Bayer HealthCare announced data from the Phase 3 PATENT-1 pulmonary arterial hypertension (PAH) trial evaluating its investigational drug riociguat in both treatment-naive patients and those pre-treated with an endothelin receptor antagonist or an oral, inhaled or subcutaneous prostanoid.

PATENT ( P ulmonary A rterial Hyper ten sion sGC-Stimulator T rial) is an ongoing Phase 3 trial to assess oral riociguat in the treatment of treatment naive patient and pre-treated patients with symptomatic PAH.  PATENT is a multi-center, multi-national program with active centers in 32 countries. The program includes a randomized, double-blind, placebo-controlled trial phase (PATENT-1) and an open label extension trial phase (PATENT-2).

In the PATENT-1 study, 445 patients with symptomatic PAH were randomized to receive either placebo or two different doses of riociguat orally over a period of 12 weeks.  The riociguat dose is titrated, over a period of eight weeks in doses of 0.5mg increments from 1mg up to 2.5mg three times daily. Patients are then followed for an additional four weeks to complete the study. Patients then have the option of participating in the open label extension study, after completing an eight-week blinded sham titration.

The study met its primary endpoint by demonstrating a statistically significant improvement in the six-minute walk distance (6MWD) with patients treated with riociguat showing an improvement of 36 meters 95% CI [20–52 meters] (P<0.0001) after 12 weeks compared with placebo. In addition to meeting its primary endpoint, trial results also showed a statistically significant improvement in 6MWD both in the treatment-naive patient group (38 meters after 12 weeks compared with placebo [95% CI 15–62 meters]) and the pre-treated patient group (36 meters after 12 weeks compared with placebo [95% CI 15–56 meters]).

Statistically significant improvements were also observed across secondary endpoints including pulmonary vascular resistance (PVR) (P<0.0001), N-terminal prohormone brain natriuretic peptide (NT-pro BNP) (P<0.0001), WHO functional class (FC) (P=0.0033), time to clinical worsening (TTCW) (P=0.0046) and Borg dyspnea score (P=0.0022). Secondary endpoints that did not achieve statistical significance include the European quality of life 5-dimensions questionnaire (EQ-5D) (P=0.0660) and living with pulmonary hypertension questionnaire (LPH) (P=0.0019).

Riociguat (BAY 63-2521) is an investigational oral soluble guanylate cyclase (sGC) stimulator. 

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