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Antibody-drug conjugate (ADC) consists of engineered antibodies and cytotoxic drugs linked via a chemical linker, and the stability of ADC plays a crucial role in ensuring its safety and efficacy. The stability of ADC is closely related to the conjugation site; however, no method has been developed to assess the stability of different conjugation sites due to the low response of conjugated peptides. In this study, an integrated strategy was developed and validated to assess the stability of different conjugation sites on ADC in serum. Initial identification of the conjugated peptides of the model drug ado-trastuzumab emtansine (T-DM1) was achieved by the proteomic method. Subsequently, a semiquantitative method for conjugated peptides was established in liquid chromatography-hybrid linear ion trap triple quadrupole mass spectrometry (LC-QTRAP-MS/MS) based on the qualitative information. The pretreatment method of the serum sample was optimized to reduce matrix interference. The method was then validated and applied to evaluate the stability of the conjugation sites on T-DM1. The results highlighted differences in stability among the different conjugation sites on T-DM1. This is the first study to assess the stability of different conjugation sites on the ADC in serum, which will be helpful for the design and screening of ADCs in the early stages of development.

Antibody pharmaceuticals have become the most popular immunotherapeutic drugs and are often administered with low serum drug dosages. Hence, the development of a highly sensitive method for the quantitative assay of antibody levels is of great importance to individualized therapy. On the basis of the dual signal amplification by the glycan-initiated site-directed electrochemical grafting of polymer chains (glyGPC), we report herein a novel strategy for the amplified electrochemical detection of antibody pharmaceuticals. The target of interest was affinity captured by a DNA aptamer ligand, and then the glycans of antibody pharmaceuticals were decorated with the alkyl halide initiators (AHIs) via boronate cross-linking, followed by the electrochemical grafting of the ferrocenyl polymer chains from the glycans of antibody pharmaceuticals through the electrochemically controlled atom transfer radical polymerization (eATRP). As the glycans can be decorated with multiple AHIs and the grafted polymer chains are composed of tens to hundreds of electroactive tags, the glyGPC-based strategy permits the dually amplified electrochemical detection of antibody pharmaceuticals. In the presence of trastuzumab (Herceptin) as the target, the glyGPC-based strategy achieved a detection limit of 71.5 pg/mL. Moreover, the developed method is highly selective, and the results of the quantitative assay of trastuzumab levels in human serum are satisfactory. Owing to its uncomplicated operation and cost-effectiveness, the glyGPC-based strategy shows great promise in the amplified electrochemical detection of antibody pharmaceuticals.

A liquid chromatography-tandem mass spectrometry method is presented for the quantitative determination of the in vivo deamidation of the biopharmaceutical proteins trastuzumab and pertuzumab at an asparagine in their complementarity determining regions (CDRs). For each analyte, two surrogate peptides are quantified after tryptic digestion of the entire plasma protein content: one from a stable part of the molecule, representing the total concentration, and one containing the deamidation-sensitive asparagine, corresponding to the remaining non-deamidated concentration. Using a plasma volume of 10 µL and a 2-h digestion at pH 7, concentrations between 2 and 1000 µg/mL can be determined for the various protein forms with values for bias and CV below 15% and without unacceptable in vitro deamidation taking place. A considerable difference between the total and non-deamidated concentrations, and thus a substantial degree of deamidation, was observed in plasma for both trastuzumab and pertuzumab. After a 56-day forced deamidation test 40% of trastuzumab and 68% of pertuzumab was deamidated, while trastuzumab and pertuzumab showed up to 47% and 35% of deamidation, respectively, in samples collected from breast cancer patients during treatment with a combination of both drugs. A good correlation between the non-deamidated concentration results and those of a receptor binding assay indicate a loss of receptor binding for both trastuzumab and pertuzumab along with the deamidation in their CDRs. Deamidated trastuzumab also lost its capability to inhibit the growth of breast cancer cells in a cell-based viability assay, suggesting a relation between the degree of deamidation and pharmacological activity., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: ABP 980 (KANJINTI ™ ) is a biosimilar to reference product HERCEPTIN ® (trastuzumab RP). The goal of this study was to characterize the safety, tolerability, and immunogenicity of ABP 980 plus pertuzumab (PERJETA ® ) when co-administered in a single infusion bag in healthy subjects., Methods: This randomized, double-blind, single-dose, 2-arm, parallel-group study (LAVENDER Study) evaluated an intravenous (IV) infusion of ABP 980 (6 mg/kg) plus pertuzumab (420 mg) combined in a single infusion bag relative to an IV infusion of trastuzumab RP (6 mg/kg) plus pertuzumab (420 mg) combined in a single infusion bag given over 60 min. The subjects were followed for 92 days post dosing., Results: A total of 42 subjects were enrolled in the study and treated with investigational product. Due to an operational issue during dosing, the first 6 subjects enrolled in the study were replaced. A total of 36 randomized subjects, n = 18 for ABP 980 plus pertuzumab and n = 18 for trastuzumab RP plus pertuzumab, were treated. Resulting serum concentrations of ABP 980 and trastuzumab RP were similar. There were no serious adverse events, no deaths, and no cardiac disorders during the study. No subject developed anti-drug antibodies throughout the study., Conclusions: This study demonstrated the safety and tolerability of ABP 980 and pertuzumab admixture in a single infusion bag. The safety profiles and pharmacokinetic parameters of ABP 980 and pertuzumab were consistent with what is known for trastuzumab RP and pertuzumab., Clinical Trial Listing: EudraCT 2018-002903-33., (© 2021. The Author(s).)

