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Abstract
Presentation during EHA2022: All Oral presentations will be presented between Friday, June 10 and Sunday, June 12 and will be accessible for on-demand viewing from Monday, June 20 until Monday, August 15, 2022 on the Congress platform.

Abstract: S291

Type: Oral Presentation

Session title: Thrombocytopenia - Management insights in ITP and TTP

Background
Immune thrombocytopenia (ITP) is an autoimmune disease associated with autoantibody-mediated platelet destruction and impaired platelet production, resulting in thrombocytopenia and high bleeding risk. In a global phase I/II trial (NCT03395210) of heavily pretreated patients with long-standing disease, the Bruton tyrosine kinase inhibitor rilzabrutinib showed a rapid and durable platelet count increase and was well tolerated. We present results for patients initiating rilzabrutinib 400 mg BID who are continuing in the long-term extension (LTE).

Aims
Assess if the efficacy and safety of rilzabrutinib 400 mg BID continue to be maintained in LTE patients on rilzabrutinib ± concomitant medication.

Methods
Patients with 2 baseline platelet counts <30×109/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. The main treatment period was 24 weeks; patients who achieved platelet counts ≥50×109/L at ≥50% of the visits during the last 8 weeks of the main period were permitted to continue 400 mg BID in the LTE. Primary endpoints were safety and efficacy (≥2 consecutive platelet counts ≥50×109/L and increased ≥20×109/L from baseline without requiring rescue medication). Stable doses of concomitant ITP medication (thrombopoietin-receptor agonists [TPO-RA] and corticosteroids [CS]) were allowed for patients with inadequate platelet response. Patients who received rescue medication discontinued from the study. All patients provided informed consent.

Results
At baseline, the 45 patients initiating 400 mg BID in the main period had a median age of 49 years, median duration of ITP of 6.1 years, median platelet count of 15×109/L, and a median of 4 unique prior therapies (24% prior splenectomy). A total of 15 patients (33%) received rilzabrutinib monotherapy, and 30 had concomitant therapy (TPO-RA n=13 [29%], CS n=12 [27%], TPO-RA + CS n=5 [11%]). Primary platelet response was achieved by 18 patients (40%): 6  on monotherapy and 12 on concomitant medication. Platelet counts of ≥50×109/L, ≥30×109/L, and ≥20×109/L from baseline were maintained for a median of 71%, 95%, and 87% of weeks, respectively. As of 21Jan2022, 16/60 patients in the main study population had proceeded to LTE, of whom 11 were ongoing. Five LTE patients (31%) continued on rilzabrutinib monotherapy and 11 used concomitant medication (TPO-RA n=2 [13%], CS n=7 [44%], TPO-RA + CS n=2 [13%]; Figure); 1 patient used rescue medication. Median platelet count at LTE entry was 87×109/L. In patients on rilzabrutinib monotherapy, the median platelet count was 68×109/L, which was sustained at 6 months of follow-up (Table). In all LTE patients, platelet counts ≥50×109/L, ≥30×109/L, and ≥20×109/L from baseline were maintained for a median of 88%, 100%, and 97% of weeks, respectively. In patients on rilzabrutinib ± concomitant medication, results were consistent at 3 and 6 months of follow-up (Table). Three patients (19%) experienced related treatment-emergent adverse events (TEAEs), including 1 grade 2 upper respiratory tract infection. Three patients (19%) discontinued rilzabrutinib due to a TEAE. Six patients had ≥1 bleeding event, none were treatment-related; no related serious adverse events or deaths. The average ITP-BAT bleeding scale score at 6 months showed no increase in bleeding in the LTE.

Conclusion
With extended treatment duration, rilzabrutinib 400 mg BID showed durable clinical efficacy and was well tolerated in patients on rilzabrutinib ± concomitant medication.

