There was some good news in the clinical sphere for Gilead Sciences (GILD -0.32%) on Thursday, and this drove its stock price up by almost 3% that trading session. A late-stage clinical trial of an investigational drug yielded encouraging initial results, hence the rise. In comparison, the S&P 500 index inched up by 0.8% on the day.

HIV drug does well in the lab

Gilead's news was that its second phase 3 trial of HIV drug lenacapavir met its key efficacy endpoints for preventing the disease. An interim analysis of the study found that the drug reduced new infections with the disease by 96% when compared to background HIV incidence. Lenacapavir, which is only administered twice annually, was more efficacious than the healthcare company's classic once-per-day HIV medication Truvada.

HIV, which causes acquired immunodeficiency syndrome (AIDS), was a major health scourge when it exploded in the 1980s. Since then, increasingly more sophisticated and efficacious drugs -- notably Truvada -- have been developed to treat it.

In its press release trumpeting the drug's performance, Gilead quoted its CEO Daniel O'Day as saying: "With such remarkable outcomes across two Phase 3 studies, lenacapavir has demonstrated the potential to transform the prevention of HIV and help to end the epidemic."

Next step: Approval?

Sensibly enough, Gilead will use the data from both clinical trials in filings for regulatory approval. The company added that it will begin to make such submissions by the end of this year. It did not get more specific with timing, or provide details of where it'll be submitting.