Abstract

The CD40/CD40L pathway plays a major role in multiple inflammatory processes involving different immune and stromal cells. Abnormal activation of this pathway has been implicated in pathogenesis of complex autoimmune diseases such as SLE, RA and Sjogren's Syndrome. We completed in vitro and in vivo preclinical characterization of KPL-404, a novel humanized monoclonal Fc-silent IgG4 anti-CD40 antibody, in order to demonstrate potency, efficacy, and long pharmacokinetic profile; safety issues were also important to evaluate considering previously-seen CD40 antagonist-related issues. In vitro, KPL-404 bound recombinant human and cynomolgus monkey CD40 demonstrate comparable affinity in the nanomolar range. KPL-404 binding to cell surface CD40 did not induce antibody or complement-mediated cytotoxicity of CD40-expressing cells. Pharmacological antagonistic activity of KPL-404 was demonstrated in vitro by inhibition of CD40-mediated downstream NF-kB activation. In an 8-week in vivo study with cynomolgus monkeys, KPL-404 administered intravenously for a single dose (10mg/kg) or multiple doses (1 and 5 mg/kg) did not induce any observable safety findings, including activation of platelets. KPL-404 engaged CD40 expressed on peripheral B cells for 2 and 4 weeks after a single administration of 5 and 10 mg/kg IV without depletion of peripheral B cells. At 5 mg/kg IV, KPL-404 blocked both primary and secondary responses to T-cell dependent antibody responses to antigens KLH and TT. These in vivo data illustrated the relationship between KPL-404 serum concentrations and pharmacodynamic effects of CD40 targeting in periphery and lymphoid tissue. The data herein support clinical development of KPL-404 as a potential therapeutic in autoimmune diseases.

Significance Statement We aimed to develop a potent and efficacious CD40 antagonist. In vitro and in vivo findings characterize KPL-404 as a blocking anti-CD40 antibody that potently inhibits primary and secondary antibody responses at pharmacologically relevant concentrations with a favorable pharmacokinetic profile and did not deplete B-cells by antibody dependent cellular cytotoxicity or apoptosis (“non-depleting”). These findings support clinical development of KPL-404 as a potential therapeutic in autoimmune diseases.