Slowly but surely, a new group of drugs known as “PARP” inhibitors are starting to become fixtures in the regimens for women with ovarian cancer—and perhaps more. With the approval of a drug called rucaparib (Rubraca) from Clovis Oncology, two have now been approved since 2014—and a third, from Waltham, MA-based Tesaro (NASDAQ: [[ticker:TSRO]]), could soon follow.
The FDA today approved Boulder, CO-based Clovis’s (NASDAQ: [[ticker:CLVS]]) rucaparib on an “accelerated” basis, or on thinner evidence than is typically required. The drug is approved for women whose ovarian cancer has been treated with at least two prior chemotherapy regimens, and whose tumors have certain genetic signatures—mutated BRCA genes. A companion diagnostic test from Foundation Medicine (NASDAQ: [[ticker:FMI]]) is used to detect the mutation, which is found in approximately 15 to 20 percent of ovarian cancer patients.
The approval was based on two single-arm trials of ovarian cancer patients with BRCA mutations; 54 percent of the 106 participants had a complete or partial response to treatment lasting a median of 9.2 months. The most common side effects are nausea, fatigue, vomiting, anemia, abdominal pain, gastrointestinal problems. The drug is also associated with an increased risk of some serious diseases of the bone marrow—myelodysplastic syndrome and leukemia—and fetal damage.
An estimated 22,280 women are expected to be diagnosed with ovarian cancer this year, according to the National Cancer Institute, and 14,240 will die of the disease. Standard treatment is surgery followed by chemotherapy, but there are other options for those whose cancer recurs, among them bevacizumab (Avastin) and the emerging “PARP” blockers.
“PARP” stands for poly ADP-ribose polymerases, enzymes that help cancer respond to DNA damage. They’ve become increasingly important as a cancer target because blocking their activity hampers the ability of cancer cells to repair their DNA after the DNA has been damaged by, say, chemotherapy.
PARP blockers have had their share of ups and downs, but after some high-profile setbacks, AstraZeneca won FDA approval of the first PARP-blocking drug, olaparib (Lynparza) in 2014. Like rucaparib, olaparib was approved for patients with certain forms of ovarian cancer and defective BRCA genes who have failed multiple chemo regimens. Another PARP drug, niraparib, from Tesaro, is currently under FDA review. It’s unclear just how much of the market rucaparib will be able to capture in light of the competition.
Even with this progress in ovarian cancer, the current reach of PARP blockers remains limited. But it’s possible that could change over the next few years. Pfizer, for instance, bought Medivation for $14 billion in part for an experimental PARP blocker, talazoparib, being tested in breast, lung, and prostate cancers. Tesaro’s niraparib is being tested in breast cancer, and AstraZeneca is exploring olaparib’s use in a variety of cancers as well.
Clovis priced rucaparib at $6,870 per 15-day supply, or roughly $165,000 per year. AstraZeneca’s rival olaparib costs about $11,000 per month, or $132,000 per year.
Shares of Clovis surged about 13.5 percent in midday trading on Monday.
Photo of FDA headquarters by This is Bossi via Creative Commons license.
