The Phase 2 FUSION Trial of BTK Inhibitor BIIB091: Diana Gallagher, MD


The head of Biogen’s MS and Immunology Department Unit discussed FUSION, a new phase 2, 2-part study assessing the efficacy and safety of BIIB091, an investigational Bruton’s tyrosine kinase inhibitor. [WATCH TIME: 3 minutes]

WATCH TIME: 3 minutes

"Based on our early SAD (single-ascending dose) and MAD (multiple-ascending dose) studies, we’re going to try to target a dose selection that will get us 90% [B cell] suppression on B cell activation."

Bruton’s tyrosine kinase (BTK) plays a nonredundant signaling role downstream of the B-cell receptor in B cells and the receptors for the Fc region of immunoglobulins in myeloid cells. As the treatment landscape for multiple sclerosis (MS) has expanded over the past several decades, industry leaders have turned to BTK as a potential treatment pathway, with numerous agents currently in phase 2 and 3 trials. One such agent, BIIB091 (Biogen), has shown promising preclinical and phase 1 data as a novel, potent reversible inhibitor of BTK.

By reversibly inhibiting BTK in myeloid cells in addition to its effects in B cells, BIIB091 is thus expected to provide additional clinical benefits over B cell only therapeutic agents without the potential safety liability associated with long-term B cell depleting agents or poorly selective covalent BTK inhibitors. At MSMilan 2023, the 9th Joint ECTRIMS-ACTRIMS Meeting, held October 11-13, in Milan, Italy, investigators presented the outline for a phase 2 study, dubbed FUSION (NCT05798520), that will assess the efficacy and safety of BIIB091 in patients with relapsing MS.

FUSION is a 2-part, randomized, blinded, active-controlled trial assessing BIIB091 as a monotherapy or in combination with diroximel fumarate (Vumerity; Biogen), a previously approved disease-modifying therapy. The study plans to enroll 125 participants in Part 1 and 150 in Part 2, with safety as the primary end point for Part 1 and reductions in T1 gadolinium-enhancing lesions as Part 2. To learn more about the trial’s design, NeurologyLive® sat down with Diana Gallagher, MD, head of Biogen’s MS and Immunology Department Unit. Gallagher provided an overview of the study, details of its design, and the advantages BIIB091 has over other BTK inhibitors.

Click here for more coverage of MSMilan 2023.

1. Torres JA, Fox RJ, Arnold DL, et al. Design of the phase 2 FUSION trial of reversible non-covalent BTK inhibitor BIIB091 in participants with relapsing forms of multiple sclerosis. Presented at: MSMilan 2023; October 11-13; Milan, Italy. Abstract 1865
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