01:31 PM EDT, 06/20/2024 (MT Newswires) -- Gilead Sciences ( GILD ) said Thursday its experimental twice-yearly Lenacapavir shot to prevent HIV was 100% effective in women in a late-stage trial, sending the drugmaker's shares soaring.

The Purpose 1 phase 3 trial is assessing the safety and efficacy of Lenacapavir for pre-exposure prophylaxis, or PrEP, and once-daily oral Descovy in more than 5,300 cisgender women and adolescent girls aged between 16 and 25 years in South Africa and Uganda. A third group was assigned once-daily oral Truvada. Topline results from an interim analysis of the trial showed it met its key efficacy endpoints of superiority of Lenacapavir to Truvada.

Lenacapavir was generally well-tolerated, with no significant or new safety concerns identified. The results have prompted the independent data monitoring committee to recommend that Gilead stop the trial's blinded phase and offer open-label Lenacapavir to all participants, the company said.

"With zero infections and 100% efficacy, twice-yearly Lenacapavir has demonstrated its potential as an important new tool to help prevent HIV infections," Chief Medical Officer Merdad Parsey said.

The company's shares were up 9.1% in afternoon trading.

Lenacapavir is likely to be "an important growth driver" for Gilead over the medium- to longer-term, Mizuho Securities said in a note. The US PrEP market may only currently be about one-third penetrated, while the company believes that could expand to up to 60% overall.

"Market penetration could be augmented (with) potentially greater adherence with long-acting injectables (versus daily orals like Truvada/Descovy), essentially a tailwind to sales," the brokerage said.

Gilead expects results from its ongoing Purpose 2 trial in late 2024 or early 2025. That trial is evaluating twice-yearly Lenacapavir for PrEP among men who have sex with men, transgender men, transgender women and gender non-binary individuals who have sex with partners assigned male at birth.

The company said the regulatory filing for Lenacapavir for PrEP will include the results of both Purpose 1 and 2 trials, if positive.

Price: 69.06, Change: +5.91, Percent Change: +9.36