New target, new drug in breast cancer

Many breast cancers depend on hormones including estrogen or progesterone for their survival and proliferation. Eight years of lab work at the University of Colorado Cancer Center and elsewhere suggest that the androgen (AR) receptor is an additional hormonal target in many breast cancers. Block AR+ breast cancer's ability to access androgen and you block the cancer's ability to survive.

That's what the drug enzalutamide does, according to a CU Cancer Center study, presented today at the American Society of Clinical Oncology (ASCO) meeting in Chicago.

"Preliminary results are promising and show that androgen receptor blockade may indeed be therapeutic," says Anthony Elias, MD, investigator at the University of Colorado Cancer Center and professor of medical oncology at the University of Colorado School of Medicine.

Elias points out that about 88 percent of estrogen-positive breast cancers, 50 percent of HER2+ breast cancers and 25 percent of triple-negative breast cancers are androgen-positive (75 percent of all breast cancers), making androgen receptors a possible first target for many cancers, or a likely second target for cancers that resist other therapies.

"Targeting androgen receptors may be especially important for patients whose cancers haven't responded to existing treatments that target estrogen or progesterone," Elias says.

The Medivation drug enzalutamide blocks the proliferative power of androgen receptors in breast cancer. In breast cancers that were both ER+ and AR+, the effect of enzalutamide against androgen was similar to the effect of the proven drug tamoxifen against estrogen.

"This is a possible, new first-line target for breast cancer care," Elias says.