Pharmacology of AMG 181, a human anti-α4 β7 antibody that specifically alters trafficking of gut-homing T cells

BACKGROUND AND PURPOSE

AMG 181 is a human anti-α4 β7 antibody currently in phase 1 and 2 trials in subjects with inflammatory bowel diseases. AMG 181 specifically targets the α4 β7 integrin heterodimer, blocking its interaction with mucosal addressin cell adhesion molecule-1 (MAdCAM-1), the principal ligand that mediates α4 β7 T cell gut-homing.

EXPERIMENTAL APPROACH

We studied the in vitro pharmacology of AMG 181, and the pharmacokinetics and pharmacodynamics of AMG 181 after single or weekly i.v. or s.c. administration in cynomolgus monkeys for up to 13 weeks.

KEY RESULTS

AMG 181 bound to α4 β7 , but not α4 β1 or αE β7 , and potently inhibited α4 β7 binding to MAdCAM-1 (but not vascular cell adhesion molecule-1) and thus inhibited T cell adhesion. Following single i.v. administration, AMG 181 Cmax was dose proportional from 0.01 to 80 mg·kg(-1) , while AUC increased more than dose proportionally. Following s.c. administration, dose-proportional exposure was observed with single dose ranging from 5 to 80 mg·kg(-1) and after 13 weekly doses at levels between 20 and 80 mg·kg(-1) . AMG 181 accumulated two- to threefold after 13 weekly 80 mg·kg(-1) i.v. or s.c. doses. AMG 181 had an s.c. bioavailability of 80%. The linear elimination half-life was 12 days, with a volume of distribution close to the intravascular plasma space. The mean trend for the magnitude and duration of AMG 181 exposure, immunogenicity, α4 β7 receptor occupancy and elevation in gut-homing CD4+ central memory T cell count displayed apparent correlations.

CONCLUSIONS AND IMPLICATIONS

AMG 181 has in vitro pharmacology, and pharmacokinetic/pharmacodynamic and safety characteristics in cynomolgus monkeys that are suitable for further investigation in humans.

The cytoplasmic domains of complement regulatory protein CD46 interact with multiple kinases in macrophages

Membrane cofactor protein (CD46), which normally protects autologous cells from complement lysis, is the human cell receptor for measles virus (MV). Interaction between MV and CD46 on monocytes can lead to suppression of monocyte activation. We have investigated the interaction between the cytoplasmic sequences of CD46 and kinases in a mouse macrophage cell line. Glutathione-S-transferase (GST) fusion proteins bearing the Cyt1 or Cyt2 alternative cytoplasmic domain of CD46 associate with macrophage kinase activity, which phosphorylates multiple proteins co-purified with the GST fusion proteins. Association with the macrophage kinase activity correlates with tyrosine phosphorylation of the CD46 cytoplasmic domains. Removing the CD46 sequences or introducing a frame-shift mutation abrogates the association with macrophage kinase activity. Renaturation studies reveal multiple kinases with apparent molecular mass of 82, 79, 58, and 50/49 kDa, which associate specifically with both CD46 cytoplasmic domains. Alanine substitutions at a juxtamembrane Tyr-X-X-Leu motif in the Cyt1 domain completely abrogate the association with macrophage kinases and tyrosine phosphorylation of Cyt1; but similar substitutions in the Cyt2 domain only partially reduce the association with kinases and tyrosine phosphorylation of Cyt2. These results reveal a specific interaction between complement regulatory protein CD46 and macrophage kinases. These findings may provide an important clue for understanding immune modulation by MV.

Production of purified hepatitis B surface antigen from Alexander hepatoma cells grown in artificial capillary units

An artificial capillary system was devised for growth of hepatoma cells that yields very high titers of hepatitis B surface antigen (HBsAg). High yield of antigen was facilitated by slowing cellular metabolism through reduction of incubation temperature and addition of 0.1 mM caffeine. Deletion of serum from the medium did not reduce the yield of antigen. HBsAg prepared from the culture fluid by affinity chromatography and additional chemical and enzymatic steps was essentially pure and was indistinguishable from HBsAg prepared from infected human plasma. Preparation of HBsAg from the cell culture source presents advantages over that of human plasma and might be a source of HBsAg for vaccine preparation.