Development and Validation of an Immuno-PET Tracer as a Companion Diagnostic Agent for Antibody-Drug Conjugate Therapy to Target the CA6 Epitope.

PURPOSE: To develop and compare three copper 64 ((64)Cu)-labeled antibody fragments derived from a CA6-targeting antibody (huDS6) as immuno-positron emission tomography (immuno-PET)-based companion diagnostic agents for an antibody-drug conjugate by using huDS6. MATERIALS AND METHODS: Three antibody fragments derived from huDS6 were produced, purified, conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and evaluated in the following ways: (a) the affinity of the fragments and the DOTA conjugates was measured via flow cytometry, (b) the stability of the labeled fragments was determined ex vivo in human serum over 24 hours, and (c) comparison of the in vivo imaging potential of the fragments was evaluated in mice bearing subcutaneous CA6-positive and CA6-negative xenografts by using serial PET imaging and biodistribution. Isotype controls with antilysozyme and anti-DM4 B-Fabs and blocking experiments with an excess of either B-Fab or huDS6 were used to determine the extent of the antibody fragment (64)Cu-DOTA-B-Fab binding specificity. Immunoreactivity and tracer kinetics were evaluated by using cellular uptake and 48-hour imaging experiments, respectively. Statistical analyses were performed by using t tests, one-way analysis of variance, and Wilcoxon and Mann-Whitney tests. RESULTS: The antibody fragment (64)Cu-DOTA-B-Fab was more than 95% stable after 24 hours in human serum, had an immunoreactivity of more than 70%, and allowed differentiation between CA6-positive and CA6-negative tumors in vivo as early as 6 hours after injection, with a 1.7-fold uptake ratio between tumors. Isotype and blocking studies experiments showed tracer-specific uptake in antigen-positive tumors, despite some nonspecific uptake in both tumor models. CONCLUSION: Three antibody fragments were produced and examined as potential companion diagnostic agents. (64)Cu-DOTA-B-Fab is a stable and effective immuno-PET tracer for CA6 imaging in vivo.

An end-to-end automated platform process for high-throughput engineering of next-generation multi-specific antibody therapeutics.

Next-generation multi-specific antibody therapeutics (MSATs) are engineered to combine several functional activities into one molecule to provide higher efficacy compared to conventional, mono-specific antibody therapeutics. However, highly engineered MSATs frequently display poor yields and less favorable drug-like properties (DLPs), which can adversely affect their development. Systematic screening of a large panel of MSAT variants in very high throughput (HT) is thus critical to identify potent molecule candidates with good yield and DLPs early in the discovery process. Here we report on the establishment of a novel, format-agnostic platform process for the fast generation and multiparametric screening of tens of thousands of MSAT variants. To this end, we have introduced full automation across the entire value chain for MSAT engineering. Specifically, we have automated the in-silico design of very large MSAT panels such that it reflects precisely the wet-lab processes for MSAT DNA library generation. This includes mass saturation mutagenesis or bulk modular cloning technologies while, concomitantly, enabling library deconvolution approaches using HT Sanger DNA sequencing. These DNA workflows are tightly linked to fully automated downstream processes for compartmentalized mammalian cell transfection expression, and screening of multiple parameters. All sub-processes are seamlessly integrated with tailored workflow supporting bioinformatics. As described here, we used this platform to perform multifactor optimization of a next-generation bispecific, cross-over dual variable domain-Ig (CODV-Ig). Screening of more than 25,000 individual protein variants in mono- and bispecific format led to the identification of CODV-Ig variants with over 1,000-fold increased potency and significantly optimized production titers, demonstrating the power and versatility of the platform.

Trispecific broadly neutralizing HIV antibodies mediate potent SHIV protection in macaques.

