Fig. 6: Plasma protein binding of covalent drug candidates using intact protein LC-MS. | Nature Communications

Fig. 6: Plasma protein binding of covalent drug candidates using intact protein LC-MS.

From: Mass spectrometry methods and mathematical PK/PD model for decision tree-guided covalent drug development

Fig. 6

Covalent drugs were incubated with human serum albumin (HSA), the most abundant plasma protein, to test albumin-binding and to provide a go/no go decisions in the covalent discovery workflow. a Raw and deconvoluted (inset) spectra for control HSA (black). b Disulfiram ( + 147 Da) (purple), (c) cisplatin ( + 225 Da) (pink), and (d) ebselen ( + 274 Da) (blue) showed drug-related mass shifts with HSA, which affects their METE in vivo (D5 = No Go). As expected, rationally designed covalent drugs (e) afatinib (green), and (f) ibrutinib (orange), showed minimal binding to HSA. Additionally, (g) sotorasib (dark red) and (h) S-XL6 (red) showed negligible binding to HSA, which with S-XL6 is enabled by the unique ability to reversibly bind off-target lone cysteine residues, while covalently cross-linking closely spaced pairs of cysteines such as SOD1’s. *denotes cysteinylation (average mass: 66564.28 Da), which blocks the binding of cysteine-targeting drugs disulfiram and ebselen, but does not block the binding of cisplatin, presumably due to reaction with additional nucleophilic amino acids. Total ion current is represented as a.u. (arbitrary units).

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