Soligenix's stock sinks 38% after FDA refuses to consider lymphoma therapy application

Despite phase 3 data last year that demonstrated the effectiveness of Soligenix’s cutaneous T-cell lymphoma (CTCL) treatment, the FDA has halted the biotech's  approval plan in its tracks. The agency has sent a refuse-to-file letter, leaving the company scrambling to decide on a path to market and its stock sinking.

Soligenix submitted an approval application Dec. 14 for HyBryte, a synthetic form of hypericin. The thinking behind the photodynamic ointment is that hypericin—which occurs naturally in St. John’s wort—can be taken up by malignant T cells and inhibit their growth when activated by fluorescent light.

The theory appeared to be justified in a phase 3 readout last year in patients with CTCL. Patients who received HyBryte saw a lesion response rate of 49% after three cycles of treatment, compared to 4% who received one cycle of placebo treatment.

Despite the data, the FDA decided in a preliminary review of Soligenix’s application that it “was not sufficiently complete,” the biotech announced in a Feb. 14 release. The company is now deciding next steps, which will include requesting a meeting with the agency to clarify the issues and getting some further guidance on the requirements for an acceptable application.

"We are fully determined to work with the FDA staff as quickly as possible to better understand the open issues and clarify the potential path to successfully resubmitting our application," CEO Christopher Schaber, Ph.D., said in the release. "We remain focused on advancing HyBryte as a potential new first-in-class treatment option for the CTCL community of patients, families and healthcare professionals."

It’s a major setback for Soligenix, which at the time hailed the submission of the application for approval of HyBryte as a “significant milestone." As the drug had been granted both orphan-drug and fast-track designations by the FDA, the biotech had optimistically anticipated approval in the second half of 2023 with eyes on a U.S. launch in the first quarter of 2024.

In this context, it’s perhaps unsurprising that investors took today’s news badly, sending the biotech’s stock plummeting 38% in premarket trading to $3.60 a share.

Behind HyBryte in Soligenix’s biotherapeutics pipeline is SGX942, which is in a phase 3 trial for oral mucositis, and SGX302, which is in a phase 2 trial for psoriasis. There is also SGX203, which the company claims has the potential to be the first approved therapy for mild to moderate Crohn’s disease in children.