Clinical Impact Of Dose Modification On Response To Ponatinib In Patients With Chronic Phase Chronic Myeloid Leukemia (CP-CML)

Ponatinib is a potent oral pan–BCR-ABL tyrosine kinase inhibitor (TKI) that has demonstrated significant clinical activity in heavily pretreated CP-CML pts. A multivariate analysis of CP-CML pts in the PACE trial found significant associations between major cytogenetic response (MCyR) and higher dose intensity; however, dose reductions and/or interruptions (DR/I) of ponatinib occur often in pts who experience adverse events (AEs). The clinical significance of such DR/I are not well known.

To assess the impact of DR/I and dose intensity of ponatinib on clinical outcomes in pts with CP-CML enrolled in the PACE trial.

A total of 270 CP-CML pts were enrolled in this ongoing, phase 2, international, open-label clinical trial. The efficacy population (N=267) was included in this post hoc analysis. Dose reductions were defined as any reduction below the standard 45 mg daily dose; interruptions were defined as a period in which ponatinib was held for ≥3 consecutive days between non-missing doses. Up to 2 reductions (to 30 or 15 mg/day) were permitted for managing AEs. To assess the impact of dose modification on response, pts were grouped according to tertiles of average dose intensity (mg/day), calculated as the cumulative dose divided by treatment exposure. All variables were calculated within 12 mos of the first dose to correspond to the primary outcome measure of MCyR by 12 mos. Secondary efficacy endpoints included complete cytogenetic response (CCyR) and major molecular response (MMR). Responses were assessed every 3 mos. The Cochran–Armitage trend test was used to assess whether response rates increased with higher average dose intensity tertiles; all P-values were 2-sided. Data are as of 01 Apr 2013, with a median follow-up of 20 (0.1–28) mos. Minimum follow-up for pts still on study was 18 mos.

A total of 209 (78%) pts required DR/I at least once within 12 mos: 172 pts (64%) had at least 1 dose reduction (median time to first dose reduction was 64 days). In pts with >1 dose reduction (n=75, 28%), the median time between the first and second reduction was 91 days. Among pts with a dose reduction at any time, 35% re-escalated to 45 mg daily. Dose interruption was experienced by 199 (75%) pts (median total duration of 35 days). The most common reason for DR/I was thrombocytopenia (33%).

For pts with average dose intensity ≤27 mg/day (N=89), >27 to ≤42 mg/day (N=88), and >42 mg/day (N=90), respectively, the median age was 62, 62, and 56 yrs; median time since initial diagnosis was 11, 7, and 6 yrs; each group had received a median of 3 prior TKIs. Among these tertiles, the best response to the most recent dasatinib- or nilotinib-containing regimen was MCyR or better in 21%, 22%, and 35%; CCyR or better in 11%, 14%, and 23%; MMR or better in 1%, 2%, and 6%, respectively. Within 12 mos of the first dose, median duration of treatment exposure was 356 (26–366), 366 (51–366) and 366 (3–366) days, respectively.

Twenty-nine pts had <3 mos of treatment exposure. Of those, 11 had a post-baseline cytogenetic assessment (1 had MCyR). Responses to ponatinib according to tertile are presented below (Table) for pts with ≥3 mos follow-up (N=238). MCyR, CCyR, and MMR rates increased with higher average dose intensity. Comparable response rates were seen between pts with average dose intensity >27 to ≤42 mg/day and >42 mg/day. Response rates were lower in pts with average dose intensity ≤27 mg/day; however, these pts still achieved MCyR, CCyR, and MMR rates that substantially exceeded those reported with the most recent dasatinib- or nilotinib-containing regimen.

Higher dose intensity of ponatinib was associated with higher response rates in this heavily pretreated CP-CML population, but lower dose intensity still led to positive clinical outcomes. It should be noted that higher responses to the most recent dasatinib- or nilotinib-containing regimen were also seen in pts with higher average dose intensity. In summary, these data indicate that although optimal responses were seen with average ponatinib dose intensity >42 mg/day, pts can be effectively managed with dose reduction or interruption if clinically indicated.

Pinilla-Ibarz:Novartis, Ariad: Research Funding; Novartis, Ariad, BMS and Pfizer: Speakers Bureau. Cortes:Ariad, Pfizer, Teva: Consultancy; Ariad, BMS, Novartis, Pfizer, Teva: Research Funding. Kim:BMS, Novartis, IL-Yang: Consultancy; BMS, Novartis, Pfizer, ARIAD, IL-Yang: Research Funding; BMS, Novartis, Pfizer, IL-Yang: Honoraria; BMS, Novartis, Pfizer: Speakers Bureau; BMS, Pfizer: Membership on an entity’s Board of Directors or advisory committees. Le Coutre:Novartis: Research Funding; Novartis, BMS, Pfizer: Honoraria. Paquette:Ariad, BMS, Novartis: Consultancy; Ariad, BMS, Novartis: Honoraria; Ariad, BMS, Novartis: Speakers Bureau. Chuah:Novartis, BMS: Honoraria. Nicolini:Novartis, ARIAD, Teva: Consultancy; Novartis, BMS: Research Funding; Novartis, BMS, Teva, Pfizer, ARIAD: Honoraria; Novartis, BMS, TEva: Speakers Bureau; Novartis, ARIAD, Teva, Pfizer: Membership on an entity’s Board of Directors or advisory committees. Apperley:Novartis: Research Funding; Ariad, Bristol Myers Squibb, Novartis, Pfizer, Teva: Honoraria. DeAngelo:Araid, Novartis, BMS: Consultancy. Abruzzese:BMS, Novartis: Consultancy. Rea:BMS, Novartis, Pfizer, Ariad, Teva: Honoraria. Baccarani:ARIAD, Novartis, BMS: Consultancy; ARIAD, Novartis, BMS, Pfizer, Teva: Honoraria; ARIAD, Novartis, BMS, Pfizer, Teva: Speakers Bureau. Muller:Novartis, BMS, ARIAD: Consultancy; Novartis, BMS: Research Funding; Novartis, BMS, ARIAD: Honoraria. Gambacorti-Passerini:Pfizer: Research Funding; Pfizer, BMS: Honoraria. Lustgarten:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Rivera:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc. Other, Employment. Clackson:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Turner:ARIAD: Employment. Haluska:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Deininger:BMS, ARIAD, NOVARTIS: Consultancy; BMS, NOVARTIS, CELGENE, GILEAD: Research Funding; ARIAD, NOVARTIS: Advisory Boards, Advisory Boards Other. Hochhaus:Ariad, Novartis, BMS, MSD, Pfizer: Research Funding; Novartis, BMS, Pfizer: Honoraria. Hughes:Novartis, BMS, ARIAD: Honoraria, Research Funding. Goldman:ARIAD: Honoraria. Shah:Ariad, Bristol-Myers Squibb: Consultancy, Research Funding. Kantarjian:ARIAD, Novartis, BMS, Phizer: Research Funding. Talpaz:Ariad, BMS, Sanofi, INCYTE: Research Funding; Ariad, Novartis: Speakers Bureau; Ariad, Sanofi, Novartis: Membership on an entity’s Board of Directors or advisory committees.