KLK3 and neoplasm: The NCT00503984 trial also showed a significant reduction in methylation levels of GADD45A in circulating tumor DNA (ctDNA) from blood plasma in 10 patients, 6 of whom showed a PSA response (60%), whereas no PSA response was observed in the patients with increased GADD45A methylation [168], confirming the biological activity of the drug in responsive patients.