AstraZeneca (AZN) and Merck (MRK), known as MSD outside the United States and Canada, today announced final results from the Phase 3 PROfound trial which showed LYNPARZA demonstrated a statistically significant and clinically meaningful improvement in overall survival (OS) versus enzalutamide or abiraterone in men with metastatic castration-resistant prostate cancer (mCRPC) who have BRCA1/2 or ATM gene mutations. Patients had progressed on prior treatment with enzalutamide and/or abiraterone.

Prostate cancer is the second most common type of cancer in men, with an estimated 1.3 million new patients diagnosed worldwide in 2018. Approximately 20-30% of men with mCRPC have an homologous recombination repair (HRR) gene mutation, of which BRCA1/2 and ATM mutations are a subpopulation. Approximately 10-20% of early stage hormone-sensitive prostate cancer cases will develop into CRPC within approximately five years.

In the key secondary endpoint of OS in men with BRCA1/2 or ATM gene mutations, LYNPARZA reduced the risk of death by 31% vs. retreatment with enzalutamide or abiraterone (HR 0.69 [95% CI, 0.50, 0.97], p=0.0175). Median OS was 19.1 months for LYNPARZA vs. 14.7 months for enzalutamide or abiraterone, despite 66% of men on these treatments having crossed over to receive treatment with LYNPARZA following disease progression.

An exploratory analysis also showed a non-statistically significant improvement in OS in the overall trial population of men with HRR gene mutations (BRCA1/2, ATM, CDK12 and 11 other HRR-mutated [HRRm] genes), reducing the risk of death by 21% with LYNPARZA vs. enzalutamide or abiraterone (HR 0.79 [95% CI, 0.61, 1.03]. Median OS was 17.3 months vs. 14 months for enzalutamide or abiraterone.

The most common adverse reactions (ARs) ≥15% were anemia (50%), nausea (43%), fatigue/asthenia (42%), decreased appetite (31%), diarrhea (21%), vomiting (20%) and constipation (19%). Grade 3 or above ARs were anemia (23%), nausea (2%), fatigue or asthenia (3%), decreased appetite (2%) and diarrhea (1%). Twenty percent of patients on LYNPARZA discontinued treatment due to ARs and 23% had their dose reduced due to an AR.

Dr. Johann de Bono, one of the principal investigators of the PROfound trial and head of drug development at the Institute for Cancer Research and the Royal Marsden Hospital, said, “LYNPARZA has demonstrated significant clinical benefit across key endpoints in PROfound and the final overall survival results for men with BRCA1/2 or ATM mutations reinforce its potential to change the standard of care for men with metastatic castration-resistant prostate cancer. The PROfound trial shows that LYNPARZA can play an important role in this new era of precision medicine in prostate cancer, bringing targeted therapy at a molecular level to patients with a historically poor prognosis and few treatment options.”

Dr. José Baselga, executive vice president, Oncology R&D, AstraZeneca said, “These results help to transform the treatment landscape in certain men with metastatic castration-resistant prostate cancer, where overall survival has been very difficult to achieve. LYNPARZA is the only PARP inhibitor to demonstrate overall survival versus enzalutamide or abiraterone for men with BRCA or ATM mutations. We look forward to continuing to bring LYNPARZA to these patients around the world.”

Dr. Roy Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories, said, “The PROfound trial is the first positive Phase 3 trial using molecular biomarker testing to help identify treatment options for certain men with metastatic castration resistant prostate cancer. These results further underpin the importance of genomic testing for HRR gene mutations to help identify this at-risk patient population and help physicians make treatment decisions. These results demonstrate the potential of LYNPARZA for mCRPC patients with certain HRR mutations.”

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