Matthew D. Linnik, Patricia A McNeeley, G. Michael Iverson.

La Jolla Pharmaceutical Co, San Diego, CA

Anti-dsDNA antibodies are thought to contribute to renal inflammation and deterioration in patients with lupus nephritis. Clinical studies have established a link between anti-dsDNA antibodies, typically high-affinity IgG, and renal exacerbations in lupus. LJP 394 is an experimental compound that was designed to specifically deplete anti-dsDNA antibodies and tolerize the B cells that produce these antibodies without causing the generalized immunosuppression observed with current therapy. LJP 394 is a tetravalent conjugate composed of 4 copies of synthetic, 20 mer double stranded oligonucleotide covalently attached to a triethyleneglycol-based scaffold. Preclinical studies have demonstrated that LJP 394 is capable of crosslinking and tolerizing anti-dsDNA-specific B cells. Clinical studies have shown that LJP 394 can reduce anti-dsDNA antibodies in lupus patients in a dose dependent manner. The present study sought to determine if the affinity of anti-dsDNA antibodies for the LJP 394 epitope could predict which patients were most likely to benefit from drug treatment. A surface plasmon resonance-based equilibrium binding assay was employed to measure the affinity of patient IgG to LJP 394. Serum samples from a multicenter, double blind, placebo controlled trial were evaluated in patients prior to drug treatment and following 4 months of weekly treatment with 10 mg LJP 394 (n = 6), 50 mg LJP 394 (n = 4) or placebo (n = 9). The equilibrium dissociation constant (Kd') was determined for each sample by measuring the binding at equilibrium for several dilutions of IgG to immobilized LJP 394 and determining the Kd based on fitting the data to a single site binding model. Baseline Kd' values were similar in the placebo and drug treatment groups and ranged from 0.05 to 0.51 mg IgG/ml. After 4 months of treatment, there was a dose dependent reduction in affinity for LJP 394 in the 10 mg/wk and 50 mg/wk groups, while the placebo group was unchanged (p < 0.05 and p < 0.01 in the 10 and 50 mg groups, respectively). Patients with highest initial affinity in the 50 mg group demonstrated the greatest percentage change in affinity over the course of treatment, suggesting that patients with highest affinity for LJP 394 have the greatest capacity to respond to drug treatment. These studies suggest it may be possible to use an epitope-specific affinity assay to prospectively define lupus patients that are most likely to respond to LJP 394.

Presented at the Keystone Symposia 2000 "Mechanisms of Immunologic Tolerance and its Breakdown," March 31-April 6, 2000, Steamboat Springs, CO.