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The investigational therapy QTI571 (imatinib) significantly improves exercise capacity in patients with pulmonary arterial hypertension (PAH), according to the findings of a pivotal Phase III clinical trial presented at the European Respiratory Society (ERS) Annual Congress in Amsterdam.
Evidence indicates that QTI571 targets an underlying cause of PAH by counteracting uncontrolled growth of arterial smooth muscle cells.
The IMPRES study met its primary endpoint by demonstrating a significant improvement in the six-minute walk distance (6MWD) test in patients with elevated pulmonary vascular resistance (PVR) despite treatment with two or more specific PAH vasodilator therapies.
In the study, patients treated with QTI571 increased their mean 6MWD by 31.8 metres compared with placebo (p=0.002).
The study’s secondary endpoints showed that QTI571 produced statistically significant improvements compared to placebo in pulmonary arterial pressure, cardiac output and pulmonary vascular resistance (all p<0.001), but not in time to clinical worsening (i.e. death, hospitalisation due to PAH, worsening of functional class, or >=15% drop in 6MWD) (p=0.563).
“These results are impressive as they were achieved in patients who were already receiving two or more established PAH drugs,” said Marius Hoeper MD, Associate Professor, Department of Respiratory Medicine at Hannover Medical School, Germany.
Safety data showed that the overall incidence of adverse events was similar for QTI571 and for placebo. Serious adverse events and discontinuations due to serious adverse events were more frequent with QTI571.
Adverse events were as expected for this patient population and class of drug, and were similar to those previously reported with QTI571.
IMPRES was a 24-week randomised placebo-controlled, double-blind, multi-centre clinical trial evaluating the efficacy and safety of oral QTI571 as an add-on therapy in the treatment of patients with PAH.
The study involved a total of 202 patients with elevated PVR of >=800 dynes.sec.cm-5 despite treatment with at least two other specific PAH medications (i.e. endothelin receptor antagonists, phosphodiesterase-5 inhibitors and/or prostacyclins).
Treatment was initiated at a dose of 200 mg once-daily, which was increased to 400 mg once-daily after two weeks if well tolerated. The dose could be reduced to 200 mg once-daily if treatment was not well tolerated.
QTI571 is currently not approved to treat PAH and is due to be submitted for regulatory approval later this year for the treatment of this disease.
Imatinib, the active ingredient in QTI571, is currently available under the trade names Glivec® and Gleevec® for use in certain oncology indications.