A 28-year-old man from Delhi presents with a 6-month history of bloody diarrhea, abdominal pain, and weight loss. Colonoscopy shows continuous mucosal inflammation limited to the colon with crypt abscess formation and surface ulceration. Histology confirms inflammation confined to the mucosa and submucosa. Laboratory tests show elevated ESR and CRP. He has no extraintestinal manifestations. What is the most appropriate next step in management?