FDA Pauses New Enrollment in Merck KGaA’s Evobrutinib Trials

German drugmaker Merck KGaA announced in a press release that the FDA has placed evobrutinib, its investigational Bruton’s tyrosine kinase (BTK) inhibitor, on partial clinical hold. Specifically, the hold applies to the initiation of new participants on evobrutinib and those who have been taking the experimental drug for less than 70 days. The BTK inhibitor is being assessed in a phase 3 clinical called EVOLUTION as a possible treatment of relapsing multiple sclerosis (MS).

The FDA decision is based on increased liver enzyme levels seen in two participants during the phase 3 studies that suggested drug-induced liver injury. Merck reported that both patients were asymptomatic, and neither required medical attention. After treatment discontinuation, the liver enzyme levels of both participants returned to normal.

The current hold applies only to the two affected patients, since the EVOLUTION Phase 3 trials are fully enrolled with more than 2,000 participants who have all been taking the study drug for longer than 70 days. The company plans to continue the studies with an estimated completion date in 2026 and top-line results expected by the end of this year.

Merck has been in front of the race to develop the first-in-class BTK inhibitor. Other candidates in late-stage trials include Sanofi’s tolebrutinib, Biogen and InnoCare’s orelabrutinib, Novartis’ remibrutinib and and Roche and Genentech’s fenebrutinib. Both tolebrutinib and orelabrutinib were placed on partial clinical hold by the FDA last year due to similar cases of drug-induced liver injury.

The company said it will be conferring with an independent data monitoring committee and other experts about identifying any predisposing factors contributed to the liver injury.

“Merck KGaA, Darmstadt, Germany is working closely with the FDA to establish the best path forward for the benefit of patients in current and future trials with evobrutinib,” said the press release.