Study to Evaluate the Efficacy and Safety of Oral Rilzabrutinib in Adults With Immune Thrombocytopenia (ITP) Who Failed First-line Treatment

Overall platelet response

Percentage of participants able to achieve 2 platelet counts at least 5 days apart of ≥50 000/μL (or ≥30 000/μL and \<50 000/μL and at least double from baseline) without rescue therapy in the 4 weeks prior to the first elevated platelet count

Time frame: Until Week 28

Duration of platelet response

Cumulative number and proportion of non-missing weeks with platelet counts ≥50 000/μL (or ≥30 000/μL and \<50 000/μL and at least double from baseline) in absence of rescue therapy in the 4 weeks prior to the elevated platelet count in participants who achieve a response (single platelet count)

Time frame: Until Week 28

Change from baseline in the immune thrombocytopenia bleeding scale (IBLS) score at the end of week 28

Time frame: Until Week 28

Percentage of participants able to discontinue or reduce CS dose by at least 50% or to <5 mg/day (prednisone equivalent) from baseline at the end of week 28

Time frame: Until Week 28

Frequency and severity of treatment emergent adverse events (TEAEs, including serious adverse events [SAEs], bleeding TEAEs, adverse event of special interest [AESI] and adverse events leading to discontinuation)

Time frame: Until Week 80