Trastuzumab deruxtecan (DS-8201) is a human epidermal growth factor receptor 2 (HER2)-targeting antibody-drug conjugate with a novel enzyme-cleavable linker, a topoisomerase I inhibitor payload, and a drug-to-antibody ratio of ≈ 8. We have characterized the population pharmacokinetics (PK) of trastuzumab deruxtecan and released drug (topoisomerase I inhibitor) in patients with HER2-positive breast cancer or other solid tumor malignancies. This analysis includes pooled data from five clinical studies with 639 patients. Trastuzumab deruxtecan doses ranged from 0.8 to 8.0 mg/kg every 3 weeks. Serum concentrations of trastuzumab deruxtecan and released drug were analyzed using a sequential two-step approach, with the nonlinear mixed-effects modeling methods. Covariate assessment was based upon stepwise forward-addition and backward-elimination process, followed by both univariate and multivariate analysis quantifying their impact on steady-state exposure of trastuzumab deruxtecan and released drug. A two-compartment model with linear elimination best described PK profiles of intact trastuzumab deruxtecan, while a one-compartment model with time-varying release-rate constant and linear elimination described released-drug PK profiles. Statistically significant covariates (country, tumor size, sex, formulation, age, body weight, albumin, total bilirubin, and aspartate aminotransferase) resulted in < 20% change in steady-state area under the concentration-time curve of trastuzumab deruxtecan and released drug, except for increased body weight (95th percentile, 86 kg) and decreased albumin (5th percentile, 31 g/L). Analysis of patients stratified by country, race, renal function, and hepatic function found no clinically meaningful differences in steady-state exposure of intact trastuzumab deruxtecan or released drug. Overall, results suggest that no dose adjustment based on tested covariates or in specific patient populations is warranted., (© 2020 Daiichi Sankyo Inc. Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Volumetric absorptive microsampling (VAMS) is increasingly utilized for both nonclinical and clinical pharmacokinetic studies. Currently, VAMS is employed as the sampling method for the detection of antibodies for coronavirus disease 2019. Biotherapeutics whole blood stability on VAMS presents as a critical concern for the health and pharmaceutical industries. In this follow-up to our previous publication, we evaluated daclizumab and trastuzumab whole blood sample stability on VAMS. The drug recovery data we observed at room temperature for short term and -80°C for long term was very encouraging. The knowledge could help us better understand and plan important investigation timelines, especially pandemic situations where human whole blood samples from a large population are collected and in urgent need of data analysis.

Coupling of surface plasmon resonance (SPR) detection to asymmetric flow field-flow fractionation (AF4) offers the possibility to study active fractions of bio-separations on real samples, such as serum and saliva, including the assessment of activity of possibly aggregated species. The coupling of SPR with AF4 requires the possibility to select fractions from a fractogram and redirect them to the SPR. The combination of SPR with chromatography-like methods also requires a mechanism for regeneration of the receptor immobilised onto the SPR sensor surface. In recent work, the combination of size exclusion chromatography (SEC) with SPR was pioneered as a successful methodology for identification, characterisation and quantification of active biocomponents in biological samples. In this study, the approach using AF4 is evaluated for the antibody trastuzumab in buffer and serum. The particular object of this study was to test the feasibility of using AF4 in combination with SPR to detect and quantify proteins and aggregates in complex samples such as blood serum. Also, in the investigation, three different immobilisation methods for the receptor HER-2 were compared, which involved (1) direct binding via EDC/NHS, the standard approach; (2) immobilisation via NTA-Ni-Histag complexation; and (3) biotin/avidin-linked chemistry using a regenerable form of avidin. The highest specific activity was obtained for the biotin-avidin method, while the lowest specific activity was observed for the NTA-Ni-Histag linkage. The data show that AF4 can separate trastuzumab monomers and aggregates in blood serum and that SPR has the ability to selectively monitor the elution. This is an encouraging result for automated analysis of complex biological samples using AF4-SPR.

Receptor-mediated transcytosis (RMT) is used to enhance the delivery of monoclonal antibodies (mAb) into the central nervous system (CNS). While the binding to endogenous receptors on the brain capillary endothelial cells (BCECs) may facilitate the uptake of mAbs in the brain, a strong affinity for the receptor may hinder the efficiency of transcytosis. To quantitatively investigate the effect of binding affinity on the pharmacokinetics (PK) of anti-transferrin receptor (TfR) mAbs in different regions of the rat brain, we conducted a microdialysis study to directly measure the concentration of free mAbs at different sites of interest. Our results confirmed that bivalent anti-TfR mAb with an optimal dissociation constant (K D ) value (76 nM) among four affinity variants can have up to 10-fold higher transcytosed free mAb exposure in the brain interstitial fluid (bISF) compared to lower and higher affinity mAbs (5 and 174 nM). This bell-shaped relationship between K D values and the increased brain exposure of mAbs was also visible when using whole-brain PK data. However, we found that mAb concentrations in postvascular brain supernatant (obtained after capillary depletion) were almost always higher than the concentrations measured in bISF using microdialysis. We also observed that the increase in mAb area under the concentration curve in CSF compartments was less significant, which highlights the challenge in using CSF measurement as a surrogate for estimating the efficiency of RMT delivery. Our results also suggest that the determination of mAb concentrations in the brain using microdialysis may be necessary to accurately measure the PK of CNS-targeted antibodies at the site-of-actions in the brain.

We present a simple and robust LC-MS/MS assay for the simultaneous quantitation of an antibody cocktail of trastuzumab and pertuzumab in monkey serum. The LC-MS/MS method saved costs, decreased the analysis time, and reduced quantitative times relative to the traditional ligand-binding assays. The serum samples were digested with trypsin at 50°C for 60 min after methanol precipitation, ammonium bicarbonate denaturation, dithiothreitol reduction, and iodoacetamide alkylation. The tryptic peptides were chromatographically separated using a C18 column (2.1 × 50 mm, 2.6 μm) with mobile phases of 0.1% formic acid in water and acetonitrile. The other monoclonal antibody, infliximab, was used as internal standards to minimize the variability during sample processing and detection. A unique peptide for each monoclonal antibody was simultaneously quantified using LC-MS/MS in the multiple reaction monitoring mode. Calibration curves were linear from 2.0 to 400 μg/mL. The intra- and inter-assay precision (%CV) was within 8.9 and 7.4% (except 10.4 and 15.1% for lower limit of quantitation), respectively, and the accuracy (%Dev) was within ±13.1%. The other validation parameters were evaluated, and all results met the acceptance criteria of the international guiding principles. Finally, the method was successfully applied to a pharmacokinetics study after a single-dose intravenous drip administration to cynomolgus monkeys., (© 2020 John Wiley & Sons, Ltd.)

Radionuclide molecular imaging of cancer-specific targets is a promising method to identify patients for targeted antibody therapy. Radiolabeled full-length antibodies however suffer from slow clearance, resulting in high background radiation. To overcome this problem, a pretargeting system based on complementary peptide nucleic acid (PNA) probes has been investigated. The pretargeting relies on sequential injections of primary, PNA-tagged antibody and secondary, radiolabeled PNA probe, which are separated in time, to allow for clearance of non-bound primary agent. We now suggest to include a clearing agent (CA), designed for removal of primary tumor-targeting agent from the blood. The CA is based on the antibody cetuximab, which was conjugated to PNA and lactosaminated by reductive amination to improve hepatic clearance. The CA was evaluated in combination with PNA-labelled trastuzumab, T-ZHP1, for radionuclide HER2 pretargeting. Biodistribution studies in normal mice demonstrated that the CA cleared ca. 7 times more rapidly from blood than unmodified cetuximab. Injection of the CA 6 h post injection of the radiolabeled primary agent [ 131 I]I-T-ZHP1 gave a moderate reduction of the radioactivity concentration in the blood after 1 h from 8.5 ± 1.8 to 6.0 ± 0.4%ID/g. These proof-of-principle results could guide future development of a more efficient CA.

