New data from the longest continuous belimumab treatment in a clinical trial of patients with systemic lupus erythematosus (SLE) indicate similar or lower adverse events each year and maintenance of efficacy for up to 13 years in those who initially respond to and stay on treatment.
First author Daniel J. Wallace, MD, and his colleagues reported in Arthritis & Rheumatology on 298 patients who continued from a phase 2 trial of 476 patients and its extension phase to a continuation study with belimumab (Benlysta) plus standard of care. These patients entered the continuation study having gone from placebo to 10 mg/kg belimumab or continued on 1, 4, or 10 mg/kg belimumab or escalated treatment up to 10 mg/kg. They needed to have an improvement in Physician’s Global Assessment (PGA) score, compared with baseline, and had no severe flare in the last 30 days of the extension study.
At year 5, 70% of patients were still in the study, and this declined to 44% at year 10 and 32% (96 patients) at the end of the study. There were stable or declining rates of the most common adverse events from year 1 to year 11 or later, and serious infections and infestations occurred at a stable rate, from 3.7 per 100 patient-years in year 1 to 6.7 per 100 patients-years through year 11, despite a reduction in immunoglobulin G levels during the study. A total of 15% of patients overall withdrew because of adverse events.
The overall SLE Responder Index response rate rose as the number of participants declined, going from 33% at 1 year and 16 weeks to 76% at 12 years and 32 weeks.
In addition to consistently low flare rates starting at year 5, “those patients remaining had reduced requirements for corticosteroids, and the percentage achieving low disease activity increased. Furthermore, patients continued to have serological improvements. ” Dr. Wallace and his coauthors wrote.
“Patients who remained in the study were likely to be those who responded better or tolerated belimumab better than patients who withdrew; hence, the findings may not be representative of all patients with SLE,” they said.
GlaxoSmithKline and Human Genome Sciences funded the study. Most of the investigators received grants, research support, or consulting fees; held shares in; or were employees of GlaxoSmithKline.