Polymyxin B-Induced Kidney Injury Assessment of a Novel Formulation of Polymyxin B (VRP-034) in Rats

Despite the crucial role of Polymyxin-B in treating life-threatening gram-negative infections, its clinical utility is limited due to the risk of acute kidney injury. In response, a novel formulation of polymyxin-B is being developed to mitigate drug-induced kidney injury. In this study, we have assessed the toxicity of four variants of that novel formulation (VRP034_F21-F24) in comparison with standard polymyxin-B using kidney injury biomarkers in rats. Sprague-Dawley rats were subcutaneously administered either polymyxin-B (control) or one of the four polymyxin-B formulations at a dose of 25 mg/kg/day (HED: 4 mg/kg/day) in four divided doses for two days. Serum samples were collected at baseline and at the end of day 2 for the determination of serum biomarkers. Necropsy was done on day 2 and kidney was collected for histopathological evaluation. In the control group, statistically significant increase (p < 0.0001) in all biomarkers was observed on day 2 as compared to baseline values [urea: 311%; creatinine: 700%; KIM-1: 180%; cystatin-C: 66%] and 50% of the animals died (one after the 7th dose and two after the 8th dose) before scheduled necropsy. In contrast, animals treated with novel formulations did not show a significant increase across any of the biomarkers and no mortality was observed. Histopathology of the control group kidney confirmed necrotic changes in tissues with congestion and vacuolization, whereas only minor tubular damage was noted in two formulation groups (VRP034_F21, F24) and no appreciable damage was detected in the other two groups (VRP034_F22-23). The novel formulation of polymyxin-B tested in this study significantly reduced the risk of polymyxin-induced kidney injury in rats.