Background: Subcutaneous trastuzumab (T-SC) administration does not allow the historical target concentration of 20 µg/mL for efficacy to be reached, from the start of treatment in patients with a body mass index (BMI) >30 kg/m 2 . Objectives: To analyze the influence of the strategy of dosification (fixed vs adjusted patient's body weight dose) on the initial minimum plasma concentration ( C min ) of trastuzumab in obese patients. Methods: This was an observational, prospective study, which included patients with HER2-positive nonmetastatic breast cancer treated with trastuzumab. The determination of the C min of trastuzumab was performed on day +21 of the first cycle using the ELISA technique. Patients were stratified according to the strategy of dosification and BMI. Results: A total of 50 patients were included; 16 patients received the drug intravenously and 34 in a fixed dosage subcutaneous (T-SC) regimen. The proportion of patients who achieved an adequate plasma concentration since the beginning of treatment was significantly higher when the drug was administered intravenously (93.8% vs 67.6%, P = 0.042). These differences are especially greater in T-SC patients with BMI >30 kg/m 2 , with only 20% of patients exceeding the pharmacokinetic target. Conclusion and Relevance: Our study suggests that trastuzumab SC fixed dose of 600 mg is not equivalent to IV administration, especially in obese patients. An adequate trastuzumab exposure in this population needs patient weight-adjusted IV dosage in the first administration. The clinical relevance of these findings remains to be elucidated, and further research, including larger controlled trials, is warranted.

Glycosylation influences the structure and functionality of glycoproteins, and is regulated by genetic and environmental factors. The types and abundance of glycans on glycoproteins can vary due to diseases such as cancer, inflammation, autoimmune and neurodegenerative disorders. Due to the crucial role glycans play in modulating protein function, glycosylation analysis could lead to the discovery of novel biomarkers and is of prime importance in controlling the quality of glycoprotein biopharmaceuticals. Here, we present a method for the identification and quantification of glycoforms directly on intact proteins, after immunoaffinity purification from biological fluids. The method was validated and applied to serum transferrin and the biopharmaceutical trastuzumab. The accuracy of the method, expressed as the relative error (RE), ranged from 2.1 (at high concentrations) to 7.9% (at low concentrations), and intra- and inter-day precision, expressed as relative standard deviation (RSD), was 3.2 and 8.2%, respectively. The sensitivity and linearity of the method were suitable for serum analysis and the LOQ was calculated to be 3.1 and 4.4 μg mL-1 for transferrin (TFN) and trastuzumab (TRA), respectively. Its application to transferrin from five healthy human serum samples yielded concentrations between 1.61 and 3.17 mg mL-1, which are in agreement with blood reference levels. In parallel, the structure of the identified glycans was determined by ion mobility spectrometry coupled with tandem mass spectrometry. No chromatographic separation was required and sample preparation was performed in a semi-automatic manner, facilitating the handling of up to 12 samples at a time. This method should be useful for clinical laboratories and for the quality control of large batches of biopharmaceuticals.

Clinical translation of DNA-based administration of monoclonal antibodies (mAbs) is uncertain due to lack of large animal data. To bridge the clinical gap, we evaluated a panel of novel plasmid DNA (pDNA)-encoded mAbs in 40-70 kg sheep with a clinical intramuscular electroporation protocol. Injection of 4.8 mg of pDNA, encoding ovine anti-human CEA mAb (OVAC), led to peak plasma mAb titers of 300 ng/mL. OVAC remained detectable for 3 months and was boosted by a second pOVAC administration. Hyaluronidase muscle pretreatment increased OVAC concentrations up to 10-fold. These higher plasma titers, however, led to anti-drug antibodies (ADAs) toward the OVAC variable regions, resulting in loss of mAb detection and of adequate redosing. Transient immune suppression avoided ADA formation, with OVAC peaking at 3.5 μg/mL and remaining detectable for 11 months after pOVAC injection. DNA-based delivery of ovine anti-human EGFR mAb (OVAE), identical to OVAC except for the variable regions, preceded by hyaluronidase, allowed for at least three consecutive administrations in an immune-competent sheep, without ADA response. When tripling the pOVAE dose to 15 mg, transient ADAs of limited impact were observed; plasma OVAE peaked at 2.6 μg/mL and was detected up to 7 months. DNA-based anti-HER2 trastuzumab in sheep gave no detectable mAb concentrations despite previous validation in mice, highlighting the limitations of relying on small-rodent data only. In conclusion, our results highlight the potential and caveats of clinical DNA-based antibody therapy, can expedite preclinical and clinical development, and benefit the field of gene transfer as a whole.

We describe the characterization of antigen binding fragments (Fab)-drug conjugates prepared using a dual maleimide pyrrolobenzodiazepine dimer cytotoxic payload (SG3710). Pyrrolobenzodiazepine dimers, which are DNA cross-linkers, are a class of payloads used in antibody-drug conjugates (ADCs). SG3710 was designed to rebridge two adjacent cysteines, such as those that form the canonical interchain disulfide bond between the light and heavy chain in Fab fragments. The rebridging generated homogenous Fab conjugates, with a drug-to-Fab ratio of one, as demonstrated by the preparation of rebridged Fabs derived from the anti-HER2 trastuzumab antibody and from a negative control antibody both prepared using recombinant expression and papain digestion. The resulting anti-HER2 trastuzumab Fab-rebridged conjugate retained antigen binding, was stable in rat serum, and demonstrated potent and antigen-dependent cancer cell-killing ability. Disulfide rebridging with SG3710 is a generic approach to prepare Fab-pyrrolobenzodiazepine dimer conjugates, which does not require the Fabs to be engineered for conjugation. Thus, SG3710 offers a flexible and straightforward platform for the controlled assembly of pyrrolobenzodiazepine dimer conjugates from any Fab for oncology applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: The present work analyzed the stability of trastuzumab  concentrations in blood and plasma samples stored at 4 °C and -20 °C., Method: Blood samples of patients treated with trastuzumab (Herceptin ®)  were analyzed. Stability of trastuzumab was analyzed under different conditions: whole blood stored at 4 °C during 72 hours, blood  plasma stored at 4 °C during 120 hours and blood plasma stored at -20 °C during 365 days., Results: In whole blood trastuzumab concentration at 72 hours was 99.01 ± 0.02%, and in plasma samples at 120 hours it was 98.6 ± 2.0%. The  concentration of trastuzumab was 95.22 ± 3.20% after 12 months' storage  at -20 ºC., Conclusions: The concentration of trastuzumab remains stable for at least  72 hours in whole blood stored at 4 °C, five days in plasma stored at 4 °C  and one year in plasma stored at -20 °C., (Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.)

