Enestop 192-Week Results: Treatment-Free Remission (Tfr) In Patients (Pts) With Chronic Myeloid Leukemia In Chronic Phase (Cml-Cp) After Stopping Second-Line (2l) Nilotinib (Nil).

7005 Background: In the ENESTop study (NCT01698905) of TFR in pts with CML-CP who achieved a sustained deep molecular response (MR) with 2L NIL, 57.9% remained in TFR 48 wks after stopping NIL (primary endpoint). Analyses at 144 wks showed durability of TFR. Data from longer follow-up (192 wks) evaluating the maintenance of TFR are reported. Methods: Pts treated with ≥2 y NIL after > 4 wks imatinib (≥3 y total) and achieving MR4.5 ( BCR-ABL1IS ≤0.0032%) on NIL were eligible. After a 1 y consolidation, pts with no confirmed loss of MR4.5 could attempt TFR. NIL was resumed upon loss of major MR ( BCR-ABL1IS ≤0.1%) or confirmed loss of MR4 ( BCR-ABL1IS ≤0.01%). At the data cut-off (Sep 24 2018), all pts had completed ≥192 wks of TFR, resumed NIL, or discontinued the study. Results: By the data cut-off, of 126 pts entering TFR, 56 were ongoing, 59 had resumed NIL, and 11 had discontinued. TFR rate at 192 wks was 46.0% (58/126; 95% CI, 37.1–55.1%); all but 1 of the 58 pts were in MR4.5. Only 1/61 pts in TFR at 144 wks lost response by 192 wks (confirmed loss of MR4); another 2 pts discontinued due to serious AE (polycythemia vera) and pt/guardian decision, respectively. Of 59 pts who resumed NIL, 56 (94.9%) and 55 (93.2%) regained MR4 and MR4.5, respectively. 40/56 pts (71.4%) who regained MR4 had stable MR4 at 96 wks (12 discontinued < 96 wks, and 4 remained on study with < 96 wks, after regaining MR4); 37/55 pts (67.3%) who regained MR4.5 had stable MR4.5 at 96 wks (12 discontinued < 96 wks, and 6 remained on study with < 96 wks, after regaining MR4.5). There were no disease progressions, deaths due to CML, or new deaths since the 144-wk analysis. The 192 wk treatment-free survival rate was 50.3% (95% CI, 41.2–58.7%). Of 62 pts who remained in TFR for > 144 wks, 11.3%, 53.2%, 21.0%, 14.5% and 3.2% had musculoskeletal pain AEs during consolidation and each subsequent 48 wk period of TFR. Among 59 pts who resumed NIL, most common AEs were hypertension (20.3%) and arthralgia (13.6%); the majority of AEs were grade 1/2. Conclusions: Results demonstrate long-term durability and safety of TFR following 2L NIL, with no disease progressions or CML-related deaths, and musculoskeletal pain AEs were transient. Clinical trial information: NCT01698905.