GlaxoSmithKline (NYSE: GSK) is increasing its ownership stake in drug development partner Theravance (Nasdaq: THRX).

The drug giant, which maintains its U.S. headquarters in RTP, said Monday it would buy 10 million shares of Theravance at a price of $21.29 per share for a total value of nearly $213 million.

The share price is 7.5 percent higher than the five-day average selling price ending March 30.

GSK and Theravance are working together on asthma and chronic obstructive pulmonary disease drugs. They formed a partnership in 2002.

The latest stock buy will increase GSK’s ownership in Theravance to 26.8 percent, pending Theravance shareholder and federal regulatory approval.