Tolerability of Switch to Macitentan from Bosentan in Pulmonary Arterial Hypertension

Objectives: Pulmonary arterial hypertension (PAH) is a progressive disease that can be treated with several medications. Macitentan, an endothelin receptor antagonist (ERA), has received approval as a PAH therapy. We report our data regarding the tolerability in patients with PAH who were switched from bosentan to macitentan. Methods: At the Baylor Pulmonary Hypertension Program, 24 patients with PAH who had been taking bosentan and were switched to macitentan were identified in this retrospective study. Data from these patients who switched from bosentan 125 mg orally twice per day to macitentan 10 mg orally daily (between October 2013 and February 2015) when macitentan became commercially available were collected. Patients were advised to take their last evening dose of bosentan and then take the first dose of macitentan the following morning within 12 to 24 hours of the last bosentan dose. Baseline data and postswitch data, including 6-minute walk distance, brain naturietic peptide, alanine transaminase (ALT) and aspartate transaminase (AST) levels, World Health Organization Functional Class (WHO FC), Borg dyspnea score, presence of peripheral edema. Results: At the time of the switch, the mean age was 58 ± 13 (mean ± standard deviation) years, the duration of disease was 6.6 ± 4.4 years, 21 patients were women, 54% were white, and 25% had idiopathic PAH. The mean duration of follow-up after the switch was 5.7 ± 1.5 months. The 6-minute walk distance was 344 ± 106 m preswitch and 319 ± 85 m postswitch (P = 0.18). Brain naturietic peptide levels were 91 ± 170 pg/mL preswitch and 90 ± 137 pg/mL postswitch (P = 0.93). At the time of the switch, 42% were WHO FC II and 50% had edema, and 55% had edema. AST and ALT remained unchanged postswitch. Two patients did not tolerate the switch to macitentan and had to be returned to bosentan: one patient with portopulmonary hypertension developed elevated AST and ALT and the second patient's macitentan was stopped because of malaise and tachyarrhythmia. One patient who underwent a successful liver transplant had macitentan stopped following the transplant. Conclusions: A rapid switch from bosentan to macitentan was well tolerated and safe with maintained WHO FC, with no significant change in edema and liver enzyme levels. The switch from bosentan to macitentan eliminates the need for monthly liver function test monitoring and removes the potential for bosentan treatment interruption.