TORONTO — In patients with pulmonary arterial hypertension (PAH), switching from a phosphodiesterase type 5 (PDE5) inhibitor to riociguat improves pulmonary arterial compliance (PAC) significantly, according to findings from a prospective open-label phase 3b trial presented at CHEST 2017, held October 28 to November 1, in Toronto, Ontario, Canada.
Researchers presented data from the RESPITE (Riociguat clinical Effects Studied in Patients with Insufficient Treatment response to PDE5 inhibitors) study, which included patients with PAH (n=61) who had a poor response to PDE5 inhibitors. Riociguat was administered at a dose of up to 2.5 mg 3 times a day.
PAC rose by 0.22 mL/mm Hg (SD, 0.64; n=48) at 24 weeks compared with baseline values (95% CI, 0.036-0.407; P =.02). Participants who had World Health Organization (WHO) functional class of I/II at 24 weeks (n=26) demonstrated a 0.41-mL/mm Hg increase in PAC from baseline. No change was observed in patients who had WHO FC III disease (n=22).
The combined clinical end point of freedom from clinical worsening, WHO functional class I/II, and ≥30-minute increase in the 6-minute walking distance was met by 16 patients. Of these, all experienced greater PAC improvement (+0.55 mL/mm Hg; SD, 0.81) compared with patients who did not reach this end point (n=32; +0.06 mL/mm Hg; SD, 0.46).
In addition, investigators noted that a PAC baseline change was significantly associated with a change in cardiac index (r =0.46, P =.0009), pulmonary vascular resistance (r =–0.55, P <.0001), and mean pulmonary arterial pressure (r =–0.55, P <.0001).
“This post hoc analysis demonstrates the clinical relevance of assessing PAC for a more complete assessment of right ventricular function,” according to the investigators, “and suggests that determination of PAC may help to predict outcomes in patients with PAH.”
Thenappan T, Hoeper MM, PA Corris PA, et al. Effect of riociguat on pulmonary arterial compliance in patients with pulmonary arterial hypertension (PAH) in the RESPITE study. Presented at: CHEST 2017; October 28-November 1, 2017; Toronto, Ontario, Canada. Abstract 2743201.