Multiple sclerosis patients on fenebrutinib had low relapse rates with data showing no active brain lesions or disability progression after nearly two years of treatment, according to the latest findings for an investigational BTK inhibitor from the Phase II FENopta open-label extension. Phase III studies for fenebrutinib in relapsing and primary progressive MS are expected to start reading out at year end.

According to Genentech researchers, the data shows patients treated with fenebrutinib experienced an annualized relapse rate equal to one relapse every 17 years and no observed disability progression for up to two years. 

Ninety-nine patients entered the open-label extension and 93 remained in the open-label extension after 96 weeks. During that period, patients treated with fenebrutinib for up to 96 weeks had a low annualized relapse rate of .06, and during this time there was no disability progression, as measured by the Expanded Disability Status Scale. 

MRI scans showed that fenebrutinib treatment suppressed disease activity in the brain. At 96 weeks, zero new T1 gadolinium-enhancing lesions, which are markers of active inflammation, were detected. In the treatment group that switched from placebo to fenebrutinib in the open-label extension, the annualized rate of new or enlarging T2 lesions, which represent chronic disease burden, decreased from 6.72 at the end of the 12 week double-blind period to 0.34 by 96 weeks.

The safety profile of fenebrutinib in the open-label extension was consistent with previously reported data, with no new safety concerns identified at 96 weeks. The most common adverse events in 5 percent of patients were COVID-19, urinary tract infection, pharyngitis, and respiratory tract infection. Serious adverse events occurred in two patients. During the open-label extension, one patient experienced asymptomatic alanine aminotransferase elevation at open-label extension week four, after 16 weeks on treatment, which resolved with treatment discontinuation. 

Three Phase III clinical trials are ongoing, including the FENhance 1 and 2 trials in RMS and the FENtrepid trial in primary progressive MS. The first data from these studies, which will characterize the effects of fenebrutinib on disease progression across the multiple sclerosis spectrum, are expected at the end of 2025.

The findings were presented at the Consortium of Multiple Sclerosis Centers Annual Meeting in Phoenix, Arizona.