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PK10453, a Non-Selective PDGF Receptor Inhibitor, Prevents the Progression of Pulmonary Arterial Hypertension

Venkatrao Medarametla

Stephen Festin

Amir Naqwi

Timothy Wiedmann

Lawrence Zisman

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Conference: 2014 International PHA Conference and Scientific Sessions

Release Date: 06.22.2014

Presentation Type: Abstracts

File Download: 2014 Conference Abstract - Lawrence Zisman

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PDGF signaling is activated in human pulmonary arterial hypertension (PAH) and in animal models of the disease. This study tested the hypothesis that a novel non-selective inhaled PDGF receptor inhibitor, PK10453, would decrease PAH both in the rat monocrotaline (MCT) and the rat MCT plus pneumonectomy (+ PN) models of PAH.

Background: PDGF signaling is activated in human pulmonary arterial hypertension (PAH) and in animal models of the disease. This study tested the hypothesis that a novel non-selective inhaled PDGF receptor inhibitor, PK10453, would decrease PAH both in the rat monocrotaline (MCT) and the rat MCT plus pneumonectomy (+ PN) models of PAH.

Methods: PK10453 and imatinib were characterized by Z-lyte kinase assays. In cell Westerns were used to determine IC50 for inhibition of PDGFAA and PDGFBB stimulated AKT phosphorylation in human fetal lung fibroblasts. PK10453 was delivered by inhalation, three times a day for two weeks, in the MCT  and MCT+PN models. Pulmonary artery pressures were monitored with implanted telemetry devices, and right ventricular pressure volume loops were obtained. Pulmonary arteriolar hypertrophy and neointimal proliferation were quantified. The distribution of PDGFAA, PDGFBB, PDGFR alpha and PDGFR beta, as well was phosphorylated PDGF receptors were examined with immunohistochemistry. Immunoassays were performed to quantify phosphorylated AKT, STAT3, and ERK1/2 in lungs of animals with MCT+PN induced PAH.

Results: PK10453 decreased right ventricular  systolic pressure (RVSP) in both the rat MCT and rat MCT+PN models: vehicle MCT group (n=6) RVSP was 80.4± 2.6 mm Hg; in the D4 (four minute aerosol exposure 3x/day) MCT group (n=6), 44.4 ±5.8 mm Hg; and in the D8 (eight minute exposure 3x/day) MCT group (n=5), 37.1± 4.5  mm Hg (p<0.001 vs. vehicle); in the vehicle MCT+PN group (n=9) RVSP was 75.7±7.1 mm Hg; in the D4 MCT+PN group (n=10), 40.4±2.7 mm Hg, and in the D8 MCT +PN group (n=8), 43.0±3.0 mm Hg (p<0.001). In the MCT + PN model, telemetry monitoring of pulmonary artery pressures demonstrated that PK10453 prevented the progression of PAH. Imatinib given by inhalation was equally effective in the MCT model, but was not effective in the MCT+PN model. Phosphorylated PDGF beta receptor was increased compared to the PDGF alpha receptor in neointimal and perivascular lesions found in the MCT+PN model. Imatinib was selective for the PDGF alpha receptor whereas PK10453 had a lower IC50 for inhibition of kinase activity of both the PDGF alpha and beta receptors. PK10453  decreased the ratio of phosphorylated AKT (Ser473) to total AKT, phosphorylated STAT3  (Y705) to total STAT3, the ratio of diphosphorylated ERK1 to total ERK1 and the ratio of monophosphorylated ERK1 to total ERK1 in lung extracts from MCT + PN animals.  

Conclusion: PK10453, when delivered by inhalation, significantly decreased the progression of PAH in the  MCT and MCT + PN models. Inhibition of both PDGF alpha and beta receptor kinases  may have a therapeutic advantage over selective PDGFR alpha inhibition in PAH.

Type: Basic Science