Forte Biosciences (NASDAQ:FBRX) said FB102 showed statistically significant improvement in a small placebo-controlled vitiligo study, with Chief Executive Officer Paul Wagner highlighting continued improvement after patients stopped treatment as a key feature of the results.
On a company data call, Wagner said the trial evaluated FB102, an antibody designed to block CD122 and modulate IL-2 and IL-15 signaling involved in pathogenic T-cell activity. Forte is studying the drug in autoimmune diseases, including vitiligo and celiac disease.
Trial Design and Primary Endpoint
The vitiligo study enrolled 43 subjects randomized three-to-one, with 32 patients receiving FB102 and 11 receiving placebo in the intent-to-treat population. The company said patients received 12 weeks of treatment and were then followed off therapy through week 24.
The primary endpoint was mean percent improvement from baseline in facial Vitiligo Area Scoring Index, or F-VASI, at week 24, assessed by central review. David Rosmarin, Chair of the Department of Dermatology at Indiana University School of Medicine, served as the independent central reviewer for the F-VASI assessment and joined the call to discuss the results.
Wagner said the protocol-defined efficacy evaluable population excluded one placebo patient who had facial hair and experienced significant vitiligo progression during the study. He described that exclusion as providing a more conservative assessment of FB102’s activity because it removed a placebo patient who worsened.
Forte Reports Statistically Significant Improvement
Wagner said FB102 showed a statistically significant improvement in the primary endpoint at week 24 in both individual cohorts and overall. In the efficacy evaluable analysis, he described an approximately 30-point improvement from baseline for FB102 and an approximately eight-point improvement for placebo, for a placebo-adjusted difference of about 22 points.
The company also reported that the response became statistically significant by day 64 and remained statistically significant through week 24. Wagner emphasized that improvement continued after the 12-week treatment period ended, saying the pattern was consistent with earlier mouse-model findings that suggested potential disease modification after depletion of tissue-resident memory T cells.
Forte also analyzed patients with more extensive facial involvement at baseline, defined as F-VASI of at least 0.75. Wagner said this corresponded to roughly 20% to 25% facial depigmentation. In that subgroup, which included 17 FB102-treated patients and four placebo patients, he said the placebo-adjusted improvement was roughly 43 points at week 24, with a p-value of 0.006.
Wagner said 84% of FB102-treated subjects improved over the 24-week period after 12 weeks of treatment and none worsened, while three of 11 placebo subjects worsened.
Responder Data and Safety
In responder analyses, Wagner said 34% of FB102-treated patients achieved F-VASI 50 and 12.5% achieved F-VASI 75 at week 24. Among patients with baseline F-VASI of at least 0.75, he said the F-VASI 50 rate was about 60% and the F-VASI 75 rate was 23.5%.
Wagner said the responder endpoint was affected by one placebo F-VASI 75 responder and argued that baseline severity is important when interpreting responder endpoints in vitiligo studies.
On safety, Wagner said adverse events were mild to moderate and that FB102’s profile looked favorable relative to placebo. He said the findings were consistent with safety observations from Forte’s Phase 1b celiac disease study.
Expert and Analyst Discussion
Rosmarin characterized the study as a “resounding success,” citing evidence across three treatment goals in vitiligo: preventing progression, repigmenting patients and maintaining repigmentation. He said the observation that patients continued improving after stopping therapy was consistent with the proposed mechanism and prior mouse studies.
Rosmarin also said the placebo-controlled design gave him confidence in the findings and that the Phase 2 program had been “de-risked” by the Phase 1 execution. He cautioned, however, that the number of patients was small and that safety will not be fully understood until later-stage studies.
During the question-and-answer session, analysts asked about the relevance of the F-VASI 0.75 cutoff, the durability of response after treatment stopped, comparisons with JAK inhibitors and the contribution of IL-2 blockade in FB102’s mechanism. Wagner and Rosmarin said the higher baseline severity subgroup helped reduce the chance that results were driven by placebo fluctuation in small lesions.
Wagner said Forte has evaluated different dosing approaches but declined to disclose details of the second cohort for proprietary reasons. He added that the company is looking forward to an imminent readout from its Phase 2 celiac disease study.
About Forte Biosciences (NASDAQ:FBRX)
Forte Biosciences, Inc is a clinical-stage biotechnology company focused on developing innovative treatments to restore skin health by targeting the underlying biology of the skin barrier and microbiome. Headquartered in San Diego, California, Forte leverages proprietary platforms to discover and advance topical live biotherapeutic products and skin barrier therapies aimed at addressing serious dermatological conditions.
The company’s lead product candidate, FB-401, is a topical live biotherapeutic formulation designed to rebalance the skin microbiome in patients with atopic dermatitis.