Aim: Volumetric absorptive microsampling (VAM) is being increasingly applied in nonclinical pharmacokinetic studies. Although there are published results for VAM use in small molecule pharmacokinetics (PK) studies, there is limited data on the utility of VAM for protein therapeutics., Results: We describe the use of Mitra ® microsampler for blood sampling, ELISA quantitation and PK analysis of two marketed therapeutic monoclonal antibodies administered to rat. Results generated for these monoclonal antibodies using Mitra ® were compared with both serum and whole blood sampling methods in the same study., Conclusion: The low relative standard deviation among the three sets of PK data suggest that Mitra ® microsampler could be useful in early nonclinical PK studies for protein therapeutics where reduction and refinement of animal use is desirable.

Introduction: Our objective was to determine correlations between the tumor uptake and T/B ratios for 89 Zr-labeled T-DM1 ( 89 Zr-DFO-T-DM1) in mice with human BC xenografts by microPET/CT and biodistribution studies with HER2 expression and response to treatment with trastuzumab-DM1 (T-DM1)., Methods: The tumor and normal tissue uptake and T/B ratios for 89 Zr-DFO-T-DM1 (10 μg; 7.0 MBq) incorporated into a therapeutic dose (60 μg) were determined by microPET/CT and biodistribution studies at 96 h p.i. in NOD/SCID mice with s.c. MDA-MB-231 (5 × 10 4 HER2/cell), MDA-MB-361 (5 × 10 5 HER2/cell) and BT-474 (2 × 10 6 HER2/cell) human BC xenografts. Mice bearing these tumors were treated with T-DM1 (3.6 mg/kg every 3 weeks) and the tumor doubling time estimated by fitting of tumor volume vs. time curves. A tumor doubling time ratio (TDR) was calculated by dividing the doubling time for T-DM1 and normal saline treated control mice. The clonogenic survival (CS) of BC cells with increasing HER2 expression treated for 72 h in vitro with T-DM1 or trastuzumab (0-100 μg/mL) was compared. Correlations were determined between the T/B ratios for 89 Zr-DFO-T-DM1 and HER2 expression, TDR and CS, and between CS and TDR., Results: Uptake of 89 Zr-DFO-T-DM1 in MDA-MB-231, MDA-MB-361 and BT-474 tumors was 2.4 ± 0.4%ID/g, 6.9 ± 2.2%ID/g and 9.8 ± 1.1%ID/g, respectively. There was a non-linear but direct correlation between the T/B ratios for 89 Zr-DFO-T-DM1 and HER2 expression with the T/B ratio ranging from 4.5 ± 0.7 for MDA-MB-231 to 18.2 ± 1.8 for MDA-MB-361 and 35.9 ± 5.1 for BT-474 xenografts. Tumor intensity on microPET/CT images was proportional to HER2 expression. The standard uptake value (SUV) for the tumors on the images was strongly correlated with the T/B ratio in biodistribution studies. There was a direct linear correlation between the T/B ratio for 89 Zr-DFO-T-DM1 and TDR, with TDR ranging from 0.9 for MDA-MB-231 to 1.6 for MDA-MB-361 and 2.1 for BT-474 tumors. The cytotoxicity of T-DM1 in vitro on BC cells was dependent on HER2 expression but T-DM1 was more potent than trastuzumab. There was an inverse correlation between the TDR for mice treated with T-DM1 and CS of BC cells exposed in vitro to T-DM1., Conclusions: Based on the direct correlations between the T/B ratio for 89 Zr-DFO-T-DM1 by PET and HER2 expression and response to T-DM1, our results suggest that PET with 89 Zr-DFO-T-DM1 may predict response of HER2-positive BC to treatment with T-DM1., Advances in Knowledge and Implications for Patient Care: Our results suggest that PET with 89 Zr-DFO-T-DM1 may predict response to treatment with T-DM1 in HER-positive BC., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Rapid, convenient methods for monoclonal antibody (mAb) isolation are critical for determining the concentrations of therapeutic mAbs in human serum. This work uses porous nylon membranes modified with a HER2 peptide mimotope, KGSGSGSQLGPYELWELSH (KH19), for rapid affinity capture of Herceptin, a mAb used to treat breast cancer. Covalent linking of KH19 to poly(acrylic acid)-containing films in porous nylon leads to a Herceptin-binding capacity of 10 mg per mL of membrane and allows selective Herceptin capture from diluted (1:3) human serum in 5 min. Liquid chromatography-mass spectrometry demonstrates the high purity of eluted Herceptin. Moreover, the fluorescence intensity of the protein eluted from membranes increases linearly with the amount of Herceptin spiked in loading solutions containing diluted (1:3) human serum. These results demonstrate the promise of mimotope-modified membranes for Herceptin analysis that does not require secondary antibodies or derivatization with fluorescent labels. Thus, mimotope-containing membranes may form part of a simple benchtop analysis system for assessing the concentrations of therapeutic mAbs.

Background: This randomised, double-blind study compared pharmacokinetics, efficacy, safety and immunogenicity of PF-05280014 (potential trastuzumab biosimilar) and trastuzumab reference product (Herceptin) sourced from the European Union (trastuzumab-EU) as neoadjuvant treatment for operable human epidermal growth factor receptor 2 (HER2)-positive breast cancer., Methods: Patients (N = 226), stratified by primary tumour size and hormone receptor status, were randomised 1:1 to PF-05280014 or trastuzumab-EU (8 mg/kg loading dose; 6 mg/kg thereafter), each with docetaxel and carboplatin, every 3 weeks for six treatment cycles. Primary endpoint was percentage of patients with trough plasma concentration (C trough ) >20 μg/ml at Cycle 5 (Cycle 6 predose). Efficacy endpoints included pathological complete response and objective response rate. Non-inferiority of PF-05280014 to trastuzumab-EU was declared if the lower limit of the 95% confidence interval for the stratified difference between groups in the percentage of patients with Cycle 5 C trough >20 μg/ml was above the prespecified non-inferiority margin of - 12.5%., Results: For PF-05280014 vs trastuzumab-EU patients, respectively, 92.1% vs 93.3% had Cycle 5 C trough >20 μg/ml; the lower limit of the 95% confidence interval (- 8.02%, 6.49%) for the stratified difference between groups was above the non-inferiority margin (- 12.5%). Pathological complete response (47.0% vs 50.0%) and central radiology review-assessed objective response (88.1% vs 82.0%) rates were comparable. Incidence of all-causality, grade 3-4 treatment-emergent adverse events was 38.1% vs 45.5%; antidrug antibody rates were 0% vs 0.89%., Conclusions: PF-05280014 demonstrated non-inferior pharmacokinetics and comparable efficacy, safety and immunogenicity to trastuzumab-EU in patients with operable HER2-positive breast cancer receiving neoadjuvant chemotherapy.

