In vivo biodistribution and pharmacokinetics of sotrovimab, a SARS-CoV-2 monoclonal antibody, in healthy cynomolgus monkeys.

PURPOSE: Sotrovimab (VIR-7831), a human IgG1κ monoclonal antibody (mAb), binds to a conserved epitope on the SARS-CoV-2 spike protein receptor binding domain (RBD). The Fc region of VIR-7831 contains an LS modification to promote neonatal Fc receptor (FcRn)-mediated recycling and extend its serum half-life. Here, we aimed to evaluate the impact of the LS modification on tissue biodistribution, by comparing VIR-7831 to its non-LS-modified equivalent, VIR-7831-WT, in cynomolgus monkeys. METHODS: 89Zr-based PET/CT imaging of VIR-7831 and VIR-7831-WT was performed up to 14 days post injection. All major organs were analyzed for absolute concentration as well as tissue:blood ratios, with the focus on the respiratory tract, and a physiologically based pharmacokinetics (PBPK) model was used to evaluate the tissue biodistribution kinetics. Radiomics features were also extracted from the PET images and SUV values. RESULTS: SUVmean uptake in the pulmonary bronchi for 89Zr-VIR-7831 was statistically higher than for 89Zr-VIR-7831-WT at days 6 (3.43 ± 0.55 and 2.59 ± 0.38, respectively) and 10 (2.66 ± 0.32 and 2.15 ± 0.18, respectively), while the reverse was observed in the liver at days 6 (5.14 ± 0.80 and 8.63 ± 0.89, respectively), 10 (4.52 ± 0.59 and 7.73 ± 0.66, respectively), and 14 (4.95 ± 0.65 and 7.94 ± 0.54, respectively). Though the calculated terminal half-life was 21.3 ± 3.0 days for VIR-7831 and 16.5 ± 1.1 days for VIR-7831-WT, no consistent differences were observed in the tissue:blood ratios between the antibodies except in the liver. While the lung:blood SUVmean uptake ratio for both mAbs was 0.25 on day 3, the PBPK model predicted the total lung tissue and the interstitial space to serum ratio to be 0.31 and 0.55, respectively. Radiomics analysis showed VIR-7831 had mean-centralized PET SUV distribution in the lung and liver, indicating more uniform uptake than VIR-7831-WT. CONCLUSION: The half-life extended VIR-7831 remained in circulation longer than VIR-7831-WT, consistent with enhanced FcRn binding, while the tissue:blood concentration ratios in most tissues for both drugs remained statistically indistinguishable throughout the course of the experiment. In the bronchiolar region, a higher concentration of 89Zr-VIR-7831 was detected. The data also allow unparalleled insight into tissue distribution and elimination kinetics of mAbs that can guide future biologic drug discovery efforts, while the residualizing nature of the 89Zr label sheds light on the sites of antibody catabolism.

Evaluation of organic anion transporting polypeptide 1B1 and 1B3 humanized mice as a translational model to study the pharmacokinetics of statins.

Organic anion transporting polypeptide (Oatp) 1a/1b knockout and OATP1B1 and -1B3 humanized mouse models are promising tools for studying the roles of these transporters in drug disposition. Detailed characterization of these models will help to better understand their utility for predicting clinical outcomes. To advance this approach, we carried out a comprehensive analysis of these mouse lines by evaluating the compensatory changes in mRNA expression, quantifying the amounts of OATP1B1 and -1B3 protein by liquid chromatography-tandem mass spectrometry, and studying the active uptake in isolated hepatocytes and the pharmacokinetics of some prototypical substrates including statins. Major outcomes from these studies were 1) mostly moderate compensatory changes in only a few genes involved in drug metabolism and disposition, 2) a robust hepatic expression of OATP1B1 and -1B3 proteins in the respective humanized mouse models, and 3) functional activities of the human transporters in hepatocytes isolated from the humanized models with several substrates tested in vitro and with pravastatin in vivo. However, the expression of OATP1B1 and -1B3 in the humanized models did not significantly alter liver or plasma concentrations of rosuvastatin and pitavastatin compared with Oatp1a/1b knockout controls under the conditions used in our studies. Hence, although the humanized OATP1B1 and -1B3 mice showed in vitro and/or in vivo functional activity with some statins, further characterization of these models is required to define their potential use and limitations in the prediction of drug disposition and drug-drug interactions in humans.

