Drug developers like Celgene (CELG) are constantly innovating new medicine to offset the risk of sliding sales tied to expiring patents and that means investors should always be paying attention to when patents are set to end on key, top-selling therapies, such as Celgene's Revlimid.

Read on to learn more about Celgene's top-selling drugs and the expiration dates that could impact Celgene's future sales.

Key Takeaways Drugmakers are constantly developing new medicines to help hedge the losses in revenues due to patent expirations.

Thus, knowing when patents expire is important information for investors.

Many of the patents for top drugmaker Celgene don't expire for several years.

Notably, Celegene's number one drug, Revlimid, doesn't come off patent protection until 2027 in the U.S.

Celgene Patent No. 1: Revlimid

Revlimid, Celgene's best selling drug, is the leading therapy used to treat relapsing multiple myeloma patients, with the Food and Drug Administration (FDA) approving Revlimid's use as a front-line therapy.

The FDA's go-ahead for Revlimid as a first-line treatment should boost the drug's sales beyond its already lofty $10.8 billion annual clip.

As a result, Revlimid is likely to remain Celgene's best selling drug for years to come, especially since it's covered by patent protection in the U.S. until 2027 and in Europe until 2024.

Celgene Patent No. 2: Abraxane

Celgene acquired Abraxane with its $2.9 billion deal to buy Abraxis in 2010 and thanks to growing use as a therapy for pancreatic cancer, non-small cell lung cancer, and breast cancer, Abraxane's sales topped $1 billion in 2018, with the number expected to continue to grow.

Celgene should be able to count on Abraxane contributing to its top and bottom line well into the coming decade given that Abraxane's patent doesn't expire in the U.S. until 2026 and in the EU until 2022.

Celgene Patent No. 3 Pomalyst

Since its launch as a third-line treatment for multiple myeloma in 2013, Pomalyst has become one of the indication's top-selling drugs. Pomalyst is expected to generate $2.2 billion in sales from 2019 to 2021.

If Celgene can deliver on that forecast, then it will have a third billion-dollar blockbuster drug to count on into the 2020s. Pomalyst's patents protect it until 2030.

Celgene Patent No. 4: Otezla

Otezla is the most recently launched drug in Celgene's line-up. In March 2014, The FDA approved Otezla for use in psoriatic arthritis and last September, the agency gave Celgene the go-ahead to begin marketing it in the much larger psoriasis indication.

Otezla generates annual sales of roughly $1.6 billion. It has a patent expiration date of 2024 in the U.S. and 2028 in the EU, leaving Celgene plenty of time to profit from it.

What's Ahead for Celgene?

Since Celgene's patents stretch into the 2020s, it arguably has one of the best product line-ups in the industry. Thanks to these drugs, analysts expect Celgene to generate nearly $12 per share in earnings for 2021.

That would be a marked increase from the $3.71 in EPS reported in 2014. Of course, generic drug makers have filed lawsuits in an attempt to move up their own timelines to compete, but barring any changes, this company's long-lived patent portfolio could mean that it should be a staple in long-haul portfolios.