Phosphodiesterase signaling in asthma: mechanistic insights and emerging therapeutic strategies.

Asthma is a clinically and biologically heterogeneous disease for which current anti-inflammatory therapies, including inhaled corticosteroids, remain insufficient for many patients. Therefore, repurposing other FDA-approved drugs, such as phosphodiesterase (PDE) inhibitors, may be beneficial in the management of asthma. PDEs are central regulators of cyclic nucleotide signaling, modulating airway smooth-muscle tone, mucociliary function, and immune-cell activity by compartmentalizing the control of cAMP and cGMP. Although PDE4 inhibitors have shown strong pre-clinical efficacy, their translation into clinical practice has been hindered by dose-limiting systemic toxicities, revealing a persistent gap between mechanistic promise and therapeutic utility. This review synthesizes emerging insights into PDE isoenzyme selectivity, spatial localization, and cross-regulatory interactions across structural and immunocompetent airway cells. We outline how isoform- and splice-variant-specific functions contribute to key asthmatic phenotypes and evaluate innovative therapeutic strategies, including dual PDE3/4 inhibition, inhaled delivery approaches, and next-generation selective modulators designed to overcome historical limitations. By integrating these advances within an endotype-driven precision-medicine framework, this review provides a path toward unlocking the full therapeutic potential of PDE-targeted interventions in asthma.