Gilead Sciences (GILD) has achieved a major milestone in its HIV prevention business, with PrEP sales crossing $1 billion for the first time in a single quarter during fiscal Q2 2026. This segment, which includes medicines taken by virus-negative individuals to prevent infection, doubled from a year earlier and now accounts for approximately 80% of all Descovy sales. The growth is driven primarily by two products: Descovy, an oral daily pill, and Yeztugo, a twice-yearly injection. Management attributes this strong performance to robust adoption in the U.S. market, which grew roughly 14% year-over-year, and high retention rates for the long-acting Yeztugo injection, with over 70% of users returning for a second dose within six months. While prevention revenue remains significantly smaller than Gilead's core HIV treatment business led by Biktarvy, it offers a distinct growth trajectory, with Descovy sales growing 30.5% in fiscal 2025 compared to 6.8% for Biktarvy. Looking ahead, Gilead has raised its full-year fiscal 2026 HIV category sales guidance to 9-10%, up from the previous 8% projection, signaling confidence in continued expansion. The company is also expanding its global reach through a new agreement with the Pan American Health Organization to accelerate access to lenacapavir for prevention across Latin America and the Caribbean. Investors have responded positively, driving Gilead shares to their highest level of the past year. Despite the bullish sentiment, some questions remain regarding the alignment between reported sales and third-party prescription data tracked by firms like IQVIA, though executives declined to comment on external metrics. The market is closely watching upcoming fiscal Q3 2026 results and awaits a regulatory decision expected in early 2027 for a new long-acting oral prevention option, which could further diversify Gilead's pipeline beyond its current offerings.