Preclinical evaluation of FAP-2286 for fibroblast activation protein targeted radionuclide imaging and therapy

  • Eur J Nucl Med Mol Imaging. 2022 Sep;49(11):3651-3667. doi: 10.1007/s00259-022-05842-5.
Dirk Zboralski  1 ,  Aileen Hoehne  2 ,  Anne Bredenbeck  2 ,  Anne Schumann  2 ,  Minh Nguyen  3 ,  Eberhard Schneider  2 ,  Jan Ungewiss  2 ,  Matthias Paschke  2 ,  Christian Haase  2 ,  Jan L von Hacht  2 ,  Tanya Kwan  3 ,  Kevin K Lin  3 ,  Jan Lenore  3 ,  Thomas C Harding  3 ,  Jim Xiao  3 ,  Andrew D Simmons  3 ,  Ajay-Mohan Mohan  4 ,  Nicola Beindorff  4 ,  Ulrich Reineke  2 ,  Christiane Smerling  2 ,  Frank Osterkamp  2
Affiliations
  • 1. 3B Pharmaceuticals GmbH, Magnusstraße 11, 12489, Berlin, Germany. [email protected].
  • 2. 3B Pharmaceuticals GmbH, Magnusstraße 11, 12489, Berlin, Germany.
  • 3. Clovis Oncology, Inc, Boulder, CO, USA.
  • 4. Berlin Experimental Radionuclide Imaging Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.
PMID: 35608703 DOI: 10.1007/s00259-022-05842-5
Abstract

Purpose: Fibroblast activation protein (FAP) is a membrane-bound protease that has limited expression in normal adult tissues but is highly expressed in the tumor microenvironment of many solid cancers. FAP-2286 is a FAP-binding peptide coupled to a radionuclide chelator that is currently being investigated in patients as an imaging and therapeutic agent. The potency, selectivity, and efficacy of FAP-2286 were evaluated in preclinical studies.

Methods: FAP expression analysis was performed by immunohistochemistry and autoradiography on primary human Cancer specimens. FAP-2286 was assessed in biochemical and cellular assays and in in vivo imaging and efficacy studies, and was further evaluated against FAPI-46, a small molecule-based FAP-targeting agent.

Results: Immunohistochemistry confirmed elevated levels of FAP expression in multiple tumor types including pancreatic, breast, and sarcoma, which correlated with FAP binding by FAP-2286 autoradiography. FAP-2286 and its metal complexes demonstrated high affinity to FAP recombinant protein and cell surface FAP expressed on fibroblasts. Biodistribution studies in mice showed rapid and persistent uptake of 68Ga-FAP-2286, 111In-FAP-2286, and 177Lu-FAP-2286 in FAP-positive tumors, with renal clearance and minimal uptake in normal tissues. 177Lu-FAP-2286 exhibited antitumor activity in FAP-expressing HEK293 tumors and sarcoma patient-derived xenografts, with no significant weight loss. In addition, FAP-2286 maintained longer tumor retention and suppression in comparison to FAPI-46.

Conclusion: In preclinical models, radiolabeled FAP-2286 demonstrated high tumor uptake and retention, as well as potent efficacy in FAP-positive tumors. These results support clinical development of 68Ga-FAP-2286 for imaging and 177Lu-FAP-2286 for therapeutic use in a broad spectrum of FAP-positive tumors.

Keywords
CAF; FAP; PTRT; Theranostic.
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