Background: Despite the benefits of reperfusion therapy after myocardial infarction (MI), one-year mortality and morbidity rates remain high. Silver Creek Pharmaceuticals is engineering a new class of protein therapeutics, termed Smart Growth Factors (SGFs), designed to act directly on cardiomyocytes (CMs) to promote survival and regeneration after ischemia/reperfusion (I/R) injury. Our approach is to maximize pro-survival growth factor signaling in damaged cells by creating targeted molecules with optimized pharmacokinetics and dynamics.
Methods and Results: Computer model simulations guided the design of a panel of SGFs comprising various growth factors, targeting arms, half-life modulators, and linkers. SGF constructs were cloned and subsequently produced using a HEK 293F expression system. This panel was screened in vitro for signaling pathway activation and target affinity. The top hits were assayed for pro-survival activity in a chemical injury model in human CMs, where a targeted SGF significantly reduced caspase activation (p<0.0084; SGF-treated 3.82±0.64-fold, IGF1-treated 16.25±3.6-fold) Based on these data and additional simulations, a class of SGFs that utilized annexin V to target IGF1 to apoptotic cells via phosphatidylserine binding was selected for screening in animal models. In vivo, these SGFs extended pAKT signaling in heart tissue compared to wild-type IGF1 and had increased accumulation in the infarcted region of mouse hearts after MI. Preliminary data suggests that a single low intravenous dose (16 pmol) of SGF delivered one hour after LAD ligation could significantly reduce scar size in animals assessed at 12 weeks post MI (p<0.05; SGF-treated 9.3±1.3%, n=10; vehicle 18.1±3.13%, n=8). Finally, SGF treatment at the time of reperfusion in a rat I/R model was able to significantly reduce infarct size (p<0.05; SGF-treated 27.0±1.8% n=7; vehicle 33.6±1.92% n=8).
Conclusions: This work demonstrates an enhanced ability of SGFs in preventing apoptosis in vitro and reducing infarct sizes in animal models of MI. By taking a systems biology approach to SGF engineering, Silver Creek is developing cardioprotective therapies with the hope of improving patient health and addressing unmet medical need.