Assay pH and critical reagent optimization in measuring concentrations of a monoclonal antibody and its target.

Aim: To mitigate assay interference in the drug and target assays to support the development of monoclonal antibody REGN-Z. Results: Mild acidic assay conditions and capture and detection antibodies with different affinities and t1/2 under different assay pHs were used to mitigate interference in the total drug and total target assays. A free target assay was also developed using a lower-affinity capture antibody with a much slower association and dissociation rate. The impact of sample incubation, dilution and storage on the accurate detection of the free target was also evaluated. Conclusion: The total drug, total and free target assays can accurately quantitate drug and target concentrations when tested with a subset of clinical study samples.

Inhibition of complement pathway activation with Pozelimab, a fully human antibody to complement component C5.

Complement is a key component of the innate immune system. Inappropriate complement activation underlies the pathophysiology of a variety of diseases. Complement component 5 (C5) is a validated therapeutic target for complement-mediated diseases, but the development of new therapeutics has been limited by a paucity of preclinical models to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) properties of candidate therapies. The present report describes a novel humanized C5 mouse and its utility in evaluating a panel of fully human anti-C5 antibodies. Surprisingly, humanized C5 mice revealed marked differences in clearance rates amongst a panel of anti-C5 antibodies. One antibody, pozelimab (REGN3918), bound C5 and C5 variants with high affinity and potently blocked complement-mediated hemolysis in vitro. In studies conducted in both humanized C5 mice and cynomolgus monkeys, pozelimab demonstrated prolonged PK and durable suppression of hemolytic activity ex vivo. In humanized C5 mice, a switch in dosing from in-house eculizumab to pozelimab was associated with normalization of serum C5 concentrations, sustained suppression of hemolytic activity ex vivo, and no overt toxicity. Our findings demonstrate the value of humanized C5 mice in identifying new therapeutic candidates and treatment options for complement-mediated diseases.

Kappa-on-Heavy (KoH) bodies are a distinct class of fully-human antibody-like therapeutic agents with antigen-binding properties.

We describe a Kappa-on-Heavy (KoH) mouse that produces a class of highly diverse, fully human, antibody-like agents. This mouse was made by replacing the germline variable sequences of both the Ig heavy-chain (IgH) and Ig kappa (IgK) loci with the human IgK germline variable sequences, producing antibody-like molecules with an antigen binding site made up of 2 kappa variable domains. These molecules, named KoH bodies, structurally mimic naturally existing Bence-Jones light-chain dimers in their variable domains and remain wild-type in their antibody constant domains. Unlike artificially diversified, nonimmunoglobulin alternative scaffolds (e.g., DARPins), KoH bodies consist of a configuration of normal Ig scaffolds that undergo natural diversification in B cells. Monoclonal KoH bodies have properties similar to those of conventional antibodies but exhibit an enhanced ability to bind small molecules such as the endogenous cardiotonic steroid marinobufagenin (MBG) and nicotine. A comparison of crystal structures of MBG bound to a KoH Fab versus a conventional Fab showed that the KoH body has a much deeper binding pocket, allowing MBG to be held 4 Å further down into the combining site between the 2 variable domains.

A novel bispecific antibody platform to direct complement activity for efficient lysis of target cells.

Harnessing complement-mediated cytotoxicity by therapeutic antibodies has been limited because of dependency on size and density of antigen, structural constraints resulting from orientation of antibody binding, and blockade of complement activation by inhibitors expressed on target cells. We developed a modular bispecific antibody platform that directs the complement-initiating protein C1q to target cells, increases local complement deposition and induces cytotoxicity against target antigens with a wide-range of expression. The broad utility of this approach to eliminate both prokaryotic and eukaryotic cells was demonstrated by pairing a unique C1q-recruiting arm with multiple targeting arms specific for Staphylococcus aureus, Pseudomonas aeruginosa, B-cells and T-cells, indicating applicability for diverse indications ranging from infectious diseases to cancer. Generation of C1q humanized mice allowed for demonstration of the efficacy of this approach to clear disease-inducing cells in vivo. In summary, we present a novel, broadly applicable, and versatile therapeutic modality for targeted cell depletion.

ImmunoPET Imaging of Endogenous and Transfected Prolactin Receptor Tumor Xenografts.