Discovery of RXFP2 genetic association in resistant hypertensive men and RXFP2 antagonists for the treatment of resistant hypertension.

Hypertension remains a leading cause of cardiovascular and kidney diseases. Failure to control blood pressure with ≥ 3 medications or control requiring ≥ 4 medications is classified as resistant hypertension (rHTN) and new therapies are needed to reduce the resulting increased risk of morbidity and mortality. Here, we report genetic evidence that relaxin family peptide receptor 2 (RXFP2) is associated with rHTN in men, but not in women. This study shows that adrenal gland gene expression of RXFP2 is increased in men with hypertension and the RXFP2 natural ligand, INSL3, increases adrenal steroidogenesis and corticosteroid secretion in human adrenal cells. To address the hypothesis that RXFP2 activation is an important mechanism in rHTN, we discovered and characterized small molecule and monoclonal antibody (mAb) blockers of RXFP2. The novel chemical entities and mAbs show potent, selective inhibition of RXFP2 and reduce aldosterone and cortisol synthesis and release. The RXFP2 mAbs have suitable rat pharmacokinetic profiles to evaluate the role of RXFP2 in the development and maintenance of rHTN. Overall, we identified RXFP2 activity as a potential new mechanism in rHTN and discovered RXFP2 antagonists for the future interrogation of RXFP2 in cardiovascular and renal diseases.

Overcoming challenges associated with the bioanalysis of cysteine-conjugated metabolites in the presence of antibody-drug conjugates.

Aim: Investigations have shown that for the antibody-drug conjugate (ADC) belantamab mafodotin, concentrations of the cysteine-conjugated metabolite, Cys-mcMMAF, were overestimated in the presence of the ADC during sample processing when utilizing a historical SPE method. Results: A new assay was developed utilizing an acidic protein precipitation to remove the ADC early in the extraction process, thus eliminating the risk of overestimating Cys-mcMMAF in the presence of belantamab mafodotin. In vitro experiments demonstrated a linear relationship between the concentration of belantamab mafodotin and the release of Cys-mcMMAF. Extensive stability assessments were performed to cover storage of study samples. Conclusion: This work emphasized the critical importance of understanding the performance of a bioanalytical method for free toxic payload in the presence of the ADC.

Microflow UPLC and high-resolution MS as a sensitive and robust platform for quantitation of intact peptide hormones.

Aim: Recent advances in microflow ultra performance liquid chromatography (UPLC) systems offer higher sensitivity with robustness to meet the routine bioanalytical demands. Modern high-resolution mass spectrometers (HRMS) enable the development of highly selective methods with broad dynamic range. Results: The quantitative performances of tandem quadrupole MS and HRMS were comprehensively compared using seven intact peptide hormones up to 9.4 kDa. Results show comparable performance between two platforms in sensitivity, accuracy and linearity. For some peptides, HRMS provided lower background interference. The benefit of increased sensitivity using microflow UPLC was also demonstrated. Conclusion: HRMS is a versatile platform capable of both basic characterization and reliable quantitation in complex matrices. Microflow UPLC provides lower LLOQs than conventional flow systems, even with less sample volume injected.

Toward best practices in data processing and analysis for intact biotherapeutics by MS in quantitative bioanalysis.

