First-in-Human Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single and Multiple Ascending Oral Doses of BIIB091, an Oral BTK Inhibitor, in Healthy Adult Participants.

INTRODUCTION

Multiple sclerosis (MS) affects 2.8 million people globally. Despite available disease-modifying therapies (DMTs), more effective treatments are needed to prevent/slow disability progression. BIIB091 is a selective, non-covalent oral Bruton's tyrosine kinase (BTK) inhibitor. This Phase 1, first-in-human study evaluated safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of BIIB091.

METHODS

Participants received single ascending doses (SAD; 50-1200 mg) or multiple ascending doses (MAD; 50-300 mg twice daily [BID] for 14 days) of BIIB091 or placebo. Safety assessments included labs, vitals, physical examinations, electrocardiograms, and adverse event (AE) recordings. PK was evaluated through blood and urine samples; PD was evaluated through blood samples, including BTK phosphorylation and B-cell receptor-mediated CD69 upregulation. Additional objectives assessed PK/PD relationship and food's effect on PK.

RESULTS

Sixty-four participants were randomized (SAD n=40; MAD n=24). BIIB091 showed rapid absorption, dose-proportional PK, and no significant accumulation. BIIB091 suppressed B cell activation, achieving >90% inhibition of CD69 expression on CD19+ within 1 hour at all study doses; inhibition was sustained up to 24 hours at 1200 mg. A high-fat meal delayed Tmax by ~5.2 hours and increased AUC and Cmax about 2.046- and 1.420-fold. A single 300 mg dose prolonged the CD69 inhibition duration, maintaining >90% 24 hours post-dose versus 42% in fasted state. MAD >150 mg BID maintained rapid and consistent CD69 inhibition over 14 days. Mild AEs were reported in 14 participants, with no dose-limiting AEs, serious AEs, or withdrawals. Nausea and headache were the most common AEs.

CONCLUSION

BIIB091 was well tolerated at single doses up to 1200 mg and repeated doses up to 300 mg BID, showing dose-linear PK and sustained effective B cell activation suppression. BIIB091 PK appeared to be sensitive to food effect. These important insights support its continued development for MS.