Sanofi-Aventis expanded its consumer health business in China with a $520.6 million takeover, showing it remains in the market for smaller bolt-on deals as it tries to buy U.S. biotech Genzyme.

French drugmaker Sanofi said on Thursday it would buy BMP Sunstone for $10 a share in cash - a 30% premium to the company's closing share price on Oct. 27.

China is the world's second-biggest consumer health market after the United States.

BMP Sunstone sales last year were about $147 million, roughly 60% of which were made in consumer healthcare through brands like paediatric cough and cold medicine Hao Wa Wa or GoodBaby.

The acquisition comes as Sanofi fights a $18.5 billion hostile takeover battle for Genzyme.

Consumer healthcare and emerging markets are among Sanofi's growth areas to deal with sales losses from patent expiries or challenges and subsequent and generic competition.

Sales at Sanofi's consumer healthcare rose 45.8% in the third quarter to €576 million while revenues from emerging markets rose 13% to €2.3 billion, accounting for nearly 30% of total sales.

Sanofi said it ranked 5th in consumer healthcare worldwide and that estimates valued the Chinese consumer healthcare market at €12 billion this year.

The completion of the takeover is subject to the approval of BMP Sunstone stockholders and the receipt of certain regulatory approvals in China. Stockholders owning 23% of BMP Sunstone's shares have already committed to the deal.