OC 13.3 - Pooled Analysis of the Efficacy and Safety of Oral Bruton Tyrosine Kinase Inhibitor Rilzabrutinib in Patients With Previously Treated Immune Thrombocytopenia: Phase 2 Study

Background: Rilzabrutinib has shown rapid and durable platelet response with a favorable safety profile in adult patients with immune thrombocytopenia (ITP).

Aims: Analyze pooled results from part A (dose-finding) and part B (selected single-dose) of the phase 2 LUNA 2 study (NCT03395210) with rilzabrutinib monotherapy or rilzabrutinib with concomitant ITP therapy.

Methods: Eligible ITP adults had baseline platelet counts < 30x10^9/L and had responded to ≥1 prior ITP therapy but were unable to maintain adequate response to prior/concomitant therapies. Oral rilzabrutinib 400 mg BID was given for 24 weeks in the main treatment period. The primary efficacy endpoint (per part A) for the pooled analyses was ≥2 consecutive platelet counts ≥50x10^9/L and increased ≥20x10^9/L from baseline without rescue medication.

Results: As of 31Jan2023, 71 ITP patients from part A (n=45) and part B (n=26) were included. At enrollment, patients had a median age of 52 years (range, 19-75), median duration of ITP for 7.3 years (range, 0.4-52.5), and 32% were splenectomized. Twenty-nine (41%) patients met the primary endpoint (ie, responders), including 10/24 (42%) patients receiving rilzabrutinib monotherapy and 19/47 (40%) rilzabrutinib with concomitant ITP therapy. For patients receiving rilzabrutinib monotherapy or with concomitant ITP therapy, median platelet counts and time to first platelet count ≥50x10^9/L were similar for responders (Figure 1-2) and overall (Figure 2). Responders had a median time to first platelet count ≥50x10^9/L of 12 days (95% CI, 8-16). During main treatment, 19 (27%) patients achieved ≥8 of the last 12 platelet counts ≥50x10^9/L. All treatment-related adverse events were transient, grade 1/2 events with no related bleeding or thrombotic events, serious adverse events, or deaths.

Conclusion(s): Pooled analyses of parts A and B of the phase 2 study demonstrated rapid and durable platelet count increases in adult patients with ITP receiving rilzabrutinib monotherapy or rilzabrutinib with concomitant ITP therapy.