Preventing multiple sclerosis (MS) disease progression is critical in preserving function and quality of life. Fenebrutinib is a potent, highly selective Bruton’s tyrosine kinase (BTK) inhibitor with a dual mechanism of action. Fenebrutinib targets acute and chronic aspects of MS by decreasing B-cell activation and limiting myeloid proinflammatory responses. This profile and studies of fenebrutinib in patients with other inflammatory diseases suggest a potentially favorable benefit-risk ratio, although there are no studies yet in patients with MS.
To describe the unique design aspects of the Phase III fenebrutinib clinical trial program as they relate to understanding disease progression across the MS spectrum.
We developed a Phase III program that will assess disease progression in two identical clinical trials in relapsing MS (RMS) and one trial in primary progressive MS (PPMS).
To understand the effects of fenebrutinib on disease progression, all three trials include 12-week composite Confirmed Disability Progression (cCDP12) as a primary endpoint; the RMS trials also include annualized relapse rate as a co-primary endpoint. The cCDP12 requires at least one of the following: (1) an increase in Expanded Disability Status Score (EDSS) score of ≥1.0 point from a baseline (BL) score of ≤5.5 points, or a ≥0.5 point increase from a BL score of >5.5 points; (2) a 20% increase from BL in time to complete the 9-Hole Peg Test; (3) a 20% increase from BL in the Timed 25-Foot Walk Test. The cCDP12 is a more sensitive assessment of disability than the EDSS, especially at early disease stages, as it provides a quantitative assessment of upper limb function. Comparator arms will include active disease-modifying treatments with known effects on disability progression (PPMS=ocrelizumab; RMS=teriflunomide). Treatment assignments will be 1:1, with estimated enrollment of 734 patients in each of the RMS trials and 946 in the PPMS trial. Study durations will be event driven, with the primary analysis occurring after a prespecified number of cCDP12 events (≥96 or ≥120 weeks in the RMS and PPMS trials, respectively).
Fenebrutinib will be investigated in RMS and PPMS and may offer a unique approach to slowing disease progression in MS. Furthermore, the use of the cCDP12 as a primary endpoint may provide a clearer, more complete picture of disability progression or improvement than the EDSS alone.