AIM: Typically, quantitation of biotherapeutics from biological matrices by LC-MS is based on a surrogate peptide approach to determine molecule concentration. Recent efforts have focused on quantitation of the intact protein molecules or larger mass subunits of monoclonal antibodies. To date, there has been limited guidance for large or intact protein mass quantitation for quantitative bioanalysis. METHODOLOGY: Intact- and subunit-level analyses of biotherapeutics from biological matrices are performed at 12-25 kDa mass range with quantitation data presented. RESULTS: Linearity, bias and other metrics are presented along with recommendations made on the viability of existing quantitation approaches. CONCLUSION: This communication is intended to start a discussion around intact protein data analysis and processing, recognizing that other published contributions will be required.

Application of high-resolution MS for development of peptide and large-molecule drug candidates.

BACKGROUND: For quantitative bioanalysis utilizing MS, the instrument of choice is typically a triple quadruple mass spectrometer. However, advances in high-resolution MS have allowed sensitivity and dynamic ranges to approach that of triple quadrupole instruments. RESULTS: A matrix-free protein digest, a digested therapeutic protein and the intact peptide therapeutic liraglutide were each analyzed on high-resolution and triple quadrupole mass spectrometers with data compared. Samples from a mouse PK study with liraglutide were analyzed using the two different instruments, and equivalent PK exposure data were demonstrated. CONCLUSION: High-resolution and triple quadrupole mass spectrometers can generate data resulting in identical PK parameters from an in-life sample set, thus giving confidence in either technique in support of biotherapeutic PK exposure studies.

A whole-molecule immunocapture LC-MS approach for the in vivo quantitation of biotherapeutics.

AIM: Large-molecule biotherapeutic quantitation in vivo by LC-MS has traditionally relied on enzymatic digestion followed by quantitation of a 'surrogate peptide' to infer whole-molecule concentration. MS methods presented here measure the whole molecule and provide a platform to better understand the various circulating drug forms by allowing for variant quantitation. RESULTS: An immunocapture LC-MS method for quantitation of a biotherapeutic monoclonal antibody from human plasma is presented. Sensitivity, precision and accuracy for each molecular portion are presented along with an example of glycoform variant quantitation. CONCLUSION: The method is presented as a basic platform to be further developed for Good Practice (GxP) applications, critical quality attribute analysis or general understanding of molecular forms present as required for the wide range of drug development processes.

Modify on the fly: triple quad to high resolution in support of a dermal clinical study requiring an ultra low LLOQ.

BACKGROUND: FTIH studies can be challenging due to the varying dosing regimens and rapid data delivery. Chemists are asked to provide ultra-low limits of quantitation to provide an understanding of patient efficacy and safety in order to progress drug development. In a recent dermal study it became necessary to reduce the LLOQ of a small molecule drug from 50 to 1 pg/ml due to reductions in the dose and surface area of drug application. METHODOLOGY: The 50-fold increase in assay sensitivity necessitated the use of a high-resolution mass spectrometer (LC-HRMS) to separate matrix interferences observed when using a unit resolution triple quadrupole MS. CONCLUSION: A sensitive, robust assay was validated to support of a FTIH study using a LC-HRMS.

Comparison of the quantification of a therapeutic protein using nominal and accurate mass MS/MS.

BACKGROUND: The quantification of proteins and peptides in in vivo samples is a critical part of supporting the drug development process for biotherapeutics. LC-MS/MS using tandem quadrupole mass spectrometers is well established as the technology of choice for the quantification of small-molecule drugs and their metabolites in biological fluid. The application of accurate mass MS for quantification in a DMPK environment has attracted considerable interest in recent years. MATERIALS & METHODS: In this article we describe and compare the application of LC-high-resolution MS and LC-selected reaction monitoring (SRM) for the quantification of a therapeutics proteins. RESULTS: The accurate mass instrumentation showed acceptable linearity and sensitivity to quantify the protein therapeutic to the level of 10 ng/ml. The accurate mass instrument was operated in accurate mass SRM using high resolution (SRM-HR), the assay was demonstrated to be linear over three orders of magnitude. By narrowing the mass window from 100 mDa to 40 mDa and then to 20 mDa the assay specificity was significantly improved, hence increasing the S/N and improving the assay sensitivity. CONCLUSION: The high-resolution instrument was demonstrated to be reproducible over the course of the assay. The accurate mass method sensitivity was determined to be within one order of magnitude of that obtained with a tandem quadrupole MS/MS assay.

