Diabetic macular edema (DME) remains a leading cause of vision loss worldwide. DME is commonly treated with intravitreal injections of vascular endothelial growth factor (VEGF)neutralising antibodies. Anti-VEGFs are effective but not all patients fully respond to them.Given their potential side effects, inconvenience and high cost, identifying who may notrespond appropriately to anti-VEGFs and why is essential. Herein, we determine first the response to anti-VEGFs in a cohort of DME patients usingspectral-domain optical coherence tomography scans obtained throughout the first year oftreatment. We found that in 28% of eyes full clearance of fluid occurred at any time duringthe first year (“full responders”); in 66% fluid cleared only partly (“partial responders”); in 6% fluid remained unchanged (“non-responders”). To understand this differential response, we generated induced pluripotent stem cells (iPS) from “full responders” and “non-responders”and from diabetic subjects with no DME and age-matched non-diabetic volunteers and differentiated them into endothelial cells (iPS-ECs). Monolayers of iPS-ECs derived fromdiabetics showed marked and prolonged increased permeability upon exposure to VEGFwhen compared with non-diabetic controls; the response was significantly exaggerated in iPSECs from “non-responders” when compared with “full responders”. Moreover, phosphorylation of key cellular proteins in response to VEGF, including VEGFR2, and geneexpression profiles, such as Neuronal Pentraxin 2 (NPTX2) expression, differed between “fullr esponders” and “non-responders”. In the current study, iPS were used to predict patient response to anti-VEGF and identify keymechanisms underpinning the differential outcomes observed in the clinic. This approach hasidentified NPTX2 as playing a significant role in patient-linked responses and has potential asa new therapeutic target for DME.