Amgen paid $27.8 billion for Horizon Therapeutics in 2023. The prize: Tepezza, the only approved drug for thyroid eye disease. Three years later, sales are flat at $1.90 billion, barely below the 2022 peak of $1.96 billion but nowhere near the growth that justifies that price tag.
A phase 3 trial released Monday shows the subcutaneous Tepezza, delivered via on-body injector, hit a 77% proptosis response rate at 24 weeks — versus 20% for placebo. The original IV approval was backed by 83%. Not a downgrade.
The current IV regimen is brutal: eight infusions over 21 weeks, each running 60-90 minutes. An on-body injector changes the calculus entirely on who’s willing to start treatment.
Viridian’s elegrobart posted a 54% response rate in phase 3 last week — lower than Tepezza’s numbers, and results that didn’t impress investors. Sling Therapeutics’ oral candidate linsitinib (phase 2b/3) came in at 52%. Tepezza’s efficacy still leads, but a convenience gap could level the field fast.
Amgen hasn’t filed yet. A spokesperson said it’s “too early to comment on approval timing.”
— Sarah Chen