Low-Dose Interleukin-2 as an Alternative Therapy for Refractory Lupus Nephritis

Low-dose interleukin-2 (IL-2) selectively restores disturbances of regulatory T cells (Treg) and conventional T cells, resulting in the induction of remission in patients with systemic lupus erythematosus. However, to date no research has been carried out on the efficacy of low-dose IL-2 in the treatment of refractory lupus nephritis (LN). The aim of the study reported here was to investigate the renal response to low-dose IL-2 in patients with refractory LN.

The study population comprised ten patients with refractory LN who failed to achieve complete response or who had relapsed while being treated with at least two conventional immunosuppressive agents. One treatment cycle consisted of IL-2 at a dose of 1 million IU administered subcutaneously every other day for 2 weeks followed by a 2-week break. All patients received three cycles of IL-2 and were then followed up for another 12 weeks without any increase in the dose of previous immunosuppressive agents and steroids.

Of the ten patients enrolled in the study, seven (70%) achieved ≥ 50% improvement in proteinuria at 12 weeks after initiating treatment with IL-2. Median proteinuria was significantly reduced by 50.3% at week 12, from 1.83 (interquartile range [IQR] 1.23-3.21)  g/24 h at baseline to 0.91 (IQR 0.52-1.60)  g/24 h at 12 weeks (P = 0.005). This was accompanied by a 71% reduction in urine erythrocytes, from 64/µl (IQR 24-102/µl) at baseline to 18/µl (IQR 2-20/µl) at 12 weeks (P = 0.018). Anti-dsDNA was decreased from 27.9 (IQR 7.6-40.28) IU/ml at baseline to 14.1 (IQR 7.3-20.12) IU/ml (P = 0.021) at week 12, while complements C3 and C4 were slightly increased (P = 0.445, P = 0.241, respectively). A significant expansion of Treg cells, from 9.3% at baseline to 16.6% at 12 weeks, was also found (P < 0.05). No serious adverse events occurred during the treatment period.

Low-dose IL-2 therapy may have a promising role in the treatment of refractory LN as an alternative and safe therapeutic approach. It may be used as multi-target combination therapy in clinical practice.