Things change relatively quickly in the pharmaceutical world. Even a best-selling drug can only hold its top spot for a while before its sales fade and a newer treatment takes its place. 

EvaluatePharma's recently released World Preview 2019, Outlook to 2024 report underscores this point. The market research company projected sales for all drugs on the market, as well as those that are expected to launch over the next few years, to forecast which will be the best-selling drugs in 2024. Three of 2018's five biggest sellers are expected to fall off the list in 2024 -- and two of them aren't even expected to make the top 10.

Let's review the five biggest blockbuster drugs of 2024, according to EvaluatePharma's projections, and the pharmaceutical stocks that are most likely to be winners for investors because of those drugs' successes.

Pills stuck together to form a dollar sign

Image source: Getty Images.

1. Keytruda

Merck's (NYSE:MRK) Keytruda is one of the fastest-rising drugs on the market. The cancer immunotherapy was first launched in 2014. Last year, Keytruda ranked as the third-best-selling drug in the world, with growing sales fueling Merck's impressive stock gain of close to 36% in 2018.

By 2024, EvaluatePharma forecasts that Keytruda will become the world's top-selling drug with annual sales of $17 billion -- more than double the $7.2 billion in revenue it generated last year. Underlying that is the expectation that the drug will be approved for more indications. Merck made pretty good progress on that score in 2018, when the blockbuster cancer drug picked up two new indications. 

2. Humira

Humira's sales of $20.5 billion in 2018 made it the best-selling drug in the world, but its reign will come to an end soon. AbbVie (NYSE:ABBV) faces biosimilar competition for the enormously successful immunology drug in Europe already, and will battle biosimilars in the U.S. beginning in 2023.

But Humira will keep making plenty of money for AbbVie for a while longer. EvaluatePharma projects it will have annual sales of $12.4 billion in 2024, good enough to hold on to the second-place spot among best-selling drugs.

3. Eliquis

Bristol-Myers Squibb (NYSE:BMY) landed two drugs in EvaluatePharma's top five list of blockbuster drugs of the future last year. Anticoagulant Eliquis was the lower-ranked of the two drugs then, coming in at No. 5. However, strong sales momentum for Eliquis have led the analysts to revise their outlooks, and this time around, it claims the No. 3 spot.

EvaluatePharma now thinks that Eliquis will generate annual revenue of more than $12 billion in 2024 -- almost twice the $6.4 billion it made last year. Bristol-Myers Squibb doesn't keep all of that money to itself, though: The company partners with Pfizer (NYSE:PFE) in marketing Eliquis.

4. Opdivo

In 2018, Bristol-Myers Squibb's Opdivo held the No. 3 spot on the five-year forecast of best-sellers. This year, the company's leading immunotherapy slipped a spot to No. 4. 

Although Keytruda appears to be on track to be the bigger winner in the battle between the top two immunotherapies, Opdivo is still on course to rake in $11.3 billion annually by 2024, up from $7.6 billion last year.

5. Imbruvica

Bristol-Myers Squibb isn't the only big pharma company with two drugs in 2024's top five list. AbbVie partners with Johnson & Johnson (NYSE:JNJ) in marketing cancer drug Imbruvica, which moves up from No. 6 last year to take the fifth spot on the ranking of future top blockbuster drugs this year.

EvaluatePharma projects that Imbruvica will make $9.5 billion in sales in 2024. That's more than twice the nearly $4.5 billion that the drug pulled in last year. That would also make Imbruvica the top-five drug with the second-fastest sales growth over the next few years, ranking behind only Keytruda.

The stocks most likely to soar

You might think that Merck would be the stock most likely to reward investors, based on these forecasts. As Keytruda rises to the top of the world, Merck certainly will see its sales increase nicely. However, the company also has some baggage, due to the declining sales of several of its older drugs.

On the other hand, Humira losing its top spot might suggest that among these pharmaceutical companies, AbbVie could be in the most trouble. Yet it has other drugs that have strong momentum -- Imbruvica among them -- and promising candidates in the pipeline that I think should help the stock perform solidly over the next five years.

My hunch is that Bristol-Myers Squibb might be the biggest winner of them all. This view isn't just based on the idea that the company's likely to claim two of the world's top-selling drugs in 2024. I think that its pending acquisition of Celgene (NASDAQ:CELG) will be a game-changer for the company. Celgene's pipeline is chock-full of candidates with blockbuster potential that I suspect will turbocharge growth for Bristol-Myers Squibb well beyond 2024. 

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.