The development of an effective AIDS vaccine has been challenging because of viral genetic diversity and the difficulty of generating broadly neutralizing antibodies (bnAbs). We engineered trispecific antibodies (Abs) that allow a single molecule to interact with three independent HIV-1 envelope determinants: the CD4 binding site, the membrane-proximal external region (MPER), and the V1V2 glycan site. Trispecific Abs exhibited higher potency and breadth than any previously described single bnAb, showed pharmacokinetics similar to those of human bnAbs, and conferred complete immunity against a mixture of simian-human immunodeficiency viruses (SHIVs) in nonhuman primates, in contrast to single bnAbs. Trispecific Abs thus constitute a platform to engage multiple therapeutic targets through a single protein, and they may be applicable for treatment of diverse diseases, including infections, cancer, and autoimmunity.

CODV-Ig, a universal bispecific tetravalent and multifunctional immunoglobulin format for medical applications.

Bispecific immunoglobulins (Igs) typically contain at least two distinct variable domains (Fv) that bind to two different target proteins. They are conceived to facilitate clinical development of biotherapeutic agents for diseases where improved clinical outcome is obtained or expected by combination therapy compared to treatment by single agents. Almost all existing formats are linear in their concept and differ widely in drug-like and manufacture-related properties. To overcome their major limitations, we designed cross-over dual variable Ig-like proteins (CODV-Ig). Their design is akin to the design of circularly closed repeat architectures. Indeed, initial results showed that the traditional approach of utilizing (G4S)x linkers for biotherapeutics design does not identify functional CODV-Igs. Therefore, we applied an unprecedented molecular modeling strategy for linker design that consistently results in CODV-Igs with excellent biochemical and biophysical properties. CODV architecture results in a circular self-contained structure functioning as a self-supporting truss that maintains the parental antibody affinities for both antigens without positional effects. The format is universally suitable for therapeutic applications targeting both circulating and membrane-localized proteins. Due to the full functionality of the Fc domains, serum half-life extension as well as antibody- or complement-dependent cytotoxicity may support biological efficiency of CODV-Igs. We show that judicious choice in combination of epitopes and paratope orientations of bispecific biotherapeutics is anticipated to be critical for clinical outcome. Uniting the major advantages of alternative bispecific biotherapeutics, CODV-Igs are applicable in a wide range of disease areas for fast-track multi-parametric drug optimization.

Spectroscopic properties of PSI-IsiA supercomplexes from the cyanobacterium Synechococcus PCC 7942.

The cyanobacterium Synechococcus PCC 7942 grown under iron starvation assembles a supercomplex consisting of a trimeric Photosystem I (PSI) complex encircled by a ring of 18 CP43' or IsiA light-harvesting complexes [Nature 412 (2001) 745]. Here we present a spectroscopic characterization by temperature-dependent absorption and fluorescence spectroscopy, site-selective fluorescence spectroscopy at 5 K, and circular dichroism of isolated PSI-IsiA, PSI and IsiA complexes from this cyanobacterium grown under iron starvation. The results suggest that the IsiA ring increases the absorption cross-section of PSI by about 100%. Each IsiA subunit binds about 16-17 chlorophyll a (Chl a) molecules and serves as an efficient antenna for PSI. Each of the monomers of the trimeric PSI complex contains two red chlorophylls, which presumably give rise to one exciton-coupled dimer and at 5 K absorb and fluoresce at 703 and 713 nm, respectively. The spectral properties of these C-703 chlorophylls are not affected by the presence of the IsiA antenna ring. The spectroscopic properties of the purified IsiA complexes are similar to those of the related CP43 complex from plants, except that the characteristic narrow absorption band of CP43 at 682.5 nm is missing in IsiA.

Electric field effects on red chlorophylls, beta-carotenes and P700 in cyanobacterial Photosystem I complexes.

