13 leading drugmakers' top 3 drugs by revenue in 2020

The best-selling drug in the world in 2020 was AbbVie's Humira, an immunology drug used to treat rheumatoid arthritis and other inflammatory diseases, according to a report published March 22 by S&P Global.

In 2020, Humira generated $19.83 billion in revenue for a 3.5 percent increase over 2019.