Bayer initiates trial to assess riociguat for resistant pulmonary arterial hypertension

Bayer HealthCare announced enrollment of the first participant in the phase 3b RESPITE study.

The open-label, multicenter, international pilot study will assess the soluble guanylate cyclase stimulator riociguat (Adempas) in patients with pulmonary arterial hypertension who are resistant to treatment with phosphodiesterase-5 (PDE5) inhibitors, according to a press release.

The trial will include approximately 60 patients with PAH who received at least 3 months of prior treatment with sildenafil (Viagra/Revatio, Pfizer) or tadalafil (Cialis, Lilly) and did not demonstrate sufficient clinical responsiveness to PDE5 inhibitor treatment. Participants will receive 24 weeks of riociguat after a wash-out period, with assessed outcomes including improvements in 6-minute walk distance, cardiac index, quality of life, WHO functional class, nitric oxide biomarkers and other relevant parameters, according to the release.

“In many guidelines and for many regulatory bodies worldwide, PDE5 inhibitors are currently an established therapy for patients with PAH in WHO functional class II and III, and for many patients they are a well-tolerated and effective treatment option,” researcher Marius M. Hoeper, MD, from Hannover University Medical School in Germany, stated in the release. “However, there is still a substantial number of PAH patients who do not reach treatment goals while receiving PDE5 inhibitors. The RESPITE study is designed as a first step to provide important data on the clinical effects of riociguat in this particular patient population.”

The RESPITE study follows results from the phase 3 PATENT-1 study, in which riociguat demonstrated efficacy across several clinically relevant endpoints for this population, both alone and in combination with prostacyclin analogue or endothelin receptor antagonist therapies, according to the release.

Riociguat was approved in the United States to treat chronic thromboembolic pulmonary hypertension and PAH in October 2013. The drug can be administered in combination with endothelin receptor antagonists and prostacyclin analogues, but combination with PDE5 inhibitors is contraindicated as it can adversely impact BP, according to the release.