Safety and Efficacy of Olverembatinib (HQP1351) Combined with Lisaftoclax (APG-2575) in Children and Adolescents with Relapsed/Refractory Philadelphia Chromosome–Positive Acute Lymphoblastic Leukemia (R/R Ph+ ALL): First Report from a Phase 1 Study
Format: Poster Presentation
Abstract#: 1443
Session: 613. Acute Lymphoblastic Leukemias: Therapies Excluding Allogeneic Transplantation: Poster I
Time: Saturday, December 7, 2024; 5:30 PM - 7:30 PM
First Author: Prof. Jingliao Zhang, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences
Highlights:
Background: Olverembatinib, a novel third-generation TKI, is well tolerated and exerts strong and durable antileukemic activity in patients with heavily pretreated CP-CML with or without the T315I mutation. Investigational lisaftoclax, a novel Bcl-2 inhibitor, has shown clinical antitumor benefits in patients with multiple hematologic malignancies. Currently, there are no effective treatment options available for pediatric patients with R/R Ph+ ALL. This study was designed to explore the safety, efficacy, and pharmacokinetic (PK) profile of olverembatinib alone or combined with lisaftoclax in children and adolescents with R/R Ph+ ALL.
Methods:
This was an open-label, Phase Ib study that enrolled children and adolescents aged < 18 years with R/R Ph+ ALL resistant or intolerant to at least 1 TKI (prior use of TKIs was not considered if patients had T315I mutation). Patients were required to have adequate Karnofsky/Lansky performance status score and organ function. Patients with symptomatic central nervous system disorders or significant bleeding, which were unrelated to Ph+ ALL, were excluded.
Olverembatinib was administered orally at 40 mg adult equivalent dose (AED) every other day for 2 weeks (Days [D] 1-14), followed by the same dose of olverembatinib in combination with lisaftoclax at an assigned dose of 200/400/600 mg (AED) daily (QD) on D13-42 (a 3-day dose ramp-up from D13-15 was needed). Dexamethasone at 6 mg/m2/day was administered orally QD from D15-42. The primary endpoints included safety assessments, overall response rate (ORR), measurable residual disease (MRD) negativity rate, and pharmacokinetic (PK) characteristics of olverembatinib alone or in combination with lisaftoclax.
Patient Enrollment: From September 2022 to June 2024, a total of 10 patients were enrolled. The median (range) age was 13.0 (11-15) years, and 6 patients were male. The median (range) body weight was 49.85 (35.9-86.0) kg. Nine (90.0%) patients expressed the p190 transcript, and 1 patient (10.0%) expressed the p210 transcript. Three patients harbored BCR::ABL1 mutations [2, T315I; 1, F317L (c.951C>A)] at baseline. After 1 patient discontinued from the trial because of seizure on D1 of Course 1 (C1D1), 9 eligible patients were included in the 3+3 dose escalation model (n = 6, R/R; n = 3, intolerant): 3 patients in each Arm (A, B, and C) at assigned lisaftoclax dose levels of 200, 400, and 600 mg (AED), respectively. These patients completed 42 days of treatment and were assessed for the primary endpoints.
Efficacy Results: Among 6 patients evaluable for morphologic responses, 2 patients achieved complete responses with incomplete count recovery (CRis), 2 achieved partial responses (PRs) at the end of olverembatinib monotherapy (EOM), resulting in an overall response rate (ORR) of 66.7%; and 5 (83.3%) patients achieved CRis at the end of olverembatinib and lisaftoclax combination course (EOC). In the 7 patients who were evaluable for molecular responses, 5 (71.4%) achieved MRD negativity, of which 1 was at EOM and 4 at EOC.
Safety Results: 6 of 10 patients experienced grade ≥ 3 hematologic TEAEs, including anemia (3/10), neutropenia (7/10), and thrombocytopenia (3/10); 1 patient had grade 3 alanine aminotransferase increase leading to treatment discontinuation, and 1 patient discontinued the trial after experiencing a seizure at C1D1.
PK Analyses: Preliminary PK analyses revealed similar PK characteristics and comparable exposure between pediatric and adult populations for olverembatinib and lisaftoclax. There was no significant accumulation after multiple doses, and no drug-drug interactions were observed between olverembatinib and lisaftoclax.
Conclusions: These preliminary data showed that olverembatinib in combination with lisaftoclax appears to be a safe and effective regimen in pediatric patients with R/R Ph+ ALL. This regimen resulted in a promising CR rate of 83.3% and MRD negativity rate of 71.4% without intensive chemotherapy or immunotherapy. The study is currently in the dose-expansion phase.