Development and validation of a LC-MS/MS method for the quantification of the checkpoint kinase 1 inhibitor SRA737 in human plasma.

Aim SRA737 is an orally active small-molecule inhibitor of checkpoint kinase 1 being investigated in an oncology setting. A HPLC-MS/MS method for quantifying plasma concentrations of SRA737 was validated.Methods & results Sample preparation involved protein precipitation with acetonitrile following addition of 13C15N-deuterated SRA737 as internal standard. A rapid and selective method was fully validated across a range of 5-20,000 ng/ml, exhibiting good sensitivity, overall precision (expressed as coefficient of variation) ≤8.0% and accuracy 96-102%. Consistently high recovery was observed, with no matrix effect and a lower limit of quantitation of 5 ng/ml.Conclusion A novel method for analyzing SRA737 in human plasma has been validated and is now being utilized for quantification of SRA737 in a Phase I trial

Influence of pharmacogenetics on response and toxicity in breast cancer patients treated with doxorubicin and cyclophosphamide

BACKGROUND: Doxorubicin and cyclophosphamide (AC) therapy is an effective treatment for early-stage breast cancer. Doxorubicin is a substrate for ABCB1 and SLC22A16 transporters. Cyclophosphamide is a prodrug that requires oxidation to 4-hydroxy-cyclophosphamide, which yields a cytotoxic alkylating agent. The initial oxidation is catalysed by cytochrome P450 enzymes including CYP2B6, CYP2C9, CYP2C19 and CYP3A5. Polymorphic variants of the genes coding for these enzymes and transporters have been identified, which may influence the systemic pharmacology of the two drugs. It is not known whether this genetic variation has an impact on the efficacy or toxicity of AC therapy. METHODS: Germ line DNA samples from 230 patients with breast cancer on AC therapy were genotyped for the following SNPs: ABCB1 C1236T, G2677T/A and C3435T, SLC22A16 A146G, T312C, T755C and T1226C, CYP2B6*2, *8, *9, *3, *4 and *5, CYP2C9*2 and *3, CYP3A5*3 and CYP2C19*2. Clinical data on survival, toxicity, demographics and pathology were collated. RESULTS: A lower incidence of dose delay, indicative of less toxicity, was seen in carriers of the SLC22A16 A146G, T312C, T755C variants. In contrast, a higher incidence of dose delay was seen in carriers of the SLC22A16 1226C, CYP2B6*2 and CYP2B6*5 alleles. The ABCB1 2677A, CYP2B6*2, CYP 2B6*8, CYP 2B6*9, CYP 2B6*4 alleles were associated with a worse outcome. CONCLUSION: Variant alleles in the ABCB1, SLC22A16 and CYP2B6 genes are associated with response to AC therapy in the treatment of breast cancer