Moderate to Severe Psoriasis and Psoriatic Arthritis: Biologic Drugs. Biologic drugs, or biologics, are given by injection or intravenous (IV) infusion. A biologic is a protein-based drug derived from living cells cultured in a laboratory. While biologics have been used to treat disease for more than 100 years, modern-day techniques have made biologics much more widely available as treatments in the last decade.