Electrospray triple quadrupole mass spectrometry guides pathologists to suggest appropriate molecular testing in the identification of rare hemoglobin variants

Background

The presumptive diagnosis of hemoglobinopathies relies on routine tests such as Complete Blood Count (CBC), peripheral blood smear, Liquid Chromatography (LC), and Capillary Electrophoresis (CE), along with clinical findings. Pathologists suggest molecular sequencing of HBA and HBB genes to correlate blood picture with clinical findings in order to identify unknown rare haemoglobin (Hb) variants or variants that coelute with Hb. This paper presents a low-resolution mass spectrometry (MS)-based method for presumptive identification of variants that eluted in zone 12 of CE, followed by molecular sequencing of the HBB gene for a definitive diagnosis of hemoglobinopathies.

Methods

Eight patient samples with a variant peak in zone 12 of CE (Sebia) were analyzed using MS. The mass-to-charge ratio (m/z) observed was deconvoluted to determine the mass of Hb variants. The β variants were subsequently confirmed through molecular sequencing.

Results

Based on the intact mass of the variants, there were two samples of the α variant (α + 58 Da and α + 44 Da), and six samples of the β variant. Out of these six β variant samples, three were the β + 58 Da variant, and three were the β + 30 Da variant. By correlating the intact mass information with the CE pattern and considering the ethnicity of the patients, it was presumed that the α variants were HbJ Meerut (α + 58 Da, x-axis 102) and HbJ Paris-I (α + 44 Da, x-axis 80). Molecular analysis confirmed the identity of β variants as Hb Rambam/HbJ Cambridge, HbJ Bangkok (+58 Da), and Hb Hofu (+30 Da).

Conclusion

The mass information of Hb variants obtained using Electrospray triple quadrupole MS assists pathologists in recommending the appropriate molecular sequencing for identifying unknown variants.

Bioanalytical method development and validation of highly selective and sensitive LC-MS/MS method for determination of teriparatide (parathyroid hormone fragment 1-34) in human serum through direct detection of intact teriparatide molecule

Teriparatide is a novel recombinant peptide fragment of the first 1-34 amino acids of human parathyroid recommended for treatment of osteoporosis. Therapeutic proteins and peptides are routinely estimated using ligand binding assay formats however LC-MS/MS technique which is routinely used in bioanalysis of small molecules has now gained importance in large molecule bioanalysis for the advantages it can offer over LBAs in terms of improved accuracy, selectivity and anti-body free method development. This paper presents a sensitive bioanalytical method for determination of teriparatide in human serum using ultra performance liquid chromatography aligned with tandem mass spectrometric detection. Teriparatide was isolated from human serum using solid phase extraction. The intact peptide was separated on a chromatograph and the multiply charged ion (+7) was detected using a mass spectrometer. The total run time was 4.0 min. The internal standard used was rat PTH 1-34 fragment. The mass transitions of m/z 589.3 > 656.3 for teriparatide and m/z 677.4 > 778.6 for internal standard were used for MS/MS detection. The sample extraction involved a solid phase extraction method followed by concentration of the eluent by evaporation and subsequent reconstitution. The non-specific binding effect caused by the adherence of the peptides/proteins to the vials/tube walls was significantly reduced by using BSA solution as blocking agent. The method has been validated over a linear range of 15.07-913.3 pg/mL with a correlation coefficient ≥ 0.99. The precision (%RSD) was 6.36 to 10.85 and accuracy was within 96.71% to 100.88%. A two-treatment, two-period, cross over study was conducted to establish bioequivalence between test and reference formulation (20 mcg/80 mL - solution for injection) and the method was successfully applied to quantify teriparatide in serum samples of this clinical study and about 1220 human serum samples were analyzed to determine teriparatide. This method is a promising anti-body free LC-MS/MS based methodology for estimation of teriparatide in human serum and may be applied as starting method for other such peptide molecules.

An oligonucleotide bioanalytical LC-SRM methodology entirely liberated from ion-pairing

Aim: Reliable quantitative LC-MS methodology has been established and validated for an oligonucleotide in plasma in a fresh and unique fashion, free of ion-pairing reagents and the various associated deleterious effects from primary solution preparation through sample preparation and extraction to the LC-MS analytical end point, offering a highly selective mixed-mode solid-phase extraction with hydrophilic-interaction liquid chromatography as the chromatographic element prior to SRM detection. Results: Inter- and intra-assay accuracy and precision ranged from 97.9 to 111% and 2.75 to 9.66%, respectively. Recoveries of 50% were attained, and there was no significant matrix effect manifestation. Conclusion: The method demonstrated rugged performance and reliability under the optimized conditions, indicating a possible exciting new avenue, free of ion-pairing, for general application in oligonucleotide quantitative LC-MS.

