CDR-restricted engineering of native human scFvs creates highly stable and soluble bifunctional antibodies for subcutaneous delivery.

While myriad molecular formats for bispecific antibodies have been examined to date, the simplest structures are often based on the scFv. Issues with stability and manufacturability in scFv-based bispecific molecules, however, have been a significant hindrance to their development, particularly for high-concentration, stable formulations that allow subcutaneous delivery. Our aim was to generate a tetravalent bispecific molecule targeting two inflammatory mediators for synergistic immune modulation. We focused on an scFv-Fc-scFv format, with a flexible (A4T)3 linker coupling an additional scFv to the C-terminus of an scFv-Fc. While one of the lead scFvs isolated directly from a naïve library was well-behaved and sufficiently potent, the parental anti-CXCL13 scFv 3B4 required optimization for affinity, stability, and cynomolgus ortholog cross-reactivity. To achieve this, we eschewed framework-based stabilizing mutations in favor of complementarity-determining region (CDR) mutagenesis and re-selection for simultaneous improvements in both affinity and thermal stability. Phage-displayed 3B4 CDR-mutant libraries were used in an aggressive "hammer-hug" selection strategy that incorporated thermal challenge, functional, and biophysical screening. This approach identified leads with improved stability and>18-fold, and 4,100-fold higher affinity for both human and cynomolgus CXCL13, respectively. Improvements were exclusively mediated through only 4 mutations in VL-CDR3. Lead scFvs were reformatted into scFv-Fc-scFvs and their biophysical properties ranked. Our final candidate could be formulated in a standard biopharmaceutical platform buffer at 100 mg/ml with<2% high molecular weight species present after 7 weeks at 4 °C and viscosity<15 cP. This workflow has facilitated the identification of a truly manufacturable scFv-based bispecific therapeutic suitable for subcutaneous administration.

Novel immunotherapeutic approaches to the treatment of infections caused by Gram-negative bacteria.

The rise in infections caused by Gram-negative bacteria and the spread of resistance to conventional antibiotics provide significant challenges to the pharmaceutical industry. Monoclonal antibodies have achieved impressive recent clinical successes in a variety of indications, but to date there are no licensed immunotherapeutics that target bacterial infections, despite several promising studies in animal models of infection. Several key questions remain, in particular relating to the target(s), mechanism of action, and mode of delivery of any potential novel immunotherapeutic. This short review discusses recent approaches being taken to develop novel immunotherapeutic molecules for the treatment of Gram-negative bacterial infections.

The Caenorhabditis elegans p120 catenin homologue, JAC-1, modulates cadherin-catenin function during epidermal morphogenesis.

The cadherin-catenin complex is essential for tissue morphogenesis during animal development. In cultured mammalian cells, p120 catenin (p120ctn) is an important regulator of cadherin-catenin complex function. However, information on the role of p120ctn family members in cadherin-dependent events in vivo is limited. We have examined the role of the single Caenorhabditis elegans p120ctn homologue JAC-1 (juxtamembrane domain [JMD]-associated catenin) during epidermal morphogenesis. Similar to other p120ctn family members, JAC-1 binds the JMD of the classical cadherin HMR-1, and GFP-tagged JAC-1 localizes to adherens junctions in an HMR-1-dependent manner. Surprisingly, depleting JAC-1 expression using RNA interference (RNAi) does not result in any obvious defects in embryonic or postembryonic development. However, jac-1(RNAi) does increase the severity and penetrance of morphogenetic defects caused by a hypomorphic mutation in the hmp-1/alpha-catenin gene. In these hmp-1 mutants, jac-1 depletion causes failure of the embryo to elongate into a worm-like shape, a process that involves contraction of the epidermis. Associated with failed elongation is the detachment of actin bundles from epidermal adherens junctions and failure to maintain cadherin in adherens junctions. These results suggest that JAC-1 acts as a positive modulator of cadherin function in C. elegans.

The C. elegans hmr-1 gene can encode a neuronal classic cadherin involved in the regulation of axon fasciculation.

Nervous system morphogenesis is characterized by extensive interactions between individual axon growth cones and their cellular environments. Selective cell adhesion is one mechanism by which the growth of an axon can be modulated, and members of the classic cadherin group of cell adhesion molecules have been shown to play a role in this process in both vertebrates and Drosophila. In Drosophila, there are two classic cadherins: one involved primarily in regulating the morphogenesis of epithelia, and the other, DN-cadherin, required almost exclusively in neuronal development. In contrast, C. elegans has a single classic cadherin gene, hmr-1, whose function is required for epithelial morphogenesis. We show here that hmr-1 also encodes a second classic cadherin via a novel mechanism involving an alternative, neuron-specific promoter, coupled with alternative splicing. This novel HMR-1 isoform is very similar to DN-cadherin, and a mutant strain that specifically lacks the function of this isoform displays defects in the fasciculation and outgrowth of a subset of motor neuron processes; a phenotype that resembles loss of DN-cadherin function in Drosophila. These results indicate that Drosophila and C. elegans share a conserved, cadherin-dependent mechanism involved in regulating axonal patterning and fasciculation.