We have probed the absorption changes due to an externally applied electric field (Stark effect) of Photosystem I (PSI) core complexes from the cyanobacteria Synechocystis sp. PCC 6803, Synechococcus elongatus and Spirulina platensis. The results reveal that the so-called C719 chlorophylls in S. elongatus and S. platensis are characterized by very large polarizability differences between the ground and electronically excited states (with Tr(Deltaalpha) values up to about 1000 A(3) f(-2)) and by moderately high change in permanent dipole moments (with average Deltamu values between 2 and 3 D f(-1)). The C740 chlorophylls in S. platensis and, in particular, the C708 chlorophylls in all three species give rise to smaller Stark shifts, which are, however, still significantly larger than those found before for monomeric chlorophyll. The results confirm the hypothesis that these states originate from strongly coupled chlorophyll a molecules. The absorption and Stark spectra of the beta-carotene molecules are almost identical in all complexes and suggest similar or slightly higher values for Tr(Deltaalpha) and Deltamu than for those of beta-carotene in solution. Oxidation of P700 did not significantly change the Stark response of the carotenes and the red antenna states C719 and C740, but revealed in all PSI complexes changes around 700-705 and 690-693 nm, which we attribute to the change in permanent dipole moments of reduced P700 and the chlorophylls responsible for the strong absorption band at 690 nm with oxidized P700, respectively.

The calpain inhibitor MDL 28170 prevents inflammation-induced neurofilament light chain breakdown in the spinal cord and reduces thermal hyperalgesia.

Since long-term hyperexcitability of nociceptive neurons in the spinal cord has been suggested to be caused and maintained by changes of protein expression we assessed protein patterns in lumbar spinal cord during a zymosan induced paw inflammation employing two-dimensional (2D) gel electrophoresis. 2D PAGE revealed a time-dependent breakdown of scaffolding proteins one of which was neurofilament light chain (NFL) protein, which has been previously found to be important for axonal architecture and transport. Nociception induced breakdown of NFL in the spinal cord and dorsal root ganglias was prevented by pretreatment of the animals with a single dose of the specific inhibitor of the protease calpain (MDL-28170) which has been shown to be the primary protease involved in neurofilament degradation in neurodegenerative diseases. Treatment with the calpain inhibitor also provided anti-inflammatory and anti-hyperalgesic effects in the zymosan-induced paw inflammation model irrespective of whether the drug was administered systemically (i.p.) or delivered onto the lumbar spinal cord. This suggests that the activation of calpain is involved in the sensitization of nociceptive neurons what is partly due to neurofilament breakdown but cleavage of other calpain substrates may also be involved. Our results indicate that inhibition of pathological calpain activity may present an interesting novel drug target in the treatment of pain and inflammation.

Adaptation to iron deficiency: a comparison between the cyanobacterium Synechococcus elongatus PCC 7942 wild-type and a DpsA-free mutant.

To learn more about the adaptive response of Synechococcus elongatus PCC 7942 to iron starvation and the role of DpsA, presumably a protein protecting chromosomal DNA against oxidative damage, we performed a comparative analysis of S. elongatus PCC 7942 wild-type and a DpsA-free mutant, called K11. Relative to wild-type, the DpsA-free mutant had significantly higher amounts of phycocyanin and allophycocyanin, even upon iron limitation. While the Photosystem I activity in mutant K11 remained high under iron deficiency, the Photosystem II activity dropped severely with respect to wild-type. The DpsA content in wild-type was already fairly high under regular growth conditions and did not significantly increase under iron deficiency nor in the presence of 0.3 mM 2'2'-dipyridyl in iron-sufficient BG11 medium. Nevertheless, the absence of DpsA in K11 resulted in a significantly altered transcriptional/translational activity of genes known to be involved in adaptation to iron starvation. The amount of isiA/B transcript was about two-fold lower than in wild-type, resulting in a lower 77 K chlorophyll a fluorescence at 685 nm, implying a lower concentration of Photosystem I-IsiA supercomplexes. While in wild-type idiA, idiB, and irpA transcripts were highly up-regulated, hardly any were detectable in mutant K11 under iron limitation. The concentration of mapA transcript, however, was greatly increased in K11 compared to wild-type. Measurements of acridine yellow fluorescence with intact wild-type and K11 cells revealed that iron deficiency caused an increased contribution of cyclic electron transport to membrane energisation and ATP synthesis being in agreement with the formation of the Photosystem I-IsiA supercomplex. In addition, mutant K11 had a much higher respiratory activity compared to wild-type under iron limitation.

Purification of recombinant BtpA and Ycf3, proteins involved in membrane protein biogenesis in Synechocystis PCC 6803.

