CTEPH Drug Therapy Safe and Effective During Phase 3 Extension Study

Approximately 5,000 Americans are diagnosed with chronic thromboembolic pulmonary hypertension (CTEPH) each year. The condition is a result of persistent obstruction of pulmonary blood vessels due to unresolved blood clots from previous episodes of acute pulmonary embolism. If patients do not receive treatment for CTEPH, they may develop pulmonary hypertension.

The current treatment of choice is pulmonary endarterectomy (PEA). Since PEA is a surgical procedure, patients considered to be inoperable are not candidates, and those who are operable see only a 70-80% success rate. Fortunately, a new treatment is on the horizon. A new drug from Bayer called Adempas (riociguat), which was approved by the European Commission in April, showed benefits in a long-term extension Phase 3 clinical trial.

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The trial, CHEST-2, was an extension of the successful 16-week CHEST-1 Phase 3 trial. “The pivotal study, CHEST-1, showed significant improvements in exercise capacity and hemodynamics in patients treated with riociguat,” said Marius Hoeper, MD, from the German Hannover Medical School, in a news article. “However, the study was relatively short, and CHEST-2 adds important information on the long-term tolerability and efficacy of riociguat in patients with CTEPH.”

Patients were treated in the CHEST trials for one year. At the conclusion of CHEST-1, a significant improvement in six-minute walking distance was seen in riociguat-treated patients compared to placebo. During CHEST-2, all enrolled patients were treated with riociguat, and only 6% withdrew from the study due to adverse events. At the end of CHEST-2, six-minute walking distance improved by 54 meters for inoperable patients and 44 meters for persistent/recurrent CTEPH patients. Furthermore, World Health Organization Functional Class improved in 46% of inoperable patients and 47% of persistent/recurrent patients. Only 5% of inoperable patients worsened, and no persistent/recurrent patients worsened.

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The CHEST-2 trial, which was presented at the 2014 American Thoracic Society International Conference, represented 237 patients in total, with 73% considered inoperable. Riociguat, a guanylate cyclase stimulator that induces vasodilation to allow easier blood flow, may soon be an important therapeutic to help these and other patients with CTEPH.