Antibodies labeled with positron-emitting isotopes have been used for tumor detection, predicting which patients may respond to tumor antigen-directed therapy, and assessing pharmacodynamic effects of drug interventions. Prolactin receptor (PRLR) is overexpressed in breast and prostate cancers and is a new target for cancer therapy. We evaluated REGN2878, an anti-PRLR monoclonal antibody, as an immunoPET reagent. REGN2878 was labeled with Zr-89 after conjugation with desferrioxamine B or labeled with I-131/I-124. In vitro determination of the half-maximal inhibitory concentration (IC50) of parental REGN2878, DFO-REGN2878, and iodinated REGN2878 was performed by examining the effect of the increasing amounts of these on uptake of trace-labeled I-131 REGN2878. REGN1932, a non-PRLR binding antibody, was used as a control. Imaging and biodistribution studies were performed in mice bearing tumor xenografts with various expression levels of PRLR, including MCF-7, transfected MCF-7/PRLR, PC3, and transfected PC3/PRLR and T4D7v11 cell lines. The specificity of uptake in tumors was evaluated by comparing Zr-89 REGN2878 and REGN1932, and in vivo competition compared Zr-89 REGN2878 uptake in tumor xenografts with and without prior injection of 2 mg of nonradioactive REGN2878. The competition binding assay of DFO-REGN2878 at ratios of 3.53-5.77 DFO per antibody showed IC50 values of 0.4917 and 0.7136 nM, respectively, compared to 0.3455 nM for parental REGN2878 and 0.3343 nM for I-124 REGN2878. Imaging and biodistribution studies showed excellent targeting of Zr-89 REGN2878 in PRLR-positive xenografts at delayed times of 189 h (presented as mean ± 1 SD, percent injected activity per mL (%IA/mL) 74.6 ± 33.8%IA/mL). In contrast, MCF-7/PRLR tumor xenografts showed a low uptake (7.0 ± 2.3%IA/mL) of control Zr-89 REGN1932 and a very low uptake and rapid clearance of I-124 REGN2878 (1.4 ± 0.6%IA/mL). Zr-89 REGN2878 has excellent antigen-specific targeting in various PRLR tumor xenograft models. We estimated, using image-based kinetic modeling, that PRLR antigen has a very rapid in vivo turnover half-life of ∼14 min from the cell membrane. Despite relatively modest estimated tumor PRLR expression numbers, PRLR-expressing cells have shown final retention of the Zr-89 REGN2878 antibody, with an uptake that appeared to be related to PRLR expression. This reagent has the potential to be used in clinical trials targeting PRLR.

Preparation and characterization of albumin conjugates of a truncated peptide YY analogue for half-life extension.

Recombinant human serum albumin (HSA) conjugates of a 15-amino-acid truncated peptide YY (PYY) analogue were prepared using three heterobifunctional linkers [succinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (SMCC), 6-maleimidohexanoic acid N-hydroxysuccinimide ester (MHS), and N-[γ-maleimidobutyryloxy]sulfosuccinimide ester (GMBS)] in 2 synthetic steps involving (1) reaction of succinimidyl ester on linker with ε-amine of Lys2 on the peptide and (2) reaction of maleimide on peptide linker with free thiol of Cysteine 34 (Cys34) on albumin. In-process controls using ESI LC-MS were used to follow reactions and identify reaction products. Proteolytic digests of the conjugate revealed that peptide conjugation occurs at Cys34 on HSA. Conjugates were assayed in cell-based assays to determine potency at the human Y2-receptor, and selectivity at the human Y1-, Y4-, and Y5-receptors using a calcium flux assay. All three conjugates assayed were selective agonists of the Y2-receptor, and displayed nanomolar potencies. MCC and MH conjugates were selected for acute PK/PD studies in DIO mice. Significant reduction in food intake was observed with the MH conjugate, which lasted for 24 h at the 10 mg (or 4 µmol)/kg dose. While the MCC conjugate exhibited greater potency in vitro, it was slightly less effective than the MH conjugate in vivo with respect to reduction in food intake. Both conjugates were significantly less active than the peptide coupled to a 30 kDa PEG. The observed T1/2 (8-9 h) for both conjugates was significantly lower than that observed for the PEGylated peptide (∼25 h). These results suggest that, as compared with the unmodified and PEGylated peptide, the extended circulation half-life of albumin conjugates is mediated through uptake and recirculation by FcRn, and allometric scaling methods are necessary to account for interspecies variation in pharmacokinetic properties.

Affinity purification and characterization of an anti-PEG IgM.

Anti-PEG IgM was purified by affinity chromatography using variable length PEG chains (5, 10, 20 and 30 kDa) as affinity ligands. Maximal binding of anti-PEG IgM was observed using the 30 kDa PEG-derivatized NuGel (single passage). Purified anti-PEG IgM was characterized for binding to PEG functionalized proteins/peptides by surface plasmon resonance, western blotting and ELISA. Anti-PEG IgM, in solution and adsorbed on 20 kDa PEG-derivatized NuGel, was subjected to pepsin digestion followed by affinity chromatography. SDS-PAGE analysis of eluates in both preparations yielded one fragment that was similar in size. However, an additional lower molecular weight band was observed in solution-digested affinity purified material that was not present in the eluate from the material subjected to pepsin digestion on the affinity matrix. The lower MW fragment could be eluted under milder conditions, suggesting loss of binding multiplicity. Analysis by mass spectrometry yielded molecular weights of 132 kDa (both) and 82 kDa (solution) for the respective fragments. N-terminal sequencing of both fragments resulted in primary sequences (heavy and light chains) that were not only identical to each other but also to those of native IgM. The anti-PEG IgM fragments were characterized for binding to pegylated interferon alfa-2a by ELISA. The results from these studies suggest that affinity purified anti-PEG IgM and fragments can be used as probes in detection assays for PEG functionalized biotherapeutics in pre-clinical and clinical studies.

