A group of medications that are derived from living sources, as opposed to synthesised chemicals, and that block specific steps in the inflammation process. Biologic response modifiers are a subset of the disease-modifying anti-rheumatic drugs (DMARDs), and likewise are used in the treatment of rheumatoid arthritis, psoriatic arthritis, psoriasis and ankylosing spondylitis. They are useful not only for easing the signs and symptoms of disease but also for slowing or stopping its progression. Current biologic response modifiers must be injected or infused, although oral versions, such as liquids, are being developed.