A major rejigging of the structure of ViiV Healthcare, the HIV entity set up by GlaxoSmithKline and Pfizer, will see Shionogi take a stake in the venture in return for giving up its rights to the much-touted investigational drug dolutegravir.

Under the terms of the agreement, ViiV will acquire the exclusive global rights to the assets that were being developed by the JV and the Japanese company, namely dolutegravir and other early-stage integrase inhibitor compounds. In return, Shionogi will receive a royalty on sales of the integrase inhibitor portfolio "averaging in the high teens" and become a 10% shareholder in ViiV, also getting a seat on the board. Previously, there was a 50/50 profit split scheduled for drugs coming out of the ViiV/Shionogi joint venture.

ViiV was established in 2009, with GSK taking an 85% stake and Pfizer the other 15%. This will now change to 76.5% and 13.5% and should dolutegravir be approved in the USA and the European Union, GSK would be entitled to 1.8% additional equity, which will not dilute Shionogi's stake.

ViiV chairman David Redfern said the JV with Shionogi "has been extremely productive", with dolutegravir scheduled to commence filings before the end of the year. He added that both firms "believe that now is the right time to simplify and evolve their existing arrangement", as "we will also unlock synergies through simplifying processes and avoiding duplication".

Excitement over dolutegravir has grown since promising initial late-stage data was presented in July which suggests that the drug is superior to Gilead Sciences' big-selling Atripla (efavirenz/emtricitabine/tenofovir).