Mucocutaneous lesions of Behcet's disease.

Behcet's disease is particularly prevalent in "Silk Route" populations, but it has a global distribution. The diagnosis of the disease is based on clinical criteria as there is as yet no pathognomonic test, and mucocutaneous lesions, which figure prominently in the presentation and diagnosis, may be considered the diagnostic hallmarks. Among the internationally accepted criteria, painful oral and genital ulcers, cutaneous vasculitic lesions and reactivity of the skin to needle prick or injection (the pathergy reaction) are considered hallmarks of Behcet's disease, and often precede other manifestations. Their recognition may permit earlier diagnosis and treatment, with salutary results. This paper describes the various lesions that constitute the syndrome and focuses on those that may be considered characteristic.

A benefit/risk assessment of existing therapeutic alternatives for the treatment of painful inflammatory conditions.

Pain remains the leading reason for which patients consult their doctors. Pain also motivates over-the-counter sales of analgesic medicines, to be taken orally or even transcutaneously. Prescription medicines usually follow attempts at self-medication that fail to achieve the desired results. Acute pain usually subsides spontaneously but medicines are needed until that occurs; in arthritic conditions--especially osteoarthritis--anti-inflammatory drugs work best in short-term administration for flares that aggravate chronic but tolerable pain. In cases of chronic pain that exceeds the level of easy tolerance, anti-inflammatory drugs can reduce the pain to tolerable levels more effectively than simple analgesics and narcotic combinations. The non-steroidal anti-inflammatory drugs (NSAIDs) are among the most useful medicines providing an array of drugs that differ chiefly in time of onset of action, duration of action and persistence in the blood. The benefit they provide is pain amelioration; none is curative. The risks are well known and do not differ greatly among the drugs; unwanted gastrointestinal (GI) effects are the most common, but the skin, kidneys, liver and blood forming organs may also be affected. As the benefits are similar, when balancing risk and benefit it is important to: consider the cause and expected duration of pain, balance the risks (GI unwanted effects far outnumber others), assess the severity and likelihood of specific reactions, and consider the costs--not only of the medicines themselves but also those of treating untoward reactions. Thus NSAIDs number among the most successful therapeutic options of modern medicine and, as pain will continue to require intervention, will likely continue--at least as ancillary medications--even as more definitive treatments are developed. In addition, the target population, its characteristics and the duration and acceptance of the intervention need to be considered.

Back pain.

Back pain is ubiquitous and probably plagues almost everyone in all cultures and ethnic groups at some time (around 20% annually), and in up to 50% of these at least once a year. The WHO-COPCORD epidemiologic investigations have established its prevalence even in countries that had been unaware of its frequency in their populace, and factors involving type of work and training probably accounted for this misperception. Medical journals are replete with articles addressing diagnosis and treatment, but the majority fail to meet the standards needed for metaanalysis or comparison. A task force of the Agency for Health Care Policy and Research of the United States Department of Health and Human Services screened more than 10,000 abstracts, eliminated the majority of these studies and papers, and still was unable to recommend the best approach even to acute back pain; the problem of subacute and chronic back pain is even more formidable. Yet back pain has been identified as perhaps the major cause of disability and absenteeism from the workplace worldwide. WHO chiefly addressed subacute back pain, as most acute back pain is self-limited and ends spontaneously, almost regardless of the treatment. Subacute pain is the intermediate stage toward chronic pain, which defies most treatments. Specific causes for back pain, such as infections, tumors, osteoporosis, spondyloarthropathies, and trauma, actually represent a minority of such pain syndromes, qualifying for specific therapeutic approaches. A major problem in defining the burden of disease for back pain has been a dearth of agreed-upon outcome measures by which to judge the various interventions, and this was the task that the WHO Low Back Pain Initiative took upon itself. Among measures recommended to be included in all studies, so that valid comparisons could be made, were measurement of pain by visual analog scales, somatic perception, the Oswestry disability and modified Zung questionnaires, and a modified Schober test of spinal mobility. These measures are needed for studies, not for diagnosis or treatment of individual patients. They have been translated into various major languages and validated by back-translations, and applied in comparative studies in various cultures to medical, chiropractic, and other common interventions. The importance of such scientifically sound studies cannot be overemphasized, as the costs of health care are mounting everywhere and it therefore becomes imperative to develop cost-effective approaches. All the more so as conversion of acute back pain to chronic back pain is often iatrogenic, with strong psychosocial factors as well, so that not only what to do but also what not to do become important public health issues. The general lack of attention to back pain by governments and organizations probably results from the fact that it is perceived as a syndromic presentation with myriad causes rather than as a specific disease entity. Even if the "disease" names classify like presentations but are not necessarily etiologically discrete, syndromic diagnoses that subsume a variety of causes receive less attention; international rankings of common disabilities and public health problems tend to emphasize the named disorders rather than the grouped disorders. Moreover, back pain is often self-treated with nonprescription medications or alternative therapies, and by nonmedical practitioners or treatments in many parts of the world. Validation of outcomes therefore not only reduces invalidism and direct costs but also reduces the indirect costs of absenteeism and medical care.