The Distribution, Metabolism, and Elimination of Clofarabine in Rats

Abstract The distribution, metabolism and elimination of intravenous 14C-clofarabine was studied in Fischer 344 male rats under a once daily for 5 days dosing schedule of 25 or 50 mg/kg/day. Also, the in vitro metabolism in rat, dog, and human hepatocytes was studied. Plasma radioactivity (of which clofarabine accounted for 63% to 93%) exhibited three phases of exponential elimination with half-lives of 0.3, 1.3, and 12.8 hours after administration of the 25 mg/kg/d regimen. Unscheduled deaths occurred after 1 to 3 doses with the 50 mg/kg regimen, possibly due to nonlinear pharmacokinetics, and so mass balance and radiokinetic profiles could not be obtained. A total of 77.1% (of which 87.2% was clofarabine) and 10.8% (of which 6.9% was clofarabine) of the dose was recovered in urine and feces, respectively. 6-ketoclofarabine, believed to be formed via adenosine deaminase, was the metabolite of greatest concentration found in urine and feces, but in each matrix accounted for only 7% of the daily recovery of radioactivity. 6-ketoclofarabine was also found in myocardium and liver, but accounted for less than 2% of the total radioactivity in those tissues. Clofarabine was the major analyte found in myocardium (> 97% region of integration) and liver (> 94% region of integration). Whole body autoradiography demonstrated that the highest postdistributive concentrations of radioactivity were in the excretory organs, kidney, bladder and GI tract, with no remarkable suborgan distribution. In rat, dog, and human hepatocytes, 95, 96, and 99.8%14C-clofarabine remained, respectively, after 6 hours incubation. Eleven metabolites were observed with the largest constituting 2.5% of the radioactivity

Comparison of Different Intravenous and Oral Dose Schedules on Clofarabine-Induced Hematological Toxicity in Male Rates.

Abstract Clofarabine is approved by FDA for the treatment of pediatric patients 1 to 21 years old with relapsed or refractory acute lymphoblastic leukemia (ALL) after at least two prior regimens. This use is based on the induction of complete responses. Randomized trials demonstrating increased survival or other clinical benefit have not been conducted. Also, activity has been observed in clinical trials involving adults with AML and MDS (BLOOD.2003;102:2379–2386; BLOOD.2005;105:940–947; BLOOD.2006;108:45–51). However, clinical development of clofarabine in the treatment of lymphomas and solid tumors has been challenging due to observed dose-limiting hematotoxicity, at relatively low doses. Preclinical animal models have shown orally administered clofarabine to have good bioavailability (∼60% in rats) and increased anticancer activity in human hematological and solid tumor mouse xenograft models when compared with IV administration. Additionally, prolonged oral administration at lower daily doses has shown superior activity when compared to IV or PO administration on a daily ×5 dosing schedule. The objective of the present study was to determine the effect of oral administration on a daily ×5 or daily ×21 dosing schedule when compared to IV daily ×5 administration in a male Fischer 344 rat model. For the comparative study, the same daily doses (i.e., 25 and 40 mg/kg/day) were used for both the daily ×5 PO and IV dose schedules. Rats on the PO daily ×21 schedule were administered the same approximate total dose/course of treatment as the daily ×5 treated rats (i.e., 6 and 10 mg/kg/day for 21 days). Circulating blood cells (e.g., RBCs, WBCs, neutrophils, lymphocytes, platelets) were evaluated at various times (days 8, 15, 22, 29, 36, and 43 of study) during and/or following treatment. Approximately 50% of the rats dosed IV at the high dose level (40 mg/kg/day) died during the five day treatment period. No deaths were observed for rats dosed the low dose (25 mg/kg/day) IV group or for any rats dosed PO on a daily ×5 or daily ×21 dose schedule. Circulating RBCs were largely unaffected by IV or PO clofarabine administration. Maximum changes occurred on Day 8 for WBC, neutrophil, lymphocyte, and platelets in all IV and PO dose groups. Most cell types recovered by Day 15 or 22 of study. Statistically significant decreases in circulating neutrophils were seen both for the low (56% decrease) and high (72% decrease) dose IV groups. Statistically significant decreases in circulating lymphocytes were observed on Day 8 for the low (41% decrease) and high (84% decrease) dose IV groups, low (37% decrease) and high (37% decrease) dose daily ×5 PO groups, and the high (26% decrease) dose daily ×21 PO group (p≤0.01). Neutrophil counts recovered rapidly, whereas full recovery of lymphocyte counts was delayed until Day 43 of study. The platelet counts were increased for most groups on Day 8, except for the high dose IV group which was decreased by approximately 50%. In conclusion, the rapid time course for the decrease and recovery of circulating white cell counts in rats indicates that cell types other than stem cells are affected by clofarabine administration. The less severe adverse effects on WBCs seen after prolonged (daily ×21) oral administration suggests that myelosuppression in clinical studies may be reduced with the use of a prolonged oral administration strategy.</jats:p

Assessment of the soluble proteins HMGB1 , CD40L and CD62P during various platelet preparation processes and the storage of platelet concentrates: The BEST collaborative study

International audienceAbstract Background Structural and biochemical changes in stored platelets are influenced by collection and processing methods. This international study investigates the effects of platelet (PLT) processing and storage conditions on HMGB1, sCD40L, and sCD62P protein levels in platelet concentrate supernatants (PCs). Study Design/Methods PC supernatants ( n = 3748) were collected by each international centre using identical centrifugation methods ( n = 9) and tested centrally using the ELISA/Luminex platform. Apheresis versus the buffy coat (BC‐PC) method, plasma storage versus PAS and RT storage versus cold (4°C) were investigated. We focused on PC preparation collecting samples during early (RT: day 1–3; cold: day 1–5) and late (RT: day 4–7; cold: day 7–10) storage time points. Results HMGB1, sCD40L, and sCD62P concentrations were similar during early storage periods, regardless of storage solution (BC‐PC plasma and BC‐PC PAS‐E) or temperature. During storage and without PAS, sCD40L and CD62P in BC‐PC supernatants increased significantly (+33% and +41%, respectively) depending on storage temperature (22 vs. 4°C). However, without PAS‐E, levels decreased significantly (−31% and −20%, respectively), depending on storage temperature (22 vs. 4°C). Contrastingly, the processing method appeared to have greater impact on HMGB1 release versus storage duration. These data highlight increases in these parameters during storage and differences between preparation methods and storage temperatures. Conclusions The HMGB1 release mechanism/intracellular pathways appear to differ from sCD62P and sCD40L. The extent to which these differences affect patient outcomes, particularly post‐transfusion platelet increment and adverse events, warrants further investigation in clinical trials with various therapeutic indications