Qualification of M30 and M65 ELISAs as surrogate biomarkers of cell death: long term antigen stability in cancer patient plasma

Purpose M30 and M65 ELISAs are proposed as surrogate biomarkers of tumour cell death in patients and are being applied increasingly in the pharmacodynamic (PD) evaluation of anticancer drugs during clinical trials. In the absence of such data, we have studied the long-term stability of the antigens of both assays in plasma of cancer patients stored at -80 degrees C over 2 years. Results No evidence was detected of degradation in the M65 antigen. However, in a proportion of patients significant increases in levels of M30 antigen were detected Conclusion Plasma samples for M65 analysis can be stored at -80 degrees C for 2 years; however, caution is recommended when considering long-term storage of samples for the M30 assay.