Gilead Sciences (GILD -0.21%) has been a top stock to own this year, with its shares rising 17% and dwarfing the S&P 500 and its 21% loss over the same stretch. And the company may have given investors a reason to remain bullish on the stock. Health officials have given the green light on another one of its HIV treatments, which promises to improve lives and potentially generate billions in revenue for the business. Is now the time to load up on Gilead's stock?

FDA approves lenacapavir

On Dec. 22, Gilead Sciences issued a press release announcing that the Food and Drug Administration (FDA) had approved its HIV treatment, lenacapavir, which will be sold under the name Sunlenca. The treatment is approved for people who have multidrug-resistant HIV. The twice-yearly injectable will also mean a longer-lasting option than the daily pills many HIV patients rely on today. It's important to note that it is not approved for all people with HIV -- only for those who "cannot be successfully treated with other available treatments due to resistance, intolerance, or safety considerations."

For investors, this is an important win as it could lead to a blockbuster for Gilead. Analysts project that lenacapavir could bring in $1.5 billion in revenue at its peak. That would represent about 5.5% of the $27 billion in product sales that Gilead reported last year.

In terms of monetary value, it may not sound like a game changer, but it's a significant accomplishment for Gilead nonetheless. CEO Daniel O'Day said, "Gilead scientists have developed a unique and potent antiretroviral medicine in Sunlenca with the potential for flexible dosing options. Our goal is to deliver multiple long-acting options for treatment."

Gilead has effectively set itself up to be in the pole position to take advantage of the growth in the need for HIV treatments. According to estimates from Fortune Business Insights, the global HIV drug market will be worth more than $45 billion by 2028, growing at a compound annual growth rate of 5.9% until then.

Gilead could use a growth catalyst

One of the recent challenges for Gilead has been finding a way to generate consistent growth, and Sunlenca could help with that. Over the past three quarters, Gilead's revenue, when excluding its COVID-19 treatment Veklury, totaled $16.7 billion and rose by just 7% year over year. And the growth rate in its largest segment, HIV, was even lower at just 5%. So Sunlenca's approval gives investors something positive to rally around and could lead to better growth numbers in the future.

Today, the stock trades at a forward price-to-earnings multiple of 13 (less than the healthcare average of 17), suggesting that investors are a bit cautious about the business and aren't convinced of its growth potential. Shares of Gilead didn't take off on the news of the FDA approval, but the stock has arguably already been red hot over the past few months thanks in part to a strong earnings report and the market's more favorable outlook on growth stocks in general. While an important victory for the company, the approval may not have been enough (from a financial perspective) to have tipped the scales for the stock to climb even higher than it already has.

Is Gilead Sciences stock a buy?

Gilead Sciences has a strong HIV business that just got another shot in the arm due to the approval of Sunlenca. Although its valuation has been rising, Gilead's stock isn't overpriced and appears to still be a good value buy. And with a 3.5% dividend yield, there's even some additional incentive to buy and hold the healthcare stock as it's an investment that can also be an excellent source of recurring cash flow for your portfolio.