United Therapeutics Corporation is a biotechnology company focused on the development and commercialization of products to address the unmet medical needs of patients with chronic and life-threatening conditions. Its therapeutic products and product candidates include: Prostacyclin Analogues, Phosphodiesterase Type 5 (PDE-5) Inhibitor, Adcirca, Monoclonal Antibodies (MAbs), Glycobiology Antiviral Agents, Cell-Based Therapy, and Engineered Lungs and Lung Tissue for Transplantation. Prostacyclin analogues are stable synthetic forms of prostacyclin. Its product is Remodulin (treprostinil) Injection (Remodulin). PDE-5 inhibitors act to inhibit the degradation of cyclic guanosine monophosphate (cGMP) in cells. Its PDE-5 inhibitor product is Adcirca (tadalafil) tablets (Adcirca), a once-daily oral therapy for the treatment of pulmonary arterial hypertension (PAH). MAbs act by targeting tumor-associated antigens on cancer cells to activate a patient's immune system against the cancer cells.