Horizon sunny as thyroid eye disease drug hits the mark

Horizon Pharma shares rose strongly after it reported a positive phase 3 trial of teprotumumab for the treatment of active thyroid eye disease (TED), which causes proptosis or eye bulging.

The OPTIC study showed that more patients treated with teprotumumab had a meaningful improvement in proptosis than those on placebo, with almost 83% of those taking the antibody meeting the primary endpoint of a 2mm reduction compared to 9.5% of the control arm.

All secondary endpoints were also met, with a manageable safety profile, and Dublin-based Horizon says it will now press ahead with a US regulatory filing for teprotumumab in mid-2019. The drug has already been granted breakthrough, orphan drug and fast track designations by the FDA.

TED is an autoimmune disease in which the eye muscles and fatty tissue behind the eyes become inflamed, causing them to be pushed forward, and in severe cases can lead to blindness. It’s most often caused by an overactive thyroid gland (Graves’ disease), and occurs in around one in four people with that condition.

Graves-related proptosis famously affected British actor, writer and comedian Marty Feldman, who rose to prominence in the 1960s and 1970s and among his many accomplishments played the role of Igor in Mel Brooks’ comedy classic Young Frankenstein in 1974.

Other than anti-thyroid drugs to treat Graves’ disease itself, there are few treatments available for TED, and many people are left with a permanent change in the appearance of their eyes and sometimes double vision.

Along with an improvement in proptosis, teprotumumab – an inhibitor of the insulin-like growth factor (IGF) type 1 receptor – also reduced double vision and improved quality of life, according to Horizon.

Eye specialist Raymond Douglas of Cedars-Sinai Medical Centre in the US, one of the principal investigators in the trial, said that the reduction in proptosis with teprotumumab was “unprecedented”. At the moment proptosis is only treatable via surgery after the active disease has ended, he explained.

“If approved, teprotumumab would give physicians the first medicine shown to reduce proptosis during active thyroid eye disease, in addition to treating other painful symptoms.”

Analysts have suggested the drug could not only be a means of avoiding surgical intervention but also as be an option in less severe patients who are not necessarily headed for surgery.

After Horizon presented phase 2 results with teprotumumab last year, analysts at JMP Securities described the drug as a “game-changer” that could conservatively achieve sales of $20m by 2025.