The top line results show that none of the 36 patients enrolled in the 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).
One patient had a transient serum aminotransferase test result greater than three-times the upper limit of the normal range (3xULN) at week 12 that resulted in dose reduction from 5mg to 2.5mg ambrisentan. This patient remains on ambrisentan therapy and has not had a recurrence of serum aminotransferases greater than 3xULN.
Patients have continued to receive ambrisentan therapy for periods up to nine months (mean exposure of six months) and no further occurrence of serum aminotransferase concentrations greater than 3xULN has been observed.
“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,” stated Dr Michael Gerber, senior vice president of clinical development and regulatory affairs at Myogen. “I believe ambrisentan has the potential to be an important therapeutic option for these patients with PAH and their physicians.”