In this subset analysis, researchers examined blood samples from 49 patients (27 received combination therapy) to evaluate whether changes in circulating blood cells that reflected the activity of the histone deacetylase (HDAC) inhibitor could be detected. Researchers measured protein lysine acetylation, a biological marker of entinostat activity, in B cells, T cells and monocytes in blood samples taken at pretreatment and one, eight and 15 days after therapy with entinostat, which is taken once a week.
While levels of lysine acetylation after one day were not linked to clinical benefit, levels measured eight and 15 days after therapy were related to clinical benefit, Ordentlich said. Researchers found that patients with elevated levels of protein lysine acetylation had a 68 percent reduced risk for disease progression compared with those patients who did not have sustained elevated levels.
Researchers found that hyperacetylation was also associated with longer median progression-free survival across cell lines: B cells, 8.5 vs. 1.9 months; T cells, 6.6 vs. 1.8 months; and monocytes, 6.2 vs. 1.9 months. "Those patients who were able to maintain acetylation did well," Ordentlich said.
He added that entinostat's long half-life and unique pharmacology allow researchers to quickly gauge the agent's activity. In this way, "we gain insight into how to use HDAC inhibitors, as a class of cancer drugs, in a variety of solid tumors," he said.
|Contact: Jeremy Moore|
American Association for Cancer Research