The safety and efficacy of abetimus sodium (abetimus) has been evaluated in 13 controlled and uncontrolled clinical trials involving > 800 patients or subjects. The two pivotal trials enrolled a total of 547 patients with systemic lupus erythematosus (SLE) who had a history of lupus nephritis. Evidence of clinical effectiveness of abetimus comes from analyses of data from patients with SLE and high-affinity antibodies to the DNA epitope of abetimus at baseline; a retrospective subgroup in the pivotal Phase II/III LJP-394-90-05 trial (90-05 trial) and the intent-to-treat population in the Phase III LJP-394-90-09 trial (90-09 trial). These studies enrolled SLE patients who had experienced prior renal manifestations of their disease and had elevated anti-dsDNA antibodies at baseline by Farr assay. Both were long-term studies, with a mean duration of treatment participation of 371 days in 90-05 and 310 days in 90-09 for the population of patients with high-affinity antibodies at baseline. The 90-05 and 90-09 studies, as well as all other clinical studies of abetimus, consistently showed that treatment with abetimus resulted in durable and persistent reductions in anti-dsDNA antibodies in SLE patients. Treatment with abetimus was associated with statistically significant decreases in anti-dsDNA antibody levels from baseline compared with placebo in both the 90-09 and 90-05 trials. Positive trends were noted for the incidence of renal flares and major SLE flares in patients treated with abetimus. Abetimus appeared to be well tolerated for treatment periods of ≤ 22 months.