PET imaging of an optimized anti-PD-L1 probe Ga-NODAGA-BMS986192 in immunocompetent mice and non-human primates.

BACKGROUND

Adnectin is a protein family derived from the 10th type III domain of human fibronectin (Fn3) with high-affinity targeting capabilities. Positron emission tomography (PET) probes derived from anti-programmed death ligand-1 (PD-L1) Adnectins, including F- and Ga-labeled BMS-986192, are recently developed for the prediction of patient response to immune checkpoint blockade. The Ga-labeled BMS-986192, in particular, is an attractive probe for under-developed regions due to the broader availability of Ga. However, the pharmacokinetics and biocompatibility of Ga-labeled BMS-986192 are still unknown, especially in non-human primates, impeding its further clinical translation.

METHODS

We developed a variant of Ga-labeled BMS-986192 using 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA) as the radionuclide-chelator. The resultant probe, Ga-NODAGA-BMS986192, was evaluated in terms of targeting specificity using a bilateral mouse tumor model inoculated with wild-type B16F10 and B16F10 transduced with human PD-L1 (hPD-L1-B16F10). The dynamic biodistribution and radiation dosimetry of this probe were also investigated in non-human primate cynomolgus.

RESULTS

Ga-NODAGA-BMS986192 was prepared with a radiochemical purity above 99%. PET imaging with Ga-NODAGA-BMS986192 efficiently delineated the hPD-L1-B16F10 tumor at 1 h post-injection. The PD-L1-targeting capability of this probe was further confirmed using in vivo blocking assay and ex vivo biodistribution studies. PET dynamic imaging in both mouse and cynomolgus models revealed a rapid clearance of the probe via the renal route, which corresponded to the low background signals of the PET images. The probe also exhibited a favorable radiation dosimetry profile with a total-body effective dose of 6.34E-03 mSv/MBq in male cynomolgus.

CONCLUSIONS

Ga-NODAGA-BMS986192 was a feasible and safe tool for the visualization of human PD-L1. Our study also provided valuable information on the potential of targeted PET imaging using Adnectin-based probes.