New treatment strategies in cystic fibrosis: rhDNase.

Cystic fibrosis (CF) is the commonest inherited disease of the Caucasian population, with a high morbidity and mortality from pulmonary disease. The high viscoelasticity of CF sputum is due, in part, to the high deoxyribonucleic acid (DNA) content. Recombinant human deoxyribonuclease I (rhDNase) has been developed and in vitro studies have shown that it reduces the viscoelasticity of CF sputum. This article reviews the in vivo clinical studies conducted to determine the safety and efficacy of rhDNase in the treatment of pulmonary disease in CF. Initial Phase I studies showed preliminary safety and some evidence of clinical benefit. Subsequently, two Phase II studies were conducted in the US and UK during which patients received rhDNase for 10 days. A Phase III study of 24 weeks duration involving 968 patients in 51 centres in North America is also reported in detail. Longer term open-label studies, the results of intermittent administration, administration to severely ill patients and the use of different delivery systems are reviewed. The Phase II study reported improvements in pulmonary function and had a good safety profile. The Phase III study showed improvement in forced expiratory volume in one second (FEV1) of 5.8 and 5.6% in patients treated once and twice daily, respectively. The risk of developing an exacerbation was reduced by 28% with once daily treatment and 37% with twice daily treatment compared to placebo. The drug was safe and there was some improvement in quality of life data. Recombinant human deoxyribonuclease is a new therapy for pulmonary disease in cystic fibrosis which has been shown to benefit patients when used in conjunction with conventional therapy.