Experimental Class of Breast Cancer Drugs Inhibit Recurrent Disease

A novel, first-in-class drug shows the ability to inhibit the growth of estrogen receptor-positive breast cancer, according to a study published by eLife.

The drug, called ERX-11, has also been able to inhibit recurrent breast cancer tumors, which could be used as treatment to attack primary and recurrent disease.

“Most breast cancers in women require estrogen or progesterone — the 2 female hormones — to grow. To treat hormone-dependent cancers, you must either block the hormone or block the receptor that receives the hormone to prevent the development of the cancer,” said principal investigator Ratna Vadlamudi, PhD. “However, in many patients, tumors become resistant to the current therapy and tumors recur. Our team at UT Health discovered a new molecule that blocks the estrogen receptor signaling that occurs in resistant tumors and tested a drug based on the molecule in preclinical studies in the lab.”

When breast cancer becomes drug resistant, patients face higher risks of mortality due to fewer effective treatment options. The new molecule may bypass pathways known to result in resistance.

“Developing this drug is important because it targets a unique site on the estrogen receptor and blocks its interactions with critical proteins that contribute to breast cancer progression,” Dr Vadlamudi said. “This drug will be useful in treating breast cancers that are sensitive to current therapies and that are resistant to therapy.”

In the study, the authors synthesized the drug that blocked the interaction. They also conducted mechanistic studies and experiments in primary human breast cancer tumors.

“Implanting mice with the human breast cancer cells usually causes the mice to develop the breast tumors, but when we gave the mice ERX-11 as an oral medication, the cancer growth was dramatically reduced,” Dr Vadlamudi said.

The authors reported that there were no observed toxic side effects associated with ERX-11 in mice studies, unlike traditional therapies. These findings suggest that the experimental drug may be a good candidate for human clinical trials, according to the study.

With the high rate of breast cancers and few treatment options, ERX-11 may be crucial in the fight against the disease, the authors noted.

“The next steps are to synthesize the drug under the FDA’s drug development guidelines and conduct formal toxicity studies to ensure the drug can be safely tolerated,” Dr. Vadlamudi concluded. “Additional work needs to be done before we can move forward with Phase I clinical trials. We expect human trials to begin soon.”