[177Lu]pentixather: Comprehensive Preclinical Characterization of a First CXCR4-directed Endoradiotherapeutic Agent

Theranostics. 2017 Jun 11;7(9):2350-2362. doi: 10.7150/thno.19119. eCollection 2017.

Abstract

Purpose: Based on the clinical relevance of the chemokine receptor 4 (CXCR4) as a molecular target in cancer and on the success of [68Ga]pentixafor as an imaging probe for high-contrast visualization of CXCR4-expression, the spectrum of clinical CXCR4-targeting was expanded towards peptide receptor radionuclide therapy (PRRT) by the development of [177Lu]pentixather. Experimental design: CXCR4 affinity, binding specificity, hCXCR4 selectivity and internalization efficiency of [177Lu]pentixather were evaluated using different human and murine cancer cell lines. Biodistribution studies (1, 6, 48, 96h and 7d p.i.) and in vivo metabolite analyses were performed using Daudi-lymphoma bearing SCID mice. Extrapolated organ doses were cross-validated with human dosimetry (pre-therapeutic and during [177Lu]pentixather PRRT) in a patient with multiple myeloma (MM). Results: [177Lu]pentixather binds with high affinity, specificity and selectivity to hCXCR4 and shows excellent in vivo stability. Consequently, and supported by >96% plasma protein binding and a logP=-1.76, delaying whole-body clearance of [177Lu]pentixather, tumor accumulation was high and persistent, both in the Daudi model and the MM patient. Tumor/background ratios (7d p.i.) in mice were 499±202, 33±7, 4.0±0.8 and 116±22 for blood, intestine, kidney and muscle, respectively. In the patient, high tumor/kidney and tumor/liver dose ratios of 3.1 and 6.4 were observed during [177Lu]pentixather PRRT (7.8 GBq), with the kidneys being the dose-limiting organs. Conclusions: [177Lu]pentixather shows excellent in vivo CXCR4-targeting characteristics and a suitable pharmacokinetic profile, leading to high tumor uptake and retention and thus high radiation doses to tumor tissue during PRRT, suggesting high clinical potential of this [68Ga]pentixafor/[177Lu]pentixather based CXCR4-targeted theranostic concept.

Keywords: CXCR4; PRRT; endoradiotherapy.; pentixafor; pentixather.

MeSH terms

  • Animals
  • Antineoplastic Agents / administration & dosage
  • Antineoplastic Agents / pharmacokinetics*
  • Cell Line, Tumor
  • Disease Models, Animal
  • Humans
  • Lutetium / administration & dosage
  • Lutetium / pharmacokinetics*
  • Lymphoma / drug therapy*
  • Mice, SCID
  • Molecular Targeted Therapy / methods*
  • Multiple Myeloma / drug therapy*
  • Peptides, Cyclic / administration & dosage
  • Peptides, Cyclic / pharmacokinetics
  • Radioisotopes / administration & dosage
  • Radioisotopes / pharmacokinetics*
  • Radiotherapy / methods*
  • Receptors, CXCR4 / metabolism*

Substances

  • Antineoplastic Agents
  • CXCR4 protein, human
  • CXCR4 protein, mouse
  • Peptides, Cyclic
  • Radioisotopes
  • Receptors, CXCR4
  • Lutetium
  • Lutetium-177