Technology comparisons for anti-therapeutic antibody and neutralizing antibody assays in the context of an anti-TNF pharmacokinetic study

Biology of anti-TNF agents in immune-mediated inflammatory diseases: therapeutic implications

Biologics are increasingly being used to modify the course of immune-mediated inflammatory diseases. Some main agents are monoclonal antibodies and a fusion-protein that target TNF. This group includes adalimumab, infliximab, certolizumab pegol, golimumab and etanercept. Although the efficacy of anti-TNFs is supported by numerous randomized clinical trials, their pharmacokinetics depend on many factors, in particular immunogenicity, which can cause marked and rapid clearance and a consequent decrease in efficacy. Kinetics involve receptors that recognize the Fc fragment of the antibody and are responsible for various processes. Pharmacological advances permit optimizing the pharmacokinetics of anti-TNFs. In this review, we examine the kinetics of anti-TNF biologics, and consequent therapeutic implications, and overview some latest developments in the field. First draftsubmitted: 17 May 2016; Accepted for publication: 15 September2016; Published online: 14 October 2016.

Effects of altered FcγR binding on antibody pharmacokinetics in cynomolgus monkeys

Antibody interactions with Fcγ receptors (FcγRs), like FcγRIIIA, play a critical role in mediating antibody effector functions and thereby contribute significantly to the biologic and therapeutic activity of antibodies. Over the past decade, considerable work has been directed towards production of antibodies with altered binding affinity to FcγRs and evaluation of how the alterations modulate their therapeutic activity. This has been achieved by altering glycosylation status at N297 or by engineering modifications in the crystallizable fragment (Fc) region. While the effects of these modifications on biologic activity and efficacy have been examined, few studies have been conducted to understand their effect on antibody pharmacokinetics (PK). We present here a retrospective analysis in which we characterize the PK of three antibody variants with decreased FcγR binding affinity caused by amino acid substitutions in the Fc region (N297A, N297G, and L234A/L235A) and three antibody variants with increased FcγRIIIA binding affinity caused by afucosylation at N297, and compare their PK to corresponding wild type antibody PK in cynomolgus monkeys. For all antibodies, PK was examined at a dose that was known to be in the linear range. Since production of the N297A and N297G variants in Chinese hamster ovary cells results in aglycosylated antibodies that do not bind to FcγRs, we also examined the effect of expression of an aglycosylated antibody, without sequence change(s), in E. coli. All the variants demonstrated similar PK compared with that of the wild type antibodies, suggesting that, for the six antibodies presented here, altered FcγR binding affinity does not affect PK.

Modeling approach to investigate the effect of neonatal Fc receptor binding affinity and anti-therapeutic antibody on the pharmacokinetic of humanized monoclonal anti-tumor necrosis factor-α IgG antibody in cynomolgus monkey

PURPOSE

Several neonatal Fc receptor (FcRn) variants of an anti-tumor necrosis factor (TNF)-α humanized monoclonal IgG antibodies (mAbs) were developed but the effect of their differential FcRn binding affinities on pharmacokinetic (PK) behavior were difficult to be definitively measured in vivo due to formation of anti-therapeutic antibody (ATA). A semi-mechanistic model was developed to investigate the quantitative relationship between the FcRn binding affinity and PK of mAbs in cynomolgus monkey with the presence of ATA.

METHODS

PK and ATA data from cynomolgus monkeys which received a single intravenous dose of adalimumab, wild-type or two FcRn variant (N434H and N434A) anti-TNF-α mAbs were included in the analysis. Likelihood-based censored data handling method was used to include many PK observations with BQL values for model development. A fully integrated PK-ATA model was developed and used to fit simultaneously to the PK/ATA data.

RESULTS AND CONCLUSIONS

The PK and ATA time-profiles and effect of FcRn-binding affinity on PK of mAbs were well described by the model and the parameters were estimated with good precision. The model was used successfully to construct quantitative relationships between FcRn binding affinity and PK of anti-TNF-α mAbs in the presence of the ATA-mediated elimination and interferences.

An automated immunoassay for early specificity profiling of antibodies

Antibody-based therapeutics are of great value for the treatment of human diseases. In addition to functional activity, affinity or physico-chemical properties, antibody specificity is considered to be one of the most crucial attributes for safety and efficacy. Consequently, appropriate studies are required before entering clinical trials. High content protein arrays are widely applied to assess antibody specificity, but this commercial solution can only be applied to final therapeutic antibody candidates because such arrays are expensive and their throughput is limited. A flexible, high-throughput and economical assay that allows specificity testing of IgG or Fab molecules during early discovery is described here. The 384-well microtiter plate assay contains a comprehensive panel of 32 test proteins and uses electrochemiluminescence as readout. The Protein Panel Profiling ( 3P) was used to analyze marketed therapeutic antibodies that all showed highly specific binding profiles. Subsequently, 3P was applied to antibody candidates from early discovery and the results compared well with those obtained with a commercially available high content protein chip. Our results suggest that 3P can be applied as an additional filter for lead selection, allowing the identification of favorable antibody candidates in early discovery and thereby increasing the speed and possibility of success in drug development.

Improved analytical methods for the detection and quantification of neutralizing antibodies to biopharmaceuticals

Biopharmaceuticals are used extensively for the treatment of a number of chronic debilitating and fatal diseases such as cancer and inflammatory or autoimmune diseases. Although biopharmaceuticals are in general well tolerated, the development of anti-drug antibodies can impair their safety and efficacy. Assessment of immunogenicity is essential for a more effective and rational use of biopharmaceuticals, and is dependent upon the establishment of efficient standardized assays that allow direct comparison of immunogenicity data with clinical outcome. Although regulatory authorities recommend the use of cell-based assays that reflect the mechanism of action of the drug for the detection of neutralizing anti-drug antibodies, conventional cell-based assays are difficult to standardize and often give variable results. A number of strategies have been adopted to improve the performance of cell-based assays, including quantification of drug-induced proteins using either real-time RT-PCR or branched DNA to detect mRNA, or ELISAs to detect protein, bridging assays using immobilized cells and the use of reporter gene assays. The relative merits and limitations of each of these methods is reviewed herein.

