• Written informed consent

• Male or female, 18-80 years old

• Patients with active (Clinical Activity Score ≥ 3 in 7-item scale) and moderate-to-severe GO, diagnosed according to the EUGOGO guidelines, after the completion of MP pulse treatment, WITH

• o Deterioration of GO (in 1 or 2 eyes) when two of the following occurred:

• increase in palpebral aperture by at least 2 mm;

• deterioration in CAS by at least 2 points (7-point CAS)

• increase in exophthalmos by at least 2 mm;

• worsening of diplopia (appearance or change in the degree)

• worsening in ocular motility by 8o

• o Incomplete response in both eyes to intravenous methylprednisolone pulse therapy; defined changes smaller than previously defined in any of the mentioned parameters.

• Euthyroid for at least 6-8 weeks (serum free hormone concentrations within 30% of normal range) on either anti-thyroid medications (tyonamides) to control hyperthyroidism or L-thyroxine for replacement therapy for hypothyroidism.

• Negative pregnancy test in women of fertile age.

• All female patients of fertile age must use a reliable contraceptive method to prevent pregnancy during the study period, and at least during a period of six months following the last dose of the investigational medicinal product.