Jan 20 (Reuters) - Japan's Shionogi & Co 4507.T said on Tuesday it would pay $2.13 billion for new shares in joint venture ViiV Healthcare, increasing its stake in the HIV drugmaker to 21.7% as U.S. drugmaker Pfizer PFE.N exits its 11.7% stake.

British drugmaker GSK GSK.L will retain its 78.3% majority stake in ViiV Healthcare.

(Reporting by Yadarisa Shabong in Bengaluru; Editing by Rashmi Aich)

((Yadarisa.Shabong@thomsonreuters.com; +91 9742735150;))