Treatment-free remission (TFR) following frontline (1L) nilotinib (NIL) in patients (pts) with chronic myeloid leukemia in chronic phase (CML-CP): 192-week data from the ENESTfreedom study

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Background: In ENESTfreedom (NCT01784068), which evaluated TFR following 1L NIL in CML-CP pts, 51.6% remained in TFR 48 wks after stopping treatment (primary endpoint) and durability of TFR was demonstrated at 144 wks. Data from longer follow-up (192 wks) evaluating maintenance of TFR are reported. Methods: Pts with MR4.5 ( BCR-ABL1IS ≤0.0032%) and ≥2y of 1L NIL entered a 1y consolidation; pts with sustained deep molecular response (MR) were eligible for TFR. NIL was resumed after loss of major MR (MMR; BCR-ABL1IS ≤0.1%). At the latest data cut-off (Sep 17 2018), all pts had completed ≥192 wks of TFR, resumed NIL, or discontinued the study. Results: By the data cut-off, of 190 pts entering TFR, 87 were ongoing, 91 had resumed NIL, and 12 had permanently discontinued. The TFR rate at 192 wks was 44.2% (84/190, 95% CI: 37.0–51.6%). Of 89 pts with successful TFR at 144 wks, 5 were not assessable for TFR at 192 wks as 2 had discontinued by 192 wks due to pt/physician decision, and 3 with MR4.5 previously did not have 192 wk PCR data. Of 91 pts who resumed NIL, 90 (98.9%) regained MMR and 84 (92.3%) regained MR4.5. 75/90 and 73/84 pts, respectively, had stable MMR and MR4.5 at 48 wks later. There were no cases of disease progression or new deaths. 10 deaths were reported in the 144-wk analysis, none due to CML. The 192-wk treatment-free survival rate was 48.7% (95% CI 41.4–55.6%). Of 89 pts remaining in TFR for > 144 wks (including 87 pts for > 192 wks), all-grade AE rates during consolidation and each subsequent 48 wk period of TFR were 84.3%, 77.5%, 70.8%, 48.3%, and 52.8%, respectively. All-grade musculoskeletal pain AE rates were 15.7%, 40.4%, 9.0%, 3.4% and 3.4%, respectively; cardiovascular event rates were low across these periods. Among pts who resumed NIL, most common AEs were nasopharyngitis (18.7%) and pruritus, fatigue, and increased lipase (14.3% each); the majority of AEs were grade 1/2. Conclusions: Results continue to support the long-term durability and safety of TFR at 192 wks after stopping 1L NIL; overall AE rates declined during the TFR phase and musculoskeletal pain AEs were transient. Pts should continue to be regularly monitored during TFR. Clinical trial information: NCT01784068.