The Regencor-proprietary variant of the human protein FSTL1 (REG101) promotes cardiac regeneration after myocardial infarction in multiple rodent and adult pig models. The overall goal of the TRAN1-12907 grant program was to produce GMP-like REG101 and to demonstrate safety and efficacy in infarcted pigs treated with subcutaneously administered REG101 using the Evolve wearable Injector, and to submit the resulting data to FDA for a Pre-IND meeting. A secondary goal was to demonstrate that REG101 safely exerted its beneficial effects on heart muscle cells in culture derived from both genders and multiple genetic backgrounds. Both the overall goal and the secondary goal were successfully achieved, and all grant milestones were met successfully.

GMP-like Production of REG101

The original reagent-grade FSTL1 protein was produced by fermentation in bacteria. Three well known US bacterial fermentation CROs were unable to scale or improve the bacterial process to yield material that could be advanced to large animal or clinical studies. We then re-engineered the human FSTL1 gene to enable its production in mammalian cells without glycosylation (addition of large carbohydrate groups) which is required for regenerative activity. WuXi Biologics performed this work under contract with Regencor and successfully produced, at scale, highly purified and well characterized REG101 that met our release specs and was therefore suitable for animal and clinical testing.

Evolve Wearable Injector

Working with Becton Dickinson, we tested Regencor’s FSTL1 protein delivery (rate, completeness of delivery volumes, physical compatibility, etc.) using the Evolve Wearable Injector and found that the device worked very well and could be optimized to deliver subcutaneously the required volumes over the required time frames for clinical application. However, when we determined the kinetics of absorption and distribution of REG101 injected subcutaneously in animals, we found a much longer exposure after a single injection than we had observed with the bacterially produced version of FSTL1, thereby obviating the need for continuous SQ infusion using the wearable injector – REG101 could be simply administered as a single, SQ bolus injection once a day (or less) over a 2–4-week treatment period.

Pig Pilot Safety and Efficacy

Given the favorable pharmacokinetics discussed above, we performed dose-ranging studies using single bolus SQ injections over multiple dosing regimens in infarcted pigs which demonstrated cardiac functional recovery by ECHO at a minimum effective daily SQ dose of 1.2 mg/kg body weight given for 2 weeks.

We then tested SQ FSTL1 in the Ossabaw diabetic pig model of MI to determine if cardiac regenerative activity was retained in the setting of diabetes, the most common comorbidity in human MI patients. The Ossabaw pig is rendered diabetic by a four-month high fat diet. Animals were infarcted, allowed to recover for one month and then treated with SQ FSTL1 for two weeks, allowed to recover for an additional 2 weeks and then analyzed. FSTL1 treated pigs showed improved lung weight, improved diastolic and systolic function, improved left ventricular dimensions, reduced infarct scar volume, improved mitochondrial function and improved coronary and peripheral vascular function compared to untreated controls. 

REG101 Responsiveness on Cardiac Cells of Varying Gender and Racial Backgrounds

We acquired a battery of human induced pluripotent stem cells (hiPSCs) containing both genders and White, African American and Hispanic/Latino genetic backgrounds. These hiPSCs were turned into functional cardiomyocytes using a standardized protocol and analyzed using an automated instrument that measures the number of functional contractile cardiomyocytes induced by REG101 treatment in vitro. REG101 treatment resulted in a statistically significant increase in the number of functional cardiomyocytes in 4 of the 6 lines tested – a positive outcome that showed no effects of gender or race on the cellular in vitro responsiveness to REG101.

FDA Pre-IND Meeting

We submitted a full dossier to FDA requesting an “Interact Meeting”. FDA granted us a Type C Meeting and responded to our dossier questions in writing, essentially agreeing with our development plan including the preclinical plan, manufacturing plan and the First in Human Clinical Trial design.

Summary

The TRAN1-12907 grant program enabled Regencor to advance REG101 manufacturing development, animal testing, product characterization, validation of gender/racial responsiveness, and early FDA feedback for a promising cardiac regenerative therapeutic that reverses the effects of myocardial infarction, restores cardiac function to nearly pre-infarct levels and prevents the progression to heart failure.