Faculty Bibliography

OBJECTIVE: Individualized therapy based on genetic background and monitoring of metabolites can optimize drug safety and efficacy. Such an approach is available for azathioprine (AZA), the thiopurine antimetabolite. AZA exerts therapeutic effects when metabolized to the active thiopurine nucleotide, 6-thioguanine (6-TGN). In inflammatory bowel disease (IBD), 6-TGN levels in the target range of 235-400 pmol/8x10(8) red blood cells (RBC) are associated with a high likelihood of response. Our objective was to evaluate whether drug escalation based on metabolite levels improves efficacy and maintains safety in patients with systemic lupus erythematosus (SLE). METHODS: We conducted a 6-month open-label dose-escalation clinical study of patients with active SLE treated with azathioprine dosed by body weight and metabolite levels. The primary endpoint was >or=50% improvement in any one parameter of disease activity, or 50% decrease in glucocorticoid dose. RESULTS: Of 50 patients enrolled in the study, 21 achieved clinical responses, 13 of whom had 6-TGN<235 pmol/8 x10(8) RBC. Ten patients had no clinical response at 6 months, yet achieved either therapeutic IBD 6-TGN levels (>235, n=4) or received maximum AZA dose>or=3.5 mg/kg (n=6). In 19 patients the drug was discontinued prematurely due to side effects or SLE activity. For those patients in whom either liver function test or white blood cell count abnormalities were encountered, metabolites guided attribution to drug or disease activity. CONCLUSION: Clinical responses in SLE can occur at levels of 6-TGN lower than the target range established for IBD. During followup, measurements of AZA metabolites may provide a rational approach to safety

OBJECTIVE: Serial measurements of anti-double-stranded DNA (anti-dsDNA) and complement are routine in the management of systemic lupus erythematosus (SLE), but their utility as biomarkers in preemptive treatment to prevent flares remains a subject of controversy. We hypothesized that concomitant elevation of anti-dsDNA and C3a can predict SLE activity in patients with stable or inactive disease and that short-term treatment with corticosteroids can avert flares. METHODS: In this prospective, randomized, double-blind, placebo-controlled trial, 154 patients were evaluated monthly for up to 18 months, with measurements of C3a, C3, C4, CH50, and anti-dsDNA levels. Patients who remained clinically stable but showed serologic evidence of an SLE flare (elevation of both the anti-dsDNA level by 25% and the C3a level by 50% over the previous 1-2 monthly visits) were randomized to receive either prednisone or placebo therapy at a dosage of 30 mg/day for 2 weeks, 20 mg/day for 1 week, and 10 mg/day for 1 week. RESULTS: Forty-one patients (21 randomized to prednisone and 20 randomized to placebo) experienced a serologic flare. Analysis of severe flares occurring </=90 days from randomization revealed that 6 occurred in patients taking placebo and none occurred in patients taking prednisone (P = 0.007). Severe flares resulted in an increase in the prednisone dosage to >40 mg/day and/or the addition of an immunosuppressive agent. Furthermore, improvement in scores on the Systemic Lupus Erythematosus Disease Activity Index, decreased levels of anti-dsDNA antibodies, and increased levels of C4 occurred 1 month after initiation of prednisone treatment. CONCLUSION: These preliminary data support our hypothesis that in a subset of clinically stable SLE patients with a combination of elevated C3a and anti-dsDNA levels, short-term corticosteroid therapy may avert a severe flare