Increased vascular endothelial growth factor B (VEGF-B) expression in patients with diabetic kidney disease (DKD) is associated with increased lipid deposition in glomerular podocytes. Reducing VEGF-B activity in animal models of DKD using an anti-VEGF-B antibody improved histological evidence of glomerular injury and reduced albuminuria; effects attributed to prevention of ectopic lipid deposition in the kidney. CSL346 is a novel humanized monoclonal antibody that binds VEGF-B with high affinity. Targeting VEGF-B in patients with type 2 diabetes mellitus may improve DKD progression markers. An international, randomized, double-blind, placebo-controlled, phase 2a study (NCT04419467) assessed CSL346 (8 mg/kg or 16 mg/kg subcutaneously every 4 weeks for 12 weeks) in participants with type 2 diabetes mellitus and a urinary albumin-to-creatinine ratio (UACR) ≥150 mg/g (17.0 mg/mmol), and eGFR >20 mL/min/1.73m2. Efficacy, safety/tolerability, pharmacokinetics, and pharmacodynamics of CSL346 were evaluated. The primary analysis compared the change from baseline in log-transformed UACR between the two CSL346 dose groups combined versus placebo at Week 16. In total, 114 participants were randomized. CSL346 did not significantly reduce UACR compared with placebo at Week 16 (combined CSL346 group difference from placebo 95% confidence interval]: 4.0% [-14.7, 26.8]). Furthermore, no effect was seen in participant subgroups (degree of kidney impairment or sodium-glucose cotransporter 2 [SGLT2] inhibitor use) or on urinary biomarkers reflecting proximal tubular injury. CSL346 was generally well tolerated; however, diastolic blood pressure was significantly higher with CSL346 16 mg/kg versus placebo from Week 2 onwards, with differences ranging from +3.8 to +5.3 mmHg (P = 0.002 at Week 16). CSL346 did not reduce UACR compared with placebo at 16 weeks in participants with type 2 diabetes mellitus and DKD, and was associated with an increase in diastolic blood pressure.