Efficacy and Safety of Ponatinib According to Prior Approved Tyrosine Kinase Inhibitor (TKI) Therapy in Patients with Chronic Myeloid Leukemia in Chronic Phase (CP-CML): Results From the PACE Trial

Ponatinib is a potent pan-BCR-ABL inhibitor that is active against native and mutated forms of BCR-ABL, including the uniformly TKI-resistant T315I mutant. The efficacy and safety of ponatinib (45 mg orally once daily) in patients with CP-CML were evaluated in a pivotal phase 2, international, open-label clinical trial.

This prospectively defined analysis was performed to evaluate the impact that previous exposure to approved TKIs had on the efficacy and safety of ponatinib treatment among patients with CP-CML.

The PACE trial enrolled 449 patients, including 270 patients with CP-CML. Enrolled patients were required to be resistant or intolerant (R/I) to dasatinib or nilotinib, or they had to have the T315I mutation at baseline. Patients with CP-CML were assigned to 1 of 2 cohorts: R/I (N=203) or T315I (N=64). Three patients were post-imatinib and did not have T315I at baseline; they were treated but not assigned to a cohort. The primary endpoint was major cytogenetic response (MCyR) at any time within 12 months after treatment initiation. The trial is ongoing. Data as of 23 July 2012 are reported, with a minimum follow-up of 9 months (median 12 [0.1 to 19] months). The efficacy and safety of ponatinib according to prior approved TKI therapy (imatinib, dasatinib, nilotinib) is presented for the total CP-CML (N=270) population.

The median age of CP-CML patients was 60 (18 to 94) years. Median time from initial diagnosis to start of ponatinib was 7 (0.5 to 27) years. Patients were heavily pretreated: 97% had received prior imatinib, 80% dasatinib, 68% nilotinib; 7% of patients had received 1 prior approved TKI, 40% 2 prior approved TKIs, 53% all 3 prior approved TKIs; 60% had received ≥3 prior approved/investigational TKIs. In patients previously treated with dasatinib or nilotinib (N=256), 84% had a history of resistance and 16% were purely intolerant to dasatinib or nilotinib.

At the time of analysis, 66% of patients remained on study. The most common reasons for discontinuation were adverse events (AEs; 12%) and progressive disease (7%). Response rates according to the number of prior approved TKIs are shown in the table below. Patients receiving fewer prior approved TKIs had higher response rates. The difference in MCyR rate was statistically significant for patients previously treated with 1 vs. 3 approved TKIs (p=0.003) and for patients previously treated with 2 vs. 3 approved TKIs (p=0.011). Differences in MMR rates were not statistically significant. Of patients achieving MCyR, 98% of patients receiving 2 prior approved TKIs and 83% of patients receiving 3 prior approved TKIs were predicted (Kaplan-Meier) to remain in MCyR at 1 year. Of patients achieving MMR, 86% of patients receiving 2 prior approved TKIs and 80% of patients receiving 3 prior approved TKIs were predicted (Kaplan-Meier) to remain in MMR at 1 year. Kaplan-Meier estimates were not calculable for patients receiving 1 prior TKI. The most common treatment-related AEs according to number of prior approved TKIs (1, 2, 3, respectively) were thrombocytopenia (32%, 38%, 44%), rash (37%, 37%, 39%), dry skin (37%, 36%, 39%), abdominal pain (21%, 26%, 28%), and headache (26%, 28%, 19%). Rash, dry skin, abdominal pain, and headache were generally grade 1 or 2 in severity. Thrombocytopenia was typically reported early in treatment and was manageable with or without dose reductions and/or dose interruptions.

Ponatinib has substantial activity in patients with CP-CML, with higher response rates and improved tolerability observed in patients receiving fewer prior approved TKIs. Data with a minimum follow-up of 12 months will be presented.

Kim:Novartis, BMS, Pfizer, ARIAD, and Il-Yang: Consultancy, Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Cortes:Novartis, BMS, ARIAD, Pfizer, and Chemgenex: Consultancy, Research Funding. Pinilla-Ibarz:Novartis, BMS: Research Funding, Speakers Bureau. le Coutre:Novartis and BMS: Honoraria. Paquette:ARIAD: Consultancy. Chuah:Novartis and Bristol Myers-Squibb: Honoraria. Nicolini:Novartis, Bristol Myers Squibb, Pfizer, ARIAD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Apperley:Novartis, Bristol Myers-Squibb, and ARIAD: Honoraria, Research Funding. Talpaz:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Millenium: Research Funding; Celgene: Research Funding; ARIAD: Research Funding; Deciphera: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Abruzzese:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees. Rea:Bristol Myers-Squibb, Novartis, and Teva: Honoraria. Baccarani:ARIAD, Novartis, Bristol Myers-Squibb, and Pfizer: Consultancy, Honoraria, Speakers Bureau. Muller:ARIAD: Consultancy. Wong:MolecularMD Corp: Employment, Equity Ownership. Lustgarten:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Rivera:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Clackson:ARIAD: Employment, Equity Ownership. Turner:ARIAD: Employment, Equity Ownership. Haluska:ARIAD: Employment, Equity Ownership. Guilhot:ARIAD: Honoraria. Hochhaus:ARIAD, Novartis, Bristol Myers-Squibb, Pfizer, and MSD: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hughes:Novartis, BMS, ARIAD: Honoraria, Research Funding. Goldman:Novartis, Bristol Myers-Squibb, and Amgen: Honoraria. Shah:ARIAD: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Novartis: Consultancy. Kantarjian:Pfizer: Research Funding; BMS: Research Funding; Novartis: Consultancy, Research Funding; ARIAD: Research Funding.