Immune-modulating enzyme indoleamine 2,3-dioxygenase is effectively inhibited by targeting its apo-form.

For cancer cells to survive and proliferate, they must escape normal immune destruction. One mechanism by which this is accomplished is through immune suppression effected by up-regulation of indoleamine 2,3-dioxygenase (IDO1), a heme enzyme that catalyzes the oxidation of tryptophan to N-formylkynurenine. On deformylation, kynurenine and downstream metabolites suppress T cell function. The importance of this immunosuppressive mechanism has spurred intense interest in the development of clinical IDO1 inhibitors. Herein, we describe the mechanism by which a class of compounds effectively and specifically inhibits IDO1 by targeting its apo-form. We show that the in vitro kinetics of inhibition coincide with an unusually high rate of intrinsic enzyme-heme dissociation, especially in the ferric form. X-ray crystal structures of the inhibitor-enzyme complexes show that heme is displaced from the enzyme and blocked from rebinding by these compounds. The results reveal that apo-IDO1 serves as a unique target for inhibition and that heme lability plays an important role in posttranslational regulation.

Chemoselective Methionine Bioconjugation: Site-Selective Fluorine-18 Labeling of Proteins and Peptides.

Chemoselective methionine bioconjugation with alkyne-bearing oxaziridine and alkyne-bearing iodonium salts was investigated as a new platform for site-selective radiolabeling of proteins and peptides with fluorine-18. Alkyne-bearing sulfimide conjugates, resulting from oxaziridine modification, underwent copper-assisted alkyne-azide cycloaddition (CuAAC) with an 18F-labeled PEGylated azide to afford 18F-labeled triazoles in excellent radiochemical yields. Diazoester sulfonium salt bioconjugates, formed from alkyne-bearing 2-diazoiodonium salts, gave low yields of 18F-labeled triazoles and were shown to be unstable to CuAAC conditions. Photolytic removal of the diazo group, however, afforded the trialkylsulfonium salt which smoothly underwent CuAAC with the 18F-labeled PEGylated azide to afford high radiochemical yields of the desired 18F-labeled click product. Overall, the results establish the viability of chemoselective methionine bioconjugation as a method for preparing site-selective 18F-labeled PET radioligands.

Direct Carbon Isotope Exchange through Decarboxylative Carboxylation.

A two-step degradation-reconstruction approach to the carbon-14 radiolabeling of alkyl carboxylic acids is presented. Simple activation via redox-active ester formation was followed by nickel-mediated decarboxylative carboxylation to afford a range of complex compounds with ample isotopic incorporations for drug metabolism and pharmacokinetic studies. The practicality and operational simplicity of the protocol were demonstrated by its use in an industrial carbon-14 radiolabeling setting.

Determination of Real Time in Vivo Drug Receptor Occupancy for a Covalent Binding Drug as a Clinical Pharmacodynamic Biomarker by Immunocapture-LC-MS/MS.

We report a novel immunocapture (IC)-LC-MS/MS methodology to directly measure real time in vivo receptor occupancy (RO) for a covalent binding drug in blood lysate. A small molecule quencher was added immediately after sample collection to convert the free receptor to a quencher-bound receptor (QB-R) which was measured with the drug-bound receptor (DB-R) simultaneously by LC-MS/MS after immunocapture enrichment, followed by trypsin digestion. Addition of the quencher is necessary to prevent the free receptor from ex vivo binding with the drug. The real time RO was calculated based on the concentrations of DB-R and the free receptor (which is now QB-R) that were obtained from each sample. This strategy has been successfully applied to the measurement of the RO for Bruton's tyrosine kinase (BTK) in the blood lysate of monkeys after dosing with branebrutinib (BMS-986195), a covalent BTK inhibitor being evaluated to treat rheumatoid arthritis. A custom-made quencher, which is more reactive to BTK than branebrutinib, was added in excess amount to bind with all available free BTK to form quencher-bound BTK (QB-BTK) during blood sample collection. To measure a wide range of % BTK RO, including those of <5% or >95%, the required LLOQ at 0.125 nM for QB-BTK and 0.250 nM for drug-bound BTK (DB-BTK) in blood lysate were successfully achieved by using this IC-LC-MS/MS strategy. This proof-of-concept assay demonstrated its suitability with high throughput for real time in vivo BTK RO measurement as a pharmacodynamic (PD) biomarker for clinical drug development.

