Efficacy and Safety of Ponatinib in CML and Ph+ ALL Patients in Real-World Clinical Practice: Data from a Belgian Registry

Background

Ponatinib is a third-generation tyrosine kinase inhibitor (TKI) indicated for adult patients with resistant or intolerant chronic phase (CP), accelerated phase, or blast phase chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), or those with the T315I mutation. In Belgium, ponatinib has been commercially available since March 2016. The goal of this registry was to collect efficacy and safety data in CML and Ph+ ALL patients and to evaluate ponatinib in routine clinical practice in Belgium.

Methods

This ongoing, prospective, multi-center registry includes patients ≥18 years of age with CML or Ph+ ALL, who have initiated ponatinib treatment. Demographic, efficacy and safety data were collected for patients enrolled from March 2016 (day 0) onwards. Results up to study month 24 are presented. Data were analyzed by descriptive statistics. Ethics Committee approval was obtained and all patients provided informed consent.

Results

At time of data analysis, 34 patients (21 CP-CML and 13 Ph+ ALL) were enrolled. The median age of CP-CML and Ph+ ALL patients was 57 and 55 years, respectively. Patients were heavily pretreated: 90% of CML and 92% of Ph+ ALL patients had received ≥2 prior TKIs. Several patients had one or more risk factors for TKI cardiovascular toxicity: hypertension (10), history of cardiovascular disease (11), smoker (10), hypercholesterolemia (5), and diabetes (4). Median follow-up was 539 days for CML and 135 days for Ph+ ALL patients.

The reasons for starting ponatinib therapy were related to refractoriness to previous TKIs (36%), progression (18%), presence of the T315I mutation (18%) or intolerance (29%). Eighty percent (8/10) of the patients who started ponatinib due to intolerance to previous TKIs had received ≥3 prior TKIs. At entry, 17 of the 34 patients (50%) had a confirmed BCR-ABL mutation. Of these 17, 10 (59%; 5 CML and 5 Ph+ ALL) had the T315I mutation. Starting doses of ponatinib in CML patients were 45 mg (76%), 30 mg (10%) and 15 mg (14%) once daily. Starting doses in Ph+ ALL patients were 45 mg (85%), 30 mg (8%) and 15 mg (8%). At latest follow up, the median treatment duration for the 21 CML patients was 531 days (range 15 - 2483) and for the 13 Ph+ ALL patients it was 123 days (range 13 - 1945).

Best response was a major molecular response (MMR), which was obtained in 71% of CML patients and 38% of Ph+ ALL patients. The median time-to-best response was 175 days in CML and 35 days in Ph+ ALL patients. In the 10 patients (7 CML and 3 Ph+ ALL) who started ponatinib because of intolerance to several previous TKIs, 80% achieved MMR. The median time to achieve best response in these patients was 192 days for CML and 31 days for Ph+ ALL patients.

Treatment-related adverse events (AEs) were reported in 20 patients (59%); the most common were rash (26%), dry skin (9%) and constipation (9%). Three patients reported ≥1 treatment-related serious AE (SAE): thrombocytopenia (n=1), cholecystitis (n=1) and hepatocellular injury (n=1). Three serious cardiovascular events were observed in 1 patient, who had a history of congenital cardiomyopathy and aortic prosthesis. They were scored as not related to ponatinib.

Dose reductions or interruptions occurred in 33 cases (20 in CML and 13 in Ph+ ALL patients), with the following reasons most frequently mentioned: AEs (76%), to prevent AEs (18%) and other (6%). Dose increases occurred in 12 cases (10 in CML and 2 in Ph+ ALL patients), for the following reasons: good tolerance of treatment (58%), no or low response (33%) or other (8%). At time of analysis, 19 patients (9 CML and 10 Ph+ ALL) had discontinued treatment, of which 32% due to AEs, 5% due to an SAE, 21% due to planned allogeneic transplant, 16% due to disease progression and 26% due to other reasons.

[Note: Percentages may not total 100 due to rounding]

Conclusion

Real-world evidence from this Belgian registry shows that ponatinib has a favorable efficacy and safety profile in, and supports its use in CML and Ph+ ALL patients who are resistant or intolerant to previous therapies or those with the T315I mutation. Deep molecular responses were obtained in the majority of patients. No new safety signals emerged with ponatinib treatment than those previously reported.

Funding: Incyte Biosciences Benelux BV