In a new study, Yale researchers have reported preliminary results that show an experimental anti-cancer drug called phenoxodiol may help kill cancer cells and increase the effectiveness of standard chemotherapy.

Researchers administered the drug to female patients at Yale New-Haven Hospital with recurrent ovarian cancers, many of which were unresponsive to chemotherapy treatments. The main goal of the study was to determine the toxicity of phenoxodiol, and to decide the proper dosage of the drug to give to patients, in conjunction with other chemotherapy drugs.

“We used four different concentrations of [phenoxodiol], and we didn’t find any toxicity,” said Gil Mor M.D., PhD, Yale School of Medicine associate professor of obstetrics and gynecology.

The drug also resulted in significant disease stabilization when administered twice a week as a monotherapy.

Of the 40 women enrolled in the study, the first 20 women had ovarian cancers previously unresponsive to treatment. Thirteen of these patients finished the study without disease progression and five were determined to have disease stabilization. Once treatment stopped, the cancers continued to progress.

After completing the 12 week treatment with phenoxodiol, nine patients were given paclitaxel, the standard chemotherapy drug. Four of those patients had ovarian cancers that were paclitaxel-resistant. However, eight of the women showed positive response to the therapy.

“In our observations, though this is not a primary endpoint of the study, patients who had previously been resistant to standard chemotherapy treatment — after being treated with phenoxodiol, responded to [it],” said David O’Malley, M.D., instructor in the Department of Obstetrics, Gynecology & Reproductive Sciences at the Yale School of Medicine. “These [results] supported our findings in the lab.”

While phenoxodiol has been shown to stop ovarian cancer in animals on its own, the drug is being developed as a chemo-sensitizer, meant to increase the sensitivity of cancer cells to chemotherapy drugs. It will be used in conjunction with chemotherapy.

“We [believe phenoxodiol] would make the most difference in patients’ lives and treatments as a combination therapy,” O’Malley said.

The drug is currently being tested on other cancer types. At Yale-New Haven Hospital, the effect of phenoxodiol on the treatment of cervical and vaginal cancers is also being explored.

Follow-up studies will continue to examine possible individual and combination therapies, as well as how the drug should be administered.

The FDA has recently approved investigative drug status for the oral form of phenoxodiol. In the study, it was administered intravenously.

Phenoxodiol may be available to all ovarian cancer patients in the next few years, depending on approval by the Federal Drug Administration (FDA).

“Depending on the FDA approval process — we would hope within a year or two we would have enough data to convince the FDA [phenoxodiol] should be used on ovarian cancer patients,” O’Malley said.

The principal investigator on the study is Thomas Rutherford, M.D., associate professor of gynecology at the Yale School of Medicine.