Teprotumumab for the Treatment of Thyroid Eye Disease: Why Should We Keep Our Eyes "Wide Open"?-A Clinical and Pharmacovigilance Point of View.

Objectives: Thyroid eye disease (TED) treatment has been recently revolutionized with the approval of teprotumumab, a targeted insulin growth factor 1 receptor (IGF1R) inhibitor. To date, teprotumumab is the only FDA-approved drug for treating TED. In this article, we would like to temper the current enthusiasm around IGF1R inhibitors. Methods: critical review of the literature by independent academic practitioners. Results: several questions should be raised. First, "how an orphan drug has become a blockbuster with annual sales exceeding $1 billion?" Teprotumumab infusions are expensive, costing about USD 45,000 for one infusion and USD 360,000 for eight infusions in a 75 kg patient. Teprotumumab approval was based on two randomized clinical trials investigating active (clinical activity score ≥ 4) TED patients. Despite this, teprotumumab was approved by the FDA for "the treatment of TED" without distinguishing between active and inactive forms. The second question is as follows: "how can a new drug, compared only to a placebo, become the new standard without being compared to historically established gold standard medical or surgical treatments?" Teprotumumab has never been compared to other medical treatments in active TED nor to surgery in chronic TED. Up to 75% of patients may experience proptosis regression after treatment discontinuation. Finally, ototoxicity has emerged as a potentially devastating side effect requiring frequent monitoring. Investigation into the long-term side effects, especially in women of childbearing age, is also warranted. Conclusions: Teprotumumab is undoubtedly a major treatment option in TED. However, before prescribing a drug, practitioners should assess its benefit/risk ratio based on the following: (i) evidence-based medicine; (ii) their empirical experience; (iii) the cost/benefit analysis; (iv) the long-term outcomes and safety profile.