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.
Riociguat has been approved under the trade name Adempas® by Health Canada for the treatment of inoperable, or persistent /recurrent chronic thromboembolic pulmonary hypertension (CTEPH) after surgery in adult patients with WHO Functional Class II or III pulmonary hypertension in September.
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)
PAH, one of the five types of pulmonary hypertension (PH), is a progressive and life-threatening disease in which the blood pressure in the pulmonary arteries is significantly increased due to vasoconstriction and which can lead to heart failure and death. PAH is characterized by morphological changes to the endothelium of the artery 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. PAH is a rare disease and affects an estimated 52 people per million globally. It is more prevalent in younger women than men. In most cases, PAH has no known cause and, in some cases, it can be inherited.
Despite the availability and advantages of several approved PAH therapies, the prognosis of patients remains poor and new treatment options are needed. Mortality of PAH patients remains high and is still 15% at 1 year; 32% at 3 years after diagnosis.
About Chronic Thromboembolic Pulmonary Hypertension (CTEPH)
CTEPH is a progressive and life-threatening disease and a type of PH, in which it is believed that thromboembolic occlusion (organized blood clots) of pulmonary vessels gradually lead to an increased blood pressure in the pulmonary arteries, resulting in an overload of the right heart. CTEPH is a rare disease and is comparable in terms of population size to PAH, though there are fewer diagnoses made so far. CTEPH may evolve after prior episodes of acute pulmonary embolism, but the pathogenesis is not yet completely understood. The standard and potentially curative 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, a considerable number of patients with CTEPH (20%-40%) are not operable and in up to 35% of patients, the disease persists or reoccurs after PEA. To date, no approved pharmacological therapy exists for CTEPH and, as a result, there is an urgent unmet medical need for patients who are unable to undergo surgery or who have persistent or recurrent pulmonary hypertension (PH) after surgery.
Riociguat (BAY 63-2521) is a soluble guanylate cyclase (sGC) stimulator, the first member of a novel class of compounds, discovered and developed by Bayer as an oral treatment to target a key molecular mechanism underlying PH. Riociguat is being investigated as a new and specific approach to treat different types of PH. sGC is an enzyme found in the cardiopulmonary system and the receptor for nitric oxide (NO). When NO binds to sGC, the enzyme enhances synthesis of the signaling molecule cyclic guanosine monophosphate (cGMP). cGMP plays an important role in regulating vascular tone, proliferation, fibrosis, and inflammation.
PH is associated with endothelial dysfunction, impaired synthesis of NO and insufficient stimulation of sGC. Riociguat has a unique mode of action - it sensitizes sGC to endogenous NO by stabilizing the NO-sGC binding. Riociguat also directly stimulates sGC via a different binding site, independently of NO. Riociguat, as a stimulator of sGC, addresses NO deficiency by restoring the NO-sGC-cGMP pathway, leading to increased generation of cGMP.
With its novel mode of action, Riociguat has the potential to overcome a number of limitations of currently approved PAH therapies, including NO dependence, and is the first drug which has shown clinical benefits in CTEPH, where no pharmacological treatment is approved.
About Bayer HealthCare
The Bayer Group is a global enterprise with core competencies in the fields of health care, agriculture and high-tech materials. Bayer HealthCare, a subgroup of Bayer AG with annual sales of EUR 18.6 billion (2012), is one of the world's leading, innovative companies in the healthcare and medical products industry and is based in Leverkusen, Germany. The company combines the global activities of the Animal Health, Consumer Care, Medical Care and Pharmaceuticals divisions. Bayer HealthCare's aim is to discover, develop, manufacture and market products that will improve human and animal health worldwide. Bayer HealthCare has a global workforce of 54,900 employees (Dec 31, 2012) and is represented in more than 100 countries.