Synthesis of 2-(14)C-iminothiolane and 2-(13)C,(15)N-iminothiolane (Traut's reagent).

2-Iminothiolane has found utility in the growing area of antibody-drug conjugates by serving as a lysine-thiolating agent and the junction between the antibody and the cytotoxic payload during random conjugation of a monoclonal antibody. 2-(14)C-Iminothiolane was prepared from commercially available [(14)C]KCN using a four-step sequence in an overall 10% radiochemical yield. Stable-labeled 2-(13)C,(15)N-iminothiolane was also prepared from [(13)C(15)N]KCN in a similar manner. The ˙ labeled Traut's reagent produced by this sequence showed comparable reactivity as the commercially available unlabeled reagent with a representative monoclonal antibody and could serve as highly informative analytical tools to investigate antibody-drug conjugate formation via the random conjugation process.

Innovative use of LC-MS/MS for simultaneous quantitation of neutralizing antibody, residual drug, and human immunoglobulin G in immunogenicity assay development.

Immunogenicity testing for antidrug antibodies (ADA) faces challenges when high levels of the drug are present in clinical patient samples. In addition, most functional cell-based assays designed to characterize the neutralizing ability of ADA are vulnerable to interference from endogenous serum components. Bead extraction and acid dissociation (BEAD) has been successfully applied to extract ADA from serum samples prior to conduction of cell-based assays. However, in the BEAD, certain amounts of the drug and endogenous serum components (so-called residual drug and serum components) from serum samples are carried over to final BEAD eluates due to formation of protein complexes with ADA or nonspecific binding with the beads. Using current enzyme-linked immunosorbent assay (ELISA)-based ligand-binding assays, it is difficult to evaluate the residual drug, which is complexed with excessive amounts of ADA and endogenous serum components in the BEAD eluates. Here, we describe an innovative application of LC-MS/MS for simultaneous detection of the residual human monoclonal antibody drug and endogenous human IgG and the neutralizing antibody positive-control (NAb-PC) in the BEAD eluates. In this study, the low levels of the residual drug and human IgG in the BEAD eluates indicate that the BEAD efficiently removed the high-concentration drug and serum components from the serum samples. Meanwhile, the NAb-PC recovery (∼42%) in the BEAD provided an acceptable detection limit for the cell-based assay. This novel application of LC-MS/MS to immunogenicity assay development demonstrates the advantages of LC-MS/MS in selectivity and multiplexing, which provides direct and fast measurements of multiple components for immunogenicity assay development.

Synthesis of a stable isotopically labeled universal surrogate peptide for use as an internal standard in LC-MS/MS bioanalysis of human IgG and Fc-fusion protein drug candidates.

The synthesis of a 16-residue, stable isotopically labeled peptide is described for use as a LC-MS/MS (Liquid chromatography-mass spectrometry/mass spectrometry) internal standard in bioanalytical studies. This peptide serves as a single universal surrogate peptide capable of quantifying a wide variety of immunoglobulin G and Fc-fusion protein drug candidates in animal species used in pre-clinical drug development studies. An efficient synthesis approach for this peptide was developed using microwave-assisted solid phase peptide synthesis (SPPS) techniques, which included the use of a pseudoproline dipeptide derivative. The corresponding conventional room temperature SPPS was unsuccessful and gave only mixtures of truncated products. Stable-labeled leucine was incorporated as a single residue via manual coupling of commercially available Fmoc-[(13) C6 , (15) N]-l-leucine onto an 11-unit segment followed by automated microwave-assisted elaboration of the final four residues. Using this approach, the desired labeled peptide was prepared in high purity and in sufficient quantities for long-term supplies as a bioanalytical internal standard. The results strongly demonstrate the importance of utilizing both microwave-assisted peptide synthesis and pseudoproline dipeptide techniques to allow the preparation of labeled peptides with highly lipophilic and sterically hindered side-chains.

