Sanofi shared positive results from the Phase II trial of rilzabrutinib in patients with moderate to severe chronic spontaneous urticaria (CSU).

The Phase II RILECSU study (NCT05107115) showed an improvement in CSU symptoms such as itching, hives and urticaria in CSU patients whose symptoms are inadequately controlled by H1-antihistamines.

The RILECSU trial formed the basis of the Phase III study, which is expected to start later this year.

Rilzabrutinib is a Burton tyrosine kinase (BTK) inhibitor acquired by Sanofi in 2020 as part of its $3.68bn acquisition of Principia. The drug has yet to show positive results in late-stage clinical trials. In 2021, rilzabrutinib failed to show improvement in the Phase III trial (NCT03762265) as a treatment for a rare autoimmune skin disease, pemphigus.

The drug also failed to meet the eczema area and severity endpoint in the Phase II atopic dermatitis trial (NCT05018806). Sanofi noted that “numerical improvements were seen in other important clinical components” of atopic dermatitis.

The RILECSU trial met its primary endpoint by demonstrating a reduction in weekly itch severity score (ISS7) and weekly urticaria activity score (UAS7) at 12 weeks compared to baseline. Patients in the rilzabrutinib group also showed a reduction in weekly hives severity score (HSS7) at 12 weeks compared to the baseline. The treatment-emergent adverse effects included diarrhoea, nausea, headache, and abdominal pain.

Chronic spontaneous urticaria, also known as chronic hives, is a skin condition that causes red, raised, and itchy hives that are occasionally painful. The hives last for six weeks or more and are managed symptomatically with antihistamines, antipruritic, and anti-inflammatories.

Sanofi also has another CSU therapy in its portfolio, Dupixent (dupilumab). The blockbuster therapy was developed in partnership with Regeneron. This month, it was approved as a treatment for CSU in patients aged 12 years and older by the Japanese Ministry of Health, Labor and Welfare

Sanofi is also evaluating rilzabrutinib in multiple autoimmune indications, including a Phase III trial (NCT04562766) for heavily pre-treated immune thrombocytopenia and Phase II trials in warm autoimmune haemolytic anaemia (NCT05002777), IgG4-related disease (NCT04520451), and moderate to severe asthma (NCT05104892). The readouts from the Phase II trials are expected this year.