Pliant Reports Positive Data in Phase 2a PSC Study
February 5, 2024
Rare Daily Staff
Pliant Therapeutics said 12-week interim data from the 320 mg dose group of the INTEGRIS-PSC phase 2a clinical trial of bexotegrast in patients with primary sclerosing cholangitis and suspected moderate to severe liver fibrosis met its primary and secondary endpoints.
The data showed that bexotegrast was well tolerated over a 12-week treatment period and its plasma concentrations increased with dose, there was no dose relationship for adverse events, and pruritus and cholangitis occurred less frequently on bexotegrast than on placebo.
Primary sclerosing cholangitis (PSC) is a rare, progressive liver disease of unknown origin, which frequently occurs in the setting of inflammatory bowel disease. PSC affects more than 30,000 patients in the United States and more than 100,000 patients worldwide. The disease can occur in all ages, genders, and races. PSC is characterized by inflammation and fibrosis, with progressive liver and biliary damage leading to cirrhosis and liver failure. Currently there are no FDA or EMA-approved therapies for patients with PSC. Therefore, there is a high unmet need for new therapeutic options to address the symptoms and modify the disease progression of this grievous illness.
INTEGRIS-PSC is a multinational, randomized, dose-ranging, double-blind, placebo-controlled phase 2a trial evaluating bexotegrast at multiple, once-daily oral doses or placebo for 12 weeks in 121 patients with PSC. The highest dose group enrolled 27 patients in the active arm and added nine new patients to the pooled placebo arm.
The trial’s exploratory efficacy endpoints assessed changes in the liver fibrosis markers, Enhanced Liver Fibrosis (ELF) score and PRO-C3 levels, as well as liver biochemistry and magnetic resonance imaging (MRI) of the liver. Consistent with the results from the lower doses tested, bexotegrast-treated patients at the 320 mg dose showed a reduction in both ELF score and PRO-C3 levels relative to placebo at Week 12. Bexotegrast-treated patients also showed stabilization of alkaline phosphatase (ALP) levels, relative to an increase on placebo at Week 12. In addition, MRI imaging continued to show evidence of improved hepatocyte function and bile flow with bexotegrast at the highest dose relative to placebo.
Pliant believes INTEGRIS-PSC to be the first randomized clinical trial to use an enrichment strategy to enroll patients with suspected moderate to severe liver fibrosis based on liver stiffness measure, ELF score or historical liver biopsy. Baseline characteristics of the trial population reflected this enrichment. The highest dose group will continue until all patients have been treated for at least 24 weeks, with final data expected in mid-2024.
“Results from INTEGRIS-PSC continue to build on the favorable safety and tolerability data for bexotegrast which is critically important in the setting of vulnerable patient populations and the need for chronic therapies,” said Éric Lefebvre, chief medical officer of Pliant. “As the therapeutic profile of bexotegrast comes into focus with these data, it’s encouraging to see bexotegrast’s treatment effects manifested across multiple endpoints, suggesting its potential to impact PSC where therapies are urgently needed.”
The primary endpoint of the INTEGRIS-PSC trial is the evaluation of the safety and tolerability of bexotegrast. The secondary endpoint is an assessment of its pharmacokinetics.
Bexotegrast at the highest dose was well tolerated with no dose relationship observed for adverse events. Of the 27 patients treated with bexotegrast at the highest dose, 26 (96 percent) completed 12 weeks of treatment with no drug-related severe or serious adverse events (SAE). Most treatment-emergent adverse events (TEAEs) were mild or moderate in severity and consistent with PSC disease symptoms. In addition, adverse events of pruritus and cholangitis occurred less frequently on all doses of bexotegrast relative to placebo. Patients in the trial who had concomitant inflammatory bowel disease (IBD) saw no change in their IBD symptoms as measured by partial Mayo Score while on treatment.
The exploratory endpoints of the INTEGRIS-PSC trial include changes in liver fibrosis markers, ELF and PRO-C3, liver biochemistry and MRI imaging. Consistent with the lower doses tested, bexotegrast at the highest dose reduced ELF score relative to placebo at Week 12. The ELF score is a well-established prognostic marker of liver disease severity and liver-related events in patients with advanced fibrosis and is strongly associated with transplant‐free survival in PSC and may be useful as a surrogate marker in clinical trials. Consistent with the lower doses tested, bexotegrast at the highest does also reduced PRO-C3 levels relative to placebo. PRO-C3 is a biomarker of active fibrogenesis with higher levels associated with greater disease activity.
MRI relative enhancement using gadoxetate contrast is a measure of hepatocyte function, with increased enhancement suggesting improved hepatocyte function. Consistent with the lower doses tested, bexotegrast at the highest dose showed an increase in relative enhancement on contrast MRI compared to a decrease observed in the placebo group at Week 12. In addition, consistent with the lower doses tested, bexotegrast at the hightest dose reduced time to arrival to the common bile duct compared to placebo, suggesting improved bile flow.
Patients with PSC often experience pruritus, or itch, as part of their disease. Bexotegrast at the highest dose demonstrated statistically significant reductions in the Itch Numerical Rating Scale relative to placebo at Week 12.
“Consistent with prior observations from the INTEGRIS-PSC trial, bexotegrast continues to demonstrate a very favorable safety profile while also maintaining efficacy signals,” said Kris Kowdley, director, Liver Institute Northwest and professor of Medicine, Elson S. Floyd College of Medicine at Washington State University. “These promising results present a strong rationale for the further study of bexotegrast in patients with PSC as part of a larger late-stage trial.”
Pliant is planning to share these data from the INTEGRIS-PSC trial with regulatory authorities to discuss the potential path to registration.
Photo: Éric Lefebvre, chief medical officer of Pliant
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