Rationale: The cassette-dosing technique is a technique that administers various drugs to a single animal at once and quantitated simultaneously. The purpose of this study was to evaluate the feasibility of cassette-dosing as a means of increasing throughput and decreasing animal usage for pharmacokinetic studies of biopharmaceuticals using liquid chromatography/time-of-flight mass spectrometric (LC/TOF-MS) analysis., Methods: Brentuximab, trastuzumab, cetuximab and adalimumab were used as model biopharmaceuticals. The method consisted of immunoprecipitation followed by tryptic digestion for sample preparation and LC/TOF-MS analysis of specific signature peptides in the positive ion mode using electrospray ionization. The specific signature peptides used for quantification were from the complementarity-determining regions of each mAb. All rats received a single intravenous bolus injection containing either a single mAb or a mixture of four mAbs., Results: The proposed method has been qualified in linearity range of 1-100 μg/mL with correlation coefficients higher than 0.990. The qualification run met the acceptance criteria of ±25% accuracy and precision values for quality control (QC) samples. This qualified LC/TOF-MS method was successfully applied to a pharmacokinetic study in the rat. The PK properties of mAbs administered as a cassette-dosage were similar to the pharmacokinetics of each antibody drug when administered as a single entity., Conclusions: These findings suggest that the cassette-dosing approach could be used to evaluate the PK properties of biopharmaceuticals in the early drug discovery stage. Also, this method would be useful for other preclinical sample analysis without developing new reagents for sample preparation., (Copyright © 2018 John Wiley & Sons, Ltd.)

Aim: Compared with small molecules, LC-MS quantitation of larger biotherapeutic proteins such as antibodies and antibody-drug conjugates at the intact level presents many challenges in both LC and MS due to their higher molecular weight, bigger size, structural complexity and heterogeneity., Results & Conclusion: In this study, quantitation of an intact lysine-linked antibody-drug conjugate, trastuzumab emtansine is presented. Trastuzumab emtansine was extracted from rat plasma using bead-based immunoaffinity capture; after elution from the beads, it was directly analyzed on a LC-HRMS system. Quantitation using both extracted ion chromatogram and deconvoluted mass peaks was evaluated. A limit of quantitation was approximately 20 ng on column with a linear dynamic range from 5 to 100 μg/ml. In addition, the reproducibility and distribution of the drug-to-antibody ratio at different trastuzumab emtansine concentrations were discussed.

Monitoring the levels of therapeutic antibodies in individual patients would allow patient-specific dose optimization, with the potential for major therapeutic and financial benefits. Our group recently developed a new platform of bioluminescent sensor proteins (LUMABS; LUMinescent AntiBody Sensor) that allow antibody detection directly in blood plasma. In this study, we targeted four clinically important therapeutic antibodies, the Her2-receptor targeting trastuzumab, the anti-CD20 antibodies rituximab and obinutuzumab, and the EGFR-blocking cetuximab. A strong correlation was found between the affinity of the antibody binding peptide and sensor performance. LUMABS sensors with physiologically relevant affinities and decent sensor responses were obtained for trastuzumab and cetuximab using mimotope and meditope peptides, respectively, with affinities in the 10 -7 M range. The lower affinity of the CD20-derived cyclic peptide employed in the anti-CD20 LUMABS sensor ( K d = 10 -5 M), translated in a LUMABS sensor with a strongly attenuated sensor response. The trastuzumab and cetuximab sensors were further characterized with respect to binding kinetics and their performance in undiluted blood plasma. For both antibodies, LUMABS-based detection directly in plasma compared well to the analytical performance of commercial ELISA kits. Besides identifying important design parameters for the development of new LUMABS sensors, this work demonstrates the potential of the LUMABS platform for point-of-care detection of therapeutic antibodies.

THIOMAB antibody technology utilizes cysteine residues engineered onto an antibody to allow for site-specific conjugation. The technology has enabled the exploration of different attachment sites on the antibody in combination with small molecules, peptides, or proteins to yield antibody conjugates with unique properties. As reported previously ( Shen , B. Q. , et al. ( 2012 ) Nat. Biotechnol. 30 , 184 - 189 ; Pillow , T. H. , et al. ( 2017 ) Chem. Sci. 8 , 366 - 370 ), the specific location of the site of conjugation on an antibody can impact the stability of the linkage to the engineered cysteine for both thio-succinimide and disulfide bonds. High stability of the linkage is usually desired to maximize the delivery of the cargo to the intended target. In the current study, cysteines were individually substituted into every position of the anti-HER2 antibody (trastuzumab), and the stabilities of drug conjugations at those sites were evaluated. We screened a total of 648 THIOMAB antibody-drug conjugates, each generated from a trastuzamab prepared by sequentially mutating non-cysteine amino acids in the light and heavy chains to cysteine. Each THIOMAB antibody variant was conjugated to either maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl-monomethyl auristatin E (MC-vc-PAB-MMAE) or pyridyl disulfide monomethyl auristatin E (PDS-MMAE) using a high-throughput, on-bead conjugation and purification method. Greater than 50% of the THIOMAB antibody variants were successfully conjugated to both MMAE derivatives with a drug to antibody ratio (DAR) of >0.5 and <50% aggregation. The relative in vitro plasma stabilities for approximately 750 conjugates were assessed using enzyme-linked immunosorbent assays, and stable sites were confirmed with affinity-capture LC/MS-based detection methods. Highly stable conjugation sites for the two types of MMAE derivatives were identified on both the heavy and light chains. Although the stabilities of maleimide conjugates were shown to be greater than those of the disulfide conjugates, many sites were identified that were stable for both. Furthermore, in vitro stabilities of selected stable sites translated across different cytotoxic payloads and different target antibodies as well as to in vivo stability.

