Jan 20 (Reuters) - Japan's Shionogi & Co ( SGIOF ) 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 ) exits its

11.7% ​stake.

British ‍drugmaker GSK will retain ​its 78.3% majority

stake in ViiV Healthcare.