AION is the main cause of blindness in patients with GCA. High dose steroid is the reference treatment of this condition, but medical unmet need remains. Subcutaneous tocilizumab, a targeted biotherapy, recently received marketing authorization for the treatment of GCA, but only demonstrated at yet that it can allow steroid dose sparing. The aim of this study is to assess the benefit of tocilizumab and IV steroids combination or IV steroids alone, in the treatment of AION due to GCA.

Tocilizumab will be proposed to eligible patients as an emergency treatment, in addition to the standard high-dose steroid treatment. Each patient will receive the reference treatment, i.e. one pulse of high dose intravenous methylprednisolone per day during 3 days, followed by 1 mg/kg/day oral prednisone, and low dose aspirin. Depending on the randomization, each patient will receive the reference treatment only, or will received in addition to the reference treatment four subcutaneous injections of tocilizumab 162 mg over one month (1 injection per week), the first tocilizumab injection being delivered on the same day than the first steroid IV pulse. Study visits will take place at 4, 8 and 13 weeks. The primary endpoint will be the ocular improvement at W8, defined as an increase of at least two lines of visual acuity on the ETRS chart. For each patient, the duration of participation will by of 3 months. The study duration is expected to be 15 months.

Inclusion Criteria:

1. Age of 50 years or older

2. Social insurance

3. Diagnosis of AION, characterized by sudden and painless loss of vision, of less than one week, accompanied by pallid swelling of the optic disc

4. Sudden permanent visual loss due to AION, of less than one week

5. Diagnosis of GCA based on the 1st (age ≥ 50 years) and the 3rd (Diagnosis of AION) criteria and at least one among the following :

   • One unequivocal symptom among: New onset localized headache, scalp or temporal artery tenderness, otherwise unexplained mouth or jaw pain under mastication, or unequivocal symptoms of polymyalgia rheumatic (shoulder and/or hip girdle pain associated with inflammatory stiffness).
   • Elevated erythrocyte sedimentation rate (≥ 50 at 1 hour) or C-reactive protein (≥ 10 mg/l), otherwise unexplained
   • Abnormal artery biopsy Biopsy specimen with artery showing vasculitis characterized by a predominance of mononuclear cell infiltration or granulomatous inflammation, usually with multinucleated giant cells.
   • Evidence of large or medium-size vessel vasculitis at ultrasound, magnetic resonance angiography, computed tomography angiography, or positron emission tomography-computed tomography.

Exclusion Criteria:

• Other ocular involvements related to GCA (central retinal artery occlusion, posterior ischemic optic neuropathy, transient ocular manifestations, occipital stroke), if not associated with AION
• Biological targeting therapy within 3 months preceding the study
• Evidence of active infection
• History of any malignant neoplasm except adequately treated basal or squamous cell carcinoma of the skin or solid tumors treated with curative therapy and disease-free for at least 5 years
• History of recurrent infections, diverticulitis or intestinal ulceration and ASAT/ALAT > 5 * upper limit of normal, according to the Summary of Product Characteristics of tocilizumab
• Contraindication to steroids and/or aspirin administrated in the treatment
• Breastfeeding women and women with childbearing potential without highly effective contraception.
• Pregnant or nursing (lactating) women confirmed by a positive βHCG laboratory test at the inclusion
• Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception during study treatment and for 3 months after the last administration of tocilizumab.
• Cytopenia, as defined by platelet count < 100 × 109/L (100,000/mm3), hemoglobin < 85 g/L (8.5 g/dL; 5.3 mmol/L), absolute neutrophil count < 2.0 × 109/L (2000/mm3), absolute lymphocyte count < 0.5 × 109/L (500/mm3)
• Insufficient liver function (Child Pugh C )
• Insufficient kidney function, as defined by a serum creatinine of more than 3 mg/dL or creatinine clearance of 20 ml/min or less
• Patients with previously untreated tuberculosis, previously known TDM/radiographic evidence suggestive of active and/or sequellar tuberculosis
• HIV infected, hepatitis C infected, or a positive hepatitis B surface antigen if known before study inclusion
• Contraindication to and precaution in use of tocilizumab according to the summary product description
• Inability to provide informed consent