Challenges in developing bioanalytical assays for characterization of antibody–drug conjugates

With more than 34 targets being investigated and nearly 20 clinical trials at various phases of development, antibody–drug conjugates (ADCs) hold a lot of promise for improving oncological malignancy therapy. This therapeutic strategy designed to specifically or preferentially deliver a cytotoxic agent to tumor cells through conjugation to a monoclonal antibody is not new. Although this approach is relatively simple conceptually, the history of ADCs clearly attests to the high degree of complexity in their development. Each component of an ADC is important to achieve efficacy with minimal toxicity, and the ability to monitor this multicomponent therapeutic entity is deemed to be critical for their successful optimization. In this article we review the different bioanalytical strategies that have been implemented to characterize various ADCs and discuss the challenges and issues associated with these approaches.

First-line chemoimmunotherapy in metastatic breast carcinoma: combination of paclitaxel and IMP321 (LAG-3Ig) enhances immune responses and antitumor activity

Background

IMP321 is a recombinant soluble LAG-3Ig fusion protein that binds to MHC class II with high avidity and mediates APC and then antigen-experienced memory CD8⁺ T cell activation. We report clinical and biological results of a phase I/II in patients with metastatic breast carcinoma (MBC) receiving first-line paclitaxel weekly, 3 weeks out of 4.

Methods

MBC patients were administered one dose of IMP321 s.c. every two weeks for a total of 24 weeks (12 injections). The repeated single doses were administered the day after chemotherapy at D2 and D16 of the 28-day cycles of paclitaxel (80 mg/m² at D1, D8 and D15, for 6 cycles). Blood samples were taken 13 days after the sixth and the twelfth IMP321 injections to determine sustained APC, NK and memory CD8 T cell responses.

Results

Thirty MBC patients received IMP321 in three cohorts (doses: 0.25, 1.25 and 6.25 mg). IMP321 induced both a sustained increase in the number and activation of APC (monocytes and dendritic cells) and an increase in the percentage of NK and long-lived cytotoxic effector-memory CD8 T cells. Clinical benefit was observed for 90% of patients with only 3 progressors at 6 months. Also, the objective tumor response rate of 50% compared favorably to the 25% rate reported in the historical control group.

Conclusions

The absence of toxicity and the demonstration of activity strongly support the future development of this agent for clinical use in combined first-line regimens.

Trial registration

ClinicalTrials.gov NCT00349934

Therapeutic monoclonal antibody concentration monitoring: free or total?

Most therapeutic monoclonal antibodies are designed to bind a specific antigen to elicit pharmacological effects. Accurate quantification of a therapeutic monoclonal antibody in biological matrices is essential for assessing its pharmacokinetics and selecting an effective dosing regimen. Therapeutic antibodies may exist in free, partially bound and fully bound forms in the bloodstream. The choice of which form(s) to measure and how to measure them is gaining much attention with the increase in the number of soluble therapeutic targets. This article will review the bioanalytical methods used in supporting the clinical development of the US FDA-approved therapeutic monoclonal antibodies and also discuss how different factors, such as assay format, target and antibody concentrations, and sample dilutions, can have an impact on the measurement of each form of antibody. Appreciation of which form of drug is being measured and what factors may impact measurement under different conditions are important for interpretation of the pharmacokinetics of therapeutic antibodies.

Pharmacokinetics of humanized monoclonal anti-tumor necrosis factor-{alpha} antibody and its neonatal Fc receptor variants in mice and cynomolgus monkeys

The neonatal Fc receptor (FcRn) plays a critical role in maintaining homeostasis of IgG antibodies. Recent studies have shown that the FcRn-IgG interaction can be modulated to alter the pharmacokinetics of the antibody. This has been achieved by altering amino acid residues in the FcRn-binding domain of the antibody, resulting in a change in the pH-dependent binding affinity of the antibody to FcRn. The purpose of this study was to examine the impact of the pH-dependent FcRn binding affinity on the pharmacokinetics of the antibody with changes in the Asn434 residue. Two anti-tumor necrosis factor-alpha monoclonal antibody (mAb) FcRn variants (N434A and N434H) were engineered, and pharmacokinetic studies of the two FcRn variants together with the wild type (WT) were conducted in mice and cynomolgus monkeys. N434A, which had binding properties to murine FcRn similar to those of the WT, had the same pharmacokinetic profile as the WT in mice. N434H, with the highest binding affinity to murine FcRn at pH 7.4, had a faster clearance (16.1 ml/day/kg) and a lower bioavailability (61.3%) compared with the WT (5.07 ml/day/kg, 73.2%) and N434A (5.90 ml/day/kg, 72.4%) in mice. N434A and N434H, which had higher binding affinity at pH 6.0 to monkey FcRn with comparable affinity at pH 7.4, had significantly higher areas under the serum concentration-time curve from time 0 to day 7 than the WT (749 +/- 71.9 and 819 +/- 81.5 versus 592 +/- 56.8 microg/ml . day) in monkeys. Thus, increasing the binding affinity of mAbs to FcRn at pH 6.0 while keeping a low binding affinity at pH 7.4 improves the pharmacokinetics of these molecules.