Tracleer (bosentan) is a therapy manufactured by Actelion Pharmaceuticals and approved by the U.S. Food and Drug Administration for patients with pulmonary arterial hypertension (PAH).

Although approved in Europe to treat digital ulcers in scleroderma patients, it has not yet been approved for this purpose by the FDA. Both PAH and digital ulcers can develop in scleroderma patients due to poor blood flow.

How Tracleer works

Tracleer is an endothelin receptor antagonist (ERA). It works by stopping the action of endothelin, which is a natural substance that causes blood vessels to narrow. In people with scleroderma, the abnormal formation of scar tissue around blood vessels restricts normal blood flow. By inhibiting endothelin, Tracleer allows blood to circulate more freely. This reduces the risk or delays the development of PAH and digital ulcers.

Tracleer in clinical trials for scleroderma

The effect of Tracleer on digital ulcers in scleroderma patients was evaluated in a randomized, double-blind Phase 3 clinical trial (NCT00077584). The primary objectives of the study included the number of new digital ulcers and the ulcers’ healing time after a 24-week treatment period with Tracleer. Secondary outcomes included pain, disability, and safety of the treatment.

Results of the trial, published in the scientific journal Annals of the Rheumatic Diseases, showed that Tracleer reduced the occurrence of new digital ulcers in patients with scleroderma but had no effect on the healing of existing digital ulcers.

The effects of Tracleer and other ERAs on skin fibrosis in scleroderma were tested in a cohort study conducted by the European Scleroderma Trials and Research Group. Researchers analyzed 68 patients who were treated with Tracleer and seven who were treated with others ERAs. They compared these patients with 969 patients who were not treated. Results, published in the Journal of Scleroderma and Related Disorders, showed there was no difference in the progression of skin fibrosis between patients who were treated and those who were not. The researchers concluded that the therapy was not effective for skin fibrosis in scleroderma patients.

The effects of long-term treatment with Tracleer on PAH in scleroderma patients were tested between 2003 and 2014 in a study conducted in Europe. From the 69 patients enrolled, 25 developed digital ulcers and were treated with 62.5 mg of Tracleer twice a day for four weeks, then with 125 mg of Tracleer twice a day. Patients who did not develop digital ulcers were included in the control group and were not treated with the medicine.

Results of the trial, published in the Journal of International Medical Research, showed that none of the treated patients developed PAH during the 12-year follow-up period. Moreover, patients treated with Tracleer had a better overall respiratory capability and ability to exercise as measured by the six-minute walk test, used to assess aerobic capacity and endurance, and the Borg dyspnea scale, a noninvasive test for the prediction of inspiratory muscle weakness. In contrast, patients in the control group showed a degradation in all parameters tested and some developed PAH.

Other details

The most common side effects of Tracleer are headaches, flushing, itching, runny nose, sore throat and other cold symptoms, and heartburn. Serious side effects include liver toxicity and birth defects.

Tracleer is therefore only available through a risk evaluation and mitigation strategy program, which is required by the FDA to manage serious risks associated with a certain product. According to the program, patients using Tracleer must undergo monthly liver function and pregnancy blood tests and complete a Tracleer patient enrollment and consent form.

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