Application of DBS for the quantitative assessment of a protein biologic using on-card digestion LC-MS/MS or immunoassay.

BACKGROUND: Dried blood spot (DBS) sampling has recently gained popularity in the bioanalysis community for quantitation of small molecules. Since the pharmaceutical industry continues to increase investment in biopharmaceuticals, DBS technologies were investigated to determine if immunoassay and/or LC-MS/MS techniques would be amenable for quantitation of a large protein therapeutic (>70 kDa). RESULTS: Methods were successfully qualified for the protein therapeutic utilizing DBS technology. DBS methods in rat blood were qualified for this therapeutic protein using either immunoassay or enzymatic digestion directly off the DBS card followed by UHPLC-MS/MS separation and detection. Both qualifications were carried out in accordance with current acceptable practices defined by international acceptance criteria. Card selection was critical to both DBS methods. CONCLUSION: The advantages gained by DBS technology can successfully be applied to the quantitative assessment of biologics. This UHPLC-MS/MS method illustrates that digestion of large molecules directly off blood spot cards allows quantitation of these molecules. In addition, DBS technologies are amenable to immunoassay analysis. The immunoassay was 20-fold more sensitive than the UHPLC-MS/MS method, however the UHPLC-MS/MS assay had a much broader dynamic range.

Development and validation of a sensitive and selective UHPLC-MS/MS method for simultaneous determination of both free and total eicosapentaeonic acid and docosahexenoic acid in human plasma.

A sensitive, selective, and quantitative method for the simultaneous determination of free and total eicosapentaeonic acid (EPA) and docosahexenoic acid (DHA) has been developed and validated in human plasma using fatty acid free human serum albumin as a surrogate matrix. Clean-up for free EPA and DHA employs a liquid-liquid extraction with hexane to remove plasma interferences and provide for cleaner chromatography. The method for total EPA and DHA requires a digestion of the triglycerides followed by liquid-liquid extraction with hexane. Ultra high performance liquid chromatography (UHPLC) technology on a BEH C18 stationary phase column with 1.7 µm particle size was used for chromatographic separation, coupled to tandem mass spectrometry (UHPLC-MS/MS). The method for free EPA and DHA was validated over the concentration range of 0.05-25 µg/mL, while total EPA and DHA concentration range was 0.5-250 µg/mL. The results from assay validation show that the method is rugged, precise, accurate, and well suited to support pharmacokinetic studies. To our knowledge, this work represents the first UHPLC-MS/MS based method that combines both free and total EPA and DHA with a relatively small sample volume (25 µL aliquot) and a run time of 1.5 min, facilitating automation and high throughput analysis.

Application of DBS for quantitative assessment of the peptide Exendin-4; comparison of plasma and DBS method by UHPLC-MS/MS.

BACKGROUND: An investigation was performed in order to establish if dried blood spots (DBS) could be applied to the quantitation of biopharmaceuticals in biological matrices and perform equivalently in terms of accuracy, precision and stability to traditional plasma methods. RESULTS: A method was successfully validated for the peptide Exendin-4 (39 amino acids in length) utilizing DBS technology. The validated DBS method resulted in a more sensitive and simplistic method than an existing monkey plasma method and required tenfold less sample volume. The final DBS method resulted in a 10-2000-ng/ml linear calibration range using approximately 5 µl of dried blood, compared with the plasma method in which 150 µl of plasma coupled with SPE sample preparation resulted in a 20-2000-ng/ml linear calibration range. Although not needed for DBS, SPE was required for the plasma method to reduce endogenous matrix interferences and achieve desired LLOQ. Matrix stability was also enhanced by the implementation of the DBS platform when compared with either plasma or whole blood. CONCLUSION: DBS technology can be utilized for the quantitation of biopharmaceuticals and offer advantages over traditional plasma-based methods.

