Soligenix Submits Type A Meeting Request to U.S. FDA to Review Proposed Study Design for a Second Phase 3 Study Evaluating HyBryte™ in the Treatment of Cutaneous T-Cell Lymphoma

Meeting expected to occur approximately 30 days from the FDA's receipt of meeting request

PRINCETON, N.J., April 24, 2023 /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 that the Company has submitted a Type A Meeting Request to the United States (U.S.) Food and Drug Administration (FDA) to initiate formal discussions regarding the design of a second, Phase 3 pivotal study evaluating HyBryte™ (hypericin sodium) in the treatment of early stage cutaneous T-cell lymphoma (CTCL), a rare cancer, where it has successfully demonstrated statistically significant results in the first Phase 3 clinical trial. The Type A Meeting is the highest priority classification of meeting the FDA grants and is expected to occur approximately 30 days from the FDA's receipt of the meeting request.

"During the Type A meeting in April, FDA expressed its understanding of the need for additional therapies in CTCL and its willingness to work with Soligenix. FDA provided significant insights into its thoughts on a clinical study design allowing our team to prepare a comprehensive proposal expeditiously," stated Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix. "We certainly appreciate the FDA's responsiveness and continued collaboration demonstrated by categorizing this meeting as a Type A meeting.  The proposed protocol for the confirmatory study retains the key design aspects from the FLASH study while addressing as much of the FDA's initial feedback as feasible.  We look forward to having a productive meeting with the FDA and obtaining agreement on a pivotal study design that is highly executable as quickly as possible."

About HyBryte™

HyBryte™ (research name SGX301) is a novel, first-in-class, photodynamic therapy utilizing safe, visible light for activation.  The active ingredient in HyBryte™ is synthetic hypericin, a potent photosensitizer that is topically applied to skin lesions that is taken up by the malignant T-cells, and then activated by visible light approximately 24 hours later.  The use of visible light in the red-yellow spectrum has the advantage of penetrating more deeply into the skin (much more so than ultraviolet light) and therefore potentially treating deeper skin disease and thicker plaques and lesions. This treatment approach avoids the risk of secondary malignancies (including melanoma) inherent with the frequently employed DNA-damaging drugs and other phototherapy that are dependent on ultraviolet exposure.  Combined with photoactivation, hypericin has demonstrated significant anti-proliferative effects on activated normal human lymphoid cells and inhibited growth of malignant T-cells isolated from CTCL patients.  In a published Phase 2 clinical study in CTCL, patients experienced a statistically significant (p=0.04) improvement with topical hypericin treatment whereas the placebo was ineffective.  HyBryte™ has received orphan drug and fast track designations from the FDA, as well as orphan designation from the European Medicines Agency (EMA).

The recently published Phase 3 FLASH trial enrolled a total of 169 patients (166 evaluable) with Stage IA, IB or IIA CTCL. The trial consisted of three treatment cycles. Treatments were administered twice weekly for the first 6 weeks and treatment response was determined at the end of the 8th week of each cycle. In the first double-blind treatment cycle, 116 patients received HyBryte™ treatment (0.25% synthetic hypericin) and 50 received placebo treatment of their index lesions. A total of 16% of the patients receiving HyBryte™ achieved at least a 50% reduction in their lesions (graded using a standard measurement of dermatologic lesions, the CAILS score) compared to only 4% of patients in the placebo group at 8 weeks (p=0.04) during the first treatment cycle (primary endpoint). HyBryte™ treatment in the first cycle was safe and well tolerated.

In the second open-label treatment cycle (Cycle 2), all patients received HyBryte™ treatment of their index lesions. Evaluation of 155 patients in this cycle (110 receiving 12 weeks of HyBryte™ treatment and 45 receiving 6 weeks of placebo treatment followed by 6 weeks of HyBryte™ treatment), demonstrated that the response rate among the 12-week treatment group was 40% (p