Switching to Riociguat Effective for Some Patients With PAH

Andrew D. Bowser and MDedge News

October 27, 2020

In patients with intermediate-risk pulmonary arterial hypertension (PAH) who are not at treatment goal on standard therapy, switching to riociguat is a promising strategy across a broad range of patient subgroups, an investigator said at the annual meeting of the American College of Chest Physicians, held virtually this year.

Patients switching to riociguat in the REPLACE study more frequently met the primary efficacy endpoint, compared with patients who remained on a phosphodiesterase-5 (PDE5) inhibitor, said Marius M. Hoeper, MD, of the Clinic for Respiratory Medicine at Hannover (Germany) Medical School.

That clinical benefit of switching to riociguat, a soluble guanylate cyclase (sGC) stimulator, was relatively consistent across patient subgroups including age, sex, PAH subtype, according to Hoeper.

"At the end of the day, we believe that switching from a PDE5 inhibitor to riociguat can benefit patients with PAH at intermediate risk and may serve as a new strategic option for treatment escalation," he said in a live virtual presentation of the study results.

About 40% of patients switching to riociguat met the primary endpoint of clinical improvement in absence of clinical worsening versus just 20% of patients who stayed on a PDE5 inhibitor, according to top-line results of the phase 4 REPLACE study, which were reported Sept. 7 at the annual meeting of the European Respiratory Society.

Results of REPLACE presented at the CHEST meeting show a benefit across most patient subgroups, including PAH subtype and whether patients came from monotherapy or combination treatment to riociguat. Some groups did not appear to respond quite as well to switching, including elderly patients, patients with a 6-minute walk distance (6MWD) of less than 320 meters at baseline, and patients switching from tadalafil as opposed to sildenafil. However, these findings were not statistically significant and may have been chance findings, according to Hoeper.

These results of REPLACE suggest the efficacy of riociguat "across the board" for intermediate-risk PAH patients with inadequate response to standard therapy, said Vijay Balasubramanian, MD, FCCP, clinical professor of medicine at the University of California San Francisco, Fresno.

Based on REPLACE results, switching from a PDE5 inhibitor to riociguat is now a "strong potential option" beyond adding a third drug such as selexipag or an inhaled prostacyclin to usual treatment with a PDE5 inhibitor plus an endothelin receptor antagonist, Balasubramanian said in an interview.

"We now have an evidence-based option where you can stay on a two-drug regimen and see whether the switch would work just as well," said Balasubramanian, vice chair of the Pulmonary Vascular Disease Steering Committee for the American College of Chest Physicians.

REPLACE is a randomized phase 4 study including 226 patients with PAH considered to be at intermediate risk according to World Health Organization functional class III or 6MWD of 165–440 meters. The composite primary endpoint was defined as no clinical worsening (death, disease progression, or hospitalization for worsening PAH) plus clinical improvement on at least two measures including an improvement in 6MWD, achieving WHO functional class I/II, or a decrease in N-terminal pro-brain natriuretic peptide (NT-proBNP).

The primary endpoint of REPLACE was met, showing that 45 patients (41%) who switched to riociguat had clinical improvement without clinical worsening versus 22 patient (20%) who stayed on the PDE5 inhibitor (odds ratio, 2.78; 95% confidence interval, 1.53–5.06; P = .0007), Hoeper reported.

The benefit appeared consistent across PAH subgroups, according to Hoeper. In patients with idiopathic, heritable, or drug- and toxin-induced PAH, the primary endpoint favored riociguat over PDE5 inhibitor, at 45% and 23%, respectively. Similarly, a higher proportion of patients with PAH associated with congenital heart disease or portal hypertension achieved the primary endpoint (46% vs. 8%), as did patients with PAH associated with connective tissue disease (25% vs. 16%).

Adverse events were seen in 71% of riociguat-treated patients and 66% of PDE5 inhibitor–treated patients, according to Hoeper, who said severe adverse events were more frequent with PDE5-inhibitor treatment, at 17% versus 7% for riociguat. There were three clinical worsening events in the PDE5 inhibitor group leading to death, while a fourth patient died in safety follow-up, according to the reported results, whereas there were no deaths reported with riociguat.

The REPLACE study was cofunded by Bayer AG and Merck Sharpe & Dohme, a subsidiary of Merck & Co. Hoeper reported receiving fees for consultations or lectures from Acceleron, Actelion, Bayer AG, Janssen, MSD, and Pfizer.

CHEST 2020: American College of Chest Physicians Annual Meeting. Abstract A2156-A2159.

This article originally appeared on MDEdge.com.

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