Sub-picomolar quantification of PTH 1-34 in plasma by UHPLC-MS/MS after subcutaneous injection of teriparatide and identification of PTH 1-33, its degradation product

Teriparatide (PTH 1-34, Forsteo^®) is a bioactive N-terminal fragment of the native endogenous parathyroid hormone (PTH 1-84) recommended for the treatment of osteoporosis in patients with high risk of fracture. Since PTH 1-34 may undergo proteolysis we have validated an ultra-high pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for unambiguously measuring intact PTH 1-34 with the same sensitivity as ELISA, at subpicomolar level (LLOQ at 0.4 pM). The full chromatographic run was achieved in 16.5 min. The method validation showed satisfactory intra- and inter-assay precision (CV < 13%) and excellent trueness (<5%), and almost no matrix effect (recoveries 78-92%). We found that after subcutaneous injection in two volunteers, PTH 1-34 half-life was shorter with UHPLC-MS/MS and that ELISA was overestimating PTH 1-34 late concentrations in both volunteers. Qualitative mass spectrometry was performed and led to the discovery of PTH 1-33, a fragment of PTH 1-34 with unknown function. This study emphasized the importance of switching from immunoassays to mass spectrometry when measuring bioactive peptides prompt to proteolysis into fragments that may exhibit altered bioactivity and duration of action.

Validation of an ultrasensitive LC-MS/MS method for PTH 1-34 in porcine plasma to support a solid dose PK study

BACKGROUND

The bioanalysis of Teriparatide (PTH 1-34) is extremely challenging due to the low plasma concentrations present at a therapeutic level. An LC-MS/MS-based method was developed that detected PTH 1-34 at 15 pg/ml in porcine plasma, and was validated using the bioanalytical method validation guidelines.

RESULTS

The analytical methodology demonstrated good linearity over a range of 15-1000 pg/ml, and demonstrated good precision and accuracy. The validated method was used to support a trial comparing a solid state dose to a solution-based injection (Forteo™).

CONCLUSION

The ability to quantify the peptide at low pg/ml in porcine plasma demonstrates that it is possible to develop very sensitive LC-MS/MS-based methodologies to support the bioanalysis of large peptide biotherapeutics.

Biotransformation and in vivo stability of protein biotherapeutics: impact on candidate selection and pharmacokinetic profiling

Historically, since the metabolism of administered peptide/protein drugs ("biotherapeutics") has been expected to undergo predictable pathways similar to endogenous proteins, comprehensive biotherapeutic metabolism studies have not been widely reported in the literature. However, since biotherapeutics have rapidly evolved into an impressive array of eclectic modalities, there has been a shift toward understanding the impact of metabolism on biotherapeutic development. For biotherapeutics containing non-native chemical linkers and other moieties besides natural amino acids, metabolism studies are critical as these moieties may impart undesired toxicology. For biotherapeutics that are composed solely of natural amino acids, where end-stage peptide and amino acid catabolites do not generally pose toxicity concerns, the understanding of biotherapeutic biotransformation, defined as in vivo modifications such as peripherally generated intermediate circulating catabolites prior to end-stage degradation or elimination, may impact in vivo stability and potency/clearance. As of yet, there are no harmonized methodologies for understanding biotherapeutic biotransformation and its impact on drug development, nor is there clear guidance from regulatory agencies on how and when these studies should be conducted. This review provides an update on biotherapeutic biotransformation studies and an overview of lessons learned, tools that have been developed, and suggestions of approaches to address issues. Biotherapeutic biotransformation studies, especially for certain modalities, should be implemented at an early stage of development to 1) understand the impact on potency/clearance, 2) select the most stable candidates or direct protein re-engineering efforts, and 3) select the best bioanalytical technique(s) for proper drug quantification and subsequent pharmacokinetic profiling and exposure/response assessment.

High sensitivity LC-MS/MS method for direct quantification of human parathyroid 1-34 (teriparatide) in human plasma

Teriparatide, the 1-34 fragment of human parathyroid hormone, is used to treat osteoporosis patients with a high risk of fracture by stimulating new bone formation. Routinely teriparatide is quantified using radioimmunoassay however the LC-MS/MS described here has the potential to achieve greater accuracy and precision, higher specificity, and is readily implemented in routine bioanalytical laboratories. Hence a complete method combining effective sample prep with appropriate LC separation and selected reaction monitoring (SRM) MS detection was developed to selectively separate teriparatide from closely related endogenous peptides and to reduce interferences. Samples were concentrated without evaporation, minimizing the risk of adsorptive losses. Chromatography was performed on a sub 2μm particle charged surface hybrid column, which provided significantly higher peak capacity than a traditional C18 column when formic acid was used as the mobile phase modifier. Total LC cycle time was 6min. An LOD of 15pg/mL (3.6fmol/mL) from 200μL of human plasma was readily achieved and standard curves were accurate and precise from 15pg/mL to 500pg/mL. Mean QC accuracies ranged from 90% to 106%. Mean QC precision was better than 7%. The CV of matrix factors across 6 sources of human plasma was 5%. The assay presented here is the first LC-MS method which reaches clinically relevant detection limits for teriparatide.