Complex sentence: The biochemical activity of theophylline as a PDE inhibitor was then characterized in 1958, which prompted further research and classification and its introduction as a treatment for asthma and other airway diseases (Francis et al.2011).
Split into simpler sentences: The biochemical activity of theophylline as a PDE inhibitor was then characterized in 1958, which prompted further research and classification. Soon it was introduced as a treatment for asthma and other airway diseases (Francis et al.2011).