These days, when most people think of Gilead Sciences (NASDAQ:GILD), they think of remdesivir -- the company's investigational coronavirus treatment.

The drug was recently given emergency use authorization by the Food and Drug Administration for severe cases of COVID-19, the illness caused by the novel coronavirus. Earlier this month, Japan became the first country to approve the drug as a treatment for COVID-19.

Three researchers study data in a lab.

Image source: Getty Images.

The Gilead story is far broader than its work to treat COVID-19. The company has a full pipeline and a portfolio of products in HIV, hepatitis C, oncology, and other treatment areas. Looking ahead to the coming year, three key elements for Gilead likely will be HIV treatments, a potentially big rheumatoid arthritis drug that is awaiting approval, and the question of remdesivir.

No. 1 prescribed treatment

Let's start with Gilead's HIV treatments. The FDA first approved Gilead's Biktarvy in 2018, and today it is the No. 1 prescribed treatment regimen for HIV patients in the U.S. In fact, Biktarvy sales more than doubled to nearly $1.7 billion in the first quarter compared with the year-earlier period. The treatment led gains in Gilead's HIV portfolio, which posted a 14% increase in sales for the quarter.

That trend may continue, considering the market's growth outlook. The global HIV drugs market, at a compound annual growth rate of 5.9%, is expected to reach $34.2 billion by 2023, according to The Business Research Company. And forecasts show Biktarvy has plenty of potential ahead. Sales of the drug are expected to climb to nearly $7 billion in 2024, according to EvaluatePharma. As such, it would take the spot as the No. 10 best-selling drug worldwide for that year, the research shows. So, it's pretty clear that, a year from now, the HIV program will continue to be a major growth driver for Gilead.

Moving along to the next key element for 2021, let's have a look at filgotinib, Gilead's investigational drug for moderate-to-severe rheumatoid arthritis. Gilead submitted the drug for priority review in December, which means a decision may come as early as next month. Priority review shortens the timeframe from 10 months to about six. Gilead, which is preparing for a possible launch in the second half of 2020, also aims to gain approval for the drug in Japan and Europe this year.

More than $1 billion in sales

For the rheumatoid arthritis indication, filgotinib may generate more than $1 billion in sales in the U.S. and Europe by 2025, according to a Bernstein report. Though the drug won't bring blockbuster sales to Gilead by this time next year, if approved, we can at least expect to see the beginning of this new growth story. And arthritis isn't the only treatment area for the drug. Filgotinib has the potential for launches in five new indications over the next four years, the company said earlier this year.

And finally, there is remdesivir. Gilead isn't yet selling the drug. The company has offered to donate its existing supply, totaling about 1.5 million individual doses, as it is given to patients through the emergency authorization. As part of the original 10-day treatment duration, that represented about 140,000 treatments. But data from a new trial showed the duration could be shortened, meaning more patients may be treated with the current supply.

There are two major unknowns regarding remdesivir: Gilead hasn't yet set a price for the drug, and without knowing how long the coronavirus crisis will last, we don't know if there will be strong demand for the drug after the donated doses run out. So, right now, it's impossible to determine if the drug will be significant for Gilead revenue in a year -- or if the expenses incurred will be covered by sales.

Though remdesivir's contribution to earnings remains a question mark, the potential of filgotinib and Gilead's HIV platform likely will be a big part of the biotech company's revenue story a year from now. They are two big reasons to be optimistic about Gilead in the long term.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.