Therapeutic monoclonal antibodies (mAbs) are developed for treatment of diverse cancers and autoimmune diseases. For expansion of mAbs approval against unapproved diseases and pharmaceutical development, pharmacokinetics study is very important. Bioanalysis provides one of the most essential index against pharmacokinetics information. So far, we developed useful method for bioanalysis of mAbs in plasma or serum, nSMOL: nano-surface and molecular-orientation limited proteolysis. This method can provide accurate and reproducible value of mAbs content in plasma. Quantification of mAbs using ELISA is strongly influenced by endogenous ligand or anti-drug antibodies. In this report, we exhibited the role of nSMOL proteolysis coupled to LC-MS/MS analysis against quantification of mAbs bound to some binding molecules. The ligands against mAbs do not affect quantification of mAbs concentration in plasma using nSMOL proteolysis. On the other hands, some anti-drug antibodies (ADA), such as idiotypic antibodies, inhibit quantification of mAbs using nSMOL proteolysis. Acid dissociation has some efficacy in accurate value of quantitation of ADA binding mAbs using nSMOL proteolysis coupled to LC-MS/MS analysis. Accordingly, we consider that nSMOL method will contribute to understanding of mAb PK data and therapeutic reference combining with ADA measurements., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Aims: We conducted population pharmacokinetic (PopPK) and exposure-response analyses for trastuzumab emtansine (T-DM1), to assess the need for T-DM1 dose optimization in patients with low exposure by using TH3RESA [A Study of Trastuzumab Emtansine in Comparison With Treatment of Physician's Choice in Patients With human epidermal growth factor receptor 2 (HER2)-positive Breast Cancer Who Have Received at Least Two Prior Regimens of HER2-directed Therapy] study data (NCT01419197). The randomized phase III TH3RESA study investigated T-DM1 vs. treatment of physician's choice (TPC) in patients with heavily pretreated HER2-positive advanced breast cancer., Methods: We compared a historical T-DM1 PopPK model with T-DM1 pharmacokinetics in TH3RESA and performed exposure-response analyses using model-predicted cycle 1 maximum concentration (C max ), cycle 1 minimum concentration (C min ) and area under the concentration-time curve at steady state (AUC ss ). Kaplan-Meier analyses [overall survival (OS), progression-free survival (PFS)] and logistic regression [overall response rate (ORR), safety] were stratified by T-DM1 exposure metrics. Survival hazard ratios (HRs) in the lowest exposure quartile (Q1) of cycle 1 C min were compared with matched TPC-treated patients., Results: T-DM1 concentrations in TH3RESA were described well by the historical PopPK model. Patients with higher cycle 1 C min and AUC ss exhibited numerically longer median OS and PFS and higher ORR than patients with lower exposure. Exposure-response relationships were less evident for cycle 1 C max . No relationship between exposure and safety was identified. HRs for the comparison of T-DM1-treated patients in the Q1 subgroup with matched TPC-treated patients were 0.96 [95% confidence interval (CI) 0.63, 1.47] for OS and 0.92 (95% CI 0.64, 1.32) for PFS., Conclusions: Exposure-response relationships for efficacy were inconsistent across exposure metrics. HRs for survival in patients in the lowest T-DM1 exposure quartile vs. matched TPC-treated patients suggest that, compared with TCP, the approved T-DM1 dose is unlikely to be detrimental to patients with low exposure., (© 2017 The British Pharmacological Society.)

Introduction The use of trastuzumab with a fluoropyrimidine and platinum compound is currently the standard first-line treatment of patients with metastatic HER2-positive gastric cancer, but it appears that serum levels of trastuzumab determine the clinical effectiveness of this treatment, affecting progression-free survival and overall survival. Case report We report the case of a patient with metastatic HER2-positivegastric cancer, receiving XELOX (fluoropyrimidine and oxaliplatin) plus trastuzumab at standard doses, who presented sub-therapeutic serum levels during the first two treatment cycles and rapid disease progression (progression-free survival = 5.6 months). Discussion This case reveals a possible cause of poor effectiveness of trastuzumab treatment for metastatic gastric cancer in some patients, namely low circulating levels of the drug. It highlights the importance of monitoring as a possible tool for individual dose adjustment to optimize this therapy.

Antibody-drug conjugates (ADCs) are complex drug platforms composed of monoclonal antibodies (mAbs) conjugated to potent cytotoxic drugs (payloads) via chemical linkers, enabling selective payload delivery to neoplastic cells, resulting in improved efficacy and reduced toxicity. Brentuximab vedotin (Adcetris®, SGN-35) and adotrastuzumab emtansine (Kadcyla®, T-DM1) are the two FDA-approved and commercially available ADCs, and both drugs exhibit ADC-related thrombocytopenia and neutropenia. A pharmacokinetic/pharmacodynamic (PK/PD) model for ADCs was developed to identify the analyte from each ADC that is most associated with the observed hematopoietic toxicities and to determine the role of the apparent in vivo payload release rate on the severity of thrombocytopenia and neutropenia. Murine xenograft experiments and data from literature were combined, and the PK of both ADCs and their analytes were described with two-compartment models, with linear elimination and first-order payload release rate constants (k rel ). ADC-associated hematotoxicities were captured with a previously published PD model for myelosuppression driven by various analytes. ADC half-lives were about 5 days, and k rel values were 0.46 (T-DM1) and 0.12 h -1 (SGN-35). The lifespans of platelets following T-DM1 and neutrophils following SGN-35 were 3.73 and 4.72 days. Comparison of alternate model structures suggested that mechanisms of myelosuppression are payload-driven for SGN-35 and ADC pinocytosis-dependent for T-DM1. Model simulations suggested that a 4-fold increase (T-DM1) and 70% decrease (SGN-35) in k rel would improve hematotoxicity to grade 1. The proposed model successfully captured the PK and associated myelosuppression of both ADCs and might serve as a general PK/PD platform for assessing hematological toxicities to ADCs.

Purpose To compare standard-of-care (SoC) trastuzumab plus chemotherapy with higher-dose (HD) trastuzumab plus chemotherapy to investigate whether HD trastuzumab increases trastuzumab serum trough concentration (C trough ) levels and increases overall survival (OS) in first-line human epidermal growth factor receptor 2-positive metastatic gastric or gastroesophageal junction adenocarcinoma. Patients and Methods Patients with Eastern Cooperative Oncology Group performance status 2, no prior gastrectomy, and ≥ two metastatic sites were randomly assigned at a one-to-one ratio to loading-dose trastuzumab 8 mg/kg followed by SoC trastuzumab maintenance 6 mg/kg every 3 weeks or loading-dose trastuzumab 8 mg/kg followed by HD trastuzumab maintenance 10 mg/kg every 3 weeks until progression; treatment in each arm was combined with cisplatin 80 mg/m 2 plus capecitabine 800 mg/m 2 twice per day in cycles 1 to 6. The primary objective was HD trastuzumab OS superiority (all randomly assigned patients [full-analysis set]). Final results are from an interim analysis for futility (boundary hazard ratio [HR] ≥ 0.95) at 125 deaths. Results At clinical cutoff, 248 patients had been randomly assigned. A marked increase in mean trastuzumab C trough was observed after the first HD trastuzumab cycle versus SoC trastuzumab. In the full-analysis set, median OS was 12.5 months in the SoC trastuzumab arm and 10.6 months in the HD trastuzumab arm (stratified HR, 1.24; 95% CI, 0.86 to 1.78; P = .2401). Results were similar in the per-protocol set (cycle 1 trastuzumab C trough < 12 µg/mL). Safety was comparable between arms. Conclusion HD trastuzumab maintenance dosing was associated with higher trastuzumab concentrations, no increased efficacy, and no new safety signals. HELOISE confirms standard-dose trastuzumab (loading dose of 8 mg/kg followed by 6 mg/kg maintenance dose every 3 weeks) with chemotherapy as the SoC for first-line treatment of human epidermal growth factor receptor 2-positive metastatic gastric or gastroesophageal junction adenocarcinoma.

