Over the past few years, a new class of drugs known as “PARP” inhibitors has begun to change how ovarian cancer is treated. Data released by AstraZeneca and partner Merck this morning, from a Phase 3 study of the drug olaparib (Lynparza), could continue the trend.
AstraZeneca (NYSE: AZN) and Merck (NYSE: MRK) said that olaparib succeeded in a study known as “SOLO-1.” The drug helped stop cancer from spreading longer than a placebo when used as a maintenance therapy for advanced ovarian cancer patients who had responded to chemotherapy. These patients all have a mutated BRCA gene, a known driver of ovarian cancers. About 15 percent of ovarian cancer diagnoses are tied to a BRCA mutation, according to the Dana-Farber Cancer Institute.
The two companies didn’t disclose the details of the study, so it’s unclear how significant the drug’s benefit was. They also said, without specifics, that the drug’s side effects were “consistent with previous trials.” AstraZeneca and Merck will dish details at a future medical meeting and begin discussions with regulators in the U.S. and Europe about possible approval.
Olaparib blocks an enzyme, PARP, that tumors use to repair DNA damage. After some initial clinical setbacks, three PARP blockers have won FDA approval since 2014: olaparib, Tesaro’s (NASDAQ: TSRO) niraparib (Zejula) and Clovis Oncology’s (NASDAQ: CLVS) rucaparib (Rubraca). Olaparib was first, approved for patients with certain forms of ovarian cancer and defective BRCA genes who have failed multiple chemo regimens. Rucaparib followed with a similar approval, while Tesaro’s was the first of the class to win approval for ovarian cancer patients but not require a companion diagnostic test for the BRCA mutation. (Olaparib and rucaparib have since followed, and olaparib has been approved for breast cancer patients with BRCA mutations as well.)
So far, AstraZeneca’s drug has established itself as the market leader. In its last quarter, olaparib generated $119 million in sales, though that consists of both breast and ovarian cancer sales. Tesaro’s drug pulled in $49 million last quarter. Clovis’s rucaparib (Rubraca) had $18.5 million in sales.
The SOLO-1 study could help move olaparib forward in the treatment paradigm for ovarian cancer patients, becoming the first of the three to prove its worth as a first-line treatment after chemo. The data only show a benefit for BRCA mutated ovarian cancer patients, however, not all patients. “We think there is little likelihood that AstraZeneca can leverage SOLO-1 to obtain an all-comers label,” wrote RBC Capital Markets analyst Kennen MacKay in a recent research note. AstraZeneca splits rights to the drug with Merck.