Japanese drug maker Shionogi & Co. entered a joint venture between GlaxoSmithKline (NYSE: GSK) and Pfizer (NYSE: PFZ) as the three companies prepare to seek regulatory approval for their experimental HIV medicine.

Shionogi will take a 10 percent stake in ViiV Healthcare Ltd, the venture, and get royalties in the “high teens” on sales of HIV drugs known as integrase inhibitors including the experimental dolutegravir, Glaxo said in a statement today.

The announcement comes after the companies said in July clinical trials showed dolutegravir reduced the virus in more people than Gilead Sciences Inc.’s Atripla, suggesting it may take market share away from the world’s best-selling AIDS medicine. The drug will be submitted for approval by the end of the year, Glaxo said.

The company had previously said it would be filed early next year.

David Redfern, chairman of the Board, ViiV Healthcare noted in a statement: “The Shionogi-ViiV Healthcare joint venture has been extremely productive, with the first integrase inhibitor, dolutegravir, scheduled to commence filings before the end of the year. Both ViiV Healthcare and Shionogi believe that now is the right time to simplify and evolve their existing arrangement. In doing so, we will deepen the relationship as shareholders and at Board level. We will also unlock synergies through simplifying processes and avoiding duplication. We believe this new agreement will create long-term value for ViiV Healthcare and its shareholders.”

With the new stake, Shionogi “will be able to contribute to the future direction of these compounds which we now know very well and continue to be excited about,” Chief Executive Officer Isao Teshirogi said in the statement.

After the transaction, Glaxo will own 76.5 percent of the ViiV venture and Pfizer will own 13.5 percent. If dolutegravir is approved in the U.S. and Europe, Glaxo will be entitled to an extra 1.8 percent stake.

GSK operates its North American headquarters in RTP.

[GSK ARCHIVE: Check out 10 years of GSK stories as reported in WRAL Tech Wire.]

(Bloomberg contributed to this report.)