French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Thursday that the US Food and Drug Administration has granted orphan drug designation to rilzabrutinib for warm autoimmune haemolytic anaemia (wAIHA) and IgG4-related disease (IgG4-RD), both of which currently have no approved treatments.

Orphan drug designation supports therapies for rare diseases affecting fewer than 200,000 people in the United States.

Rilzabrutinib, an investigational oral Bruton's tyrosine kinase inhibitor, is also under regulatory review in the US, the European Union and China for immune thrombocytopenia, with an FDA decision expected by 29 August 2025. The drug previously received orphan drug designation for immune thrombocytopenia in the US, EU and Japan.

A phase 2b study presented at ASH 2024 showed that rilzabrutinib delivered clinically meaningful outcomes in wAIHA. In IgG4-RD, a phase 2a study showed a reduction in disease flare and glucocorticoid use over 52 weeks.

The safety profile in both studies remained consistent with previous trials. Additional study results will be presented at an upcoming medical meeting.