The thick skin that is a hallmark of scleroderma showed meaningful improvement in 75 percent of patients treated with Corbus Pharmaceuticals’ anabasum (JBT-101), according to initial results of an extension trial.
Corbus discussed the first six months’ findings of the one-year extension study at the American College of Rheumatology Annual Meeting in San Diego, Nov. 3-8. The poster presentation was titled “Safety and Efficacy of Anabasum (JBT-101) in Diffuse Cutaneous Systemic Sclerosis (dcSSc) Subjects Treated in an Open-Label Extension of Trial JBT101-SSc-001.”
In addition to the extension, Corbus plans a Phase 3 trial of anabasum, which it expects to start before the end of the year.
The Phase 2 study (NCT02465437) tested anabasum in people with diffuse cutaneous systemic sclerosis, or scleroderma. The participants received either 20 mg of anabasum or a placebo twice a day for 84 days. They also received standard-of-care therapies for systemic sclerosis. For 92 percent of patients, those treatments included immunosuppressive drugs.
After a 28-day follow-up period, 36 of the Phase 2 trial participants enrolled in the one-year extension, continuing to receive 20 mg of anabasum twice a day.
Researchers measured patients’ skin thickness between the start of the extension study and the end of the first six months with a modified Rodnan Skin Score, or mRSS. The average score at the start of the extension was 24 points. At the end of the six months it was 15.6 points, a difference researchers considered significant.
Seventy-five percent of the participants achieved an mRSS reduction of more than 5 points, an improvement that researchers said enhanced their chance of survival. And a third of the participants ended up with an mRSS below 10.
The anabasum-treated extension participants also ended up with better rheumatoid arthritis scores. The scale researchers used was the American College of Rheumatology’s diffuse cutaneous systemic sclerosis score, or ACR CRISS.
When patients’ arthritis improves, their ACR CRISS score increases. Forty-four percent of the anabasum-treated patients in the extension study ended up with a score higher than 70 percent after six months. This was more than double the score that patients achieved with other therapies.
Researchers also saw improvements in patients’ other skin symptoms, the amount of disability they reported, and their ability to function.
Breathing difficulty is associated with scleroderma, and the anabasum-treated extension participants experienced no decline in a measure of lung function known as forced vital capacity. This is the amount of air a person can exhale during a forced breath.
“The consistency and magnitude of efficacy seen with longer dosing increases our confidence that anabasum could offer a meaningful benefit to patients with SSc [systemic sclerosis],” Dr. Barbara White, the chief medical officer of Corbus, said in a press release. “The speed and degree of improvement in multiple efficacy outcomes at this stage in the open-label extension of our Phase 2 study exceeds that previously reported in other clinical trials or registries in SSc.”
“This level of improvement in this relatively short interval is impressive,” compared with clinical trial results of other treatments, said Dr. Robert Spiera, director of the Vasculitis and Scleroderma Program at the Weill Cornell Medical College‘s Hospital for Special Surgery in New York. “I look forward to leading the Phase 3 study.”
Researchers found anabasum to be safe as well as effective. No patient experienced a severe or serious adverse event. The most common adverse events were upper respiratory tract illness in seven patients — or 19 percent of the participants — and urinary tract infection in five patients, or 14 percent.
“These safety and efficacy data are very encouraging and reinforce the positive findings in the double-blinded placebo-controlled part of the study,” said Dr. Yuval Cohen, chief executive officer of Corbus. “Systemic sclerosis is a very challenging disease, and no SSc-specific drugs have been approved by the FDA. Our focus now is to ensure the successful execution of our Phase 3 study, and we are on track to commence this before year-end.”
Anabasum has received Orphan Drug Designation and Fast Track status from the U.S. Food and Drug Administration as a treatment for systemic sclerosis, and Orphan Designation from the European Medicines Agency.