Nilotinib first-line therapy in patients with Philadelphia chromosome-negative/BCR-ABL-positive chronic myeloid leukemia in chronic phase: ENEST1st sub-analysis

Purpose: The ENEST1st sub-analysis presents data based on Philadelphia chromosome (Ph) status, i.e., Ph+ and Ph−/BCR-ABL1 + chronic myeloid leukemia. Methods: Patients received nilotinib 300 mg twice daily, up to 24 months. Results: At screening, 983 patients were identified as Ph+ and 30 patients as Ph−/BCR-ABL + based on cytogenetic and RT-PCR assessment; 76 patients had unknown karyotype (excluded from this sub-analysis). In the Ph−/BCR-ABL1 + subgroup, no additional chromosomal aberrations were reported. In the Ph+ subgroup, 952 patients had safety and molecular assessments. In the Ph−/BCR-ABL1 + subgroup, 30 patients had safety assessments and 28 were followed up for molecular assessments. At 18 months, the molecular response (MR) 4 rate [MR⁴; BCR-ABL1 ≤0.01% on International Scale (IS)] was similar in the Ph−/BCR-ABL1+ (39.3%) and Ph+ subgroups (38.1%). By 24 months, the cumulative rates of major molecular response (BCR-ABL1^IS ≤0.1%;), MR⁴, and MR^4.5 (BCR-ABL1^IS ≤0.0032%) were 85.7, 60.7, and 50.0%, respectively, in the Ph−/BCR-ABL1 + subgroup, and 80.3, 54.7, and 38.3%, respectively, in the Ph+ subgroup. In both Ph−/BCR-ABL1 + and Ph+ subgroups, rash (20 and 22%), pruritus (16.7 and 16.7%), nasopharyngitis (13.3 and 10.4%), fatigue (10 and 14.2%), headache (10 and 15.8%), and nausea (6.7 vs 11.4%) were frequent non-hematologic adverse events, whereas hypophosphatemia (23.3 and 6.8%), anemia (10 and 6.5%), and thrombocytopenia (3.3 and 10.2%) were the common hematologic/biochemical laboratory events. Conclusion: Based on similar molecular response and safety results in both subgroups, we conclude that Ph−/BCR-ABL1 + patients benefit from nilotinib in the same way as Ph+ patients.