Fully validated LC-MS/MS assay for the simultaneous quantitation of coadministered therapeutic antibodies in cynomolgus monkey serum.

An LC-MS/MS assay was developed and fully validated for the simultaneous quantitation of two coadministered human monoclonal antibodies (mAbs), mAb-A and mAb-B of IgG4 subclass, in monkey serum. The total serum proteins were digested with trypsin at 50 °C for 30 min after methanol denaturation and precipitation, dithiothreitol reduction, and iodoacetamide alkylation. The tryptic peptides were chromatographically separated with a C18 column (2.1 × 100 mm, 1.7 µm) with mobile phases of 0.1% formic acid in water and acetonitrile. Four peptides, a unique peptide for each mAb and two confirmatory peptides from different antibody domains, were simultaneously quantified by LC-MS/MS in the multiple reaction-monitoring mode. Stable isotopically labeled peptides with flanking amino acids on C- and N-terminals were used as internal standards to minimize the variability during sample processing and detection. The LC-MS/MS assay showed lower limit of quantitation (LLOQ) at 5 µg/mL for mAb-A and 25 µg/mL for mAb-B. The intra- and interassay precision (%CV) was within 10.0% and 8.1%, respectively, and the accuracy (%Dev) was within ±5.4% for all the peptides. Other validation parameters, including sensitivity, selectivity, dilution linearity, processing recovery and matrix effect, autosampler carryover, run size, stability, and data reproducibility, were all evaluated. The confirmatory peptides played a critical role in confirming quantitation accuracy and the integrity of the drugs in the study samples. The robustness of the LC-MS/MS assay and the data agreement with the ligand binding data demonstrated that LC-MS/MS is a reliable and complementary approach for the quantitation of coadministered antibody drugs.

Cytochrome P450 11A1 bioactivation of a kinase inhibitor in rats: use of radioprofiling, modulation of metabolism, and adrenocortical cell lines to evaluate adrenal toxicity.

A drug candidate, BMS-A ((N-(4-((1H-pyrrolo[2,3-b]pyridin-4-yl)oxy)-3-fluorophenyl)-1-(4-fluorophenyl) 2-oxo-1,2-dihydropyridine- 3-carboxamide)), was associated with dose- and time-dependent vacuolar degeneration and necrosis of the adrenal cortex following oral administration to rats. Pretreatment with 1-aminobenzotriazole (ABT), a nonspecific P450 inhibitor, ameliorated the toxicity. In vivo and in vitro systems, including adrenal cortex-derived cell lines, were used to study the mechanism responsible for the observed toxicity. Following an oral dose of the C-14 labeled compound, two hydroxylated metabolites of the parent (M2 and M3) were identified as prominent species found only in adrenal glands and testes, two steroidogenic organs. In addition, a high level of radioactivity was covalently bound to adrenal tissue proteins, 40% of which was localized in the mitochondrial fraction. ABT pretreatment reduced localization of radioactivity in the adrenal gland. Low levels of radioactivity bound to proteins were also observed in testes. Both M3 and covalent binding to proteins were found in incubations with mitochondrial fraction isolated from adrenal tissue in the presence of NADPH. In vitro formation of M3 and covalent binding to proteins were not affected by addition of GSH or a CYP11B1/2 inhibitor, metyrapone (MTY), but were inhibited by ketoconazole (KTZ) and a CYP11A1 inhibitor, R-(+)-aminoglutethimide (R-AGT). BMS-A induced apoptosis in a mouse adrenocortical cell line (Y-1) but not in a human cell line (H295R). Metabolite M3 and covalent binding to proteins were also produced in Y-1 and to a lesser extent in H295R cells. The cell toxicity, formation of M3, and covalent binding to proteins were all diminished by R-AGT but not by MTY. These results are consistent with a CYP11A1-mediated bioactivation to generate a reactive species, covalent binding to proteins, and subsequently rat adrenal toxicity. The thorough understanding of the metabolism-dependent adrenal toxicity was useful to evaluate cross-species adrenal toxicity potential of this compound and related analogues.

