Gilead Sciences, Inc. (NASDAQ: GILD) announced upbeat top-line results from an interim analysis of its late-stage study PURPOSE 1. PURPOSE 1 is a phase III, double-blind, randomized study evaluating the safety and efficacy of twice-yearly, subcutaneous lenacapavir for pre-exposure prophylaxis (PrEP) and once-daily oral Descovy (emtricitabine 200mg and tenofovir alafenamide 25mg; F/TAF) in more than 5,300 cisgender women and adolescent girls aged 16-25 years across 25 sites in South Africa and three sites in Uganda. Both the drugs are being tested simultaneously. While one group received twice-yearly lenacapavir, the other was given once-daily oral Descovy parallelly. In addition, a third group was assigned once-daily oral Truvada (emtricitabine 200mg and tenofovir disoproxil fumarate 300mg; F/TDF). All the study participants were randomized to receive lenacapavir, Descovy and Truvada in a 2:2:1 ratio. Top-line results indicate that the company's twice-yearly injectable HIV-1 capsid inhibitor, lenacapavir, demonstrated 100% efficacy for the investigational use of HIV prevention in cisgender women. There were zero incident cases of HIV infection among 2,134 women in the lenacapavir group and 16 incident cases among 1,068 women in the Truvada group. Thus, PURPOSE 1 study achieved its key efficacy endpoints of the superiority of twice-yearly lenacapavir to once-daily oral Truvada and background HIV incidence (bHIV). Results demonstrated the superiority of twice-yearly lenacapavir over bHIV (primary endpoint) and that of twice-yearly lenacapavir over once-daily Truvada (secondary endpoint). On the basis of these results, the independent Data Monitoring Committee recommended that Gilead stop the blinded phase of the trial and offer open-label lenacapavir to all participants. Shares of Gilead rose 8.46% on these strong study results as twice-yearly lenacapavir demonstrated its potential as a new tool to help prevent HIV infections with zero infections and 100% efficacy. Per Gilead, this is the first phase III HIV prevention study ever to show zero infections.  Lenacapavir ...