CHICAGO – Genomics may matter more than histology in predicting the response rate of patients treated with the programmed death-1 (PD-1) inhibitor Keytruda (pembrolizumab, Merck & Co. Inc.), as a phase II study has turned up the first genomic marker – mismatch repair (MMR) deficiency – that foretells success, results showed at the American Society of Clinical Oncology (ASCO) annual meeting.