Combining pegylated interferon with nilotinib improves early molecular response in newly diagnosed chronic phase chronic myeloid leukaemia

BACKGROUND: Second generation tyrosine kinase inhibitors (TKIs) have improved response rates in patients with chronic phase chronic myeloid leukaemia (CP-CML). Phase 2 trials demonstrated increased deep molecular response rates when combining second generation TKIs with pegylated interferon alfa (Peg-IFN). This trial aimed to evaluate the efficacy and the safety of combining nilotinib with Peg-IFN alfa-2a in patients with newly diagnosed CP-CML. METHODS: In PETALs, this open-label, randomised, multicentre phase 3 trial, we enrolled patients with newly diagnosed CP-CML from 27 French academic institutions via a centrally-generated electronic system in a 1:1 ratio to two groups: 300 mg oral nilotinib alone twice a day (the nilotinib only group) or 300 mg nilotinib twice a day combined with subcutaneous Peg-IFN (30 μg per week for the first month of treatment and 45 μg per week thereafter) for a maximum of 2 years. The randomly allocated patients were stratified by their Sokal index and European Treatment and Outcome Study long-term survival index. Eligible patients had major BCR::ABL1 transcripts, an Eastern Cooperative Oncology Group performance score of two or lower, who had never received TKIs, and were aged between 18 and 65 years. The primary endpoint was the cumulative rate of molecular response 4·5 (MR4·5; defined as BCR::ABL1 international scale [IS] of 0·0032% and lower), analysed in the intention-to-treat population (n=200). This trial is registered at ClinicalTrials.gov, NCT02201459, and is completed. FINDINGS: 205 patients were enrolled between Aug 6, 2014, and Sept 29, 2016, after which five patients were declared ineligible and excluded, resulting in 200 patients being randomly allocated (99 to the nilotinib group and 101 to the combination group). The median age at diagnosis was 45 years (IQR 36-55); 130 patients (65%) were male and 70 (35%) were female. Median follow-up in this cohort was 67 months (IQR 32·6-70·6). The primary objective was met, with higher rates of MR4·5 in the combination group (24% [95% CI 16·0-34·1] vs 15% [8·6-24·2], p=0·048) at month 12. There were equivalent grade 3-4 haematological side effects in the both groups (14 vs 14) with a predominance for grade 3-4 thrombocytopenia without haemorrhages (six in the combination group vs five in the nilotinib group). Psychiatric grade 3-4 events occurred in six (6%) patients in the combination group (including three unsuccessful suicide attempts) compared with five (5%) in the nilotinib group (including one unsuccessful suicide attempt). Six vascular events also occurred in six patients in the combination group and seven vascular events in five patients in the nilotinib group (all grades 3-4). INTERPRETATION: In this setting, Peg-IFN combined with nilotinib induced higher initial rates of MR4·5 compared to TKI monotherapy, despite additional side effects. The onset of psychiatric events might promote immediate cease of Peg-IFN and psychiatrist advice Whether this early molecular response translates into sustained treatment-free survival should be studied in a randomised trial sufficiently powered for this outcome. FUNDING: Novartis Pharma.