Viridian Therapeutics has reported success in a second phase 3 study of its anti-IGF-1R antibody, strengthening its position as it prepares to seek approval from the U.S. Food and Drug Administration next year and compete in a high-value thyroid eye disease market currently led by Amgen.
The trial enrolled 204 patients with thyroid eye disease (TED), randomly assigning them to receive Viridian’s candidate elegrobart either every four weeks, every eight weeks, or a placebo. The drug targets the same IGF-1 receptor pathway as Tepezza, which Amgen obtained through its nearly-$28 billion acquisition of Horizon Therapeutics. Unlike Tepezza, which is administered via intravenous infusions lasting 60 to 90 minutes every three weeks, elegrobart is delivered as a self-injected subcutaneous therapy.
Earlier this year, Viridian Therapeutics announced positive phase 3 data in patients with active TED – defined as symptom onset within 15 months. The latest results extend that success to chronic TED, involving patients whose symptoms began more than 15 months before screening.
For the primary endpoint assessed by the FDA, researchers measured the proportion of patients achieving at least a 2 mm reduction in proptosis, or eye bulging, from baseline. At the 24th week, half of the patients receiving elegrobart every four weeks met this benchmark, compared to just 15% in the placebo group. The eight-week dosing schedule produced a response rate of 54%.
Using a different primary endpoint required by the European Medicines Agency, Viridian produced similar outcomes. In the four-week dosing group, 47% of patients met the response criteria versus 15% on placebo, while the eight-week regimen again achieved a 54% response rate. Both dosing schedules showed statistically significant reductions in proptosis compared to placebo.
Results for secondary endpoints were more mixed. Measures related to diplopia, or double vision, showed improvement in the four-week group, where 61% of patients responded versus less than 40% in the placebo arm. However, the eight-week dosing regimen did not reach statistical significance, and neither treatment arm demonstrated a clear advantage over placebo in fully resolving diplopia.
Direct comparisons with Tepezza are challenging due to differences in trial design. Studies supporting Tepezza’s approval focused on patients with more recent disease onset, while a later phase 4 trial in patients with longer-standing TED reported response rates of 62% for Tepezza versus 25% for placebo at the 24th week.
Although available data suggest Tepezza may retain an efficacy advantage, Viridian Therapeutics could compete on convenience. Amgen is developing a subcutaneous version of Tepezza, but analysts from TD Cowen have noted that elegrobart’s less frequent dosing schedule may still appeal to patients.
Viridian Therapeutics plans to submit elegrobart for FDA approval in the first quarter of 2027. At the same time, the company is advancing a second TED therapy, the intravenous drug veligrotug, which is awaiting an FDA decision expected by June 30.
Both therapies are aimed at capturing share in a TED market that generated nearly $2 billion in revenue for Amgen last year.
Viridian Therapeutics continues to gain momentum in the competitive thyroid eye disease market as Viridian announced another positive Phase 3 trial result for its investigational therapy. The latest success positions Viridian closer to a potential FDA approval and intensifies competition with Tepezza, the current leading treatment in the space.
Viridian’s Latest Phase 3 Success
The new Phase 3 data showed that Viridian’s therapy achieved significant improvements in patients with thyroid eye disease (TED). According to the study, Viridian demonstrated strong reductions in eye bulging, inflammation, and other debilitating symptoms associated with the condition.
Thyroid eye disease (TED) is a rare autoimmune disorder commonly associated with Graves’ disease. The condition causes inflammation and swelling around the eyes, leading to symptoms such as bulging eyes, double vision, pain, redness, and in severe cases, vision impairment.
Although existing therapies have improved patient outcomes, many individuals still face challenges related to accessibility, treatment tolerability, and long-term disease management. This has created a strong demand for additional therapeutic options in the market.
Clinical Trial Design and Endpoints
The Phase 3 program enrolled patients with active thyroid eye disease across multiple international study sites. Researchers evaluated several endpoints, including reduction in proptosis, improvement in diplopia (double vision), clinical activity score reductions, and overall quality-of-life measures.
The study reportedly met key efficacy benchmarks, demonstrating statistically significant improvements compared to placebo. Investigators also highlighted consistency across patient subgroups, which is often viewed as a positive indicator for regulatory review.
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