Demonstration of increased biologically active CXCL12α 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 CXCL12α proteoforms in human plasma, including the biologically active CXCL12α proteoform. The assay was employed in a Phase 1 clinical study with the ACKR3 antagonist ACT-1004-1239 to quantify CXCL12α proteoforms. At baseline levels, 1.00 nM total CXCL12α and 0.10 nM biologically active CXCL12α 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 CXCL12α 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