Pharmacological Validation of Vascular KATP Channels for Modulating Ductus Arteriosus Tone

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PROJECT SUMMARY The ductus arteriosus (DA) is an essential fetal artery connecting the aorta and pulmonary artery, which shunts blood away from the developing lungs in utero . Circulatory adaptation at birth requires rapid constriction of the DA to facilitate proper perfusion of the newly inflated lungs. Persistent patency of the neonatal DA (PDA) is a significant clinical problem that is inefficiently managed with currently available therapies. Pharmacology-based PDA therapeutics non-specifically target the prostaglandin pathway, have worrisome off target effects on other vascular beds, and are ineffective in approximately 30% of patients. While surgical ligation and catheter-based closure are effective alternatives, these mechanical approaches come with their own risks and limitations. Consequently, there is a significant need to identify and rigorously validate novel drug targets for manipulating DA tone. An emerging body of physiological and genetic data from our group and others has implicated vascular ATP-regulated potassium (KATP) channels as novel drug targets for regulating DA tone. Specifically, we show here for the first time that KATP channels comprised of pore-forming Kir6.1 and regulatory SUR2B subunits are highly enriched in smooth muscle cells of the PDA and regulate DA tone in response to pharmacological modulation. Unfortunately, the lack of specific Kir6.1/SUR2B inhibitors (and activators) has precluded a rigorous assessment of the therapeutic potential of DA KATP channels for treating PDA. In this multi-PI collaboration, which will benefit from complementary expertise in potassium channel drug discovery (Drs. Denton/Lindsley) and DA physiology and pharmacology (Dr. Shelton), we propose to employ high- throughput screening (HTS) and medicinal chemistry to develop an extensive “tool kit” of vascular-specific KATP channel modulators for validating Kir6.1/SUR2B channels for regulating DA tone in vitro and in vivo. In Aim 1, we will employ a fully validated HTS assay to interrogate ~110,000 small molecules for potent and selective Kir6.1/SUR2B modulators. In Aim 2, we will use medicinal chemistry to optimize lead compounds for selectivity and potency and determine compound metabolism and pharmacokinetic properties. In Aim 3, we will evaluate the efficacy of lead compounds to regulate mouse and human DA tone using isolated vessel myography assays and in vivo mouse models of PDA. The successful completion of these aims will generate critically needed tool compounds for modulating DA tone and validate Kir6.1/SUR2B channels as novel therapeutic targets for treating PDA.