20. Genvoya

Genvoya picked up $3.98 billion in sales in 2019. (Gilead)

Company: Gilead Sciences
2019 sales: $3.98 billion
Projected 2026 sales: $1.97 billion 
Projected CAGR: -10%
Used for: HIV

As the first of Gilead's next-gen line of HIV meds, two-drug regimen Genvoya has held its own in terms of sales in its five years on the market. But as Gilead's more effective three-drug HIV med Biktarvy swallows up sales, Genvoya could be left in the dust. 

Genvoya picked up $3.98 billion in sales in 2019. In 2026, the drug's sales could drop down to $1.97 billion as pricing pressure and Biktarvy's runaway launch chip away at Genvoya's sales, Evaluate predicted. 

The user-friendly three-drug combo Biktarvy could exert pressure on Genvoya's sales over time. Even early in its launch, Biktarvy was stripping patients away from Gilead's other HIV meds, with 25% of switched patients by November having previously taken Genvoya.

RELATED: Gilead touts new data for fast-growing Biktarvy as older HIV meds show some cracks

One major concern among physicians, as industry watchers have noted, is that two-drug combos such as Dovato and Genvoya won't be strong enough to keep the virus under control over the long term, and patients might develop resistance more easily because they only contain one nucleoside reverse transcriptase inhibitor rather than the two in current standard treatments.

20. Genvoya