NEW YORK, Aug 10 (Reuters) -- Aurobindo Pharma has secured approval from U.S. regulators for its generic version of the antiepileptic drug brivaracetam as the company continues to expand its presence in the competitive CNS sector, a move that could bolster generic sales and put pricing pressure on competitors. The FDA approval for the oral formulation marks another step for the manufacturer toward capturing a significant portion of what analysts estimate will be billions of dollars in annual U.S. sales.