Immunoglobulin domain crossover as a generic approach for the production of bispecific IgG antibodies.

We describe a generic approach to assemble correctly two heavy and two light chains, derived from two existing antibodies, to form human bivalent bispecific IgG antibodies without use of artificial linkers. Based on the knobs-into-holes technology that enables heterodimerization of the heavy chains, correct association of the light chains and their cognate heavy chains is achieved by exchange of heavy-chain and light-chain domains within the antigen binding fragment (Fab) of one half of the bispecific antibody. This "crossover" retains the antigen-binding affinity but makes the two arms so different that light-chain mispairing can no longer occur. Applying the three possible "CrossMab" formats, we generated bispecific antibodies against angiopoietin-2 (Ang-2) and vascular endothelial growth factor A (VEGF-A) and show that they can be produced by standard techniques, exhibit stabilities comparable to natural antibodies, and bind both targets simultaneously with unaltered affinity. Because of its superior side-product profile, the CrossMab(CH1-CL) was selected for in vivo profiling and showed potent antiangiogenic and antitumoral activity.

Short-hairpin-RNA-mediated silencing of fucosyltransferase 8 in Chinese-hamster ovary cells for the production of antibodies with enhanced antibody immune effector function.

Antibody-producing Chinese-hamster ovary cells (CHO-DG44) were converted into cells producing antibodies with strongly enhanced ADCC (antibody-dependent cellular cytotoxicity) by knocking down FuT8 (alpha-1,6-fucosyltransferase or fucosyltransferase 8) via constitutive expression of shRNA (short-hairpin RNA) against FuT8. After the introduction of a FuT8 shRNA expression plasmid under the control of a U6 promoter, CHO-DG44 clones with less than 5% residual FuT8 mRNA expression were isolated by selection for neomycin resistance, followed by low affinity nerve growth factor receptor enrichment and selection for LCA [Lens culinaris (culinary lentil) agglutinin] resistance. The CHO-DG44 clones identified produced highly afucosylated anti-[IGF-1R (insulin-like-growth-factor-1 receptor)] antibodies (up to 88%) that exhibited considerably enhanced ADCC compared with anti-IGF-1R wild-type antibodies produced by parental CHO cells. At the same time, antibody productivity was not significantly decreased. Analysis of stability showed that the clones obtained may be suitable for up-scaling, since low residual levels of FuT8 mRNA and production of afucosylated antibodies were maintained for at least 4 weeks.

Light-regulated subcellular translocation of Drosophila TRPL channels induces long-term adaptation and modifies the light-induced current.

Drosophila phototransduction results in the opening of two classes of cation channels, composed of the channel subunits transient receptor potential (TRP), TRP-like (TRPL), and TRPgamma. Here, we report that one of these subunits, TRPL, is translocated back and forth between the signaling membrane and an intracellular compartment by a light-regulated mechanism. A high level of rhabdomeral TRPL, characteristic of dark-raised flies, is functionally manifested in the properties of the light-induced current. These flies are more sensitive than flies with no or reduced TRPL level to dim background lights, and they respond to a wider range of light intensities, which fit them to function better in darkness or dim background illumination. Thus, TRPL translocation represents a novel mechanism to fine tune visual responses.

The PDZ assembled "transducisome" of microvillar photoreceptors: the TRP/TRPL problem.

Two types of ion channels, TRP and TRPL, are activated upon light-absorption in rhabdomeral photo-receptor membranes of fly compound eyes. Whereas TRP is associated with other signaling proteins into a multiprotein complex (transducisome), the molecular organization of TRPL is discussed controversely. We analysed the TRPL content of blowfly rhabdomeral membranes and investigated by co-immunoprecipitation studies whether or not TRPL is part of the transducisome. Compared to TRP there are at least ten times less TRPL molecules present in the rhabdomeral membrane. A small fraction of the total TRPL present co-immunoprecipitates with other proteins of the transducisome and vice versa. Our data suggest that a significant fraction of TRPL is not incorporated into the transducisome. This fraction may either form independent ion channels or bind to the transducisome transiently.

A novel angiopoietin-2 selective fully human antibody with potent anti-tumoral and anti-angiogenic efficacy and superior side effect profile compared to Pan-Angiopoietin-1/-2 inhibitors.

There is increasing experimental evidence for an important role of Angiopoietin-2 (Ang-2) in tumor angiogenesis and progression. In addition, Ang-2 is up-regulated in many cancer types and correlated with poor prognosis. To investigate the functional role of Ang-2 inhibition in tumor development and progression, we generated novel fully human antibodies that neutralize specifically the binding of Ang-2 to its receptor Tie2. The selected antibodies LC06 and LC08 recognize both rodent and human Ang-2 with high affinity, but LC06 shows a higher selectivity for Ang-2 over Ang-1 compared to LC08 which can be considered an Ang-2/Ang-1 cross-reactive antibody. Our data demonstrate that Ang-2 blockade results in potent tumor growth inhibition and pronounced tumor necrosis in subcutaneous and orthotopic tumor models. These effects are attended with a reduction of intratumoral microvessel density and tumor vessels characterized by fewer branches and increased pericyte coverage. Furthermore, anti-Ang-2 treatment strongly inhibits the dissemination of tumor cells to the lungs. Interestingly, in contrast to the Ang-2/Ang-1 cross-reactive antibody LC08 that leads to a regression of physiological vessels in the mouse trachea, the inhibition with the selective anti-Ang-2 antibody LC06 appears to be largely restricted to tumor vasculature without obvious effects on normal vasculature. Taken together, these data provide strong evidence for the selective Ang-2 antibody LC06 as promising new therapeutic agent for the treatment of various cancers.