Phase 2a Results Demonstrate Safety and Efficacy of SGX302 Gel in Mild-to-Moderate Psoriasis

Today, Soligenix, Inc. announced extended top-line results from its ongoing phase 2a clinical study evaluating SGX302 (synthetic hypericin), a visible light–activated photodynamic therapy, for the treatment of mild-to-moderate psoriasis.¹ The update focuses on findings from the third exploratory cohort (Cohort 3), which assessed an optimized topical gel formulation designed to improve ease of application, particularly over larger skin surface areas.

Clinical Efficacy and Cohort Progression

The phase 2a study is an open-label, exploratory trial consisting of sequential cohorts treated over an 18-week period. In Cohort 3, 4 patients with mild-to-moderate psoriasis were enrolled and treated with the optimized SGX302 gel formulation. The gel was developed to enhance patient usability while maintaining release characteristics comparable to the ointment formulation used in prior cohorts. Over the 18-week treatment period, SGX302 gel therapy was well tolerated, with no drug-related adverse events reported.

Across the Cohort 3 participants, improvements were observed in several standard clinical and patient-reported outcome measures, including the Investigator Global Assessment (IGA), Psoriasis Area and Severity Index (PASI), simplified psoriasis index, Dermatology Life Quality Index (DLQI), and Skindex-29 questionnaire. One patient achieved an IGA score of “Almost Clear,” a widely accepted benchmark of clinical success in psoriasis trials, accompanied by a PASI improvement exceeding 50%.

These findings build on results from the earlier cohorts of the study. In Cohort 1, 5 patients received twice-weekly treatment with a 0.25% synthetic hypericin ointment for 18 weeks, with gradual escalation of visible light doses until mild erythema was achieved. While treatment was safe and well tolerated, and most patients demonstrated PASI improvement, none met the predefined criteria for treatment success (IGA score of 0 or 1) by week 18. In Cohort 2, treatment parameters were adjusted to allow more rapid light dose escalation, reaching the maximum dose earlier in the treatment course. Among four evaluable patients, 2 achieved clinical success at some point during treatment, and all showed improvement, with an average PASI reduction of approximately 50%.

Mechanism of Action and Broader Applications

SGX302 is applied topically to psoriatic lesions and subsequently activated by visible light, inducing apoptosis of dysregulated cutaneous T cells, a central driver of psoriatic inflammation. Unlike traditional phototherapies that rely on ultraviolet (UV) radiation, SGX302 uses red-yellow spectrum visible light, which offers deeper tissue penetration while avoiding DNA damage and the long-term carcinogenic risks associated with UV exposure.

Synthetic hypericin has previously demonstrated clinical activity in cutaneous T-cell lymphoma (CTCL), another T-cell–driven skin disease. In the phase 3 FLASH study in early-stage CTCL, synthetic hypericin (marketed as HyBryte) showed significant efficacy in both patch and plaque lesions.² Earlier phase 1/2 studies also demonstrated responses in patients with psoriasis, providing a rationale for continued development in this more prevalent, non-orphan indication.

"We are pleased with the preliminary findings from our ongoing Phase 2a trial," Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix, said in a statement. "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.”¹

References

1. Soligenix Announces Top-line Results of the Phase 2a Study of SGX302 (Synthetic Hypericin) in Patients with Mild-to-Moderate Psoriasis. News release. Soligenix. Published December 17, 2025. Accessed December 17, 2025. https://ir.soligenix.com/2025-12-17-Soligenix-Announces-Top-line-Results-of-the-Phase-2a-Study-of-SGX302-Synthetic-Hypericin-in-Patients-with-Mild-to-Moderate-Psoriasis

2. HyBryte™ Phase 3 FLASH Study for the Treatment of Cutaneous T-Cell Lymphoma Published in JAMA Dermatology. News release. Soligenix. Published July 20, 2022. Accessed December 17, 2025. https://ir.soligenix.com/2022-07-20-HyBryte-TM-Phase-3-FLASH-Study-for-the-Treatment-of-Cutaneous-T-Cell-Lymphoma-Published-in-JAMA-Dermatology