Basis | Challenges | |
---|---|---|
PD-L1 | IHC approach to measuring PD-L1 expression on tumour and immune cells | Variability in assays, antibodies and tumour microenvironment |
CD8+ T cells | PD-1/PD-L1 expression on CD8+ T cells predicts response to PD-1 agents | Optimal cut-off points, scoring metrics and agreement on magnitude of change needed for meaningful prediction of response |
Tumour mutation load | High mutation load resulting from various factors correlated with response to checkpoint inhibitors in exceptional responders | Availability of adequate tissue for sequencing; whole exome sequencing expensive and slow turnaround time vs. other clinical assays |
Neoantigen burden | Predict clinical benefit to ipilimumab and PD-1 blockade in melanoma and lung cancer | As above |
Gene expression profiling | IFN-induced signatures may predict response to checkpoint inhibitors | Sizable tissue collection needed to validate testing and training sets |