Abstract P3109: Identification Of Drug Transporter Genomic Variants And Inhibitors That Protect Against Doxorubicin Induced Cardiotoxicity

Multiple pharmacogenomic studies have identified the synonymous genomic variant rs7853758 (G > A, L461L) and the intronic variant rs885004 in SLC28A3 (solute carrier family 28 member 3) as statistically associated with a lower incidence of anthracycline-induced cardiotoxicity. However, the true causal variant(s), the cardioprotective mechanism of this locus, the role of SLC28A3 and other solute carrier (SLC) transporters in anthracycline-induced cardiotoxicity, and the suitability of SLC transporters as targets for cardioprotective drugs has not been investigated. To answer these questions, six well-phenotyped, doxorubicin-treated pediatric patients from the original association study cohort were recruited again, and human-induced pluripotent stem cell-derived cardiomyocytes were generated. Patient-specific doxorubicin-induced cardiotoxicity (DIC) was then characterized using assays of cell viability, activated caspase 3/7, and doxorubicin uptake. We demonstrate that patient-derived cardiomyocytes recapitulate the cardioprotective effect of the SLC28A3 locus and that SLC28A3 expression influences the severity of DIC. The role of SLC28A3 in DIC was then confirmed using overexpression and knockout of SLC28A3 in isogenic human-induced pluripotent stem cell-derived cardiomyocytes. To identify the potential causal variant, Nanopore-based fine-mapping of the SLC28A3 locus was then completed after SLC28A3 resequencing. An extended in silico haplotype and functional analysis followed by base editing, identified a novel cardioprotective single nucleotide polymorphism, rs11140490, in the SLC28A3 locus. Next, using high-throughput drug screening of 1200 drugs in patient-derived cardiomyocytes and whole organism validation in mice, we identify the SLC competitive inhibitor desipramine as protective against DIC. Finally, using eight cancer cell lines, we demonstrate that desipramine does not impede doxorubicin cytotoxicity.