Bayer Healthcare recently announced the approval of its novel drug Adempas (riociguat), which has been listed by the Régie de l’assurance malady du Québec (RAMQ), the Québec public formulary, as the one and only treatment option for patients with chronic thromboembolic pulmonary hypertension (CTEPH). Québec is the first province to provide Adempas to the public.
The decision comes after Adempas was approved in 2013 as a therapeutic remedy for treating patients with CTEPH who either cannot be operated on, or who had the persistent condition even after surgery, with functional class II or III Pulmonary Arterial Hypertension (PAH), as specified by the WHO. Health Canada had passed a second approval for the treatment of PAH in March 2014. This is the first time, however, that the drug has been approved for public use as well.
CTEPH refers to the medical condition where the presence of a blood clot in the pulmonary blood vessels increases blood pressure in the pulmonary arteries, leading to PAH, and increases stress on the right side of the heart. Vasoconstriction is a common complication in this rare condition, caused mainly as a result of increased calcium within blood vessels and injury to the endothelial cells of the pulmonary vasculature. This causes a reduction in the synthesis of nitric oxide (NO), which is a common mediator of vasodilation.
NO binds to soluble guanylate cyclase (sGC), which leads to synthesis of a second messenger — cyclic guanosine monophosphate (cGMP). cGMP in turn activates cGMP dependent protein kinase G, which helps in regulating the vascular levels of calcium ions. Once this is regulated, the contractility of the actin and myosin filaments is altered and vasodilation causes the muscles to relax, relieving the stress of PAH.
Adempas (riociguat) has the ability to stimulate sGC without being directly dependent on NO, which is secreted in considerably lesser amounts during CTEPH and PAH. Together, with the secreted NO and its own stimulation properties, it acts synergistically in restoring calcium levels and inducing vasodilation.
Todate, Adempas is the only drug with a mode of action targeting the root cause of CTEPH and PAH pathophysiology, much different compared to the current short-term symptomatic treatments available. The launch of this drug into the PH treatment market is anticipated to serve as further motivation for researchers to continue to explore the pathobiology of PAH and decipher alternate novel strategies to combat the condition.
Dr. David Langleben, Professor of Medicine at McGill University and Director of the Center for Pulmonary Vascular Disease at the Jewish General Hospital in Montreal, said during a recent event that, “The availability of Adempas represents a major advance in the treatment of CTEPH patients who are not suitable for surgery to remove the clots, or who have persistent or recurring pulmonary hypertension after surgical clot removal. Adempas is the first and only medical therapy indicated for this disease.”
Similarly, Angie Knott, National Manager, Pulmonary Hypertension Association of Canada, added to this, saying, “PHA Canada applauds the Québec Government for its leadership in recognizing the severity and unmet medical need for patients with CTEPH. We would like to see this treatment available to all Canadians who need it in the very near future.”