A 41-year-old male patient presented with recurrent episodes of bloody diarrhoea for 5 years. Despite regular treatment with adequate doses of sulfasalazine, he has had several exacerbations of his disease and required several weeks of steroids for the control for flares. What should be the next line of treatment for him?
Methotrexate
Azathioprine
Cyclosporine
Cyclophosphamide