OBJECTIVES: Systemic Lupus Erythematosus(SLE) is a debilitating illness caused by an autoimmune disorder that can affect many organs of the body, including skin, joints, kidneys, lungs and the nervous system. Therapy with steroids and immunosuppressives can lead to further organ damage. Belimumab is a fully human monoclonal antibody that has been found to be effective against SLE in trials. The current study assesses the cost-effectiveness of belimumab in Hong Kong SLE patients compared to standard care. METHODS: A lifetime microsimulation model was adapted with epidemiological and cost data from Hong Kong. The model compares the use of belimumab against standard care and incorporates the BLISS-52 and BLISS-76 trial data for the short term outcomes within one year, while long-term outcomes were based on a natural history model developed using the Johns Hopkins Lupus registry. The natural history model describes the relationship between disease activity and other covariates on the risk of dying and developing organ damage. Data available from the SLE population in Hong Kong was used as input in the modified model. The analysis was performed from a Hong Kong health-care perspective. In the base case, cost and effectiveness were discounted to the year of analysis at 5% p.a. RESULTS: The base case analysis showed that compared to standard care, treatment with belimumab increased life expectancy by 0.80 (2.77 undiscounted) and QALY by 0.60 (1.68 undiscounted) years respectively. Total incremental costs were US$47,865 (US$80,460 undiscounted). The ICER of belimumab compared to standard care was US$59,546 per life year and US$79,407 per QALY gained. Hong Kong’s GDP per capita is US$35,961. Thus, this result is within the WHO recommended threshold for cost-effectiveness, at 3 times GDP of US$107,883. CONCLUSIONS: This study shows that belimumab would be cost-effective compared to standard care for the treatment of SLE in Hong Kong.