Bayer HealthCare today announced that the U.S. Food and Drug Administration's (FDA) Office of Orphan Products Development has granted two separate orphan drug designations for its investigational, oral medication riociguat, proposed trade name Adempas®, for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). The Orphan Drug Designation program provides orphan status to drugs and biologics that are defined as those intended for the safe and effective treatment, diagnosis or prevention of rare diseases and disorders that affect fewer than 200,000 people in the U.S., or that affect more than 200,000 persons but are not expected to recover the costs of developing and marketing a treatment drug.

Bayer submitted a New Drug Application (NDA) for riociguat in February 2013 for two indications: (i) the treatment of PAH (WHO Group 1) to improve exercise capacity, improve WHO functional class and delay clinical worsening; and (ii) the treatment of persistent/recurrent CTEPH (WHO Group 4) after surgical treatment or inoperable CTEPH to improve exercise capacity and WHO functional class.

PAH and CTEPH are both life-threatening forms of pulmonary hypertension that cause significantly increased pressure in the pulmonary arteries. Riociguat is an investigational, oral medication for the treatment of adult patients with PAH or persistent/recurrent CTEPH after surgical treatment or inoperable CTEPH.  If approved by the FDA, it would create a new class of drugs available in the U.S.  Pulmonary hypertension is associated with endothelial dysfunction, impaired synthesis of nitric oxide (NO) and insufficient stimulation of soluble guanylate cyclase (sGC). Riociguat stimulates sGC independent of NO and increases the sensitivity of sGC to NO.

About Pulmonary Arterial Hypertension (PAH)

In PAH, a rare and life-threatening disease, the blood pressure in the pulmonary arteries (the arteries that take de-oxygenated blood to the lungs from the heart) is significantly increased.  PAH is characterized by morphological changes to the endothelium of the arteries of the lungs causing remodeling of the tissue, vasoconstriction and thrombosis-in-situ. As a result of these changes, the blood vessels in the lungs are narrowed, making it difficult for the heart to pump blood through to the lungs. In most cases, PAH has no known cause and, in some cases, it can be inherited.

About Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

CTEPH is also a rare and life-threatening disease in which it is believed that thromboembolic occlusion (organized blood clots) of pulmonary vessels gradually lead to an increased pressure in the pulmonary arteries, resulting in an overload of the right heart. CTEPH may evolve after prior episodes of acute pulmonary embolism, but the pathogenesis is not yet completely understood. The standard treatment for CTEPH is pulmonary endarterectomy (PEA), a surgical procedure in which the blood vessels of the lungs are cleared of clot and scar material. However, CTEPH is inoperable in an estimated 20 to 40 percent of patients, and, in some cases, the disease persists or reoccurs after surgery.