(Adds details on drug, study, background)
    July 10 (Reuters) - GlaxoSmithKline Plc's    two-drug HIV regimen Dovato was successful in suppressing the AIDS-causing virus in patients for six months at the same level of a previous three-drug treatment in a late-stage study, the drugmaker said on Wednesday.
    The study evaluated the effectiveness of Dovato, a combination of dolutegravir and lamivudine, in adults with the HIV-1 virus who switched to the regimen from at least a triple combination containing Gilead Sciences'    Vemlidy, the British company's HIV drugs division ViiV said.      
    The positive results further bolster GSK's efforts to challenge U.S. drugmaker Gilead, which currently leads the HIV treatment market.
    ViiV also said adults who used Dovato did not develop any resistance to the treatment.  
    Dovato already has the go ahead from U.S. and European authorities for use in some patients and GSK already has another double combination, Juluca, on the market for HIV. It also has a monthly-injectable, two-drug treatment in the works.    
    Pfizer Inc    and Shionogi & Co Ltd    also have small stakes in ViiV, which accounted for about 39% of GSK's group operating profit last year, according to UBS analysts.
    The HIV-1 category has the most widespread strains of the virus, which severely affects the body's immune system.

(Reporting by Pushkala Aripaka in Bengaluru; Editing by Bernard
Orr)
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