Rationale: Because of the large molecular weight, the structural complexity and the similarity with endogenous immunoglobulins present in high concentrations, in vivo quantitative studies with therapeutic monoclonal antibodies are particularly challenging. In this work, an UPLC/MRM MS-based methodology is described for the quantification of trastuzumab in human serum by monitoring a novel specific peptide marker located within its heavy chain Complementarity-Determining Region (CDR)., Methods: For maximum sensitivity and selectivity, specific transitions of this diagnostic proteotypic peptide were optimized and monitored at m/z 364.1 → 437.3 (quantitation ion) and m/z 364.1 → 358.0 (confirmation ion). As a proof-of-concept, the methodology was applied to the determination of trastuzumab in human serum over a clinically relevant range from 0.02 to 200 μg/mL. The methodology has been evaluated in terms of specificity, linearity, accuracy, precision, detection and quantitation limits., Results: An excellent linear response has been obtained in the range from 0.036 to 3.6 fmol/μL for the standard peptide and from 0.03 to 285 fmol/μL for the trastuzumab in human serum with typical R 2 values of 0.99. The limit of detection (LOD) and limit of quantification (LOQ) are 0.005 fmol/μL and 0.05 fmol/μL, respectively, with mean bias and RSD values of 18% and 1%, respectively, for quality control samples., Conclusions: The strategy used to set up the UPLC/MRM MS methodology based on monitoring specific peptide markers within CDRs can be potentially applied to the detection and quantification of other humanized or human mAbs in biological fluids. Copyright © 2017 John Wiley & Sons, Ltd., (Copyright © 2017 John Wiley & Sons, Ltd.)

Monoclonal antibodies labeled with near-infrared (NIR) fluorophores have potential use in disease detection, intraoperative imaging, and pharmacokinetic characterization of therapeutic antibodies in both the preclinical and clinical setting. Recent work has shown conjugation of NIR fluorophores to antibodies can potentially alter antibody disposition at a sufficiently high degree of labeling (DoL); however, other reports show minimal impact after labeling with NIR fluorophores. In this work, we label two clinically approved antibodies, Herceptin (trastuzumab) and Avastin (bevacizumab), with NIR dyes IRDye 800CW (800CW) or Alexa Fluor 680 (AF680), at 1.2 and 0.3 dyes/antibody and examine the impact of fluorophore conjugation on antibody plasma clearance and tissue distribution. At 0.3 DoL, AF680 conjugates exhibited similar clearance to unlabeled antibody over 17 days while 800CW conjugates diverged after 4 days, suggesting AF680 is a more suitable choice for long-term pharmacokinetic studies. At the 1.2 DoL, 800CW conjugates cleared faster than unlabeled antibodies after several hours, in agreement with other published reports. The tissue biodistribution for bevacizumab-800CW and -AF680 conjugates agreed well with literature reported biodistributions using radiolabels. However, the greater tissue autofluorescence at 680 nm resulted in limited detection above background at low (∼2 mg/kg) doses and 0.3 DoL for AF680, indicating that 800CW is more appropriate for short-term biodistribution measurements and intraoperative imaging. Overall, our work shows a DoL of 0.3 or less for non-site-specifically labeled antibodies (with a Poisson distribution) is ideal for limiting the impact of NIR fluorophores on antibody pharmacokinetics.

Aim: We aimed to establish novel, high-throughput LC-MS/MS strategies for quantification of monoclonal antibodies in human serum and examine the potential impact of antidrug antibodies., Methodology: We present two strategies using a thermally stable immobilized trypsin. The first strategy uses whole serum digestion and the second introduces Protein G enrichment to improve the selectivity. The impact of anti-trastuzumab antibodies on the methods was tested., Conclusion: Whole serum digestion has been validated for trastuzumab (LLOQ 0.25 µg/ml). Protein G enrichment has been validated for trastuzumab (LLOQ 0.1 µg/ml), bevacizumab (LLOQ 0.1 µg/ml) and adalimumab (LLOQ 0.25 µg/ml). We have shown the potential for anti-drug antibodies to impact on the quantification and we have subsequently established a strategy to overcome this impact where total quantification is desired.

Purpose: Population pharmacokinetic analyses (PPK) have been used to establish bioequivalence for small molecules and some biologicals. We investigated whether PPK could also be useful in biosimilarity testing for monoclonal antibodies (MAbs)., Methods: Data from a biosimilarity trial with two trastuzumab products were used to build population pharmacokinetic models. First, a combined model was developed and similarity between test and reference product was evaluated by performing a covariate analysis with trastuzumab drug product (test or reference) on all model parameters. Next, two separate models were developed, one for each drug product. The model structure and parameters were compared and evaluated for differences., Results: Drug product could not be identified as statistically significant covariate on any parameter in the combined model, and the addition of drug product as covariate did not improve the model fit. A similar structural model described both the test and reference data best. Only minor differences were found between the estimated parameters from these separate models., Conclusions: PPK can also be used to support a biosimilarity claim for a MAb. However, in contrast to the standard non-compartmental analysis, there is less experience with a PPK approach. Here, we describe two methods of how PPK can be incorporated in biosimilarity testing for complex therapeutics., Competing Interests: Compliance with ethical standards All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Conflict of interest The authors declare that they have no conflict of interest.

