ASCO: Myovant details speedy effects of prostate cancer med relugolix

Lynn Seely - Myovant
Myovant CEO Lynn Seely, M.D. (Myovant)

Last fall, Myovant reported phase 3 data that set its prostate cancer med up for an FDA filing, but it kept most details close to the vest. Now, it’s unveiling more as it awaits the agency’s decision.

The new data, to be presented at the virtual annual meeting of the American Society of Clinical Oncology, show just how quickly the drug, relugolix, can lower testosterone, which drives the growth of prostate cancer. After four days of treatment, more than half of the patients on relugolix had testosterone levels drop below 50 ng/dL—a  benchmark used in the treatment of prostate cancer—compared with none of the patients taking the standard of care, leuprolide. After two weeks, those numbers were 99% and 12%, respectively.

But some patients cycle on and off testosterone suppression because of side effects, including fatigue, hot flashes, loss of libido and sexual function, Neal Shore, M.D., medical director of the Carolina Urologic Research Center and lead author of the study, said in an interview, meaning it's important for a drug's effects to wear off quickly after therapy stops.

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Relugolix demonstrated it could do that, too, with 54% of patients reaching normal testosterone levels—more than 280 mg/dL—in three months. The leuprolide patients didn’t come close, with 3% reaching normal testosterone levels in the same time frame.

“A faster effect in lowering testosterone for prostate cancer patients can be clinically significant—likewise, a more rapid testosterone recovery after stopping treatment, could potentially improve a patient’s quality of life,” Shore said in a statement. “Both of these findings could make a meaningful difference in the treatment journey for men with advanced prostate cancer.”

The company previously revealed that nearly all of the patients (97%) taking relugolix kept their testosterone levels down over 48 weeks, compared with 89% of patients taking leuprolide.

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Relugolix also had a deeper effect than leuprolide: At the two-week mark, more than three-quarters of the relugolix patients had testosterone levels below 20 ng/dL, while only 1% of those on leuprolide saw the same effect. It also cut the risk of heart problems, like heart attack or stroke, in half.

“It was able to show reduction in major adverse cardiovascular events; this is a 54% reduction that is particularly important because we know cardiovascular disease is prevalent more so in men with prostate cancer than in those without prostate cancer,” Myovant CEO Lynn Seely, M.D., told FierceBiotech. “Cardiovascular disease is a leading cause of death in men with prostate cancer."

Heart disease is linked more to being older and being a man than it is to prostate cancer itself, Shore said, but these findings could still give relugolix—a drug that blocks the GnRH receptor—an advantage over current drugs such as leuprolide, which activate the same receptor. In 2010, the FDA told the makers of these drugs to add warnings about heart attack, sudden cardiac death and stroke to their products’ labels.

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One last advantage relugolix has over the standard of care is its pill form. Although it must be taken every day—unlike leuprolide, which is injected every three months—patients may prefer a pill they can get in the mail versus having to travel to a hospital or clinic for their treatment, Seely and Shore said.

And Myovant isn’t stopping at prostate cancer—it’s looking to make relugolix a triple threat. Any day now, the company will file a combination built on relugolix for FDA approval for the treatment of uterine fibroids. Last month, the company reported results from a phase 3 study in endometriosis and will read out another phase 3 study in that indication later this quarter.

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