Special Issues-03-01-2017

Antibody drug conjugates (ADCs) are an emerging category of biotherapeutic products based on monoclonal antibodies (mAbs) coupled to powerful cytotoxic drugs. The production of ADCs entails the formation of species with different number of conjugates drugs. The heterogeneity of ADCs species add to the complexity originating from the mAbs microvariability. Sheathless capillary electrophoresis-mass spectrometry (sheathless CE-MS) using complementary approaches was used to perform a detail characterization of brentuximab vedotin (Adcetris, Seattle Genetics). Sheathless CE-MS instrument used as nanoESI infusion platform was involved to perform the intact and middle-up analysis in native MS conditions. The nanoESI infusion approaches enabled estimation of the average drug to antibody ratio (DAR) alongside to drug load distribution. Sheathless CZE-MS/MS method developed was used to obtain from a single injection the characterization of the amino acid sequence with complete sequence coverage. In addition glycosylation and drug-loaded peptides could be identified from MS/MS spectra revealing robust information regarding their localizations and abundances. Drug-loaded peptide fragmentation mass spectra study demonstrated drug-specific fragments reinforcing the identifications confidence. Results reveal the ability of sheathless CZE-MS/MS method to characterize ADCs primary structure in a single experiment.

Using examples from our analysis of L-carnitine and acyl-L-carnitines, we give specific guidance for the use of mass spectrometry in quantitative analysis, as applied to clinical research and clinical pharmacology. We focus on quantitative accuracy and analytical selectivity as keys to successful implementation of mass spectrometric methods in clinical applications

Accurate evaluation of chemical modifications such as asparagine deamidation and aspartic acid isomerization is an essential component of comprehensive characterization of therapeutic monoclonal antibodies (mAbs). When located in the complementarity determining regions (CDRs), these modifications can cause a loss of function, impacting product efficacy and safety, resulting in the designation of the modification as a critical quality attribute. However, artifactual modifications can be introduced by analytical procedures, and distinguishing modifications as either critical quality attributes or method-induced artifacts is an important objective for product development. Conventional peptide mapping coupled with ultrahigh-resolution mass spectrometry offers advanced capabilities for definitive characterization of protein therapeutics. However, experimental conditions such as digestion time and pH can influence the observed level of chemical modifications, usually leading to over-estimation. In this work, a new peptide mapping method was developed specifically for mAb characterization that employs optimal enzyme pH for robustness, but short digestion times and time-course elements to minimize and monitor deamidation/isomerization, respectively, allowing a more accurate assessment of potential CDR sequence liabilities.

The isotopic profile of a material refers to the ratios of the stable isotopes of elements contained within, such as 2H/1H, 13C/12C, and 18O/16O. Biological, chemical, and physical processes cause variations in the ratios of stable isotopes; analysis of a material for its distinctive isotopic signature can thus be used to reveal information about its history. Isotope ratio mass spectrometry (IRMS) is a technique used to measure the relative abundance of isotopes in materials. Forensic investigators have used IRMS to measure a variety of materials, such as drugs, explosives, food, and human remains. In a recent web seminar, Lesley Chesson, the president of IsoForensics, Inc., explained how IRMS works and discussed the use of IRMS in forensic science, illustrating her discussion with several case examples.

A brief preview of this year’s ASMS conference, taking place June 4–8, 2017, in Indianapolis, Indiana.

Click the title above to open the March 2017 issue of Current Trends in Mass Spectrometry, Volume 15, Number 1, in an interactive PDF format.