Rates of deep molecular response by digital and conventional PCR with frontline nilotinib in newly diagnosed chronic myeloid leukemia: a landmark analysis

Abstract

ENESTnext (NCT01227577) was a single-arm, multicenter trial evaluating the rate of deep molecular response by 2 years in patients with newly diagnosed (within 6 months) chronic myeloid leukemia in chronic phase (CML-CP) treated with nilotinib 300 mg twice daily. Among 128 enrolled patients, 94 (73%) achieved major molecular response (MMR; BCR-ABL1 ≤ 0.1% on the International Scale [BCR-ABL1IS]) and 34 (27%) achieved confirmed MR4.5 (BCR-ABL1IS ≤0.0032% detectable or undetectable; primary endpoint) by 2 years. Three-month BCR-ABL1 levels were predictive of later responses. In exploratory analyses, digital polymerase chain reaction (PCR) detected BCR-ABL1 in 39.4% of samples from patients with confirmed MR4.5 and identified further decreases in BCR-ABL1 with continued nilotinib. Safety results, including cardiovascular events, were consistent with those in other nilotinib trials. These results further substantiate the molecular response rates associated with frontline nilotinib therapy and demonstrate the feasibility of monitoring very low BCR-ABL1 transcript levels using digital PCR.