Metabolism and disposition of [14C]brivanib alaninate after oral administration to rats, monkeys, and humans.

Brivanib [(R)-1-(4-(4-fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[1,2,4]triazin-6-yloxy)propan-2-ol, BMS-540215] is a potent and selective dual inhibitor of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) signaling pathways. Its alanine prodrug, brivanib alaninate [(1R,2S)-2-aminopropionic acid 2-[4-(4-fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[2,1-f][1,2,4]triazin-6-yloxy]-1-methylethyl ester, BMS-582664], is currently under development as an oral agent for the treatment of cancer. This study describes the in vivo biotransformation of brivanib after a single oral dose of [(14)C]brivanib alaninate to intact rats, bile duct-cannulated (BDC) rats, intact monkeys, BDC monkeys, and humans. Fecal excretion was the primary route of elimination of drug-derived radioactivity in animals and humans. In BDC rats and monkeys, the majority of radioactivity was excreted in bile. Brivanib alaninate was rapidly and completely converted via hydrolysis to brivanib in vivo. The area under the curve from zero to infinity of brivanib accounted for 14.2 to 54.3% of circulating radioactivity in plasma in animals and humans, suggesting that metabolites contributed significantly to the total drug-related radioactivity. In plasma from animals and humans, brivanib was a prominent circulating component. All the metabolites that humans were exposed to were also present in toxicological species. On the basis of metabolite exposure and activity against VEGF and FGF receptors of the prominent human circulating metabolites, only brivanib is expected to contribute to the pharmacological effects in humans. Unchanged brivanib was not detected in urine or bile samples, suggesting that metabolic clearance was the primary route of elimination. The primary metabolic pathways were oxidative and conjugative metabolism of brivanib.

Metabolism and disposition of [14C]BMS-690514 after oral administration to rats, rabbits, and dogs.

(3R,4R)-4-Amino-1-((4-((3-methoxyphenyl)amino)pyrrolo[2,1-f] [1,2,4]triazin-5-yl)methyl)-3-piperidinol (BMS-690514) is a potent inhibitor of human epidermal growth factor receptors 1, 2, and 4 and vascular endothelial growth factor receptors 1 through 3. BMS-690514 is an oral oncologic agent currently being developed for the treatment of patients with advanced non-small cell lung cancer and breast cancer. In this investigation, a series of studies was conducted to determine the biotransformation of [(14)C]BMS-690514 after oral administration to rats, rabbits, and dogs. After administration of a single oral dose of [(14)C]BMS-690514 to rats and dogs, the majority of the radioactive dose (61-71%) was recovered in the feces, whereas 18 to 20% was eliminated in urine. In bile duct-cannulated rats, 83 and 17% of the administered radioactivity was recovered in the bile and urine, respectively, suggesting that biliary secretion was a major route for the elimination of BMS-690514-derived radioactivity in rats. The parent compound underwent extensive metabolism in both species, with <12% of the administered radioactivity recovered as BMS-690514 in the excreta samples. Metabolite profiles in plasma were qualitatively similar in rats, rabbits, and dogs. Unchanged BMS-690514 was a prominent drug-related component in the plasma profiles from all the species. However, multiple metabolites contributed significantly to the circulating radioactivity, particularly for rabbit and dog, in which metabolites comprised 73 to 93% of the area under the time curve (0-8 h). Circulating metabolites included M6, a direct O-glucuronide conjugate; M1, a hydroxylated metabolite; and glucuronide conjugates of hydroxylated and O-demethylated metabolites. Overall, the results from these studies suggested that BMS-690514 was well absorbed and highly metabolized through multiple pathways in these preclinical species.

Metabolism and disposition of [14C]BMS-690514, an ErbB/vascular endothelial growth factor receptor inhibitor, after oral administration to humans.

