Sanofi reports positive results for BTK inhibitor from $3.7B Principia acquisition

Sanofi's BTK inhibitor rilzabrutinib has shown promising results in a Phase 3 clinical trial for treating immune thrombocytopenia (ITP), a rare autoimmune disorder that causes low platelet counts and increases the risk of bleeding and bruising. The trial data revealed that rilzabrutinib helped 23% of adult patients achieve target platelet counts, compared to none in the placebo group. This development is significant as Sanofi prepares to file for regulatory approval in the United States.

Rilzabrutinib, acquired through Sanofi's $3.7 billion purchase of Principia Biopharma in 2020, is projected to be a potential blockbuster drug. According to a recent R&D presentation, it could generate between €2 billion to €5 billion in peak sales. The trial, known as LUNA 3, included 133 adult patients who were randomized to receive rilzabrutinib. Out of these, 31 patients met the primary endpoint of achieving durable platelet response, defined as platelet counts at or above 50,000/μL for at least eight of the last 12 weeks of the 24-week treatment period without requiring rescue therapy. None of the 69 patients in the placebo group met this endpoint.

Patients participating in the trial had previously not responded to or were intolerant of other therapies. Notably, 46% of them had undergone five or more treatments, and some had been managing ITP for years. Although the trial included both adults and adolescents, the reported data focus on the adult population, highlighting this as the first efficacy and safety report for adults.

Sanofi also claimed significant improvements in secondary endpoints, including a 53% reduction in the need for rescue therapy compared to the placebo and improvements in physical fatigue. Despite a similar percentage of adverse events in both the rilzabrutinib and placebo groups, one patient with multiple risk factors experienced a Grade 3 peripheral embolism, which is a blockage in an artery, related to the treatment.

Sanofi aims to submit a regulatory filing for rilzabrutinib this year, as mentioned during the company's second-quarter earnings call in July. This Phase 3 success is particularly encouraging for Sanofi following rilzabrutinib’s previous unsuccessful Phase 2 trial in atopic dermatitis and a disappointing Phase 3 outcome in pemphigus in 2021. However, Sanofi remains committed to exploring other mid-stage programs for conditions such as asthma, chronic spontaneous urticaria, IgG4-related disease, and warm autoimmune hemolytic anemia.

The positive results from the Phase 3 trial bolster rilzabrutinib's potential as a significant treatment option for ITP, reflecting Sanofi's ongoing dedication to developing innovative therapies for challenging autoimmune disorders.