Long-Term Follow-Up and Impact of Comorbidity before Allogeneic Hematopoietic Stem Cell Transplantation in Patients with Relapsed or Refractory Acute Myeloid Leukemia-Lessons Learned from the Prospective BRIDGE Trial.

In patients with relapsed or refractory (r/r) acute myeloid leukemia (AML), allogeneic hematopoietic stem cell transplantation (HSCT) is considered to be the only treatment providing long-term disease control. The BRIDGE trial studied the safety and efficacy of a clofarabine-based salvage therapy before HSCT in patients with r/r AML. Here, we report the long-term follow-up of this phase II multicenter trial and exploratory analyses on the impact of comorbidity on outcome. Eighty-four patients with a median age of 61 years (range, 40 to 75) were enrolled. Patients were scheduled for at least 1 cycle of salvage therapy with CLARA (clofarabine 30 mg/m2; cytarabine 1 g/m2, days 1 to 5). Chemo-responsive patients with a donor received HSCT after first CLARA. The conditioning regimen consisted of clofarabine 30 mg/m2, day -6 to -3, and melphalan 140 mg/m2 day -2. The Eastern Cooperative Oncology Group (ECOG) score, the hematopoietic cell transplantation-specific comorbidity index (HCT-CI), and the Cumulative Illness Rating Scale were obtained at study enrollment as well as before HSCT. Sixty-seven percent of the patients received HSCT within the trial. After a median follow up of 40 months, the estimated 3-year overall survival (OS) for all enrolled patients and those with HSCT within the trial was 40% and 55%, respectively. Relapse-free survival for patients who underwent transplantation with a complete remission afterwards (n = 50) was 48%, calculated from the day of transplantation. In multivariate analysis, both the HCT-CI and ECOG score had a statistically significant impact on OS with a hazard ratio of 1.22 (P = .025)and 1.72 (P = .001), respectively. Using a clofarabine-based salvage therapy combined with early allogeneic HSCT, we were able to achieve good long-term results for patients with r/r AML. In this cohort, both the HCT-CI and the ECOG scores gave prognostic information on OS, showing the feasibility and clinical relevance of comorbidity evaluation at the time of diagnosis of r/r AML patients.

Impact of pharmacokinetics on the toxicity and efficacy of clofarabine in patients with relapsed or refractory acute myeloid leukemia.

Common side effects of clofarabine (CFB) are liver toxicity, particularly a transient elevation of transaminases and skin toxicity. We studied the correlation of pharmacokinetic (PK) parameters with these toxicities and the efficacy of CFB in patients with relapsed or refractory acute myeloid leukemia. Clofarabine PK parameters showed large inter-individual variability. A higher CFB area under the curve was significantly associated with higher transaminase levels (p = .011 for aspartate aminotransferase (AST), adjusted for age, sex, cumulated CFB dosage, baseline AST, and glomerular filtration rate (GFR)). No significant association could be found between maximum concentration and the liver toxicity parameters. The occurrence of skin toxicity and the response to re-induction chemotherapy evaluated at day 15 were also not associated with PK. In conclusion, a higher individual CFB exposure is associated with increased liver toxicity reflected by elevated liver enzymes, without having an impact on anti-leukemic efficacy.

Simultaneous determination of clofarabine and cytarabine in human plasma by LC-MS/MS.

Combination of cytostatic agents is a basic principle in the treatment of cancer. For the treatment of acute myeloid leukemia (AML), purine analogs, like clofarabine and cytarabine act synergistically. Little is known, however, on their interaction in vivo. We developed a method for the simultaneous determination of clofarabine and cytarabine in human plasma. The substances were extracted from plasma samples by protein precipitation with acetonitrile. Cladribine was the internal standard (IS). The analytes were separated on Synergi HydroRP column (150mm×2.0mm, 4µm) and a triple-quadrupole mass spectrometry with an electrospray ionisation (ESI) source was applied for detection. The mobile phase consisted of acetonitrile, ammonium acetate 2mM and 0.5% formic acid in a gradient mode at a flow rate of 0.5ml/min. The injection volume was 10µl and the total run time was 6.0min. Retention times were 2.46min for clofarabine, 0.97min for cytarabine and 2.43min for the IS. Calibration ranges were 8-1000ng/ml for clofarabine and 20-2500ng/ml for cytarabine. The intra-day and inter-day precision was less than 15% and the relative standard deviation was all within ±15%. This new method allows a rapid and simple determination of both clofarabine and cytarabine in human plasma. It was applied to a pharmacokinetic investigation within a hematological trial in adult patients with AML.