(3R,4R)-4-Amino-1-((4-((3-methoxyphenyl)amino)pyrrolo[2,1-f][1,2,4]triazin-5-yl)methyl)-3-piperidinol (BMS-690514), an oral selective inhibitor of human epidermal growth factor receptors 1 (or epidermal growth factor receptor), 2, and 4, and vascular endothelial growth factor receptors 1, 2, and 3, is being developed as a treatment for patients with non-small-cell lung cancer and metastatic breast cancer. The disposition of [(14)C]BMS-690514 was investigated in nine healthy male subjects (group 1, n = 6; group 2, n = 3) after oral administration of a 200-mg dose. Urine, feces, and plasma were collected from all subjects for up to 12 days postdose. In group 2 subjects, bile was collected from 3 to 8 h postdose. Across groups, approximately 50 and 34% of administered radioactivity was recovered in the feces and urine, respectively. An additional 16% was recovered in the bile of group 2 subjects. Less than 28% of the dose was recovered as parent drug in the combined excreta, suggesting that BMS-690514 was highly metabolized. BMS-690514 was rapidly absorbed (median time of maximum observed concentration 0.5 h) with the absorbed fraction estimated to be approximately 50 to 68%. BMS-690514 represented ≤7.9% of the area under the concentration-time curve from time 0 extrapolated to infinite time of plasma radioactivity, indicating that the majority of the circulating radioactivity was from metabolites. BMS-690514 was metabolized via multiple oxidation reactions and direct glucuronidation. Circulating metabolites included a hydroxylated rearrangement product (M1), a direct ether glucuronide (M6), and multiple secondary glucuronide conjugates. None of these metabolites is expected to contribute to the pharmacology of BMS-690514. In summary, BMS-690514 was well absorbed and extensively metabolized via multiple metabolic pathways in humans, with excretion of drug-related radioactivity in both bile and urine.

A convenient strategy to overcome interference in LC-MS/MS analysis: Application in a microdose absolute bioavailability study.

Stable isotope labeled (SIL) compounds have been commonly used as internal standards (IS) to ensure the accuracy and quality of liquid chromatography-mass spectrometry (LC-MS) bioanalytical assays. Recently, the application of SIL drugs and LC-MS assays to microdose absolute bioavailability (BA) studies has gained increasing attention. This approach can provide significant cost and time saving, and higher data quality compared to the accelerator mass spectrometry (AMS)-based method, since it avoids the use of radioactive drug, high-cost AMS instrumentation and complex measurement processes. It also eliminates potential metabolite interference with AMS-based assay. However, one major challenge in the application of this approach is the potential interference between the unlabeled drug, the microdose SIL drug, and the SIL-IS during LC-MS analysis. Here we report a convenient and cost-effective strategy to overcome the interference by monitoring the isotopic ion (instead of the commonly used monoisotopic ion) of the interfered compound in MS analysis. For the BMS-986205 absolute BA case study presented, significant interference was observed from the microdose IV drug [13C7,15N]-BMS-986205 to its SIL-IS, [13C7,15N, D3]-BMS-986205, since the difference of nominal molecular mass between the two compounds is only 3 mu, and there is a Cl atom in the molecules. By applying this strategy (monitoring the 37Cl ion for the analysis of the IS), a 90-fold reduction of interference was achieved, which allowed the use of a synthetically accessible SIL compound and enabled the fast progress of the absolute BA study. This strategy minimizes the number of stable isotope labels used for avoiding interference, which greatly reduces the difficulty in synthesizing the SIL compounds and generates significant time and cost savings. In addition, this strategy can also be used to reduce the MS response of the analyte, therefore, avoiding the detector saturation issue of LC-MS/MS assay for high concentration BMS-986205. A LC-MS/MS assay utilizing this strategy was successfully developed for the simultaneous analysis of BMS-986205 and [13C7, 15N]-BMS-986205 in dog plasma using [13C7,15N, D3]-BMS-986205 as the IS. The assay was successfully applied to a microdose absolute BA study of BMS-986205 in dogs. The assay was also validated in human plasma and used to support a human absolute BA study. The same strategy can also be applied to other compounds, including those not containing Cl or other elements with abundant isotopes, or other applications (e.g. selection of internal standard), and the applications were presented.

