Mallinckrodt has permanently suspended a Phase IIb clinical trial of its Acthar Gel (repository corticotropin injection) in patients with amyotrophic lateral sclerosis (ALS).

The study was designed to compare the safety and efficacy of the injection with placebo over 36 weeks in subjects aged 18 to 75.

Acthar Gel’s efficacy was measured as functional decline, including change in the ALS Functional Rating Scale-Revised from baseline, at 36 weeks following treatment.

The decision to halt the trial comes after its independent Data and Safety Monitoring Board (DSMB) highlighted higher pneumonia rate in participants on Acthar Gel versus placebo.

In addition, the DSMB noted additional adverse events and no clear efficacy signal for the patient population.

The company will immediately stop patient enrolment into the trial and existing participants will be tapered off the injection drug prior to discontinuation of use.

Mallinckrodt executive vice-president and chief scientific officer Steven Romano said: “Mallinckrodt’s primary focus is on the safety of patients and, while ALS patients are among those most in need of new therapies and treatment options, we believe this is the right decision.

“Though the probability of success for the ALS population was acknowledged as being low, this study was initiated based on compelling analyses carried out following the completion of a small pilot study and we were hopeful it would have translated into a benefit for this group of patients in great need of effective therapies.”

The company added that the suspension of this Phase IIb trial will not impact Acthar Gel’s other studies.

Mallinckrodt invested more than $500m in Acthar Gel, which currently holds US regulatory approval in 19 indications, including rheumatoid arthritis and infantile spasms.