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Demonstration of increased biologically active CXCL12Î± plasma concentrations after ACKR3 antagonist treatment in humans

ABSTRACT: CXCL12 is a chemokine that binds to its cognate receptors CXCR4 and ACKR3 (CXCR7). An increase in CXCL12 concentrations has been used as a pharmacodynamic biomarker to assess ACKR3 antagonism in healthy adults. Furthermore, increased CXCL12 concentrations have been observed in various human pathologies. To date, CXCL12 concentrations have typically been quantified using antibody-based assays with overlapping or unclear specificity for the various existing CXCL12 proteoforms. Only the N-terminal full-length CXCL12 proteoform is biologically active and can engage CXCR4 and ACKR3. However, this proteoform could so far not be quantified in healthy adults. Here, we describe a new and validated fit-for-purpose immunoaffinity mass spectrometry (IA-MS) biomarker assay for specific measurement of five CXCL12Î± proteoforms in human plasma, including the biologically active CXCL12Î± proteoform. The assay was employed in a Phase 1 clinical study with the ACKR3 antagonist ACT-1004-1239 to quantify CXCL12Î± proteoforms. At baseline levels, 1.00 nM total CXCL12Î± and 0.10 nM biologically active CXCL12Î± was quantified in placebo treated adults. The concentrations of both proteoforms increased up to two-fold in healthy adults following drug administration. At all doses, 10% of CXCL12Î± was biologically active and the simultaneous increase of all proteoforms suggests that a new equilibrium has been reached 24 h following dosing. Hence, this IA-MS biomarker assay can be used to specifically measure active CXCL12 proteoform concentrations in clinical trials. Specific quantification of active chemokines can support decision making in clinical trial and thus successful drug development.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Blood Plasma

SUBMITTER: Peter Blattmann

LAB HEAD: Peter Blattmann

PROVIDER: PXD038814 | Pride | 2024-01-27

REPOSITORIES: Pride

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Project description:Lipoprotein lipase (LPL) is responsible for the intravascular catabolism of triglyceride-rich lipoproteins and plays a central role in whole-body energy balance and lipid homeostasis. As such, LPL is subject to tissue-specific regulation in different physiological conditions, but the mechanisms of this regulation remain incompletely characterized. Previous work revealed that LPL comprises a set of proteoforms with different isoelectric points, but their regulation and functional significance have not been studied thus far. Here we studied the distribution of LPL proteoforms in different rat tissues and their regulation under physiological conditions. First, analysis by two-dimensional electrophoresis and Western blot showed different patterns of LPL proteoforms (i.e., different pI or relative abundance of LPL proteoforms) in different rat tissues under basal conditions, which could be related to the tissue-specific regulation of the enzyme. Next, the comparison of LPL proteoforms from heart and brown adipose tissue between adults and 15-day-old rat pups, two conditions with minimal regulation of LPL in these tissues, yielded virtually the same tissue-specific patterns of LPL proteoforms. In contrast, the pronounced down-regulation of LPL activity observed in white adipose tissue during fasting is accompanied by a prominent reconfiguration of the LPL proteoform pattern. Furthermore, refeeding reverts this down-regulation of LPL activity and restores the pattern of LPL proteoforms in this tissue. Importantly, this reversible proteoform-specific regulation during fasting and refeeding indicates that LPL proteoforms are functionally diverse. Further investigation of potential differences in the functional properties of LPL proteoforms showed that all proteoforms exhibit lipolytic activity and have similar heparin-binding affinity, although other functional aspects remain to be investigated. Overall, this study demonstrates the ubiquity, differential distribution and specific regulation of LPL proteoforms in rat tissues and underscores the need to consider the existence of LPL proteoforms for a complete understanding of LPL regulation under physiological conditions.

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Demonstration of increased biologically active CXCL12Î± plasma concentrations after ACKR3 antagonist treatment in humans

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