Surface plasmon resonance, Orbitrap mass spectrometry and Raman advancements: exciting new techniques in drug discovery

Figures & data

Figure 1. Schematic illustration of SPR to determine binding interactions of representative small molecule ligand (molecule in the black circle) to target protein (blue): (a) Analytes (small molecule ligands; black circle) are passed through microfluidic system (buffer) and flown over the receptor (target protein; blue ribbon structure) immobilized on the chip surface. Polarized light is directed through a prism and incident upon bottom side of sensor chip (surface of the gold film) where waves of surface plasmons are generated at the critical angle of incident light; (b) After analytes bind to the receptor, there is a change in the critical angle of the incident light and reflected as I and II; (c) SPR sensogram comprising of the association phase (I) and the dissociation phase (II). SPR response values are expressed in resonance units (RU).

Table 1. Application of surface plasmon resonance (SPR), high-resolution Orbitap mass analyzer and Raman advancement in the area of drug discovery and delivery.

Technique	Applications
SPR	1) Small Molecule Drug discovery: Fragment library screening: Sensitivity and accuracy of SPR to measure weak binding with very low molecular weight compounds (M 80–300), enables a screening of fragment libraries. For example, SPR has been successfully used for Fragment library screening against the Hepatitis C drug target, NS5B 1b, in the search for novel allosteric drug leads [4] 2) Early Lead optimization: SPR can be used to determine residence time of which optimization can enhance drug efficacy and reduce off-target mediated toxicity. Hence, determination of binding kinetics by SPR can avoid late failures of lead candidates and thus improving drug safety and tolerability. For example, a label-free technique, SPR has been employed to identify small molecule antagonists of T-cell activation where molecule strongly interact with CD80 protein on antigen presenting cells (APC) to block CD28 protein on T-cells. Silencing T-cell activation is a powerful therapeutic intervention in rheumatoid arthritis (RA). [5]. 3) Formulations: Surface Plasmon Resonance (SPR) for the characterization of Nanoparticles (NPs) SPR provides an in vitro platform to verify the ability of functionalized NPs to bind to their putative receptors. The SPR is a rapid evaluation of the binding specificity, fast method to investigate the adsorption of selected proteins onto NPs surface (corona). SPR also allows a relatively high throughput analysis [6] 4) QC in drug development: Quantitation of influenza vaccine: SPR has been successfully used as quality control tool for the quantitation of virus hemagglutinin (HA) and host cell proteins (HCPs) in influenza vaccines. Inhibition assay was used for accurate quantitation of influenza virus while a direct binding assay for the HCP concentration determination. 5) Immunogenicity test: Epitope specificity measure of anti-drug antibodies (ADAs) is important for studying immunogenicity. SPR can be used in the early screening stage to determine epitope specificity Amgen is routinely using SPR as the preferred method to detect and characterize anti-epoetin alfa and anti-darbepoetin alfa Abs in human serum [3].
High resolution Orbitap mass analyzer	1) Proteomics: Untargeted protein identification and characterization. Targeted protein quantification using top-down and bottom-up approaches. Identification of post translational modifications. 2) Metabolomics and Lipidomics: Metabolomics and lipidomics profiling, and structural elucidation. 3) Pharmaceuticals: Metabolite screening, drug impurity profiling, and characterization. 4) Biopharmaceuticals: Intact antibody characterization.
Raman advancements	1) Drug discovery: Lead compound identification, optimization and understanding the structure activity relationship 2) Preformulation: Understanding solubility profiles, polymorphism, crystallization of active pharmaceutical ingredients (API), computability/interactions studies between API and excipients etc., drug–drug interactions, drug–protein interactions. 3) Formulation:Characterization of final dosage forms and their performances, understanding of unit operations such as crystallization, blending, drying, granulations, dissolution, quality control, etc. 4) Others: Drug–biologics interactions, impurities, and counterfeit identification.

Figure 2. Schematic illustration of SPR, high-resolution orbitrap mass analyzer and Raman mechanism.

Application note: Hepatitis C drug target, NS5B 1b, in the search for novel allosteric drug leads, GE Healthcare Life Sciences, Application note 29245694 edition AA; 2017.

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Application note: Characterizing lead compounds using label-free interaction analysis: Blocking T-cell activation in rheumatoid arthritis therapy, Application Note 28-9383-78, edition AA; 2008.

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Antiochia R, Bollella P, Favero G, et al. Nanotechnology-based surface plasmon resonance affinity biosensors for in vitro diagnostics. Int J Anal Chem. 2016;2016:15.

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Meza-Sanchez DE, Maravillas-Montero JL. Clinical and biomedical applications of surface plasmon resonance systems. Rev Invest Clin. 2019;71(2):85–90.

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