Upfront Imatinib Therapy in CML Patients with Rapid Switching to Nilotinib for Failure to Achieve Molecular Targets or Intolerance Achieves High Overall Rates of Molecular Response and a Low Risk of Progression - An Update of the TIDEL-II Trial

While nilotinib and dasatinib produce faster responses than imatinib as first-line therapy in de novo Chronic Phase Chronic Myeloid Leukemia (CP-CML), an equally effective strategy may be to selectively use these more potent tyrosine kinase inhibitors (TKIs) only in patients who fail to achieve stringent early molecular targets or are intolerant. Aim: To update the molecular outcome and survival of patients in the TIDEL-II study. Method: TIDEL-II is a multicentre, single arm prospective ALLG trial for de novo CP-CML adult patients with two sequential cohorts each of 105 patients. All patients started on imatinib (IM) 600mg OD. Patients with IM trough levels <1000ng/mL on day 22 were dose escalated to 800mg OD (IM800). All patients were monitored for achievement of time-dependent molecular targets - BCR-ABL RQ-PCR of 10%, 1% and 0.1% IS at 3, 6 and 12 months (mo) respectively. Patients in cohort I who failed to meet these targets had dose escalation to IM800. Those patients who again failed to achieve these targets after a further 3 mo were switched to nilotinib 400mg BID (NIL). Patients in cohort 2 who failed their time dependent targets switched to NIL directly without escalating to IM800. In both cohorts, switching to NIL was also permitted for grade III/IV or persistent grade II non-haematological toxicity or loss of response. Primary end point was MMR at 12 mo (BCR-ABL '0.1%IS), with CMR^4.5 being a secondary end point (BCR-ABL ≤0.0032%IS). Results: At 12 mo 69% of patients achieved MMR. With median follow up (f/u) of 20mo, AP/BC progression occurred in 5 cases (2.4%) ( Table 1). The 3 mo molecular response was highly correlated with the MMR at 12mo and progression events (table 2). COHORT 1: Using intention to treat analysis (ITT) with median follow-up of 30 mo the rate of MMR at 12 and 24 mo is 66% and 81% respectively (n=105); CMR^4.5 was 12% and 24%, respectively. In total, 34/105 (32%) patients switched to NIL, 12 for failure to achieve molecular targets, 19 for intolerance and 3 for loss of response. Only 2/12 patients who failed to meet targets on IM have subsequently achieved MMR on NIL (median f/u on NIL 14 mo). Fourteen patients switched for intolerance when not in MMR, and 9 subsequently gained MMR (64%) (median f/u on NIL 19 mo). Two patients progressed to AP/BC, both in the first 12 mo in patients taking IM. One progression related death and one fatal myocardial infarction (on NIL) have been reported. Fourteen (13%) of patients remain on IM800. COHORT 2: With a median f/u of 12 mo the rates of MMR and CMR^4.5 at 12 mo (n=50) were 72% and 16%, respectively (ITT). To date, 35/105 patients, (33%) have switched to NIL, of which 23 switched for failure to meet molecular targets. Subsequently, 3/23 (13%) have achieved MMR (median 6 mo on NIL). Eleven patients have switched to NIL for intolerance, 7 of them not in MMR at time of switch; 6/7 reached MMR in the subsequent 6 mo (median 5 mo on NIL). Seven patients (7%) remain on IM800. Three patients progressed to AP/BC (3%), 2 on IM and 1 on NIL. Three deaths were reported (3%), 1 from cardiac causes and 1 from stroke, both patients on IM at the time; and 1 from CML progression. Relatively short f/u precludes a meaningful comparison of results between the 2 cohorts. Conclusion: The TIDEL-II strategy has achieved a higher rate of MMR at 12 mo of 69% compared to 47% achieved with the strategy of IM intensification previously utilised in the TIDEL-I study. The improvement in molecular response is mostly attributable to improved responses in patients intolerant of IM as deeper responses were uncommon with patients who failed their early molecular targets despite intensification of kinase inhibition. Molecular response at 3 mo is highly correlated with response and progression events, underscoring the importance of early molecular targets.

Yeung:Novartis Pharmaceuticals: Research Funding; BMS Oncology: Research Funding. Osborn:Novartis Pharmaceuticals: Research Funding; BMS Oncology: Research Funding. White:Novartis Pharmaceuticals: Research Funding. Branford:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Research Funding; Ariad: Research Funding. Slader:Novartis Pharmaceuticals: Employment, Equity Ownership. Hiwase:CSL: Research Funding. Schwarer:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Honoraria; Hospira: Membership on an entity's Board of Directors or advisory committees. Arthur:Novartis Pharmaceuticals: Honoraria; BMS Oncology: Honoraria. Ross:Novartis: Honoraria, Research Funding. Mills:Novartis Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Sponsorship to professional meetings; BMS Oncology: Sponsorship to professional meetings. Hughes:Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS Oncology: Research Funding.