Continued Treatment with SGX301 in Patients with CTCL Increases Response Rates

The open-label treatment cycle (cycle 2) of the pivotal phase III FLASH (Fluorescent Light Activated Synthetic Hypericin) study found that continued treatment with SGX301 (synthetic hypericin) twice weekly for 12 weeks increased the positive response rate to 40% (P < 0.0001 compared to placebo and P < 0.0001 compared to 6-weeks treatment), according to Soligenix, the agent’s developer. 

SGX301 is being evaluated for the treatment of patients with early-stage cutaneous T-cell lymphoma (CTCL). These highly statistically significant results confirm the benefit of continued treatment with SGX301 in patients with CTCL.

“As anticipated, the data continues to become more compelling with extended SGX301 treatment," lead investigator Ellen Kim, MD, director of the Dermatology Clinic at the Perelman Center for Advanced Medicine. "This treatment response is comparable to other, less safe, treatment alternatives, showing a statistically significant response at just 6 weeks, which continues to significantly increase with more treatment. The response rate at 12 weeks is similar to other therapies, some of which patients must take for more than a year.

“In addition to the efficacy demonstrated, SGX301 remains well tolerated with a unique mechanism of action that is not associated with DNA damage like other currently available therapies,” Kim continued. “I look forward to working with Soligenix to move this important new therapy forward with US Food and Drug Administration (FDA) so that patients may access it as soon as possible.”

Previously, Soligenix announced positive top-line results when the study achieved statistical significance (P = 0.04) in its primary endpoint over the first 6-week double-blind treatment cycle (cycle 1). 

Overall, the study enrolled 169 patients who were then randomized in a 2:1 fashion to receive either SGX301 or placebo in cycle 1. Treatments were administered twice weekly for the first 6 weeks and treatment response was then determined at the end of the 8th week of each cycle.

In cycle 1, 116 subjects received SGX301 treatment (0.25% synthetic hypericin) and 50 received placebo treatment of their index lesions. Ultimately, a total of 16% of the patients who received SGX301 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. Moreover, SGX301 in the first cycle was safe and well tolerated. 

In cycle 2, all patients received SGX301 treatment of their index lesions. In total, 155 patients were evaluated in this cycle, with 110 receiving 12 weeks of SGX301 treatment and 45 receiving 6 weeks of placebo treatment followed by 6 weeks of SGX301 treatment, demonstrating a response rate among the 12-week treatment group of 40% (P < 0.0001 vs the placebo treatment rate in cycle 1). Further, comparison of the 12-week and 6-week treatment groups also demonstrated a statistically significant improvement (P < 0.0001) between the 2 groups, suggesting that continued treatment results in better outcomes. Additionally, SGX301 continued to be safe and well tolerated.

"The availability of a safe, rapid-acting, treatment for CTCL is extremely important to patients," Susan Thornton, chief executive officer of the Cutaneous Lymphoma Foundation, the largest patient advocacy organization for CTCL, said in a press release. "From the patient perspective, you want a treatment that is safe and effective with the least amount of side effects. Many of the therapies available today either don't work for all patients, don't work for long-periods of time, can't be used by some because of their concerning side effects, or are used off-label creating access issues. As the leader of the patient organization and a patient myself, I know first-hand the importance of developing more therapies and options to support people living with this rare cancer.”

In the third optional treatment cycle (cycle 3), all subjects could receive SGX301 treatment of all their lesions. Importantly, the majority of patients already enrolled in the trial have elected to continue with optional study cycle. Even further, in a subset of patients evaluated in this cycle, it was determined that SGX301 is not systemically available, consistent with the general safety of this topical product observed to date.

Secondary measures that are also being assessed include treatment response (including duration), degree of improvement, and time to relapse and safety. Results from cycle 3 and the subsequent 6-month follow-up after completion of treatment will also be announced as the final patients complete their designated visits. 

Reference:

Soligenix Announces Positive Phase 3 FLASH Study Demonstrates Increased Efficacy with Continued Treatment in Patients with Cutaneous T-Cell Lymphoma [news release]. Princeton, NJ. Published April 30, 2020. prnmedia.prnewswire.com/news-releases/soligenix-announces-positive-phase-3-flash-study-demonstrates-increased-efficacy-with-continued-treatment-in-patients-with-cutaneous-t-cell-lymphoma-301049979.html. Accessed May 7, 2020.