While drugs like Eylea can be life-changing for patients facing the prospect of vision loss, injections in the eye are unpleasant and the possibility of extending the time between needles is enticing. Currently, patients receive Eylea every eight weeks after an initial dosing regimen; the Phase 3 studies of the 8mg option are testing injections every 12 weeks or 16 weeks.

Roche is already seeking Food and Drug Administration approval for a longer option after research showed its drug, faricimab, worked as well as Regeneron’s Eylea even if given every 12 or 16 weeks. And the Swiss drugmaker is also asking the FDA to clear a drug-delivery implant that would require refilling every six months with a formulation of its older eye drug, Lucentis.

At the same time, copycat versions of Eylea are on the horizon, with Novartis starting a Phase 3 trial of a biosimilar earlier this year.

The main advantage Eylea has is a “gold-standard” track record on safety, SVB Leerink analyst Geoffrey Porges wrote in a note to investors. Doctors may be inclined to stick with what they know if Regeneron and partner Bayer can offer the same treatment interval as rivals without new safety issues. Novartis’s Beovu eye drug, for instance, has seen limited sales amid warnings of side effects.

While many people now know Regeneron for its Covid-19 therapy used to treat former President Donald Trump, the company’s main growth driver has long been Eylea. The drug had sales of $1.4 billion in the second quarter, and Porges predicts annual revenue will grow to a peak of $11.1 billion in 2023.