The FDA has approved AstraZeneca and Merck & Co/MSD’s Lynparza for prostate cancer, a few days after rival Clovis’ Rubraca became the first drug in the PARP inhibitor class to get the nod in this new indication.

Lynparza (olaparib) – already approved to treat ovarian, breast and pancreatic cancer – has been cleared by the US regulator for metastatic castration-resistant prostate cancer (mCRPC) with homologous recombination repair (HRR) mutations – seen in 20-30% of all mCRPC cases.

Lynparza is now a second-line treatment option for men with this type of cancer who have progressed after prior treatment with Pfizer’s Xtandi (enzalutamide) or Johnson & Johnson’s Zytiga (abiraterone), and who have been tested for HRR mutations.

Last week, the FDA approved Rubraca (rucaparib) as a second-line therapy for mCRPC patients with BRCA1/2 mutations after earlier treatment with an androgen receptor-directed therapy and a taxane-based chemotherapy.

HRR mutations comprise BRCA1 and BRCA2, as well as ATM and several other biomarkers, so Lynparza is eligible for use in a broader array of patients.

Lynparza has been approved on the back of the phase 3 PROfound trial, which showed that the PARP inhibitor cut the risk of disease progression or death by 66% compared to Zytiga or Xtandi in men with BRCA 1/2 and ATM gene mutations.

The results also showed that Lynparza improved the time men with these specific mutations lived without disease progression or death – 7.4 months for those treated with the drug compared to 3.6 months for those treated with the hormonal therapies.

In the broader HRR-mutated population, Lynparza reduced progression-free survival by 51%, and also improved overall survival by 31%, extending it to a median of 19.0 months versus 14.6 months with the comparator drugs.

That survival data gives it another edge over Rubraca, and could help AZ and Merck maintain their lead in the PARP inhibitor class as use extends into prostate cancer, according to analysts.

Prostate cancer is the second-most common cancer in men and despite an increase in the number of available therapies for men with mCRPC, five-year survival remains low.