The recommended dosage for adults is an initial 10mg/kg of teprotumumab, followed by 20mg/kg for subsequent doses every three weeks, totalling eight infusions.
TEPEZZA was granted orphan drug designation in Japan, which facilitated a shortened nine-month regulatory review period, compared to the standard 12 months.
The approval was granted based on the positive data from the Phase III OPTIC-J clinical trial.
This double-masked, randomised, placebo-controlled, parallel-group, multicentre trial assessed the tolerability, efficacy and safety of TEPEZZA in treating patients with active TED in Japan.
The trial met its primary endpoint, and 89% of subjects who received the treatment experienced a clinically meaningful improvement in proptosis at week 24 versus placebo.
TEPEZZA’s safety profile in the trial was found to be in line with the complete body of clinical data supporting its use.
Amgen Research and Development executive vice-president and chief scientific officer Jay Bradner said: “This is the first approval for TEPEZZA in Asia and marks a significant milestone for the global treatment of TED.
“Historically, patients with TED have been managed with complex surgeries and high-dose steroids, which can cause further complications. With TEPEZZA, doctors have a nonsurgical and nonsteroidal option that treats a root cause of this debilitating disease.”
Additionally, a second Phase III trial is currently underway in Japan to evaluate the therapy in adults with chronic TED and a low CAS.
A progressive and vision-threatening rare autoimmune disease, TED can lead to symptoms such as proptosis, diplopia, eye redness, pain and swelling.