Discovery of Branebrutinib (BMS-986195): A Strategy for Identifying a Highly Potent and Selective Covalent Inhibitor Providing Rapid in Vivo Inactivation of Bruton's Tyrosine Kinase (BTK).

Bruton's tyrosine kinase (BTK), a non-receptor tyrosine kinase, is a member of the Tec family of kinases and is essential for B cell receptor (BCR) mediated signaling. BTK also plays a critical role in the downstream signaling pathways for the Fcγ receptor in monocytes, the Fcε receptor in granulocytes, and the RANK receptor in osteoclasts. As a result, pharmacological inhibition of BTK is anticipated to provide an effective strategy for the clinical treatment of autoimmune diseases such as rheumatoid arthritis and lupus. This article will outline the evolution of our strategy to identify a covalent, irreversible inhibitor of BTK that has the intrinsic potency, selectivity, and pharmacokinetic properties necessary to provide a rapid rate of inactivation systemically following a very low dose. With excellent in vivo efficacy and a very desirable tolerability profile, 5a (branebrutinib, BMS-986195) has advanced into clinical studies.

Metabolism and disposition of dasatinib after oral administration to humans.

SPRYCEL (dasatinib, BMS-354825; Bristol-Myers Squibb, Princeton, NJ), a multiple kinase inhibitor, is currently approved to treat chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia tumors in patients who are resistant or intolerant to imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). After a 100-mg single p.o. dose of [(14)C]dasatinib to healthy volunteers, the radioactivity was rapidly absorbed (T(max) approximately 0.5 h). Both dasatinib and total radioactivity (TRA) plasma concentrations decreased rapidly with elimination half-life values of <4 h. Dasatinib was the major drug-related component in human plasma. At 2 h, dasatinib accounted for 25% of the TRA in plasma, suggesting that metabolites contributed significantly to the total drug-related component. There were many circulating metabolites detected that included hydroxylated metabolites (M20 and M24), an N-dealkylated metabolite (M4), an N-oxide (M5), an acid metabolite (M6), glucuronide conjugates (M8a,b), and products of further metabolism of these primary metabolites. Most of the administered radioactivity was eliminated in the feces (85%). Urine recovery accounted for <4% of the dose. Dasatinib accounted for <1 and 19% of the dose in urine and feces, respectively, suggesting that dasatinib was well absorbed after p.o. administration and extensively metabolized before being eliminated from the body. The exposures of pharmacologically active metabolites M4, M5, M6, M20, and M24 in patients, along with their cell-based IC(50) for Src and Bcr-Abl kinase inhibition, suggested that these metabolites were not expected to contribute significantly toward in vivo activity.

Adnectin-drug conjugates for Glypican-3-specific delivery of a cytotoxic payload to tumors.

Tumor-specific delivery of cytotoxic agents remains a challenge in cancer therapy. Antibody-drug conjugates (ADC) deliver their payloads to tumor cells that overexpress specific tumor-associated antigens-but the multi-day half-life of ADC leads to high exposure even of normal, antigen-free, tissues and thus contributes to dose-limiting toxicity. Here, we present Adnectin-drug conjugates, an alternative platform for tumor-specific delivery of cytotoxic payloads. Due to their small size (10 kDa), renal filtration eliminates Adnectins from the bloodstream within minutes to hours, ensuring low exposure to normal tissues. We used an engineered cysteine to conjugate an Adnectin that binds Glypican-3, a membrane protein overexpressed in hepatocellular carcinoma, to a cytotoxic derivative of tubulysin, with the drug-to-Adnectin ratio of 1. We demonstrate specific, nanomolar binding of this Adnectin-drug conjugate to human and murine Glypican-3; its high thermostability; its localization to target-expressing tumor cells in vitro and in vivo, its fast clearance from normal tissues and its efficacy against Glypican-3-positive mouse xenograft models.

Quantitation of a PEGylated protein in monkey serum by UHPLC-HRMS using a surrogate disulfide-containing peptide: A new approach to bioanalysis and in vivo stability evaluation of disulfide-rich protein therapeutics.

