Monitoring mAb proteoforms in mouse plasma using an automated immunocapture combined with top-down and middle-down mass spectrometry

Gábor Transform-Based Antibody Quantitation in Serum: An Interlaboratory Liquid Chromatography/High-Resolution Mass Spectrometry Investigation

Therapeutic monoclonal antibodies (t-mAbs) are crucial for treating various conditions, including cancers and autoimmune disorders. Accurate quantitation and pharmacokinetic monitoring of t-mAbs in serum are essential, but current methods like ligand binding assays (LBAs) and bottom-up peptide liquid chromatography-tandem mass spectrometry (LC-MS/MS) can lack the sensitivity and specificity needed to meet clinical demands. Emerging techniques using high-resolution mass spectrometry (HRMS) in top-down and middle-up approaches offer improved ability to accurately quantify mAb proteoforms apart from degradation products by keeping the sample proteins intact or minimizing digestion. This study describes the first use of Gábor transform (GT)-based iFAMS Quant+ software to quantify a t-mAb (vedolizumab) from ∼400 samples using an Agilent 6545XT AdvanceBio Q-TOF at the University of Oregon. These results are compared to a previously validated laboratory-developed test (LDT) from Mayo Clinic utilizing a Thermo Q Exactive Plus Orbitrap. The Mayo method used conventional extracted ion chromatograms (XICs) of select charge states for quantitation, while the iFAMS Quant+ method utilized GT-based charge state deconvolution, background subtraction, and signal integration. Calibration and quality control (QC) analyses and Passing-Bablok regression of 351 subject samples demonstrated excellent agreement between the two methods. The iFAMS Quant+ workflow exhibited unique advantages for characterizing interferents and analyte signal anomalies due to its deconvolution-based approach.

EThcD as a Unique Tool for the Top-Down De Novo Sequencing of Intact Natural Ranid Amphibian Peptides

De novo sequencing of any novel peptide/protein is a difficult task. Full sequence coverage, isomeric amino acid residues, inter- and intramolecular S-S bonds, and numerous other post-translational modifications make the investigators employ various chemical modifications, providing a variety of specific fragmentation MSn patterns. The chemical processes are time-consuming, and their yields never reach 100%, while the subsequent purification often leads to the loss of minor components of the initial peptide mixture. Here, we present the advantages of the EThcD method that enables establishing the full sequence of natural intact peptides of ranid frogs in de novo top-down mode without any chemical modifications. The method provides complete sequence coverage, including the cyclic disulfide section, and reliable identification of isomeric leucine/isoleucine residues. The proposed approach demonstrated its efficiency in the analysis of peptidomes of ranid frogs from several populations of Rana arvalis, Rana temporaria, and Pelophylax esculentus complexes.

Solid phase microextraction device coupled with miniature mass spectrometry and mathematical model of its ion chronogram

Modern solid phase microextraction (SPME) device linked with mass spectrometry (SPME-MS) has evolved from producing ion chronogram as flat noisy signal to as unimodal-like signal. We designed a SPME device, which is closer in morphology to LC column, linked it with a miniature mass spectrometer (SPME-Mini MS), and proposed a mathematical model that elution of compound from the SPME device is equivalent to overlay of elution of the compound from the infinite LC columns with the lengths between 0 and the length of the device and it can generate an ion chronogram as right-skew unimodal signal. Rhodamine B as analyte was used for experimental verification and its unimodal signal was used to fit the parameters of a computer simulation program based on the model. The experimental results and simulations empirically cross-confirmed that SPME-Mini MS can generate ion chronogram as clean right-skew unimodal signal. Furthermore, the SPME-Mini MS system was used for quantitative analysis of psychotropic drugs (i.e. risperidone and aripiprazole) in artificial urine. The results preliminarily demonstrated that the system can utilize area under unimodal signal for quantitative analysis and has potential to be applied for on-site, fast and accurate quantification of drugs and other compounds.