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Updated Main Study Period and Long-Term Extension (LTE) Results With Oral Bruton Tyrosine Kinase Inhibitor Rilzabrutinib in Immune Thrombocytopenia (ITP)

1Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States, 2Multiprofile Hospital for Active Treatment Sveta Marina EAD, Varna, Varna, Bulgaria, 3Monash Medical Centre, Clayton, Victoria, Australia, 4Masaryk University Hospital, Brno, Moravskoslezsky kraj, Czech Republic, 5The Canberra Hospital, Garran, Australian Capital Territory, Australia, 6Erasmus MC, University Medical Center, Rotterdam, Zuid-Holland, Netherlands, 7Barts Health NHS Trust, The Royal London Hospital, London, England, United Kingdom, 8WA Centre of Thrombosis and Haemostasis (WACTH) Centre for Computational and Systems Medicine, Murdoch University; Perth Blood Institute., Perth, Western Australia, Australia, 9Princess Alexandra Hospital, Woolloongabba, Queensland, Australia, 10Leicester Royal Infirmary, Leicester, England, United Kingdom, 11University Hospital Ostrava and Faculty of Medicine University of Ostrava, Ostrava, Moravskoslezsky kraj, Czech Republic, 12University Hospital of Hradec Kralove, Hradec Kralove, Kralovehradecky kraj, Czech Republic, 13University of Washington Medical Center, Seattle, Washington, United States, 14Østfold Hospital Foundation, Sarpsborg, Ostfold, Norway, 15Sanofi US Services Inc., Bridgewater, New Jersey, United States, 16Hammersmith Hospital, London, England, United Kingdom, 17Sanofi Genzyme, Cambridge, Massachusetts, United States

Abstract Number: OC 73.1

Meeting: ISTH 2022 Congress

Theme: Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies » Acquired Thrombocytopenias

Background: Rilzabrutinib led to rapid and durable platelet responses and was well tolerated in a global phase I/II trial in adult patients with ITP (NCT03395210). We present additional findings observed during the main study period in patients who initiated 400 mg BID as well as patients who are continuing in the LTE.

Aims: Assess efficacy and safety of rilzabrutinib 400 mg BID.

Methods: Patients with 2 baseline platelet counts < 30x10^9/L were required to have responded to ≥1 prior ITP therapy, but at baseline were unable to maintain an adequate response to prior/concomitant therapies. Primary endpoints were safety and efficacy: ≥2 consecutive platelet counts ≥50x10^9/L and increased ≥20x10^9/L from baseline without requiring rescue medication. All patients provided informed consent.

Results: As of 04May2021, 60 patients received rilzabrutinib, 45 initiated a 400 mg BID dose, 16 proceeded to the LTE. At enrollment, patients were heavily pretreated with a median of 4 unique prior therapies. Median ITP duration was 6.1 years and median platelet count was 15×10^9/L. With a median treatment duration of 168 days during the main period, 18 patients (40%) achieved the primary endpoint (Table). In primary responders, platelet counts ≥50×10^9/L were maintained for a median of 72% of the weeks and the median time to first platelet count ≥50×10^9/L was 12.5 days. Figure shows subgroup analysis. Overall, LTE patients received rilzabrutinib for a median of 478 days and 13/14 patients (93%) maintained platelet counts ≥50×10^9/L for ≥50% of their monthly visits in the LTE (Table). Five patients (11%) received rescue medication during the main period + LTE. All treatment-related adverse events were grade 1/2 and transient without related thrombotic events or deaths.

Conclusion(s): Over prolonged treatment, rilzabrutinib 400 mg BID demonstrated a rapid and durable clinical activity and continued to be well-tolerated in patients with ITP.

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Table and Figure

To cite this abstract in AMA style:

Kuter D, Efraim M, Kaplan Z, Mayer J, Choi P, Jansen A, McDonald V, Baker R, Bird R, Garg M, Gumulec J, Kostal M, Gernsheimer T, Ghanima W, Yao M, Cooper N, Daak A. Updated Main Study Period and Long-Term Extension (LTE) Results With Oral Bruton Tyrosine Kinase Inhibitor Rilzabrutinib in Immune Thrombocytopenia (ITP) [abstract]. https://abstracts.isth.org/abstract/updated-main-study-period-and-long-term-extension-lte-results-with-oral-bruton-tyrosine-kinase-inhibitor-rilzabrutinib-in-immune-thrombocytopenia-itp/. Accessed September 24, 2023.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/updated-main-study-period-and-long-term-extension-lte-results-with-oral-bruton-tyrosine-kinase-inhibitor-rilzabrutinib-in-immune-thrombocytopenia-itp/