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ASCO Annual Meeting 2016
© ASCO/Matt Herp

CHICAGO—Nearly 60% of chronic myeloid leukemia (CML) patients who switch to nilotinib from imatinib maintain treatment-free remission for 48 weeks after stopping treatment, according to a new study, ENESTop, presented at the 2016 ASCO Annual Meeting (abstract 7054). 

Treatment-free remission (TFR)—stopping tyrosine kinase inhibitor therapy after achieving a sustained deep molecular response—is an emerging treatment goal for patients with CML in chronic phase (CML-CP).

Results from Evaluating Nilotinib Efficacy and Safety in Clinical Trials–Complete Molecular Response (ENESTcmr) demonstrated that patients on long-term imatinib who had not achieved MR4.5 were more likely to achieve this response by switching to nilotinib than by remaining on imatinib. 

“This suggests that, compared with remaining on imatinib, switching to nilotinib may enable more of these patients to reach a molecular response level required for attempting to achieve TFR in clinical trials,” said lead author Timothy Hughes, MD, of University of Adelaide in Australia. 

ENESTop is the first study, providing the largest set of prospective TFR data to date, to specifically assess TFR in patients who achieved a sustained deep molecular response after switching from imatinib to nilotinib. 

The trial evaluated 126 patients who were able to achieve a sustained deep molecular response with nilotinib, but not with prior imatinib therapy.

The study met its primary endpoint of the proportion of patients without confirmed loss of MR4.0 or loss of major molecular response (MMR) within 48 weeks of nilotinib discontinuation in the TFR phase. 

Some 57.9% patients who achieved a sustained deep molecular response following at least three years of nilotinib therapy maintained a molecular response 48 weeks after stopping treatment.

Of the 51 patients with confirmed loss of MR4.0 or loss of MMR who restarted nilotinib, 98.0% regained at least MMR, with 94.1% regaining MR4.0 and 92.2% regaining MR4.5. 

By weeks 12 and 13 of treatment reinitiation with nilotinib, half of retreated patients already achieved MR4.0 and MR4.5, respectively. 

One patient entered the treatment reinitiation phase, but did not regain MMR by 20 weeks and discontinued the study. 

“MR4.5 achieved following the switch from imatinib to nilotinib,” Dr Hughes said, “was durable in most patients; more than three quarters of enrolled patients were eligible to enter the TFR phase.”

No new safety signals were observed, Dr Hughes said. Consistent with reports in imatinib-treated patients, the rates of all grade musculoskeletal pain were 42.1% in the first year of the TFR phase versus 14.3% while still taking nilotinib in the consolidation phase. 

Dr Hughes said the results suggest “TFR can be maintained in the majority of patients who achieve a sustained deep molecular response with nilotinib following switch from imatinib.”

He continued, “The results from ENESTop, together with those from ENESTcmr, show that a higher proportion of patients switching to nilotinib achieve MR 4.5, suggesting that a higher proportion of patients switching to nilotinib will achieve TFR compared with patients continuing on imatinib.”

Novartis is the sponsor of ENESTop and the manufacturer of imatinib (Gleevec) and nilotinib (Tasigna). Dr Hughes disclosed that he has received honoraria and research funding from Novartis. end hematology article


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