A second IGF-1 receptor blocker clears the bar in thyroid eye disease

Veligrotug, an antibody that blocks the insulin-like growth factor-1 receptor, met every primary and secondary endpoint in its pivotal trial for active thyroid eye disease: 70% of treated patients had a meaningful reduction in eye bulging at 15 weeks against 5% on placebo [s1]. That result, from the phase 3 THRIVE study, makes it the first credible second entrant in a class where only one drug — teprotumumab — has been approved to treat the disease [s2].

Thyroid eye disease is an autoimmune disorder, usually tied to Graves' disease, in which tissue behind the eye swells and remodels. It pushes the eyeball forward (proptosis), causes double vision (diplopia), and in its active phase inflames the eye; the receptor veligrotug targets sits at the centre of that process, which is why blocking it has become the mechanism of interest [s1]. Until recently the only options were steroids, radiation, or surgery.

What THRIVE measured

THRIVE was a global, double-masked, randomised trial that enrolled 113 adults with moderate-to-severe active disease — proptosis at least 3 mm above normal and a clinical activity score of 3 or more — and assigned them 2:1 to veligrotug or placebo, 75 to the drug and 38 to placebo [s1]. Treatment was five intravenous infusions of 10 mg/kg given every three weeks, a fixed 12-week course rather than open-ended dosing [s1]. The primary endpoint at week 15 was the proptosis responder rate, a reduction of at least 2 mm, or an overall responder rate combining that with a 2-point drop in the activity score, depending on region [s1].

The separation from placebo was large and consistent. The proptosis responder rate was 70% versus 5% by exophthalmometry, and 71% versus 9% when measured on MRI or CT scans [s1]. The overall responder rate was 67% versus 5% [s1]. Mean proptosis fell by 2.90 mm on veligrotug against 0.48 mm on placebo by exophthalmometry, and by 2.96 mm against 0.58 mm on imaging [s1]. Double vision improved in 59% of treated patients versus 20%, and resolved entirely in 49% versus 12% [s1]. Every comparison reached statistical significance at P < 0.001, and improvement was already visible by week 3, after the first infusion or two [s1]. That the proptosis effect showed up on MRI and CT imaging, not only on the clinician's exophthalmometer, matters because it points to real reduction in the swollen tissue behind the eye rather than measurement drift [s1].

Durability and safety

Response held up after dosing stopped. Among patients who responded initially, 70% still had a proptosis response at week 52 — roughly nine months after the last infusion [s1]. Veligrotug was generally well tolerated: the treatment discontinuation rate was 4%, most adverse events were mild and resolved, and the authors report no serious treatment-related events and no change in the safety profile out to a year [s1].

Two caveats belong on that record. The trial was modest in size, with only 38 patients on placebo, and it was run by the drug's maker, Viridian Therapeutics, whose employees are among the authors [s1]. The week-52 durability figure also describes only the patients who had already responded, not the full enrolled group — a maintained response is not the same as a cure, and this is a chronic, relapsing disease [s1]. The trial measured proptosis, diplopia and activity score, all of which matter to patients, but not long-term recurrence.

Why a second drug matters

The value of THRIVE is less any single number than the fact of a second option approaching the clinic. IGF-1 receptor blockade transformed thyroid eye disease treatment, but a class with one member gives clinicians no fallback when a drug is not tolerated, not accessible, or not covered, and no competitive pressure on price or dosing [s2]. A shorter, five-infusion course is itself a potential practical advantage over longer regimens, though THRIVE was not designed as a head-to-head comparison and none of its numbers speak to how veligrotug performs against the approved drug [s2].

This is one blinded, company-run phase 3 trial, not a regulatory decision or a real-world track record. It sits alongside a broader move in autoimmune and endocrine disease toward drugs built for a specific mechanism rather than blanket immune suppression — the same logic behind an interleukin-6 blocker now in trials for the same condition. Whether veligrotug reaches patients, and how it is priced against an incumbent, are the questions THRIVE does not answer. This article describes trial findings and is not medical advice.