FAP and neoplasm: This treatment failure may be attributable to the possibility that the unconjugated antibodies could not achieve a sufficient effect against solid tumours.116 Narra et al found that as the Val‐boroPro (Talabostat; an inhibitor of FAP enzymatic activity) inhibited tumour progression in metastatic colorectal cancer in a phase II trial.96 Only six of 28 patients presented stable disease status, thus indicating minimal clinical efficacy.