Horizon Therapeutics has reported positive and statistically significant topline results from the phase 4 trial of TEPEZZA (teprotumumab-trbw) in patients with chronic/low clinical activity score (CAS) thyroid eye disease (TED).
The randomised, double-masked, placebo-controlled trial evaluated the efficacy and safety of TEPEZZA in 62 adults who were initially diagnosed with thyroid eye disease two to 10 years before. The participants also had low CAS, which is a measure of disease activity.
The drug was approved by the US Food and Drug Administration (FDA) in 2020 for the treatment of thyroid eye disease in adults. The phase 2 and 3 trials that formed the basis of the approval, evaluated the drug in patients with disease duration of nine months or under and higher levels of activity of the disease.
In the phase 4 trial, Horizon Therapeutics used the pre-specified primary analysis method or intent-to-treat method to collect the topline data.
Horizon Therapeutics, which agreed to be acquired by Amgen in late 2022, said that the primary efficacy objective of the trial was to assess TEPEZZA’s effect in comparison to the placebo in the change of proptosis measurements in the study eye from baseline at Week 24.
Based on the results, the subjects treated with the drug achieved a 2.41mm reduction in proptosis from baseline compared with 0.92mm for those receiving a placebo, thus meeting the primary endpoint.
Additionally, the results showed that 62% of individuals treated with TEPEZZA had a clinically meaningful improvement in proptosis at week 24 versus 25% of patients receiving placebo.
According to Horizon Therapeutics, the totality of clinical trial data of the drug continues to strongly back its efficacy across a wide spectrum of thyroid eye disease patients irrespective of disease activity or duration. Besides, the drug has been shown to have a well-established safety profile.
Horizon Therapeutics research and development EVP Elizabeth Thompson said: “With TEPEZZA, physicians have a medicine that can be used in a broad range of Thyroid Eye Disease patients, including those with long-duration disease of more than 5 years on average in this trial, which is important because we know the negative impact of the disease can be significant across all types of Thyroid Eye Disease patients.
“We look forward to discussing these data with the FDA to determine our next steps.”
