infectious Diseases (NIAID), the Defense Threat Reduction Agency (DTRA) and the Biomedical Advanced Research and Development Authority (BARDA).

For further information regarding Soligenix, Inc., please visit the Company's website at https://www.soligenix.com and follow us on LinkedIn and Twitter at @Soligenix_Inc.

This press release may contain forward-looking statements that reflect Soligenix's current expectations about its future results, performance, prospects and opportunities, including but not limited to, potential market sizes, patient populations and clinical trial enrollment. Statements that are not historical facts, such as "anticipates," "estimates," "believes," "hopes," "intends," "plans," "expects," "goal," "may," "suggest," "will," "potential," or similar expressions, are forward-looking statements. These statements are subject to a number of risks, uncertainties and other factors that could cause actual events or results in future periods to differ materially from what is expressed in, or implied by, these statements. Soligenix cannot assure you that it will be able to successfully develop, achieve regulatory approval for or commercialize products based on its technologies, particularly in light of the significant uncertainty inherent in developing therapeutics and vaccines against bioterror threats, conducting preclinical and clinical trials of therapeutics and vaccines, obtaining regulatory approvals and manufacturing therapeutics and vaccines, that product development and commercialization efforts will not be reduced or discontinued due to difficulties or delays in clinical trials or due to lack of progress or positive results from research and development efforts, that it will be able to successfully obtain any further funding to support product development and commercialization efforts, including grants and awards, maintain its existing grants which are subject to performance requirements, enter into any biodefense procurement contracts with the U.S. Government or other countries, that it will be able to compete with larger and better financed competitors in the biotechnology industry, that changes in health care practice, third party reimbursement limitations and Federal and/or state health care reform initiatives will not negatively affect its business, or that the U.S. Congress may not pass any legislation that would provide additional funding for the Project BioShield program. In addition, there can be no assurance as to the timing or success of any of its clinical/preclinical trials. Despite the statistically significant result achieved in the first HyBryte™ (SGX301) Phase 3 clinical trial for the treatment of cutaneous T-cell lymphoma or any other studies (including the open-label, investigator-initiated study), there can be no assurance that the second HyBryte™ (SGX301) Phase 3 clinical trial will be successful or that a marketing authorization from the FDA or EMA will be granted. Additionally, although the EMA has agreed to the key design components of the second HyBryte™ (SGX301) Phase 3 clinical trial, no assurance can be given that the Company will be able to modify the development path to adequately address the FDA's concerns or that the FDA will not require a longer duration comparative study. Notwithstanding the result in the first HyBryte™ (SGX301) Phase 3 clinical trial for the treatment of cutaneous T-cell lymphoma and the Phase 2a clinical trial of SGX302 for the treatment of psoriasis, there can be no assurance as to the timing or success of the clinical trials of SGX302 for the treatment of psoriasis. Additionally, despite the biologic activity observed in aphthous ulcers induced by chemotherapy and radiation, there can be no assurance as to the timing or success of the clinical trials of SGX945 for the treatment of Behçet's Disease. Further, there can be no assurance that RiVax^® will qualify for a biodefense Priority Review Voucher (PRV) or that the prior sales of PRVs will be indicative of any potential sales price for a PRV for RiVax^®. Also, no assurance can be provided that the Company will receive or continue to receive non-dilutive government funding from grants and contracts that have been or may be awarded or for which the Company will apply in the future. These and other risk factors are described from time to time in filings with the Securities and Exchange Commission (the "SEC"), including, but not limited to, Soligenix's reports on Forms 10-Q and 10-K. Unless required by law, Soligenix assumes no obligation to update or revise any forward-looking statements as a result of new information or future events.

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SOURCE SOLIGENIX, INC.

FAQ

What did Soligenix announce about SGX302 psoriasis Phase 2a Cohort 3 on Dec 17, 2025?

Soligenix said four patients received an optimized SGX302 gel for 18 weeks; three evaluable patients showed improvements in IGA, PASI, DLQI and Skindex-29, one achieved IGA “Almost Clear” with PASI >50%, and no drug-related adverse events were identified.

How many patients were evaluable in the SGX302 Cohort 3 psoriasis update (SNGX)?

Three patients were evaluable in Cohort 3; a fourth patient discontinued for personal reasons.

Did the SGX302 gel show safety issues in the Phase 2a Cohort 3 update for SNGX?

No drug-related adverse events were reported and the company described the gel as well tolerated.

How did the optimized SGX302 gel compare to the prior ointment in the Cohort 3 results (SNGX)?

The company reported outcomes were very similar to or improved relative to the ointment, citing comparable release characteristics and easier application.

What are the next clinical milestones referenced alongside the SGX302 Cohort 3 results for SNGX?

Soligenix said it will continue SGX302 development in psoriasis while advancing HyBryte Phase 3 for early-stage CTCL, with topline HyBryte results expected in the second half of 2026.