On April 28, 2026 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, reported that the Data Monitoring Committee completed the interim efficacy analysis of its pivotal Phase 3 FLASH2 (Fluorescent Light Activated Synthetic Hypericin 2) trial evaluating HyBryte (Synthetic Hypericin) in the treatment of cutaneous T-cell lymphoma (CTCL). Under the terms of the interim analysis, the study was recommended to halt for futility.
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"We are obviously very disappointed with the unanticipated outcome of the study," stated Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix. "Despite the fact that HyBryte demonstrated statistically significant reductions in CTCL lesions after 6 weeks treatment in the first FLASH study, a similar signal was not observed with 18 weeks of treatment in this study. Over the coming weeks, we will analyze the data to better determine why the study did not meet expectations. If there is any clarity gained from further analysis of the dataset, especially with respect to specific subsets of patients that may benefit from HyBryte therapy, then we intend to communicate our findings and explore follow-up discussions with the European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA)."
Dr. Schaber continued, "With approximately $5.9 million of cash, we will evaluate all strategic options moving forward, including but not limited to merger and acquisition opportunities as well as the potential of advancing dusquetide for the treatment of Behçet’s Disease, which demonstrated promising biological efficacy in a Phase 2 study last year using the intravenous formulation and has received orphan drug designation most recently from the EMA."
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 safe, 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 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 (Cycle 1), 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 modified Composite Assessment of Index Lesion Severity [mCAILS] 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 this 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<0.0001 vs the placebo treatment rate in Cycle 1). Comparison of the 12-week and 6-week treatment responses also revealed a statistically significant improvement (p<0.0001) between the two timepoints, indicating that continued treatment results in better outcomes. HyBryte continued to be safe and well tolerated. Additional analyses also indicated that HyBryte is equally effective in treating both plaque (response 42%, p<0.0001 relative to placebo treatment in Cycle 1) and patch (response 37%, p=0.0009 relative to placebo treatment in Cycle 1) lesions of CTCL, a particularly relevant finding given the historical difficulty in treating plaque lesions.
The third (optional) treatment cycle (Cycle 3) was focused on safety and all patients could elect to receive HyBryte treatment of all their lesions. Of note, 66% of patients elected to continue with this optional compassionate use / safety cycle of the study. Of the subset of patients that received HyBryte throughout all 3 cycles of treatment, 49% of them demonstrated a positive treatment response (p<0.0001 vs patients receiving placebo in Cycle 1). Moreover, in a subset of patients evaluated in this cycle, it was demonstrated that HyBryte is not systemically available, consistent with the general safety of this topical product observed to date. At the end of Cycle 3, HyBryte continued to be well tolerated despite extended and increased use of the product to treat multiple lesions.
Overall safety of HyBryte is a critical attribute of this treatment and was monitored throughout the three treatment cycles (Cycles 1, 2 and 3) and the 6-month follow-up period. HyBryte’s mechanism of action is not associated with DNA damage, making it a safer alternative than currently available therapies, all of which are associated with significant, and sometimes fatal, side effects. Predominantly these include the risk of melanoma and other malignancies, as well as the risk of significant skin damage and premature skin aging. Currently available treatments are only approved in the context of previous treatment failure with other modalities and there is no approved front-line therapy available. Within this landscape, treatment of CTCL is strongly motivated by the safety risk of each product. HyBryte potentially represents the safest available efficacious treatment for CTCL. With very limited systemic absorption, a compound that is not mutagenic and a light source that is not carcinogenic, there is no evidence to date of any potential safety issues.
Following the first Phase 3 study of HyBryte for the treatment of CTCL, the FDA and the EMA indicated that they would require a second successful Phase 3 trial to support marketing approval. With agreement from the EMA on the key design components, the second, confirmatory study, called FLASH2, has demonstrated a good safety profile in the pre-specific safety evaluations by the Data Monitoring Committee. This study is a randomized, double-blind, placebo-controlled, multicenter study that replicates the double-blind, placebo-controlled design used in the first successful Phase 3 FLASH study that consisted of three 6-week treatment cycles (18 weeks total), with the primary efficacy assessment occurring at the end of the initial 6-week double-blind, placebo-controlled treatment cycle (Cycle 1). However, this second study extends the double-blind, placebo-controlled assessment to 18 weeks of continuous treatment (no "between-Cycle" treatment breaks) with the primary endpoint assessment occurring at the end of the 18-week timepoint. In the first Phase 3 study, a treatment response of 49% (p<0.0001 vs patients receiving placebo in Cycle 1) was observed in patients completing 18 weeks (3 cycles) of therapy. In this second study, all important clinical study design components remain the same as in the first FLASH study, including the primary endpoint and key inclusion-exclusion criteria.
In light of the interim analysis results, the Company will evaluate all available data and assess potential next steps, if any, with respect to the HyBryte development program.
Additional supportive studies have demonstrated the utility of longer treatment times (Study RW-HPN-MF-01), the lack of significant systemic exposure to hypericin after topical application (Study HPN-CTCL-02) and its relative efficacy and tolerability compared to Valchlor (Study HPN-CTCL-04).
In addition, the FDA awarded an Orphan Products Development grant to support the investigator-initiated study evaluation of HyBryte for expanded treatment in patients with early-stage CTCL, including in the home use setting. The grant, totaling $2.6 million over 4 years, was awarded to the University of Pennsylvania that was a leading enroller in the Phase 3 FLASH study.
About Cutaneous T-Cell Lymphoma (CTCL)
CTCL is a class of non-Hodgkin’s lymphoma (NHL), a type of cancer of the white blood cells that are an integral part of the immune system. Unlike most NHLs which generally involve B-cell lymphocytes (involved in producing antibodies), CTCL is caused by an expansion of malignant T-cell lymphocytes (involved in cell-mediated immunity) normally programmed to migrate to the skin. These malignant cells migrate to the skin where they form various lesions, typically beginning as patches and may progress to raised plaques and tumors. Mortality is related to the stage of CTCL, with median survival generally ranging from about 12 years in the early stages to only 2.5 years when the disease has advanced. There is currently no cure for CTCL. Typically, CTCL lesions are treated and regress but usually return either in the same part of the body or in new areas.
CTCL constitutes a rare group of NHLs, occurring in about 4% of the more than 1.7 million individuals living with the disease in the U.S. and Europe (European Union and United Kingdom). It is estimated, based upon review of historic published studies and reports and an interpolation of data on the incidence of CTCL that it affects approximately 31,000 individuals in the U.S. (based on SEER [Surveillance, Epidemiology, and End Results] data, with approximately 3,200 new cases seen annually) and approximately 38,000 individuals in Europe (based on ECIS [European Cancer Information System] prevalence estimates, with approximately 3,800 new cases annually).
(Press release, Soligenix, APR 28, 2026, View Source [SID1234664863])