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

on Tuesday it would pay $2.13 ‌billion for new shares in ​ViiV

Healthcare, its joint venture with ‍British drugmaker GSK,

increasing its ⁠stake ⁠in the HIV drugmaker to 21.7% ‌as U.S.

drugmaker Pfizer ( PFE ) ​exits its 11.7% shareholding.

Under the agreement, Pfizer ( PFE ) will ⁠receive $1.88 billion ‍for

its ​11.7% holding, and GSK will get a special dividend of $250

million ‍as ViiV cancels the U.S. drugmaker's shares.

GSK will retain its 78.3% majority stake in ViiV

Healthcare. The ​British ‍firm established ViiV Healthcare with

Pfizer ( PFE ) in 2009, with ​Shionogi joining as a shareholder in 2012.

The deal streamlines ownership of ViiV Healthcare at a time

when the company is advancing ​a pipeline of long-acting

injectable HIV treatments and prevention medicines.