* Says regimen of drugs not inferior to Atripla

* Says discontinuations comparable in both study arms

* Shares up as much as 4 pct (Recasts, adds analyst comments; updates share movement)

BANGALORE, Jan 6 - Gilead Sciences Inc (GILD.O) said top-line results of a mid-stage study showed that its experimental drug regimen to treat HIV infection met the main goal, sending its shares up as much as 4 percent.

Based on 24-week data from 71 patients, Gilead's combination of four (quad) compounds showed that it was not inferior to Atripla -- a combination of Gilead Sciences' Truvada and Bristol-Myers Squibb Co's (BMY.N) Sustiva.

The data are important since the quad is a potential remedy for Gilead's 2018 HIV patent cliff, Deutsche Bank analyst Mark Schoenebaum said.

Gilead currently has two patent infringement lawsuits against Israeli generic drugmaker Teva Pharmaceutical Industries (TEVA.O) over Truvada and Atripla.

In our view, the quad program is the key pipeline program for Gilead, since we view the quad's pricing strength and hugely improved margins as having the potential to transform the Gilead profit and loss, J.P. Morgan analyst Geoffrey Meacham said in a note.

The current study was testing the drug combination of Truvada with elvitegravir -- an experimental drug to fight HIV infection -- and the boosting agent GS 9350.

We believe the quad needs to demonstrate at least comparable efficacy to Atripla and superior tolerability to gain meaningful market share, Leerink Swann analyst Joshua Schimmer said.

Analysts noted that the central nervous system side-effect profile was comparable in both arms, and any sign of liver enzyme elevations in the full dataset would be important.

Full study results will be submitted for presentation at a scientific meeting in early 2010, Gilead said.

Shares of the Foster City, California-based company were up more than 3 percent at $44.67 Wednesday morning on Nasdaq. They had touched a high of $44.83 earlier in the session. (Reporting by Vidya L Nathan in Bangalore; Editing by Anthony Kurian)