Augmented Binary Substitution: Single-pass CDR germ-lining and stabilization of therapeutic antibodies.

Although humanized antibodies have been highly successful in the clinic, all current humanization techniques have potential limitations, such as: reliance on rodent hosts, immunogenicity due to high non-germ-line amino acid content, v-domain destabilization, expression and formulation issues. This study presents a technology that generates stable, soluble, ultrahumanized antibodies via single-step complementarity-determining region (CDR) germ-lining. For three antibodies from three separate key immune host species, binary substitution CDR cassettes were inserted into preferred human frameworks to form libraries in which only the parental or human germ-line destination residue was encoded at each position. The CDR-H3 in each case was also augmented with 1 ± 1 random substitution per clone. Each library was then screened for clones with restored antigen binding capacity. Lead ultrahumanized clones demonstrated high stability, with affinity and specificity equivalent to, or better than, the parental IgG. Critically, this was mainly achieved on germ-line frameworks by simultaneously subtracting up to 19 redundant non-germ-line residues in the CDRs. This process significantly lowered non-germ-line sequence content, minimized immunogenicity risk in the final molecules and provided a heat map for the essential non-germ-line CDR residue content of each antibody. The ABS technology therefore fully optimizes the clinical potential of antibodies from rodents and alternative immune hosts, rendering them indistinguishable from fully human in a simple, single-pass process.

Methotrexate and hepatic toxicity in rheumatoid arthritis and psoriatic arthritis.

BACKGROUND: We set out in this study to demonstrate the adverse effect profile of methotrexate when used in the treatment of rheumatoid arthritis (RA) and psoriatic arthritis (PsA) in a district general hospital population, and to investigate the effect of alcohol consumption in these patients. METHODS: A prospective evaluation of 550 RA patients and 69 PsA patients was undertaken, controlling for confounding factors. Systematically randomised patients were further analysed regarding alcohol consumption. A transaminase level of three times the upper limit of normal on two or more occasions was taken to indicate hepatic injury. RESULTS: Gastrointestinal disturbance was the predominant adverse effect in RA patients (9.8%); hepatic disturbance was the most frequent in PsA patients (14.5%). Both groups had hepatic enzyme elevation; PsA patients were at significantly greater risk of elevated transaminases than RA patients (14.5% vs 7.5%, respectively, chi2 = 4.017). Alcohol consumption did not correlate with hepatic injury (mean 5.15 vs 6.6 alcohol units/week consumed by RA and PsA patients, respectively). CONCLUSION: Our data show methotrexate-treated PsA patients have a higher incidence of hepatotoxicity compared with methotrexate-treated patients with RA. It is proposed that psoriatic patients may be inherently more susceptible to methotrexate hepatotoxicity than are rheumatoid patients.