Trial in Progress: A Multicenter, Open Label, Randomized, Phase III Study of Asciminib (80 mg Once Daily) Vs Investigator-Selected TKI in Newly Diagnosed Adult Patients with Chronic Myeloid Leukemia in Chronic Phase

BACKGROUND: Patients (pts) with newly diagnosed chronic myeloid leukemia in chronic phase (CML-CP) may be treated with 1 of the 4 tyrosine kinase inhibitors (TKIs) approved for first-line (1L) use: the first-generation TKI imatinib and the second-generation (2G) TKIs bosutinib, dasatinib, and nilotinib. Deep molecular responses (DMRs) are important criteria for attempting treatment-free remission, an important goal for pts in 1L. However, in 1L, only about 30% of pts treated with imatinib and 30%-55% of pts treated with a 2G TKI achieve MR ^4.5 (BCR-ABL1levels on the International Scale≤0.0032%). More than 50% of pts with CML-CP treated with imatinib develop resistance or intolerance to therapy. Among pts treated with a 2G TKI in 1L, 30%-40% need to change therapy by 5 years. Therefore, new treatment options are needed to help pts achieve their treatment goals in 1L.

The main treatment goal for all pts is achievement of disease control, which potentially requires lifelong treatment. Therefore, highly potent, safe treatment options are needed for newly diagnosed pts with CML-CP. Asciminib is an investigational drug that inhibits the BCR-ABL1 oncoprotein through a novel mechanism of action: specifically targeting the ABL myristoyl pocket (STAMP). Due to asciminib's specifically targeting the ABL kinase family (ABL1, ABL2, BCR-ABL1), asciminib monotherapy offers the potential to improve safety and tolerability vs TKIs that target the adenosine triphosphate binding site of BCR-ABL1 and thus have varying degrees of selectivity toward ABL kinases. Asciminib has shown promising efficacy and safety in heavily pretreated adult pts with CML in phase I and III trials. In a phase III trial for pts with CML-CP treated with ≥2 prior TKIs, major molecular response (MMR) was achieved by 25.5% of pts on asciminib (40 mg twice daily [BID]) vs 13.2% on bosutinib at week 24. In the phase I trial of asciminib monotherapy at doses of 10-200 mg BID and 80-200 mg once daily (QD), 48% of pts with CML-CP treated with ≥2 prior TKIs without T315I mutations achieved or maintained MMR by 12 months. Here we present the upcoming phase III trial evaluating asciminib 80 mg QD monotherapy vs an investigator-selected approved TKI in newly diagnosed adult pts with CML-CP.

OBJECTIVE: The primary objectives of this study are to assess the efficacy of asciminib vs an investigator-selected TKI (either imatinib, bosutinib, dasatinib, or nilotinib) in 1L and to compare the efficacy of asciminib within the stratum receiving investigator-selected imatinib in 1L through the primary end point of MMR rates at week 48. DMRs and; other long-term outcomes are also of interest.

DESIGN: This is a multicenter, open-label, randomized, phase III study of asciminib at 80 mg QD compared with an approved, investigator-selected TKI (either imatinib, bosutinib, dasatinib, or nilotinib) for adult pts with newly diagnosed CML-CP in 1L (expected N=402; NCT04971226). Pts may not have received prior TKI therapy for CML, with the exception of ≤2 weeks of imatinib therapy and must have Eastern Cooperative Oncology Group performance status (ECOG PS) scores of 0 or 1. Pts who have previously received hydroxyurea or anagrelide may be included. Pts will be randomized 1:1 to the asciminib and investigator-selected TKI arms using 2 strata: European Treatment and Outcome Study (EUTOS) long-term survival (ELTS) risk score and the control arm TKI selected by the investigator prior to randomization (Figure 1). Pts randomized to the investigator-selected TKI arm will receive their selected TKIs at approved doses: imatinib, 400 mg QD; bosutinib, 400 mg QD; dasatinib, 100 mg QD; or nilotinib, 300 mg BID.

Pts will remain on study for 5 years after the last pt first treatment has occurred, unless they have discontinued early due to treatment failure, disease progression, intolerance, or investigator or pt decision. Pts who discontinue early will continue to be followed up for survival and disease progression until the end of the study.

MAIN OUTCOMES: The primary end point is MMR at week 48. Key secondary end points include MMR at week 96; exploratory end points include biomarker assessments.

CONCLUSIONS: This study will assess the efficacy of asciminib 80 mg QD in adult pts with newly diagnosed CML-CP vs currently approved TKIs in 1L.

This study is sponsored by Novartis.

Figure 1

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Figure 1

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