Metabolism of the dual FLT-3/Aurora kinase inhibitor CCT241736 in preclinical and human in vitro models: Implication for the choice of toxicology species.

CCT241736 is a dual fms-like tyrosine kinase 3 (FLT3)/Aurora kinase inhibitor in development for the treatment of acute myeloid leukaemia. The successful development of any new drug relies on adequate safety testing including preclinical toxicology studies. Selection of an appropriate preclinical species requires a thorough understanding of the compound's metabolic clearance and pathways, as well as other pharmacokinetic and pharmacodynamic considerations. In addition, elucidation of the metabolising enzymes in human facilitates improved clinical prediction based on population pharmacokinetics and can inform drug-drug interaction studies. Intrinsic clearance (CLint) determination and metabolite profiling of CCT241736 in human and four preclinical species (dog, minipig, rat and mouse) was undertaken in cryopreserved hepatocytes and liver microsomes. Recombinant human cytochrome P450 bactosomes (rCYP) were utilised to provide reaction phenotyping data and support prediction of metabolic pathways. CCT241736 exhibited low CLint in both hepatocytes and liver microsomes of human, dog, minipig and rat, but considerably higher CLint in mouse. CYP3A4 and CYP3A5 were identified as the major enzymes responsible for biotransformation of CCT241736 in human, exclusively forming five out of seven metabolites. Minipig showed greatest similarity to human with regard to both overall metabolic profile and abundance of specific metabolites relative to parent compound, and is therefore proposed as the most appropriate toxicological species. The greatest disparity was observed between human and dog. Based on metabolic profile, either mouse or rat is a suitable rodent species for toxicology studies.

Cryostored autologous skull bone for cranioplasty? A study on cranial bone flaps' viability and microbial contamination after deep-frozen storage at -80°C.

Craniectomy is a life-saving procedure. Subsequent cranioplasty with autologous skull bone has a bone resorption rate from 4% to 22.8% and an infection rate from 3.3% to 26%. There are concerns with their viability and the potential microbial contamination as they were explanted for a long period of time. Eighteen cranial bone flaps stored at Prince of Wales Hospital Skull Bone Bank during the period from June 2011 to March 2016 were identified. Ethics approval was obtained. Bone chips and deep bone swabs were collected for osteoblast culture and microbial culture. Skull Bone Bank was kept at -80°C under strict aseptic technique during the study period. The storage period ranged from 4months to 55months. For the osteoblast culture, all eighteen bone flaps had no viable osteoblast growth. For the bacterial culture, five had positive bacteria growth (27.8%). Three were Pasteurella multocida and two were Methicillin-resistant Staphylococcus aureus. The mean duration of storage of the infected bone flap was 32.9months (±15.1months) versus 19.9months (±17.9months) of those bone flaps with no bacterial growth (p=0.1716). The mean size of the infected versus non-infected bone flaps was 117.7cm2 (±44.96cm2) versus 76.8cm2 (±50.24cm2) respectively (p=0.1318). Although in this study statistical significance was not reached, it was postulated that infected bone flaps tended to be larger in size and had a longer duration of storage. In conclusion, cryostored skull bone flaps beyond four months showed no viable osteoblasts. Bacterial contamination rate of bone flaps was 27.8% in this study.