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(Reuters) - An experimental cancer drug from BioMarin Pharmaceutical Inc has proven to be effective in treating patients with breast or ovarian cancers caused by mutation in the BRCA gene that repairs damaged DNA, early data show.
The drug, BMN673, is part of a new class known as PARP inhibitors.
PARP, or poly ADP ribose polymerase, is an enzyme used by the body to repair broken DNA that can also be used by cancer cells to survive. By blocking PARP, drugmakers hope to prevent cancer cells from spreading.
Mutations in the BRCA 1 and BRCA 2 genes, which normally function by interacting with damaged DNA to help repair it, can increase a woman's risk of breast cancer 60 percent to 80 percent. The mutations are also associated with a higher risk of ovarian cancer.
BioMarin, which makes drugs for rare diseases, said it plans to begin a pivotal trial in patients with metastatic breast cancer in the fourth quarter of this year.
The data, presented at a meeting of the American Society of Clinical Oncology, showed that 11 out of 25 evaluated ovarian cancer patients had tumor shrinkage of at least 30 percent.
A health benefit was observed in 82 percent of those patients, the company said.
In the 18 BRCA breast cancer patients, seven had tumor shrinkage and 12 patients had a clinical benefit. All signs of the cancer disappeared in one patient.
Patients whose cancer is because of defects in the BRCA-gene "have no targeted treatment options ... PARP inhibitors offer that potential in BRCA-related cancers," Johann de Bono, professor of experimental cancer medicine at the Institute of Cancer Research in London, said in a statement.
The researchers said BMN673 was generally well-tolerated. Up to 20 percent of patients with chronic dosing experienced a decrease in the ability of bone marrow to produce blood cells. Fatigue, nausea and hair loss were observed in 20 percent to 30 percent of patients.
(Reporting By Deena Beasley; Editing by Maureen Bavdek)