Keyword(s): Immune thrombocytopenia (ITP), Inhibitor, Platelet, Platelet count

Presentation during EHA2022: All Oral presentations will be presented between Friday, June 10 and Sunday, June 12 and will be accessible for on-demand viewing from Monday, June 20 until Monday, August 15, 2022 on the Congress platform.

Abstract: S291

Type: Oral Presentation

Session title: Thrombocytopenia - Management insights in ITP and TTP

Background
Immune thrombocytopenia (ITP) is an autoimmune disease associated with autoantibody-mediated platelet destruction and impaired platelet production, resulting in thrombocytopenia and high bleeding risk. In a global phase I/II trial (NCT03395210) of heavily pretreated patients with long-standing disease, the Bruton tyrosine kinase inhibitor rilzabrutinib showed a rapid and durable platelet count increase and was well tolerated. We present results for patients initiating rilzabrutinib 400 mg BID who are continuing in the long-term extension (LTE).

Aims
Assess if the efficacy and safety of rilzabrutinib 400 mg BID continue to be maintained in LTE patients on rilzabrutinib ± concomitant medication.

Methods
Patients with 2 baseline platelet counts <30×109/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. The main treatment period was 24 weeks; patients who achieved platelet counts ≥50×109/L at ≥50% of the visits during the last 8 weeks of the main period were permitted to continue 400 mg BID in the LTE. Primary endpoints were safety and efficacy (≥2 consecutive platelet counts ≥50×109/L and increased ≥20×109/L from baseline without requiring rescue medication). Stable doses of concomitant ITP medication (thrombopoietin-receptor agonists [TPO-RA] and corticosteroids [CS]) were allowed for patients with inadequate platelet response. Patients who received rescue medication discontinued from the study. All patients provided informed consent.

Results
At baseline, the 45 patients initiating 400 mg BID in the main period had a median age of 49 years, median duration of ITP of 6.1 years, median platelet count of 15×109/L, and a median of 4 unique prior therapies (24% prior splenectomy). A total of 15 patients (33%) received rilzabrutinib monotherapy, and 30 had concomitant therapy (TPO-RA n=13 [29%], CS n=12 [27%], TPO-RA + CS n=5 [11%]). Primary platelet response was achieved by 18 patients (40%): 6  on monotherapy and 12 on concomitant medication. Platelet counts of ≥50×109/L, ≥30×109/L, and ≥20×109/L from baseline were maintained for a median of 71%, 95%, and 87% of weeks, respectively. As of 21Jan2022, 16/60 patients in the main study population had proceeded to LTE, of whom 11 were ongoing. Five LTE patients (31%) continued on rilzabrutinib monotherapy and 11 used concomitant medication (TPO-RA n=2 [13%], CS n=7 [44%], TPO-RA + CS n=2 [13%]; Figure); 1 patient used rescue medication. Median platelet count at LTE entry was 87×109/L. In patients on rilzabrutinib monotherapy, the median platelet count was 68×109/L, which was sustained at 6 months of follow-up (Table). In all LTE patients, platelet counts ≥50×109/L, ≥30×109/L, and ≥20×109/L from baseline were maintained for a median of 88%, 100%, and 97% of weeks, respectively. In patients on rilzabrutinib ± concomitant medication, results were consistent at 3 and 6 months of follow-up (Table). Three patients (19%) experienced related treatment-emergent adverse events (TEAEs), including 1 grade 2 upper respiratory tract infection. Three patients (19%) discontinued rilzabrutinib due to a TEAE. Six patients had ≥1 bleeding event, none were treatment-related; no related serious adverse events or deaths. The average ITP-BAT bleeding scale score at 6 months showed no increase in bleeding in the LTE.

Conclusion
With extended treatment duration, rilzabrutinib 400 mg BID showed durable clinical efficacy and was well tolerated in patients on rilzabrutinib ± concomitant medication.

Keyword(s): Immune thrombocytopenia (ITP), Inhibitor, Platelet, Platelet count

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