To quantify a therapeutic PEGylated protein in monkey serum as well as to monitor its potential in vivo instability and methionine oxidation, a novel ultra high performance liquid chromatography-high resolution mass spectrometric (UHPLC-HRMS) assay was developed using a surrogate disulfide-containing peptide, DCP(SS), and a confirmatory peptide, CP, a disulfide-free peptide. DCP(SS) was obtained by eliminating the step of reduction/alkylation before trypsin digestion. It contains an intact disulfide linkage between two peptide sequences that are essential for drug function but susceptible to potential in vivo cleavages. HRMS-based single ion monitoring (SIM) on a Q Exactive™ mass spectrometer was employed to improve assay specificity and sensitivity for DCP(SS) due to its poor fragmentation and low sensitivity with SRM detection. The assay has been validated for the protein drug in monkey serum using both surrogate peptides with excellent accuracy (within ±4.4%Dev) and precision (within 7.5%CV) with a lower limit of quantitation (LLOQ) at 10 ng mL(-1). The protein concentrations in monkey serum obtained from the DCP(SS)-based assay not only provided important pharmacokinetic parameters, but also confirmed in vivo stability of the peptide regions of interest by comparing drug concentrations with those obtained from the CP-based assay or from a ligand-binding assay (LBA). Furthermore, UHPLC-HRMS allowed simultaneous monitoring of the oxidized forms of both surrogate peptides to evaluate potential ex vivo/in vivo oxidation of one methionine present in each of both surrogate peptides. To the best of our knowledge, this is the first report of using a surrogate disulfide-containing peptide for LC-MS bioanalysis of a therapeutic protein.

Utilizing Internal Standard Responses to Assess Risk on Reporting Bioanalytical Results from Hemolyzed Samples.

Bioanalytical analysis of toxicokinetic and pharmacokinetic samples is an integral part of small molecule drugs development and liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been the technique of choice. One important consideration is the matrix effect, in which ionization of the analytes of interest is affected by the presence of co-eluting interfering components present in the sample matrix. Hemolysis, which results in additional endogenous components being released from the lysed red blood cells, may cause additional matrix interferences. The effects of the degree of hemolysis on the accuracy and precision of the method and the reported sample concentrations from hemolyzed study samples have drawn increasing attention in recent years, especially in cases where the sample concentrations are critical for pharmacokinetic calculation. Currently, there is no established procedure to objectively assess the risk of reporting potentially inaccurate bioanalytical results from hemolyzed study samples. In this work, we evaluated the effect of different degrees of hemolysis on the internal standard peak area, accuracy, and precision of the analyses of BMS-906024 and its metabolite, BMS-911557, in human plasma by LC-MS/MS. In addition, we proposed the strategy of using the peak area of the stable isotope-labeled internal standard (SIL-IS) from the LC-MS/MS measurement as the surrogate marker for risk assessment. Samples with peak areas outside of the pre-defined acceptance criteria, e.g., less than 50% or more than 150% of the average IS response in study samples, plasma standards, and QC samples when SIL-IS is used, are flagged out for further investigation.

Development and validation of an LC-MS/MS assay for the quantitation of a PEGylated anti-CD28 domain antibody in human serum: overcoming interference from antidrug antibodies and soluble target.

AIM: To support drug development of a PEGylated anti-CD28 domain antibody, a sensitive and robust LC-MS/MS assay was developed for the first in-human multiple ascending dose study. MATERIALS & METHODS: The procedure consists of a protein precipitation with acidified acetonitrile, followed by trypsin digestion of the supernatant. A surrogate peptide from the complementarity determining region was quantified with an LC-MS/MS assay using a stable isotope-labeled internal standard with flanking amino acids. An acid dissociation step was found to be essential to achieve full analyte recovery in the presence of antidrug antibodies and soluble target CD28. RESULTS & CONCLUSION: The fully validated LC-MS/MS assay demonstrates good accuracy (% deviation ≤6.3) and precision (%CV ≤5.2) with an lower limit of quantitation of 10 ng/ml.