Workshop Report: FDA Workshop on Improving Cardiotoxicity Assessment With Human-Relevant Platforms.

Given that cardiovascular safety concerns remain the leading cause of drug attrition at the preclinical drug development stage, the National Center for Toxicological Research of the US Food and Drug Administration hosted a workshop to discuss current gaps and challenges in translating preclinical cardiovascular safety data to humans. This white paper summarizes the topics presented by speakers from academia, industry, and government intended to address the theme of improving cardiotoxicity assessment in drug development. The main conclusion is that to reduce cardiovascular safety liabilities of new therapeutic agents, there is an urgent need to integrate human-relevant platforms/approaches into drug development. Potential regulatory applications of human-derived cardiomyocytes and future directions in employing human-relevant platforms to fill the gaps and overcome barriers and challenges in preclinical cardiovascular safety assessment were discussed. This paper is intended to serve as an initial step in a public-private collaborative development program for human-relevant cardiotoxicity tools, particularly for cardiotoxicities characterized by contractile dysfunction or structural injury.

Evaluation of Batch Variations in Induced Pluripotent Stem Cell-Derived Human Cardiomyocytes from 2 Major Suppliers.

Drug-induced proarrhythmia is a major safety issue in drug development. Developing sensitive in vitro assays that can predict drug-induced cardiotoxicity in humans has been a challenge of toxicology research for decades. Recently, induced pluripotent stem cell-derived human cardiomyocytes (iPSC-hCMs) have become a promising model because they largely replicate the electrophysiological behavior of human ventricular cardiomyocytes. Patient-specific iPSC-hCMs have been proposed for personalized cardiac drug selection and adverse drug response prediction; however, many procedures are involved in cardiomyocytes differentiation and purification process, which may result in large line-to-line and batch-to-batch variations. Here, we examined the purity, cardiac ion channel gene expression profile, and electrophysiological response of 3 batches of iPSC-hCMs from each of 2 major cell suppliers. We found that iPSC-hCMs from both vendors had similar purities. Most of the cardiac ion channel genes were expressed uniformly among different batches of iCells, while larger variations were found in Cor.4U cells, particularly in the expression of CACNA1C, KCND2, and KCNA5 genes, which could underlie the differences in baseline beating rate (BR) and field potential duration (FPD) measurements. Although, in general, the electrophysiological responses of different batches of cells to Na+, Ca2+, Ikr, and Iks channel blockers were similar, with Ikr blocker-induced proarrhythmia, the sensitivities were depended on baseline BR and FPD values: cells that beat slower had longer FPD and greater sensitivity to drug-induced proarrhythmia. Careful evaluation of the performance of iPSC-hCMs and methods of data analysis is warranted for shaping regulatory standards in qualifying iPSC-hCMs for drug safety testing.

Ethnic differences in DNA methyltransferases expression in patients with systemic lupus erythematosus.

PURPOSE: Systemic lupus erythematous (SLE) is a systemic autoimmune inflammatory disease with both genetic and epigenetic etiologies. Evidence suggests that deregulation of specific genes through epigenetic mechanisms may be a contributing factor to SLE pathology. There is increasing evidence that DNA methyltransferase activity may be involved. This study demonstrated modulation in expression of DNA methyltransferases (DNMTs) according to ethnicity in patients diagnosed with SLE. Furthermore, differential expression in one of the DNMTs was found in a subset of lupus patients on dehydroepiandrosterone (DHEA) therapy. METHODS: Real-time PCR analyses of DNMT1, DNMT3A and DNMT3B in peripheral blood mononuclear cells from a cohort of African American and European American lupus and non-lupus women were conducted. Also, global DNA methylation was assessed using the MethylFlash(TM) methylated quantification colorimetric assay. RESULTS: Significant increase in DNMT3A (p < 0.001) was shown in lupus patients when compared to age-matched healthy controls. This increase was associated with a higher SLEDI index. More striking was that expression levels for African American (AA) women were higher than European American women in the lupus populations. A subset of AA women on DHEA therapy showed a significant decrease (p < 0.05) in DNMT3A expression in comparison to lupus patients not on the therapy. DHEA is an androgenic steroid found in low levels in the serum of lupus patients. Supplementation of this hormone has been shown to be beneficial to some lupus patients. DHEA was not shown to effect DNMT1 or DNMT3B expression. Increased expression was also noted in DNMT3B (p < 0.05) in lupus patients compared to age-matched healthy controls. However, no significant difference was noted in DNMT1 (p = 0.2148) expression between lupus patients and healthy controls. Although increases were detected in de novo methyltransferases, a global decrease (p < 0.001) in 5-methycytosine was observed in lupus patients when compared to age-matched healthy controls. CONCLUSION: These findings suggest that epigenetic changes may play a critical role in the manifestations of the disease observed among ethnic groups, particularly African American women who often have a higher incidence of lupus. DHEA therapy effects on DNMT3A expression in AA women warrant further investigation in a larger population.