7 September 2021 - - The first patient has been enrolled in a Phase 4 clinical trial evaluating the efficacy and safety of Tepezza for the treatment of chronic (inactive) TED, Dublin-based Horizon Therapeutics plc (NASDAQ: HZNP) said.

Tepezza is the first and only medicine approved by the US Food and Drug Administration for the treatment of TED a serious, progressive and potentially vision-threatening rare autoimmune disease.

TED begins with an acute (active) phase where inflammatory signs and symptoms, such as eye pain, swelling, proptosis (eye bulging) and diplopia (double vision), progress over time.

The disease then enters a chronic phase where inflammation is no longer present or has markedly diminished, but significant signs and symptoms may remain.

This randomized, double-masked, placebo-controlled, parallel-group, multicenter trial will evaluate the efficacy, safety and tolerability of Tepezza compared to placebo in treating patients with chronic TED.

At the time of the initial screening, all participants must be at least 18 years of age and have had an initial diagnosis of TED for at least three years and less than eight years.

Participants cannot have had prior orbital irradiation, orbital decompression or strabismus surgery.

Approximately 60 adult participants who meet the trial eligibility criteria will be randomized in a 2: 1 ratio to receive an infusion of either Tepezza or placebo, 10 mg/kg for the first infusion and 20 mg/kg for the remaining seven infusions, once every three weeks, for a total of eight infusions.

The primary efficacy endpoint is change from baseline at Week 24 in proptosis in the study eye.

The trial will also assess proptosis responder rate, diplopia responder rate, change in orbital pain, change in muscle volume and change in the Graves' Ophthalmopathy Quality of Life (GO-QoL) questionnaire appearance and visual functioning subscales.

Proptosis non-responders who have completed the treatment period may choose to enter an open-label extension period where they will receive eight infusions of TEPEZZA.

Thyroid Eye Disease is a serious, progressive and potentially vision-threatening rare autoimmune disease.

TED often occurs in people living with Graves' disease, but is a distinct disease that is caused by autoantibodies activating an IGF-1R-mediated signaling complex on cells within the retro-orbital space.

This leads to a cascade of negative effects, which may cause long-term, irreversible damage. As TED progresses, the serious damage it can cause includes proptosis (eye bulging), strabismus (misalignment of the eyes) and diplopia (double vision) and in some cases can lead to blindness.

Horizon is focused on the discovery, development and commercialization of medicines that address critical needs for people impacted by rare, autoimmune and severe inflammatory diseases.