In June, the US Food and Drug Administration (FDA) launched an accelerated review of a promising new drug for advanced prostate cancer. Called relugolix, it suppresses testosterone and other hormones that speed the cancer’s growth. If approved, this new type of hormonal therapy is expected to set a new standard of care for the disease.
Doctors give hormonal therapies when a man’s tumor is metastasizing (spreading beyond the prostate), or if his PSA levels start rising after surgery or radiation. The most commonly used hormonal therapies, called LHRH agonists, will eventually lower testosterone levels in blood. But that decline happens only after testosterone flares up to high levels as an initial response to treatment. This short-term flare-up, which lasts about a month, can cause bone pain, urinary obstruction, and other symptoms. So, doctors will ordinarily give LHRH agonists together with other drugs that prevent testosterone from interacting with cells in the body.
Alternatively, men can be treated with a different class of hormonal therapies that lower testosterone levels without the initial flare. These drugs are known as GnRH antagonists, and only one is currently available in the United States. Called degarelix, it’s given once a month by injections that can in some instances cause pain, redness, and swelling. (A different injectable GnRH antagonist, called abarelix, was withdrawn from US markets in 2005 after it caused a higher-than-expected increase in allergic reactions.)
Here is where relugolix enters the picture: it’s also a GnRH antagonist, but rather than being given by monthly injections, it’s taken as a daily pill.
The FDA was prompted to speed the drug’s review based on its superior performance during a late-stage clinical trial. The study investigators enrolled 934 men from 155 hospitals in the United States and Japan. Half the men had elevated PSA levels after having been treated already for prostate cancer. The rest had newly diagnosed metastatic cancer, or more localized prostate tumors that weren’t suitable for surgery. A total of 622 were treated with relugolix, and 305 men were given an LHRH agonist called leuprolide. All the men were treated for 48 weeks.
By all measures, relugolix came out ahead.