Despite hitting its primary endpoint, Viridian’s thyroid eye disease antibody failed to ease eye bulging to the degree that analysts had been hoping for, and the biotech’s stock price fell by one-third.
Viridian Therapeutics’ investigational antibody significantly eased the abnormal bulging of the eyes in a late-stage study of thyroid eye disease, meeting its primary objective but falling short of what investors had hoped.
Viridian crashed nearly 33% on Monday to $18.53 per share.
Despite the selloff, analysts were bullish on Viridian’s data. Truist Securities called the readout encouraging, noting that the drug’s subcutaneous dosing profile “brings a path to commercialization for the asset.”
William Blair likewise viewed Viridian’s findings positively, noting in a Monday note that “these results not only support potential regulatory approvals” but also “support a compelling commercial profile and significant market opportunity” for the biotech if it brings the first subcutaneous thyroid eye disease drug to the market.
Still, William Blair acknowledged some weakness in the company’s readout, particularly as regards placebo-corrected efficacy measures. In the Phase 3 REVEAL-1 study, Viridian tested two dosing schedules of its subcutaneous anti-IGF1R antibody elegrobart: every four weeks and every eight weeks. Controls were given placebo.
Results released on Monday showed that 54% of patients given the subcutaneous drug on a monthly basis responded to the treatment, as measured by at least a 2-mm reduction in proptosis, or the abnormal bulging of the eyes. In the group receiving treatment every eight weeks, 63% responded. Proptosis responder rate (PRR) in the placebo arm was 18%, resulting in a highly significant treatment effect for elegrobart.
However, the placebo-adjusted basis PRRs of 36% and 45% for the two groups, respectively, fell “below the 51%-73% range that investors were looking for heading into the readout,” according to William Blair’s analysis of the Monday data.
“While there are several factors that may contribute to this weaker placebo-adjusted delta,” such as a strong placebo response, “the fact remains that the headline proptosis responder rate does not fully live up to expectations,” William Blair added.
Outside of the primary outcome, elegrobart also hit a key secondary endpoint, resulting in a significantly larger mean reduction in proptosis from baseline versus placebo. But the drug failed to outperform placebo in terms of clinical activity scores (CAS), a miss that William Blair attributed to a significant placebo response.
Regardless of the cause, the CAS miss rendered Viridian unable to test the significance of REVEAL-1’s other secondary outcomes, given the hierarchical nature of the study’s statistical plan. Still, the biotech on Monday touted the numerical edge of elegrobart over placebo in terms of diplopia resolution and proptosis improvement in the every-other-month regimen.
As for safety, Truist called elegrobart’s overall profile “clean,” dismissing all treatment-related adverse events as “non-serious” and “mild in nature.” Hearing-related toxicities included tinnitus, but the biotech did not report any reductions in hearing. “We believe [elegrobart’s] safety profile . . . will further support a future submission,” the analysts added.
Indeed, Viridian announced on Monday that it is awaiting a second pivotal readout in thyroid eye disease in the second quarter, with a biologics license application on track for the first quarter of 2027.
