molecules of the month

10.   The Pfizer SAM-competitive PRMT5 inhibitor, PF-06939999 is a Ph. I clinical candidate in dose escalation in solid tumors. Ph. I data has been reported showing signs of early efficacy with cytopenias as common adverse events. This is in agreement with Ph. I data that was recently reported for a JNJ SAM-competitive PRMT5 inhibitor in which thrombocytopenia was identified as a dose-limiting toxicity and an early efficacy signal may have been detected. The Pfizer team suggests that PRMT5i may be especially beneficial in cancers which are dependent on alternative splicing pathways. Furthermore, preclinical resistance studies suggest that complete resistance to SAM site inhibitors may be prevented due to structural constraints in the co-factor binding site. The discovery campaign began with the published crystal structure of PRMT5:MEP50…