Analysis of the GeneXpert System on the International Multicentre ICORG 08–02 Phase II Study of Nilotinib 300mg BID as Frontline Treatment in Patients with Early Chronic Phase Chronic Myeloid Leukemia (ECPCML),

Abstract

Abstract 3774 BACKGROUND/METHODS:Data from the ENESTnd phase III trial showed superiority of nilotinib over imatinib leading to accelerated approval of nilotinib as initial treatment of ECPCML at a dose of 300mg BID. ICORG, the All-Ireland Cooperative Oncology Research Group, has been coordinating an international open-label, single stage, multicenter, investigator-initiated phase II study (ClinicalTrials.gov NCT00809211) of the safety and efficacy of nilotinib 300 mg BID in previously untreated patients with ECPCML. The primary study endpoint is the complete cytogenetic response (CCyR) rate at 6 months; secondary endpoints include the kinetics of molecular response, determined by RQ-PCR at baseline and 3 monthly from start of treatment as well as an evaluation of a novel rapid turnaround PCR system “GeneXpert” with IS BCR-ABL1/ABL1 RQ-PCR. The study closed to accrual with 61 patients (median age 54 years [range 20 –77]) enrolled; 53% have low risk Sokal score, 25% intermediate and 22% high risk. Median follow up is currently 12 months (range 1–30) and by November 2011 all patients will have had at least 6 months follow up. RESULTS:At the time of this analysis, 6 and 12 month follow up data were available in 43 and 31 patients, respectively. By intention to treat analysis, 41/43 (95%) have achieved CCyR within 6 months with all patients still on treatment at 12 months achieving CCyR. 26/43 (60%) and 25/31 (81%) of patients have achieved a major molecular response (MMR) (BCR-ABL1/ABL1 IS ≤ 0.1%) within 6 and 12 months, respectively, with 16/31 (52%) and 11/31 (35%) patients on treatment at least 12 months achieving BCR-ABL1/ABL1 IS ≤ 0.01% and ≤ 0.0032%, respectively. Sokal risk had no apparent effect on response with 12/16 (75%) low risk and 13/15 (87%) intermediate/high risk patients achieving MMR within 12 months, p=0.65. Thus far 4/6 (67%) high risk Sokal patients achieved BCR-ABL1/ABL1 IS ≤ 0.0032% within 12 months. No patients have suffered CML progression to date. 53 patients remain on study. Six patients have been removed from study due to adverse events: 4 patients due to persistent drug-related toxicity; 2 patients non drug-related events (death due to progressive multiple system atrophy and colorectal carcinoma, respectively). In addition, one patient was enrolled but never received study drug and an additional patient was lost to follow up. Treatment was generally well tolerated and toxicities easily managed. Haematologic toxicity was minimal with grade III/IV thrombocytopenia seen in 3 (5%) patients and only a single patient (2%) each with grade III/IV neutropenia and anemia, respectively. The most common grade III/IV non-haematologic toxicity was lipase elevation, seen in 14/61 (23%). No cases of acute pancreatitis were seen. Other grade III/IV non-hematologic toxicities were uncommon (< 5% patients). While treatment was interrupted at least once in 36/59 (61%) patients, the median duration of interruptions was short (5 days). At last follow up 49/59 (83%) of patients were taking ≥ 300mg BID. The study evaluation of the “GeneXpert” PCR system consisted of paired BCR-ABL1/ABL1 measurements performed by RQ-PCR methodologies aligned to International Standard (IS) and by the Xpert BCR-ABL Monitor system on 36 evaluable patients at diagnosis and at 128 subsequent three-monthly time-points. In patients expressing e13a2 or e14a2 BCR-ABL1 transcripts, both techniques had comparable results at diagnosis: IS median BCR-ABL1/ABL1 41.0% vs 44.0% median BCR-ABL1/ABL1 on the Xpert BCR-ABL Monitor. In the 122 paired analyses, correlation between methodologies, without automated system IS conversion, over a five log range (IS BCR-ABL1/ABL1 100–0.001%) was favourable (r2=0.845), however a progressive decline in correlation was noted with each decreasing log IS BCR-ABL1/ABL1 level. No significant difference was observed between the Xpert BCR-ABL Monitor and IS RQ-PCR in identifying MMR (44.3% vs 41.8%). CONCLUSION:In ECPCML, nilotinib 300mg BID induces high rates of CCyR and MMR with a substantial fraction of patients achieving responses in the range of complete molecular response (CMR). This regimen's toxicity is modest. The GeneXpert system provides a reliable and rapid means of assessing CML patients' response to tyrosine kinase inhibitor (TKI) therapy. Development of a reagent lot-specific conversion factor to the IS would enhance GeneXpert's applicability in monitoring TKI therapy in patients with CML. Disclosures:O'Dwyer:Novartis: Honoraria, Research Funding. Giles:Novartis: Consultancy, Honoraria, Research Funding. le Coutre:Novartis: Honoraria, Research Funding, Speakers Bureau. Nagler:Novartis: Honoraria, Research Funding. Egan:Novartis: Employment. Conneally:Novartis: Honoraria.