Riociguat is approved for the treatment of inoperable or persistent/recurrent CTEPH following pulmonary endarterectomy, based on data from the CHEST-1 study, and its extension CHEST-2. The current analysis investigated application of the satisfactory clinical response (SCR) outcome measure (similar to that used in the AIR and AMBITION studies) to the CHEST data. This is the first time SCR has been applied to a database exclusively consisting of CTEPH patients.
In CHEST-1, patients received riociguat up to 2.5 mg tid or placebo for 16 weeks. All patients received riociguat up to 2.5 mg tid during CHEST-2. SCR status was calculated at CHEST-1 Week 16, and CHEST-2 Week 12. SCR was defined as: ≥10% improvement from baseline in 6MWD, WHO FC I/II, and no clinical worsening.
SCR status was determined for 250/261 patients in CHEST-1 (163 riociguat, 87 placebo). A greater proportion of riociguat-treated patients achieved SCR compared with placebo patients (39% versus 13%, respectively). In CHEST-2, SCR status was determined for 224 patients (147 former riociguat, 77 former placebo). Overall, 44% of patients achieved SCR (former riociguat, 46%; former placebo, 40%), with a greater proportion achieved in the inoperable versus persistent/recurrent CTEPH subgroup (49% versus 33%, respectively). Patients achieving components of the SCR had greater clinical worsening-free survival in CHEST-2 (Figure 1).
In CHEST-1, riociguat increased the proportion of patients achieving SCR compared with placebo. Further increases were observed during CHEST-2 and the proportion of patients achieving SCR was similar between former placebo and former riociguat patients.