Visible light-activated synthetic hypericin is a novel, first-in-class, photodynamic therapy (PDT) that is expected to avoid much of the long-term risks associated with other PDT treatments.

Soligenix, Inc. will be expanding synthetic hypericin development under the research name SGX302 into psoriasis.

The company made this move after  the validation of synthetic hypericin's biologic activity in the positive pivotal Phase 3 FLASH (Fluorescent Light Activated Synthetic Hypericin) study in cutaneous T-cell lymphoma (CTCL), as well as positive proof-of-concept (PoC) demonstrated in a small Phase 1/2 pilot study in mild-to-moderate psoriasis patients.

Visible light-activated synthetic hypericin is a novel, first-in-class, photodynamic therapy (PDT) that is expected to avoid much of the long-term risks associated with other PDT treatments. Synthetic hypericin is a potent photosensitizer that is topically applied to skin lesions and taken up 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 toxicities.  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 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 of this orphan disease caused by malignant T-cells.  Further, 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. 

"Similar to CTCL, psoriasis is a chronic disease where the management of side effects and toxicities is as important as the management of the disease itself. Having treated both CTCL and psoriasis patients for over 20 years and having seen first-hand how they struggle to find good treatment options, access to an additional effective and safe therapy would add significantly to patient care and quality of life," says Neal Bhatia, MD, Director of Clinical Dermatology at Therapeutics Clinical Research in San Diego and an investigator in the Phase 3 FLASH study, in a news release. "The success of synthetic hypericin in targeting malignant T-cells during 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. This success is further supported by both the previous synthetic hypericin PoC study in psoriasis and by the success, albeit confounded by potentially severe toxicity, of other photodynamic therapies in psoriasis."

"During the last year, we have made announcements of several important development milestones that we have achieved with HyBryte™ (synthetic hypericin) in the treatment of early stage CTCL.  We have clearly validated synthetic hypericin's biologic activity with the Phase 3 FLASH study in this orphan disease, where we expect to file a New Drug Application (NDA) in the first half of next year. We believe it is now appropriate to expand synthetic hypericin's or SGX302's development into different cutaneous T-cell diseases such as psoriasis, as a component of our long-term strategy to enhance the value of this unique compound," adds Christopher J. Schaber, PhD, President and Chief Executive Officer of Soligenix.  "Psoriasis is an ongoing unmet medical need, with as many as 7.5 million people in the U.S. and 60-125 million people worldwide affected by this incurable disease. Given our promising results with hypericin to date, including a small Phase 1/2 PoC clinical trial in mild-to-moderate psoriasis, we are hopeful synthetic hypericin will have a role to play in helping patients suffering from this difficult to treat and chronic disease."

Dr. Schaber continues, "As we get closer to initiating a follow-on Phase 2a clinical trial in mild-to-moderate psoriasis, we will provide further details regarding trial design and timeline; however, our high-level plan in the interim is to evaluate different topical formulations of synthetic hypericin to ensure optimal absorption for broadly treating this disease.  In parallel, we will be working with our psoriasis clinical experts to finalize a protocol with a plan to initiate study enrollment in the latter part of 2022.  Given our current cash position and the expected cost of the Phase 2a trial, we do not anticipate needing to raise additional capital to support this Phase 2a trial as we continue to advance towards NDA filing and U.S. commercialization of HyBryte in the treatment of CTCL."