A Study of Rilzabrutinib in Adult Patients With Immune Thrombocytopenia (ITP)

An Adaptive, Open-Label, Dose-Finding, Phase 1/2 Study Investigating the Safety, Pharmacokinetics, and Clinical Activity of PRN1008, an Oral BTK Inhibitor, in Patients With Relapsed Immune Thrombocytopenia

This was a 2 part (Part A and B) adaptive, open-label, dose-finding study of PRN1008 in patients with ITP who are refractory or relapsed with no available and approved therapeutic options, with a platelet count <30,000/μL on two counts no sooner than 7 days apart in the 15 days before treatment begins. The dose-finding portion of the study was completed. Part B treatment dose was 400 mg twice daily.

This was a 2 part (Part A and B) adaptive, open-label, dose-finding study of PRN1008 in approximately 60 patients in Part A and approximately 25 patients in Part B.

Part A enrolled patients with ITP who were refractory or relapsed with no available and approved therapeutic options. Eligible patients had a platelet count <30,000/μL on two counts no sooner than 7 days apart in the 15 days before treatment begins. The active treatment period was 24 weeks and the post-treatment follow-up period is 4 weeks. In the dose-finding part of the study, each patient enrolled in the study was allowed to up-titrate their dose after 28 days of PRN1008 therapy, if they did not experience a platelet response or a dose-limiting toxicity (DLT) at the last dose level. Patients who responded to PRN1008 per protocol may enter a long term-extension.

Part B of the study included approximately 25 patients with ITP who had relapsed or had an insufficient response to prior therapies. Eligible patients had a platelet count <30,000/µL on two occasions no less than 7 days apart, within 15 days before treatment began and a platelet count of ≤35,000/µL on Study Day 1 (SD1). The study consisted of a 28-day screening period, 24-week active treatment period, and a long-term extension. After the last dose of PRN1008 there was a 4-week safety follow-up period.

Inclusion Criteria:

• Male or female patients, aged 18 to 80 years old
• Immune-related ITP (both primary and secondary)

Exclusion Criteria:

• Pregnant or lactating women
• Current drug or alcohol abuse
• History of solid organ transplant
• Positive screening for HIV, hepatitis B, or hepatitis C