Regeneron Pharmaceuticals (NASDAQ:REGN) unveiled its first-quarter financial results before the market opened on Tuesday, reporting revenue growth of 33.2% year over year to $1.83 billion and non-GAAP earnings of $6.60 per share, up 48.3%.

Why revenue and profit accelerated

The biotech company's revenue growth was driven largely by growing sales of Dupixent, an eczema drug that secured Food and Drug Administration approval for use in asthma patients in March 2019. Dupixent revenue, which is reported by collaboration partner Sanofi (NASDAQ:SNY), surged 129% year over year to $855.2 million in Q1.

A doctor speaks through a megaphone.

IMAGE SOURCE: GETTY IMAGES.

Regeneron also benefited from a 25% increase in sales of its cholesterol-lowering drug, Praluent, a 78% increase in revenue its rheumatoid arthritis drug, Kevzara, and an increase of 179% in sales of its PD-1 inhibitor, Libtayo. Sales of Praluent and Kevzara, which are also reported by Sanofi, were $79.8 million and $60.1 million, respectively. Regeneron reports U.S. sales of Libtayo, which were 61.7 million, while Sanofi reports foreign sales, which totaled $13.1 million.

Overall, sales of these drugs resulted in Regeneron reporting Sanofi-collaboration revenue of $246.9 million, reversing an $18 million net loss in the same quarter last year.

Additionally, sales remained strong for Regeneron's biggest seller, Eylea. Used to improve vision in people with various eye disorders, including wet age-related macular degeneration (AMD), Eylea's U.S. sales totaled $1.17 billion last quarter, up from $1.07 billion in Q1, 2019. Eylea sales overseas, where it's marketed by Bayer, were $254 million, up from $249 million one year ago.

Bottom-line growth outpaced top-line growth because Regeneron's operating expenses grew more slowly than its revenue. In the quarter, research and development expenses increased by just 20%, and selling, general, and administrative expenses grew 26%.

Looking ahead, Regeneron's management expects an FDA decision on Dupixent's application for use in children 6 to 11 with moderate-to-severe eczema on May 26. It also expects to file for expanded use of Libtayo and Praluent this year.