Expanding Nilotinib Access in Clinical Trials (ENACT): an open-label, multicenter study of oral nilotinib in adult patients with imatinib-resistant or imatinib-intolerant Philadelphia chromosome-positive chronic myeloid leukemia in the chronic phase.

Background: Nilotinib is a selective, potent BCR-ABL inhibitor. Previous studies demonstrated the efficacy and safety of nilotinib in Philadelphia chromosome-positive chronic myeloid leukemia patients in chronic phase (CML-CP) or accelerated phase who failed prior imatinib.

Methods: This expanded access trial further characterized the safety of nilotinib 400 mg twice daily in patients with CML-CP (N = 1422).

Results: In this large, heavily pretreated population, nilotinib demonstrated significant efficacy, with complete hematologic response and complete cytogenetic response achieved in 43% and 34% of patients, respectively. Responses were rapid, mostly occurring within 6 months, and were higher in patients with suboptimal response to imatinib, with 75% and 50% achieving major cytogenetic response and complete cytogenetic response, respectively. At 18 months, the progression-free survival rate was 80%. Most patients achieved planned dosing of 400 mg twice daily and maintained the dose >12 months. Nonhematologic adverse events (AEs) were mostly mild to moderate and included rash (28%), headache (25%), and nausea (17%). Grade 3 or 4 thrombocytopenia (22%), neutropenia (14%), and anemia (3%) were low and managed by dose reduction or brief interruption. Grade 3 or 4 elevations in serum bilirubin and lipase occurred in 4% and 7% of patients, respectively. The incidence of newly occurring AEs decreased over time. Of patients who experienced a dose reduction because of AEs and attempted a re-escalation, 87% successfully achieved re-escalation to the full dose.

Conclusions: This large study confirms that nilotinib was well tolerated and that grade 3 or 4 AEs occurred infrequently and were manageable through transient dose interruptions.