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Combo Therapy Improves Lung Function in Cystic Fibrosis Patients

Phase II trial evaluates VX-661 and ivacaftor (Apr. 18)

In a phase II study, combination therapy with VX-661 and ivacaftor (Vertex Pharmaceuticals) showed statistically significant improvements in lung function in adults with cystic fibrosis (CF) who had two copies (homozygous) of the most common mutation (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

The study evaluated four dose levels of VX-661 (10, 30, 100, and 150 mg) dosed once daily for 28 days in combination with ivacaftor (150 mg) dosed twice daily (n = 65) in comparison with a group given placebo (n = 23). The study also evaluated a separate group of patients who received VX-661 (10, 30, 100, and 150 mg) dosed without ivacaftor for 28 days (n = 32) compared with placebo-treated patients (n = 23).

Patients in the 100-mg and 150-mg combination-therapy groups showed statistically significant mean relative improvements in lung function (percent predicted forced expiratory volume in 1 second [FEV1]) versus placebo of 9.0% (P = 0.01) and 7.5% (P = 0.02), respectively, at day 28. In contrast, patients who received placebo showed a 0.03% mean relative change in lung function at day 28.

Mean absolute and relative increases in lung function were observed in all of the VX-661 monotherapy dosing groups (10, 30, 100, and 150 mg) versus placebo at day 28, but these increases were not statistically significant.

CF is caused by a defective or missing CFTR protein resulting from mutations in the CFTR gene. In people with two copies of the F508del mutation, little or no CFTR protein reaches the cell surface. VX-661, a CFTR corrector, is believed to help CFTR proteins reach the cell surface. Ivacaftor, a CFTR potentiator, keeps cell-surface CFTR protein channels open longer to increase the flow of salt and water. Worldwide, nearly half of people with CF have two copies of the F508del mutation, and an additional one-third have one copy of the F508del mutation.

Source: Vertex Pharmaceuticals; April 18, 2013.

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