Utility of dried blood spot sampling and storage for increased stability of photosensitive compounds.

BACKGROUND: Compound stability remains a major point of concern within pharmaceutical development. In attempts to minimize degradation, scientists may utilize acidification of samples prior to storage, dark chambers, decreased freezer temperatures and a variety of other stabilization techniques. All of these steps require additional procedures, increased costs and increased validation steps. Dried blood spots (DBS) are becoming a popular alternative to plasma sampling in many small- and even large-molecule applications. An investigation was performed in order to establish if DBS would provide storage advantages over liquid-based matrices for two light-sensitive compounds, nifedipine and omeprazole, to prevent or minimize photodegradation. RESULTS: Experimental data has shown, through forced and natural photodegradation experiments, that the compounds nifedipine and omeprazole exhibit increased photostability when spotted and stored on various DBS paper, when compared with water, plasma or whole blood. For omeprazole, between 40 and 90% loss was observed in liquid matrices, while photodegradation was negligible when utilizing DBS. Some loss of nifedipine is noted during exposure conditions on DBS; however, photodegradation in liquid matrices is far more severe. CONCLUSION: Within the experimental compound set, DBS technology offers a significant reduction in the photodegradation process when compared with the liquid matrices water, plasma or blood.

Absolute quantification of a therapeutic domain antibody using ultra-performance liquid chromatography-mass spectrometry and immunoassay.

BACKGROUND: Domain antibodies (dAbs; ∼10-15 kDa) are made up of the variable heavy chain or the variable light chain of the antibody structure, and retain binding capability. dAbs have proved difficult to detect in plasma using immunoassay without specific antibodies raised against the dAb. RESULTS: A sensitive and selective UPLC-MS/MS method for the absolute quantification of a dAb in monkey plasma was developed (range: 1 to 500 ng/ml) without the need for a specific capture antibody. This method was used to analyze pharmacokinetic studies early on in drug development. Furthermore, an immunoassay was developed and the pharmacokinetic samples were reanalyzed. CONCLUSION: The two assays show good correlation (r(2) = 0.92), giving confidence in using either method for quantification of the dAb.

Development of an in vivo preclinical screen model to estimate absorption and first-pass hepatic extraction of xenobiotics. II. Use of ketoconazole to identify P-glycoprotein/CYP3A-limited bioavailability in the monkey.

The effect of P-glycoprotein (Pgp) and/or CYP3A on the disposition of xenobiotics has been extensively investigated and is often of interest during drug discovery lead optimization. We have previously described a monkey pharmacokinetic screen to rapidly estimate absorption and first-pass extraction. In the present work, this monkey screen has been expanded to include an assessment of Pgp/CYP3A effects on absorption and first-pass extraction, using ketoconazole as a prototypic dual Pgp/CYP3A inhibitor. To generate a ketoconazole dosing regimen, the pharmacokinetics of ketoconazole were first determined in the monkey and were found to be consistent with that previously described in the rat, dog, and human. Dose-ranging experiments demonstrated that a single 10-mg/kg intraduodenal ketoconazole dose would provide an appropriate exposure; this dose was used throughout subsequent interaction experiments. Next, erythromycin and propranolol were explored as positive and negative control substrates for Pgp/CYP3A interactions, respectively. As anticipated, ketoconazole produced no change in the absorption or first-pass extraction of propranolol but resulted in a substantial increase in absorption and decrease in first-pass extraction of erythromycin. Finally, this ketoconazole-based monkey screen was deployed in a drug discovery setting, and examples of such use are presented. These experiments have allowed a more complete characterization of ketoconazole as a prototypic dual Pgp/CYP3A inhibitor and its use as a tool in a preclinical setting and further demonstrate the use of the monkey to investigate the role of Pgp/CYP3A in limiting the oral bioavailability of new drug candidates.