Horizon Pharma plc, a specialty biopharmaceutical company, engages in identifying, developing, acquiring or in-licensing, and commercializing medicines for the treatment of arthritis, pain, inflammatory, and/or orphan diseases in the United States and internationally. The company offers ACTIMMUNE for reducing the frequency and severity of serious infections associated with chronic granulomatous disease; DUEXIS, a proprietary tablet formulation for the relief of signs and symptoms of rheumatoid arthritis (RA) and osteoarthritis (OA), and to decrease the risk of developing upper gastrointestinal ulcers in patients who are taking ibuprofen for these indications; PENNSAID for the treatment of pain of OA of the knee; and VIMOVO, a proprietary fixed-dose multi-layer delayed-release tablet for the relief of the signs and symptoms of OA, RA, and ankylosing spondylitis (AS). It also provides RAYOS/LODOTRA, a proprietary delayed-release formulation of low-dose prednisone for the treatment of moderate to severe active RA in adults when accompanied by morning stiffness, as well as for the treatment of polymyalgia rheumatica, psoriatic arthritis, AS, asthma, chronic obstructive pulmonary disease, and various other conditions. The company has a collaboration agreement with Fox Chase Cancer Center to study ACTIMMUNE in combination with PD-1/PD-L1 inhibitors in various forms of cancer. Horizon Pharma plc was founded in 2005 and is headquartered in Dublin, Ireland.