PROJECT SUMMARY Immune checkpoint inhibitors (ICIs) are revolutionizing cancer care, producing durable anti-tumor responses in multiple cancer types; however, by unleashing T-cell responses, ICIs can lead to immune-related toxicities in essentially any organ system, affecting 60-80% of recipients. It is conservatively estimated that 3-5% of patients develop acute interstitial nephritis (AIN) after ICIs, and a recent study found that up to 40% of patients that survive 2 years after receiving ICIs will experience rapid estimated glomerular filtration rate (eGFR) decline (>3mL/min/year). Very little is known about the mechanisms of ICI-induced kidney injury, as all prior published work in the field has been descriptive. Building on published studies showing distinctly high cytotoxic T-cell activity in immune-related adverse events after ICIs, we hypothesize that AIN and chronic kidney disease (CKD) that result from ICIs exist on a spectrum of T-cell mediated injury to the tubulointerstitial compartment of the kidney. In Aim 1, we will enroll 25 patients with biopsy-proved ICI-induced AIN (ICI-AIN) and 25 patients with clinically-adjudicated hemodynamic AKI after ICIs and use single-cell RNA sequencing of paired kidney biopsy tissue, blood, and urine specimens to uncover mechanisms of ICI-induced AIN. Single-cell transcriptional profiling of kidney tissue will offer insights into the cellular and molecular pathogenesis of ICI- AIN as well as a clear benchmark against which to compare blood and urine signatures (Aim 1B). We will then compare cell-based transcriptional biomarkers (Aim 1C) and cytokine biomarkers (Aim 1D) in blood and urine of patients with biopsy-proven ICI-AIN to hemodynamic AKI after ICIs to identify biomarkers unique for ICI-AIN and pathways to target in future interventional studies. In Aim 2, we will determine the relationship between ICIs and long-term kidney injury by prospectively evaluating blood and urine biomarkers of kidney injury over two years in ICI-treated patients with melanoma compared to control patients with early-stage melanoma who undergo surgical resection alone and do not receive ICIs (Aim 2A). To understand mechanisms promoting kidney function decline after ICIs, in Aim 2B, we will use scRNAseq to investigate the similarities between immune and non-immune cell transcriptional programs in blood and urine among patients with >20% eGFR decline after ICIs to patients with ICI-AIN from Aim 1B. In aggregate, the studies proposed will uncover mechanisms of ICI-induced kidney injury, have strong potential to lead to non-invasive diagnostics for ICI-AIN, and yield important biological insights into the role of T-cell disinhibition on kidney function. The proposal will capitalize on the expertise of the Severe Immunotherapy Complications Service at Massachusetts General Hospital (MGH), a first-of-its kind multidisciplinary team of oncologists and subspecialists studying immune- related adverse events, and the tremendous biobanking infrastructure of the MGH Cancer Center, driving the feasibility of these innovative aims. This Stephen I. Katz Early Stage Investigator Research Project Grant is a new direction for the principal investigator, launching a translational research program in onconephrology.

PROJECT NARRATIVE Immune checkpoint inhibitors (ICIs) are immunotherapies increasingly used in patients with wide varieties of cancers; however, they can also cause autoimmune toxicities affecting multiple organ systems, including the kidney. Currently, the pathogenesis of ICI-induced kidney injury is not well-understood, and epidemiologic studies suggest a high fraction of ICI-treated patients develop clinically-significant decline in kidney function over time. Using single-cell genomics and longitudinal biomarker studies, this proposal seeks to identify pathways that can help understand how acute and chronic kidney disease develops after ICIs to ultimately lead to novel diagnostic and therapeutic strategies to prevent kidney disease.