(1120-A) Using a high-throughput drug optimization platform to optimize patient-specific drug treatments for aortic valve stenosis

Abstract: Aortic valve stenosis (AVS) is a progressive cardiovascular disease characterized by the fibrosis and eventual calcification of the aortic valve leaflet, leading to patient death if left untreated. Importantly, AVS is also sexually dimorphic where female patients present with a more fibrotic phenotype relative to men who experience more calcification. Sex-specific AVS pathophysiology is largely regulated by the behavior of valvular interstitial cells (VICs), which are the resident fibroblast found in the aortic valve. During normal wound healing, these cells activate to a myofibroblast phenotype to facilitate wound repair, then return to a quiescent state. However, during AVS progression, VICs remain persistently activated to a myofibroblast phenotype and continue to secrete excessive extracellular matrix leading to valvular fibrosis. Currently, AVS is treated through valve replacement procedures, but this is an imperfect treatment due to patients frequently experiencing restenosis of the valve leaflet. Thus, there is an urgent need to develop effective drug therapies as an alternative approach to treatment. However, to date, no successful drug therapies have been developed to treat AVS, likely due to a failure to account for patient heterogeneity and cellular sex differences. Indeed, prior work has shown that female VICs are more prone to persistently activating to a myofibroblast phenotype and less responsive to drugs that target myofibroblast signaling pathways relative to male VICs. Given these findings, we believe that effective drug therapies for AVS will likely need to be customized for individual patients to account for the known sex differences in AVS pathophysiology as well as differences in patient serum factors which are known to regulate VIC drug sensitivity. We hypothesize that female VICs will be less responsive to doses of a variety of anti-fibrotic drugs individually relative to male VICs and will require drug combinations to effectively inhibit myofibroblast activation. Moreover, we hypothesize that VIC drug sensitivity will be patient-specific, as serum factors vary in concentration between patients and have been shown to modulate VIC myofibroblast activation. To test these hypotheses, we have developed a new, high-throughput drug optimization platform to rapidly screen through drug treatments and cultured VICs with serum collected from AVS patients.

We found that six drugs targeting myofibroblast signaling pathways (Y-27632, LY-294002, H1152, SB203580, TM-5441, and Losartan) were more effective in male VICs, whereas only two inhibitors were more effective in female VICs (irosustat and SD-208) as measured by the absolute EC20 value. Additionally, we found that VIC drug sensitivity is highly regulated by AVS serum factors as VICs cultured with serum from one female patient sample were resistant to 7 out of 8 anti-fibrotic drugs, whereas serum from two other female patients resulted in resistance to only one anti-fibrotic drug. Lastly, we demonstrate that low dose combinations of LY-294002 and H-1152 trend towards being more effective in female VICs relative to male VICs, motivating the further investigation of additional drug combinations.

This work demonstrates the importance of accounting for sex-specific and patient-specific biology when testing and developing drug treatments. Ongoing work includes developing drug combinations that are optimized for individual patients using AVS patient sera and expanding the capabilities of our drug screening platform. In sum, optimizing drug combination treatments and accounting for patient differences in serum factors may lead to the development of more effective drug therapies to treat AVS.