Sanofi has announced that its investigational oral Bruton’s tyrosine kinase (BTK) inhibitor rilzabrutinib failed to meet the primary and secondary endpoints in a Phase III trial.

The Phase III PEGASUS trial evaluated rilzabrutinib for the treatment of the rare autoimmune skin condition pemphigus. It enrolled adult patients with moderate-to-severe pemphigus vulgaris or pemphigus foliaceus.

The primary endpoint of the PEGASUS trial was complete remission from weeks 29 to 37 with minimal doses of corticosteroids, defined as the absence of new and established skin lesions.

However, results from the late-stage trial showed that the proportion of rilzabrutinib-treated patients who met this primary endpoint was not significantly different from placebo.

“While these results are disappointing, we believe the rilzabrutinib clinical programme holds great potential to address the unmet treatment needs of people living with immune-mediated diseases,” said Naimish Patel, head of global development, Immunology and Inflammation, Sanofi.

“Our mission is to improve outcomes by exploring new scientific approaches and novel therapies to advance the standard of care. We are committed to investigating rilzabrutinib further and progressing our clinical programmes forward to deliver new treatment options for patients,” he added.

Pemphigus encompasses a group of potentially fatal disorders, characterised by blisters and ulceration affecting the skin and mucous membranes – current treatment options are limited and include systemic corticosteroid treatment.

Aside from pemphigus, rilzabrutinib is being investigated in a Phase III trial for the treatment of the rare blood disorder immune thrombocytopenia, and in a Phase II study for the treatment of the autoimmune condition IgG4-related disease.