To assess the efficacy of long-term treatment with belimumab, a post-hoc longitudinal study has used propensity score matching to compare patients from the BLISS long-term extension study who received belimumab (and standard of care) with patients from the Toronto Lupus Cohort who received standard of care only. Belimumab treatment resulted in less organ damage progression (as assessed by change in SLICC/ACR Damage Index (SDI) score from baseline to 5 years), as well as a reduced likelihood of progression to a higher SDI score over any given year, compared with standard of care.