Myogen's study of ambrisentan for pulmonary arterial hypertension shows positive top line results

By Lisa Kerner

Erie, Pa., Feb. 13 - Myogen, Inc. reported positive top line results of its AMB-222 study, an open-label trial of ambrisentan in patients with pulmonary arterial hypertension who have previously discontinued bosentan and/or sitaxsentan treatment due to liver function abnormalities.

Pulmonary arterial hypertension is a debilitating disease characterized by severe constriction of the blood vessels in the lungs leading to very high pulmonary arterial pressures, making it difficult for the heart to pump blood through the lungs. Approximately 200,000 patients worldwide are afflicted with pulmonary arterial hypertension, according to a company news release.

Ambrisentan is an investigational drug being developed as a once daily oral therapy for patients with pulmonary arterial hypertension and has been granted orphan drug designation for the treatment of the condition in both the United States and the European Union.

Myogen said none of the 36 patients enrolled in the dose-escalated study had a recurrence of liver function abnormalities that resulted in discontinuation of ambrisentan during the initial 12-week evaluation period, the primary endpoint of the study.

"These results suggest that for patients who have had to stop treatment with other endothelin receptor antagonists due to liver function abnormalities, ambrisentan may offer an opportunity to resume treatment," Myogen senior vice president of clinical development and regulatory affairs Michael J. Gerber said in the release.

"I believe ambrisentan has the potential to be an important therapeutic option for these patients with PAH [pulmonary arterial hypertension] and their physicians. The low incidence and severity of liver function test abnormalities demonstrated in the Aries-2 trial and the AMB-222 rescue study are very encouraging."

The top line results of the Aries-2 and AMB-222 trials, as well as the results to date of Myogen's phase 2 trial of ambrisentan in PAH (AMB-220) and related long-term study (AMB-220-E) have demonstrated:

• Effectiveness with once-daily dosing and the potential for dose and flexibility;

• Low incidence and severity of liver function test abnormalities at all doses;

• Ultimately no apparent drug-drug interactions with warfarin-type anticoagulants.

Myogen is a Denver-based biopharmaceutical company focused on the discovery, development and commercialization of small molecule therapeutics for the treatment of cardiovascular disorders.

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