ATC code A includes a large variations of agents used for treating gastrointestinal disorders (e.g., antispasmodics, anti-diarrheals), antiemetics and antinauseants, agents for bile and liver therapy, anti-inflammatory agents (e.g., loperamide, rifaximin), anti-obesity preparations (e.g., orlistat, liraglutide), antidiabetic agents (e.g., insulin, metformin, sulfonylureas, SGLT-2 inhibitors), appetite stimulants, and minerals and vitamins. The gene discussed is SLC5A2; the disease is obesity due to melanocortin 4 receptor deficiency.