ImmunoPET imaging–based pharmacokinetic profiles of an antibody and its Fab targeting endothelin A receptors on glioblastoma stem cells in a preclinical orthotopic model

Synthesis and Preclinical Fluorescence Imaging of Dually Functionalized Antibody Conjugates Targeting Endothelin Receptor-Positive Tumors

“…In particular, no significant signal can be observed in the liver, which can be the case when using organic fluorescent dyes. These data are consistent with PET imaging data obtained with a 89 Zr-DFO-xiRA63 conjugate, showing that the enzymatic conjugation of the fluorescent dye did not affect the biodistribution of the antibody …”

“…The elevated concentration of ET-1 within the tumoral environment coupled with its strong affinity for its receptors presents a significant challenge for an antagonist to compete that could be responsible for the discrepancy between the preclinical and clinical results. To circumvent this issue, two high-affinity antibodieswhich do not compete with ET-1named Rendomab A63 (RA63) and Rendomab B49 (RB49), directed, respectively, against ET A and ET B receptors have been patented. , We have recently demonstrated that a chimeric version of RA63 called xiRA63 could be randomly labeled with zirconium-89 ( 89 Zr, t 1/2 = 3.3 days) and used to detect ET A + glioblastoma in a mouse model xenografted orthotopically with patient-derived Gli7 glioblastoma stem cells, thanks to immuno-positron emission tomography (immunoPET) imaging . Likewise, a chimeric version of the latter, xiRB49, was modified with a cytotoxic molecule to obtain an antibody–drug conjugate showing a very high efficacy in treating ET B + melanoma with no notable side effects on mice (Herbet et al, in preparation).…”

The functionality of a therapeutic antibody candidate restored by a single mutation from proline to threonine in the variable region

“…Identical results were obtained for our positive control, the chimeric Rendomab A63, xiRA63, already described for theranostic applications to ET A + tumors. 12 We assessed the functionality of xiRB49 and RB49 by their binding to CHO-ET B cells compared to CHO-WT cells ( Figure 1 ). No recognition for ET B was observed with xiRB49.…”

“…Indeed, chimerization of xiRA63 with the same human IgG1 constant regions, kappa, retained full functionality. 12 Conversely, xiRB49 completely lost its capacity to bind ET B . Interestingly, Fab-xiRB49 presented residual activity with an apparent affinity of 85.69 nM and a reduced Bmax of 26.19% MFI, suggesting that the activity loss of xiRB49 partially comes from the CH2 and CH3 constant domains.…”

Endothelin and the tumor microenvironment: a finger in every pie

“…Hautiere et al developed a novel radioligand targeting ETAR and demonstrated its efficacy in μPET-(positron emission tomography) CT in an orthotopic glioblastoma mouse model. In addition, Vivier et al showed a similar efficiency of their newly developed PET/near-infrared fluorescence probe targeting both ETAR and ETBR in mice with ETAR and ETBR overexpressing Chinese hamster ovary (CHO) cells [ 148 , 149 ]. A future clinical trial investigating radioligands to detect ET receptor expression as a means of stratifying patients could help identify patients who could potentially benefit from ET receptor antagonism and should ideally be designed in a longitudinal design and embedded in a clinical trial investigating ET receptor antagonists.…”