TAS-121

TAS-121 is a novel, orally available, third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) that selectively and covalently inhibits mutant forms of EGFR, including common activating mutations (Ex19del and L858R), the T790M resistance mutation, and certain uncommon mutations such as G719X and L861Q. It demonstrates high selectivity for mutant EGFR over wild-type EGFR. Preclinical studies showed potent inhibition of tumor growth in xenograft models harboring these mutations. In phase I clinical trials in patients with advanced non-small-cell lung cancer (NSCLC) previously treated with EGFR-TKIs, TAS-121 demonstrated antitumor activity—particularly in T790M-positive NSCLC—and was generally well tolerated up to the maximum tolerated dose. The most common adverse reactions included dermatological toxicity, decreased platelet count, and pyrexia[1][4][5][6].