The gene products Ycf3 (hypothetical chloroplast open reading frame) and BtpA (biogenesis of thylakoid protein) are thought to be involved in the biogenesis of the membrane protein complex photosystem I (PSI) from Synechocystis PCC 6803. PSI consists of 12 different subunits and binds more than 100 cofactors, making it a model protein to study different aspects of membrane protein biogenesis. For a detailed biophysical characterization of Ycf3 and BtpA pure proteins must be available in sufficient quantities. Therefore we cloned the corresponding genes into expression vectors. To facilitate purification we created His-tagged versions of Ycf3 and BtpA in addition to the unmodified forms. Immobilized metal affinity chromatography (IMAC) yielded His-tagged proteins which were used for the production of antibodies. Purification strategies for non-tagged proteins could also be established: Ycf3 could be purified in soluble form using a two-step purification in which ammonium sulfate precipitation was combined with anion-exchange chromatography (IEC). BtpA had to be purified from inclusion bodies by two-consecutive IEC steps under denaturing conditions. An optimized refolding protocol was established that yielded pure BtpA. In all cases, MALDI-TOF peptide mass fingerprinting (PMF) was used to confirm protein identity. Initially, size exclusion chromatography and CD-spectroscopy were used for biophysical characterization of the proteins. Both Ycf3 and BtpA show homo-oligomerization in vitro. In summary, purification protocols for Ycf3 and BtpA have been designed that yield pure proteins which can be used to probe the molecular function of these proteins for membrane protein biogenesis.

Mapping the membrane proteome of Corynebacterium glutamicum.

In order to avoid the specific problems with intrinsic membrane proteins in proteome analysis, a new procedure was developed which is superior to the classical two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) method in terms of intrinsic membrane proteins. For analysis of the membrane proteome from Corynebacterium glutamicum, we replaced the first separation dimension, i.e., the isoelectric focusing step, by anion-exchange chromatography, followed by sodium dodecyl sulfate (SDS)-PAGE in the second separation dimension. Enrichment of the membrane intrinsic subproteome was achieved by washing with 2.5 M NaBr which removed more than 35% of the membrane-associated soluble proteins. For the extraction and solubilization of membrane proteins, the detergent amidosulfobetaine 14 (ASB-14) was most efficient in a detailed screening procedure and proved also suitable for chromatography. 356 gel bands were spotted, and out of 170 different identified proteins, 50 were membrane-integral. Membrane proteins with one up to 13 transmembrane helices were found. Careful analysis revealed that this new procedure covers proteins from a wide pI range (3.7-10.6) and a wide mass range of 10-120 kDa. About 50% of the identified membrane proteins belong to various functional categories like energy metabolism, transport, signal transduction, protein translocation, and proteolysis while for the others a function is not yet known, indicating the potential of the developed method for elucidation of membrane proteomes in general.

Localization and function of the IdiA homologue Slr1295 in the cyanobacterium Synechocystis sp. strain PCC 6803.

Slr1295 (and Slr0513) in the cyanobacterium Synechocystis sp. PCC 6803 has amino acid similarity to the bacterial FbpA protein family and also to IdiA of Synechococcus PCC 6301/PCC 7942. To determine whether Slr1295 is the periplasm-located component of an iron transporter, or has a function in protecting photosystem (PS) II, subcellular localization and Deltaslr1295 mutant characterization studies were performed. Localization of Slr1295 provided evidence that it has an intracellular function, since virtually no Slr1295 was detected in the soluble protein fraction of the periplasm or in the cytoplasmic membrane. Characterization of a Deltaslr1295 Synechocystis PCC 6803 mutant indicated that PS II is more susceptible to inactivation in the mutant than in the wild-type (WT). Under mild iron limitation, modification of PS I to the PS I-IsiA complex is more advanced in the Deltaslr1295 mutant, indicating that iron deficiency leads more rapidly to changes in the photosynthetic apparatus in the mutant than in the WT. Biochemical fractionation procedures provide evidence that Slr1295 co-purifies with PS II. These results suggest a function of Slr1295 that is comparable to the function of IdiA in Synechococcus PCC 6301/PCC 7942 being a protein that protects PS II under iron limitation in an as yet unknown way.