Verona Pharma has announced positive results from a clinical trial using its formulation of RPL554, an inhaled drug under development for COPD, cystic fibrosis, and asthma.

RPL554 is an inhibitor of the phosphodiesterase 3 (PDE3) and phosphodiesterase 4 (PDE4), two enzymes known to be of importance in the development and progression of immunological respiratory diseases. The drug has the potential to act as both a bronchodilator and an anti-inflammatory, which would make it significantly different from existing drugs. RPL554 is being developed as a nebulized treatment for acute exacerbations in patients with chronic obstructive pulmonary disorder (COPD) in a hospital or home-care setting.

In the double-blind, randomised, placebo-controlled, seven way crossover Phase 2a clinical trial, 29 patients with mild to moderate persistent asthma received four doses of nebulized RPL554 (0.4 to 24 mg), two doses of nebulised salbutamol (2.5 mg and 7.5 mg), or a placebo.

The trial met its primary endpoint, showing treatment with nebulized RPL554 demonstrated a dose-dependent bronchodilator response in patients with asthma. The pharmacokinetics of RPL554 were linear across the entire dose range. At the highest doses of both drugs, RPL554 produced the same maximum bronchodilator effect as salbutamol.

Even the lowest dose of RPL554 (0.4 mg) was found to be statistically significantly superior to the placebo as a bronchodilator. All doses of RPL554 were well tolerated. Therefore, the results support the use of RPL554 in a twice-daily regimen.

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