Soligenix Provides Regulatory Update on HyBryte™

PRINCETON, N.J., April 14, 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 convened a Type A Meeting with the United States (U.S.) Food and Drug Administration (FDA). During the Type A Meeting, representatives of the Company and the FDA discussed the contents of a refusal to file (RTF) letter previously issued by the FDA regarding the Company's new drug application (NDA) for HyBryte™ (synthetic hypericin sodium) in the treatment of early stage cutaneous T-cell lymphoma (CTCL), a rare cancer, where it successfully demonstrated statistically significant results in a Phase 3 clinical trial (Study HPN-CTCL-01; also referred to as the FLASH study).

In order to accept an NDA filing for HyBryte™, the FDA is requiring positive results from a second clinical study in addition to the Phase 3, randomized, double-blind, placebo-controlled FLASH study previously conducted in this orphan indication. The FDA indicated that it is open to engaging in protocol discussions regarding the second clinical study. Based on the feedback, the Company has decided to collaboratively engage in discussions with the FDA in order to define the protocol and evaluate the feasibility of conducting the additional clinical trial.

"While we are very disappointed by this delay, Soligenix and its clinical investigators remain committed to working with the FDA and advancing HyBryte™ to market for patients suffering with CTCL," stated Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix. "The Phase 3 FLASH study was the largest double-blind, randomized, placebo-controlled clinical trial ever conducted in the CTCL population. While we are surprised that the FDA did not accept our submitted NDA for filing and review, it was very clear that the FDA's thinking has evolved in evaluating CTCL therapies since our initial protocol discussions on Study HPN-CTCL-01 and that another Phase 3 study will be required to support an NDA for HyBryte™. During the Type A meeting, we discussed elements of protocol design for the additional confirmatory study and look forward to collaborating with the FDA to advance these discussions as quickly as possible to have a reasonable study design to meet the FDA's requirements."

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 sodium, 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 phototherapies 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 (Fluorescent Light Activated Synthetic Hypericin) study 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