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Participants receiving the potent and highly selective BTK inhibitor fenebrutinib maintained low disease activity in the OLE of the FENopta study.

Participants receiving the potent and highly selective Bruton tyrosine kinase (BTK) inhibitor fenebrutinib maintained low disease activity in the open-label extension (OLE) of the FENopta study. Participants treated for 1 year had near complete suppression of acute inflammatory disease activity. Fenebrutinib maintained a favorable safety profile.

Fenebrutinib 200 mg twice daily reduced acute inflammatory disease activity and demonstrated central nervous system (CNS) penetration in people with relapsing multiple sclerosis (MS) in the 12-week, placebo-controlled, phase 2 FENopta trial (NCT05119569). Participants were 18 to 55 years old at inclusion, had relapsing MS, and an Expanded Disability Status Scale (EDSS) score of 0 to 5.5 at baseline. At the end of the double-blind study period, all 99 eligible participants joined the OLE. The 48-week results were presented by Amit Bar-Or, MD, University of Pennsylvania, Philadelphia.¹ Of the OLE participants, 65 had received fenebrutinib, and 34, placebo in the original study.

Disease activity was very low in the OLE. Of the 99 participants, 90% met no evidence of disease activity (NEDA) criteria throughout 48 weeks. The annualized relapse rate (ARR) was 0.04, and 96% were relapse-free during the OLE. At week 48, 99% of the participants were free of new T1 gadolinium-enhancing (Gd+) lesions. The mean number of new Gd+ lesions was 0.015 per scan (n=67). The ARR of new or enlarging T2-weighted lesions was reduced to 0.16 in the original fenebrutinib group and to 0.13 in the original placebo group. Fenebrutinib was associated with a decrease in T2-weighted lesion volume of –0.33 in the original fenebrutinib group. At week 48, the median EDSS score had not changed.

Reductions in immunoglobulin and B-cell levels were also observed, consistent with fenebrutinib’s mechanism of action.

In addition, fenebrutinib maintained a favorable safety profile mirrored by the high retention rate. The most common adverse events (AEs) were urinary tract infection (8%), COVID-19 (7%), and pharyngitis (5%). One participant had 2 serious AEs (urinary tract infection and nephrolithiasis).

Medical writing support was provided by Michiel Tent.
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