The reactive thiol of cysteine is often used for coupling maleimide-containing linker-payloads to antibodies resulting in the generation of antibody drug conjugates (ADCs). Currently, a numbers of ADCs in drug development are made by coupling a linker-payload to native or engineered cysteine residues on the antibody. An ADC conjugated via hinge-cysteines to an auristatin payload was used as a model in this study to understand the impact of the maleimide linkers on ADC stability. The payload was conjugated to trastuzumab by a protease-cleavable linker, maleimido-caproyl-valine-citruline-p-amino-benzyloxy carbonyl (mcVC-PABC). In plasma stability assays, when the ADC (Trastuzumab-mcVC-PABC-Auristatin-0101) was incubated with plasma over a 144-h time-course, a discrepancy was observed between the measured released free payload concentration and the measured loss of drug-to-antibody ratio (DAR), as measured by liquid chromatography-mass spectrometry (LC-MS). We found that an enzymatic release of payload from ADC-depleted human plasma at 144 h was able to account for almost 100% of the DAR loss. Intact protein mass analysis showed that at the 144 h time point, the mass of the major protein in ADC-depleted human plasma had an additional 1347 Da over the native albumin extracted from human plasma, exactly matching the mass of the linker-payload. In addition, protein gel electrophoresis showed that there was only one enriched protein in the 144 h ADC-depleted and antipayload immunoprecipitated plasma sample, as compared to the 0 h plasma immunoprecipitated sample, and the mass of this enriched protein was slightly heavier than the mass of serum albumin. Furthermore, the albumin adduct was also identified in 96 h and 168 h postdose in vivo cynomolgus monkey plasma. These results strongly suggest that the majority of the deconjugated mc-VC-PABC-auristatin ultimately is transferred to serum albumin, forming a long-lived albumin-linker-payload adduct. To our knowledge, this is the first report quantitatively characterizing the extent of linker-payload transfer to serum albumin and the first clear example of in vivo formation of an albumin-linker-payload adduct.

PEGylation of biomolecules is a major approach to increase blood stream half-life, stability and solubility of biotherapeutics and to reduce their immunogenicity, aggregation potential and unspecific interactions with other proteins and tissues. Antibodies have generally long half-lives due to high molecular mass and stability toward proteases, however their size lowers to some extent their potential because of a reduced ability to penetrate tissues, especially those of tumor origin. Fab or otherwise engineered smaller fragments are an alternative but are less stable and are much less well retained in circulation. We have here investigated the effects of various PEGylations on the binding properties and in vivo half-life of Fab fragments derived from the enzymatic splitting of Trastuzumab. We find that PEGylation increases the half-life of the molecules but also strongly affects the ability to recognize the target antigen in a way that is dependent on the extent and position of the chemical modification. Data thus support the concept that polyethylene glycol (PEG) conjugation on Trastuzumab Fabs increases half-life but reduces their affinity and this is a fine balance, which must be carefully considered for the design of strategies based on the use of antibody fragments.

An liquid chromatography-quadrupole time-of-flight (QqTOF) mass spectrometric method was developed for the determination of humanized or human monoclonal antibodies in rat plasma at the early drug discovery stage. Trastuzumab was used as a model monoclonal antibody. The method consisted of immunoprecipitation followed by tryptic digestion for sample preparation and LC-TOF-MS/MS analysis of specific signature peptides in the positive ion mode using electrospray ionization for analysis. A stable isotope-labeled signature peptide was also used as internal standard. A quadratic regression (weighted 1/concentration(2) ), with an equation y = ax(2)  + bx + c, was used to fit calibration curves over the concentration range of 0.500-100 µg/mL for trastuzumab. Samples from a pharmacokinetic study in rat were analyzed by this qualified LC-TOF-MS/MS method and concentrations were compared with those generated by enzyme linked immunosorbent assays method. The LC-TOF-MS/MS method was accurate and precise, with quantitative results comparable with those of ELISA. The qualification run met the acceptance criteria of ±25% accuracy and precision values for quality control samples. Within-run accuracy ranged from 1.53 to 9.20% with precision values ≤10.29%. This LC-TOF-MS/MS method approach could be used as a complementary method for humanized or human monoclonal antibodies at the early drug discovery stage., (Copyright © 2015 John Wiley & Sons, Ltd.)

An LC-MS/MS-based method is described for quantitatively monitoring the in vivo deamidation of the biopharmaceutical monoclonal antibody trastuzumab at a crucial position in its complementarity determining region (CDR). The multiplexed LC-MS/MS assay using selected reaction monitoring (SRM) allows simultaneous quantitation of five molecular species derived from trastuzumab after tryptic digestion: a stable signature peptide (FTISADTSK), a deamidation-sensitive signature peptide (IYPTNGYTR), its deamidated products (IYPTDGYTR and IYPTisoDGYTR), and a succinimide intermediate (IYPTsuccGYTR). Digestion of a 50 μL plasma sample is performed at pH 7 for 3 h at 37 °C, which combines a reasonable (>80%) digestion efficiency with a minimal (<1%) formation of deamidation products during digestion. Rapid in vitro deamidation was observed at higher pH, leading to a (large) overestimation of the concentrations of deamidation products in the original plasma sample. The LC-MS/MS method was validated in accordance with international bioanalytical guidelines over the clinically relevant range of 0.5 to 500 μg/mL with bias and CV values well below 15%. Deamidation of trastuzumab was observed in plasma both in a 56 day in vitro forced degradation study (up to 37% of the total drug concentration) and in samples obtained from breast cancer patients after treatment with the drug for several months (up to 25%). Comparison with a validated ELISA method for trastuzumab showed that deamidation of the drug at the CDR leads to a loss of recognition by the antibodies used in the ELISA assay.

Many therapeutic monoclonal antibodies (mAbs) are clinically administered through intravenous infusion after mixing with a diluent, e.g., saline, 5% dextrose. Such a clinical setting increases the likelihood of interactions among mAb molecules, diluent, and plasma components, which may adversely affect product safety and efficacy. Avastin® (bevacizumab) and Herceptin® (trastuzumab), but not Remicade® (infliximab), were shown to undergo rapid aggregation upon dilution into 5% dextrose when mixed with human plasma in vitro; however, the biochemical pathways leading to the aggregation were not clearly defined. Here, we show that dextrose-mediated aggregation of Avastin or Herceptin in plasma involves isoelectric precipitation of complement proteins. Using mass spectrometry, we found that dextrose-induced insoluble aggregates were composed of mAb itself and multiple abundant plasma proteins, namely complement proteins C3, C4, factor H, fibronectin, and apolipoprotein. These plasma proteins, which are characterized by an isoelectronic point of 5.5-6.7, lost solubility at the resulting pH in the mixture with formulated Avastin (pH 6.2) and Herceptin (pH 6.0). Notably, switching formulation buffers for Avastin (pH 6.2) and Remicade (pH 7.2) reversed their aggregation profiles. Avastin formed little, if any, insoluble aggregates in dextrose-plasma upon raising the buffer pH to 7.2 or above. Furthermore, dextrose induced pH-dependent precipitation of plasma proteins, with massive insoluble aggregates being detected at pH 6.5-6.8. These data show that isoelectric precipitation of complement proteins is a prerequisite of dextrose-induced aggregation of mAb in human plasma. This finding highlights the importance of assessing the compatibility of a therapeutic mAb with diluent and human plasma during product development.