Collapsing glomerulopathy (CG) has become an important cause of end-stage renal disease. Whether associated with HIV-1 or other potential etiologies, the pathogenesis of CG converges to induce aberrant proliferation of renal epithelium along the entire nephron. This raises the possibility that targeting cell-cycle progression may be an effective therapeutic strategy for CG. Here, we ask whether the cyclin-dependent kinase (CDK) inhibitor, CYC202 (R-roscovitine), could attenuate or reverse existing renal disease in Tg26 mice, a well characterized HIV-1 transgenic mouse model of CG. Tg26 mice were age and disease matched through analysis of urine (protein/creatinine) to generate 12 treatment pairs covering a range of mild to severe CG. One mouse from each pair received either vehicle or 75 mg/kg of CYC202 every 12 h for 20 d, a dose 20% above that needed to prevent the development of CG. After treatment, urinary, serologic, and histopathologic indices of nephrosis showed reversal of CG in 8 of 12 CYC202-treated mice compared with progression of CG in 10 of 12 vehicle-treated mice, demonstrating a significant therapeutic benefit from CYC202 (P < 0.05). Pharmacokinetic profiles showed that concentrations of CYC202 known to inhibit cell-cycle and transcriptional CDK in vitro were achieved in plasma at efficacious doses. However, amelioration of CG by CYC202 did not correlate with decreases in kidney HIV-1 transgene expression, indicating that suppression of HIV-1 transcription was not a prerequisite for the antiproliferative activity of CYC202. These results demonstrate a novel therapeutic strategy for CG.