REVIEW www.jasn.org Therapeutic Inhibition of VEGF Signaling and Associated Nephrotoxicities Chelsea C. Estrada,1 Alejandro Maldonado,1 and Sandeep K. Mallipattu1,2 1Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York; and 2Renal Section, Northport Veterans Affairs Medical Center, Northport, New York ABSTRACT Inhibition of vascular endothelial growth factor A (VEGFA)/vascular endothelial with hypertension and proteinuria. Re- growth factor receptor 2 (VEGFR2) signaling is a common therapeutic strategy in ports describe histologic changes in the oncology, with new drugs continuously in development. In this review, we consider kidney primarily as glomerular endothe- the experimental and clinical evidence behind the diverse nephrotoxicities associ- lial injury with thrombotic microangiop- ated with the inhibition of this pathway. We also review the renal effects of VEGF athy (TMA).8 Nephrotic syndrome has inhibition’s mediation of key downstream signaling pathways, specifically MAPK/ also been observed,9 with the clinical ERK1/2, endothelial nitric oxide synthase, and mammalian target of rapamycin manifestations varying according to (mTOR). Direct VEGFA inhibition via antibody binding or VEGF trap (a soluble decoy mechanism and direct target of VEGF receptor) is associated with renal-specific thrombotic microangiopathy (TMA). Re- inhibition. ports also indicate that tyrosine kinase inhibition of the VEGF receptors is prefer- Current VEGF inhibitors can be clas- entially associated with glomerulopathies such as minimal change disease and FSGS. sifiedbytheirtargetofactioninthe Inhibition of the downstream pathway RAF/MAPK/ERK has largely been associated VEGFA-VEGFR2 pathway: drugs that with tubulointerstitial injury. Inhibition of mTOR is most commonly associated with bind to VEGFA, sequester VEGFA, in- albuminuria and podocyte injury, but has also been linked to renal-specificTMA.In hibit receptor tyrosine kinases (RTKs), all, we review the experimentally validated mechanisms by which VEGFA-VEGFR2 or inhibit downstream pathways. A crit- inhibitors contribute to nephrotoxicity, as well as the wide range of clinical manifes- ical review of VEGFA-VEGFR2 signaling tations that have been reported with their use. We also highlight potential avenues in the kidney is necessary to fully under- for future research to elucidate mechanisms for minimizing nephrotoxicity while standthe mechanismsresponsible for the maintaining therapeutic efficacy. nephrotoxicity associated with the onco- logical use of VEGF inhibition. J Am Soc Nephrol 30: ccc–ccc, 2019. doi: https://doi.org/10.1681/ASN.2018080853 VEGF SIGNALING IN THE KIDNEY Inhibitors of vascular development were of bevacizumab, a recombinant IgG Filtration of plasma in nephrons occurs fi rst investigated as potential chemother- mAb against VEGFA, inhibiting VEGF in the glomerular capillary beds at the fi apeutic agents on the basis of study nd- signaling proved to be a promising ap- glomerular filtration barrier, which con- ings from the late 20th century regarding proach to halting neoplastic develop- sists of three layers: fenestrated endothe- 5 the critical role of angiogenesis in tumor ment. Since then, many additional lial cells, basement membrane, and the development and growth.1 Subsequent agents that block VEGF signaling and investigations led to the discovery of its downstream pathways have become vascular endothelial growth factor A available for the treatment of various (VEGFA), an essential growth factor cancers (Figure 1, i–vi). Published online ahead of print. Publication date for angiogenesis.2,3 Previous studies by Although these agents offer substan- available at www.jasn.org. Kim et al.4 used murine cancer cell lines tial benefit, both in the treatment of Correspondence: Dr. Sandeep K. Mallipattu, Department to show that treatment with an mAb many solid tumors6 as well as age- of Medicine/Nephrology, Stony Brook University, 100 Nicolls Road, HSCT16-80E, Stony Brook, NY 11794- 7 against VEGFA decreased tumor growth, related macular degeneration, their use 8176. Email: sandeep.mallipattu@stonybrookmedicine. indicating a potential therapeutic role is associated with significant nephrotoxi- edu 8 for VEGFA inhibition in cancer treat- city. Most commonly, pharmacologic Copyright © 2019 by the American Society of ment. Beginning with the development VEGF inhibition has been associated Nephrology J Am Soc Nephrol 30: ccc–ccc, 2019 ISSN : 1046-6673/3002-ccc 1 REVIEW www.jasn.org P P i. VEGFA Ab VEGFA (Bevacizumab, ii. VEGF Trap Ranibizumab) (Aflibercept) GEnC iii. VEGFR2 Ab (Ramucirumab) GBM FP VEGFR2 iv. Tyrosine Kinase Inhibitors (Axitinib, FP Tesevatinib, Nintedanib, Sunitinib) RAS/MAPK/ ERK Pathways v. BRAF Inhibitors GEnC BRAF EF (Vemurafenib, Pl3 Kinase/ Dabrafenib) AKT Pathways eNOS MTORC1 vi. mTOR Inhibitors EF (Temsirolimus, Ridaforolimus, Everolimus) Figure 1. VEGFA-VEGFR2 signaling pathways and their pharmacological inhibition occur across the glomerular filtration barrier. VEGFA is released from podocytes and binds to its receptor (VEGFR2) on glomerular endothelial cells. (i) Bevacizumab and ranibizumab are mAbs against VEGFA and inhibit angiogenesis through IgG antibody interaction with all of its isoforms. (ii) Aflibercept is a recombinant fusion protein comprising binding domains for VEGFR1 and VEGFR2 attached to the Fc portion of human IgG1, and acts as a soluble decoy receptor or “VEGF trap.” (iii) Ramucirumab is a fully humanized IgG1 mAb that specifically inhibits VEGFR2 by targeting its extracellular domain. (iv) TKIs such as sunitinib, pazopanib, sorafenib, and axitinib target VEGFR2, as well as interfere with the activity of additional RTKs such as PDGF receptor, fibroblast growth factor receptor, and EGF receptor, which all share a similar structure. (v) Agents such as vemurafenib and dabrafenib have been recently developed to specifically target B-Raf, a component of the intracellular MAPK/ERK intracellular pathway. (vi) mTOR inhibitors such as temsirolimus, ridaforolimus, and everolimus are used across several malignancies and act downstream of the phosphatidylinositide 3-kinase (PI3K)/AKT signal transduction pathway. Ab, antibody; BRAF, B-Raf Proto-Oncogene; EF, endothelial fenestrations; FP, foot process; GBM, glomerular basement membrane; GEnC, glomerular endothelial cell; P, Podocyte. foot processes of visceral epithelial cells form, which acts as a decoy receptor, in- wide range of glomerulopathies (Table 1) or podocytes. In the kidney, VEGFA is hibiting VEGFA signaling,17 and is the sole demonstrates that tight regulation of expressed by both podocytes10 and renal receptor for VEGFB.12 VEGFA signaling in the kidney is critical tubular epithelial cells11;inhumans, The functional diversity of VEGF re- to glomerular development and the main- VEGFA165 is the most abundant iso- ceptors was initially elucidated by the tenance of mature glomerular function in form.12 VEGFA binds to one of two creation of knockout mice. Mice defi- both homeostasis and disease. For example, RTKs, VEGFR1 and VEGFR213; although cient in Veg fr2 die in utero from a defect knockout of Veg fa during embryogenesis— both receptors have been identified as in hematopoietic and endothelial cell de- including global homozygous or heterozy- playing an important role in angiogenesis, velopment18; embryonic lethality of gous knockout22,23 or podocyte-specific VEGFR2 has been more extensively stud- Veg fr1 deletion is caused by endothelial knockout10—is uniformly lethal at or be- ied, as it is responsible for a majority of cell overgrowth and disorganization.19 fore birth. Mice with podocyte-specificpar- VEGFA signaling and is abundantly dis- These whole-body knockout mice un- tial deletion of Veg fa survive the perinatal tributed in stromal and malignant vascular derscore the key role of VEGF signaling period, but develop endotheliosis and renal tissues.14,15 Both receptors are primarily in endothelial cell proliferation, migra- failure by 9 weeks of age.10 localized in the glomerular and peritubu- tion, and permeability.20 In adult mice, inducible podocyte-specific lar capillary endothelium.11,16 Further- The association of VEGFA overex- Veg fa deletion produces renal-specific more, VEGFR1 also exists in a soluble pression10 or reduction8,21,10 with a TMA, which recapitulates kidney biopsy 2 Journal of the American Society of Nephrology J Am Soc Nephrol 30: ccc–ccc,2019 www.jasn.org REVIEW Table 1. Renal manifestations in VEGF-VEGFR transgenic murine models Genotype Model Effects Reference 2 2 Vegfa / Constitutive, whole-body Embryonically lethal 22,23 deletion of Vegfa 1 2 Vegfa / Constitutive, whole-body partial Embryonically lethal between days 11 22,23 deletion of Vegfa and 12; defective yolk sac blood supply 2 2 Vegfr1 / Constitutive, whole-body Embryonically lethal because of 19 deletion of Vegfr1 endothelial cell overgrowth and disorganization 2 2 Vegfr2 / Constitutive, whole-body Embryonically lethal because of defect in 18 deletion of Vegfr2 hematopoietic and endothelial cell development Nephrin-Cre; Vegfaflox/flox Constitutive deletion of Vegfa Perinatally lethal, mice die at birth or 10 from podocytes within 18 h with small glomeruli with few capillary loops 1 Nephrin-Cre; Vegfaflox/ Constitutive, partial deletion of Vegfa Endotheliosis, with eventual 10 from podocytes glomerulosclerosis and ESRD by 9–12 wk of age Podocin-rtTA; Doxycycline-inducible deletion of Vegfa Renal thrombotic microangiopathy 8 TetO-Cre; Vegfaflox/flox in podocytes Pax8-rtTA; Doxycycline-inducible