Rituximab (RTX) Therapy in Patients With Active TAO

Diffuse autoimmune hyperthyroidism or Graves' disease (GD) is a common condition mainly affecting women with 2-3% prevalence The increased production of thyroid hormones in GD is driven by autoantibodies directed against the thyroid stimulating hormone (TSH) receptor (TRab). In most cases, this autoimmunity will also affect other tissues, above all the orbital tissue by mechanisms not fully understood -Thyroid Associate Ophthalmopathy (TAO). Symptoms and signs can be mild (grittiness, dry eyes, periorbital swollen, chemosis, redness)-moderate (double eye vision, exophthalmia or severe (optic nerve compression, corneal ulcers). Serious-moderate ocular engagement in TAO is seen in approximately 10% of patients with GD.

Not only has the hyperthyroidism a marked impact on mental health, but the presence of TAO has an additional negative impact on the well-being of these patients, even many years after successful treatment of the hyperthyroidism. It has been suggested that smoking and stress are negative prognostic factors for the course of TAO indicating that a vicious circle. MRI may detect earlier changes than CT that can be used to predict the course of TAO.

The aims of treatment are to retain euthyroidism which can be achieved by anti thyrostatic drugs (ATD), radioiodine treatment or surgery (where patients are pre-treated with ATD) and to avoid TAO as long as possible. If moderate-severe TAO occurs, high dose if intravenous glucocorticoids (GC) are the gold standard considering the side effects. However, many patients are non-steroid responders and for them no treatment except for acute orbital decompression, retro bulbar irradiation and later reconstructive surgery can be offered. When patients relapse immediately after steroids often per oral steroids are given although not recommended from the literature.

Rituximab (RTX) is a mouse-human chimeric antibody designed towards pre B and mature B lymphocytes and that blocks B-cells activation without affecting the regenerating of B cells from stem cells or the plasma cells immunoglobulin production. TAO is a B- lymphocyte mediated disease and in two studies RTX inhibits the active phase of TAO. In a study by Khanna et al a positive effect from RTX is observed in six steroid resistant patients with TAO with a decrease of the inflammation in the orbit, even though no effect on strabismus or proptosis was observed. In another study by Salvi et al , RTX treatment is compared with steroids as a first line treatment for TAO and after 30 weeks of follow up in an unrandomised study design. RTX decreased the activity and severity significantly compared to the steroid group. No relapse was observed in the RTX group but in the steroid group (10%). In the RTX all patients improved, but in the steroid group only 65%. There were more side-effects in the steroid group.

Selection criteria All patients with indication for i.v GC will be evaluate for the study. The patients are recruited consecutively from the region as we are a tertial referral center and iv steroids for TAO is not given on local hospitals..

Patients and study design All patients aged 18-70 years in the western region in Sweden with TAO and indication for iv GC (CAS ≥4) will be evaluated for this prospective open study with RTX+MTX to GC non-responders. If GC respondent but relapsing after 12 weeks of iv GC treatment, patients will be randomized to RTX+MTX or per oral GC+MTX. If non respondent after 4 weeks of intravenous steroid infusion the patient will be eligible for RTX treatment Patients are seen for ophthalmological and endocrine investigations at baseline, 4, 12, 18, 32, 44, 56 and 68 weeks. At similar occasions anthropometric measurements, immunological markers and measures of GC effects (ACTH test, body composition (not all occasions)) will be performed. At baseline and after 30 weeks high quality MRI and Gallium (GA)-PET is performed. Patients undergoing Ga-PET in another study focusing on pituitary imaging (principle investigator HFN) will serve as controls for orbital muscles. The aim of the RTX study is to recruit at least 10 patients in the RTX arm and probably 40-50 patients will be included.

No study with this design has previously been published. The present situation does not offer the patients not responding to GC or with relapses after iv GC infusions any effective treatment. If the RTX proves safe and effective future non-respondent patients will be able to get this treatment. In small studies RTX have had a good effect in TAO, sometimes even better than GC and with less side-effects. It will also lay the ground for future studies that compare RTX and GC in a randomised study design as first line treatment. If GA-PET shows useful in the management of patients with TAO it may become a routine investigation.