Covington & Burling and Fenwick & West have landed the lead roles on a $3 billion Japanese pharmaceutical deal.

Japan's second-largest drugmaker, Astellas Pharma Inc., has agreed to acquire San Francisco-based drugmaker Audentes Therapeutics Inc. for about $3 billion in cash. The transaction is expected to be completed in the first quarter of 2020, subject to regulatory approval, including U.S. antitrust clearance.

"By joining together with Audentes' talented team, we are establishing a leading position in the field of gene therapy with the goal of addressing the unmet needs of patients living with serious, rare diseases," said Astellas president and chief executive officer Kenji Yasukawa in a statement.