Seventeen in '17. It might sound like a slogan, but it's actually a reference to the size of the global HIV drug market. In 2017, the HIV market topped $17 billion, according to data from market research firm IMARC Group. 

The best-selling HIV drugs last year were Genvoya, Triumeq, Truvada, Tivicay, and Atripla. Gilead Sciences (NASDAQ:GILD) claimed three of these drugs, including No. 1 Genvoya. The other two top HIV drugs -- Triumeq and Tivicay -- belonged to GlaxoSmithKline (NYSE:GSK)

But a game of musical chairs is on the way that could shake up the HIV market somewhat. EvaluatePharma recently projected which HIV drugs will be at the top six years from now. Here are the predictions of the four biggest HIV drugs of 2024 -- and which stocks are poised to profit from them.

Pills on top of paper with HIV and AIDS printed on it

Image source: Getty Images.

The top four of '24

1. Biktarvy

An HIV drug that didn't make a penny in 2017 will vault to the top of the market over the next few years, according to EvaluatePharma. Gilead's Biktarvy, which won Food and Drug Administration approval in February 2018, should become the top-selling HIV drug in the world, with estimated sales of $6.1 billion in 2024. 

Biktarvy got off to a good start after its launch, generating $35 million in its first six weeks on the market. EvaluatePharma expects that Gilead's new HIV drug will be the biggest new drug launch of 2018.

2. Triumeq

GlaxoSmithKline's Triumeq is expected to hold on to its second-place position among the best-selling HIV drugs. However, it will probably be a more distant No. 2 than it has been. EvaluatePharma projects that Triumeq will make around $4.7 billion in 2024.

3. Genvoya

The current leading HIV drug is likely to fall a couple of notches over the next few years. Sales for Genvoya are expected to slip a little by 2024, with EvaluatePharma projecting the drug will rake in $3.4 billion.

4. Tivicay

Tivicay rounds out the top four of '24. GSK's other HIV drug could generate sales of $2.7 billion in 2024, reflecting a compound annual growth rate (CAGR) of 6%.

A continued duopoly -- for the most part

While the top HIV drugs will probably change some over the next few years, the top HIV drugmakers won't. Gilead Sciences and GlaxoSmithKline appear to be on course for a continued duopoly in the HIV market. However, there will be other players with lower market shares.

For example, Teva won FDA approval for a generic version of Truvada last year. The drugmaker probably won't be able to market its generic until Gilead's U.S. patent for emtricitabine, a component of Truvada, expires in 2021.

Mylan launched generic versions of Truvada and Atripla in Canada in late 2017. Both Mylan and Teva have also introduced generic versions of Viread, an older HIV drug developed by Gilead Sciences and Bristol-Myers Squibb.

Bristol-Myers Squibb is rapidly becoming a has-been in the HIV market. Sales for the company's HIV drugs Sustiva and Reyataz are dropping in the wake of competition from generics and more powerful newer drugs from Gilead and GSK.

Blockbuster drugs, but modest overall growth

Although blockbuster HIV drugs will still rule the roost in 2024, the overall HIV market isn't expected to generate exciting growth. Through 2025, business analytics firm GlobalData projects that the global HIV market will grow by a CAGR of only a little more than 3%.

Gilead and GlaxoSmithKline are poised to profit from their HIV drugs, but the level of increased profits is likely to be relatively modest. This means that investors hoping to gain solid returns from these stocks need to look at other opportunities for Gilead and GSK. The good news is that both companies have other ways to grow.

For Gilead Sciences, there are three primary growth drivers outside of HIV. The big biotech should see sales momentum pick up for CAR-T therapy Yescarta. Gilead could have a huge success story on its hands with immunology drug filgotinib if all goes well in phase 3 clinical studies. The company also has a promising pipeline targeting treatment of non-alcoholic steatohepatitis (NASH).

GlaxoSmithKline should get a boost from its acquisition of Novartis' stake in the consumer healthcare joint venture the two drugmakers formed. GSK also is enjoying solid momentum for its newer respiratory products. The company's shingles vaccine, Shingrix, is another source of revenue growth.

In my view, Gilead is likely to be the bigger winner rather than GlaxoSmithKline over the next several years. Its HIV products will be key to its success, especially Biktarvy. However, Gilead's other areas of focus will probably be even more important growth drivers over the long run.

Keith Speights owns shares of Gilead Sciences. The Motley Fool owns shares of and recommends Gilead Sciences. The Motley Fool recommends Mylan. The Motley Fool has a disclosure policy.