Proof of Therapeutic Efficacy of a 177 Lu-Labeled Neurotensin Receptor 1 Antagonist in a Colon Carcinoma Xenograft Model

J Nucl Med. 2017 Jun;58(6):936-941. doi: 10.2967/jnumed.116.185140. Epub 2017 Mar 2.

Abstract

Increased expression of neurotensin receptor 1 (NTR1) has been shown in a large number of tumor entities such as pancreatic or colon carcinoma. Hence, this receptor is a promising target for diagnostic imaging and radioligand therapy. Using the favorable biodistribution data of the NTR1-targeting agent 111In-3BP-227, we investigated the therapeutic effect of its 177Lu-labeled analog on the tumor growth of NTR1-positive HT29 colon carcinoma xenografts. Methods: 3BP-227 was labeled with 177Lu. To assess its biodistribution properties, SPECT and CT scans of HT29-xenografted nude mice injected with 177Lu-3BP-227 were acquired, and ex vivo tissue activity was determined. To evaluate therapeutic efficacy, 2 groups of mice received the radiopharmaceutical in a median dose of either 165 MBq (129-232 MBq, n = 10) or 110 MBq (82-116 MBq, n = 10), whereas control mice were injected with vehicle (n = 10). Tumor sizes and body weights were monitored for up to 49 d. Renal function and histologic morphology were evaluated. Results: Whole-body SPECT/CT images allowed clear tumor visualization with low background activity and high tumor-to-kidney and -liver ratios. Ex vivo biodistribution data confirmed high and persistent uptake of 177Lu-3BP-227 in HT29 tumors (19.0 ± 3.6 vs. 2.7 ± 1.6 percentage injected dose per gram at 3 and 69 h after injection, respectively). The application of 177Lu-3BP-227 resulted in a distinct delay of tumor growth. Median tumor doubling time for controls was 5.5 d (interquartile range [IQR], 2.8-7.0), compared with 17.5 d (IQR, 5.5-22.5 d) for the 110-MBq and 41.0 d (IQR, 27.5-55.0) for the 165-MBg group. Compared with controls, median relative tumor volume at day 23 after injection was reduced by 55% (P = 0.034) in the 110-MBq and by 88% (P < 0.01) in the 165-MBq group. Renal histology and clinical chemistry results did not differ between radiotherapy groups and controls, suggesting absence of therapy-induced acute renal damage. Conclusion: These data demonstrate that the novel NTR1-targeting theranostic agent 3BP-227 is an effective and promising candidate for radioligand therapy, with a favorable preliminary safety profile and high potential for clinical translation.

Keywords: NTR1 radiotracer; SPECT/CT; oncology; theranostic; xenograft.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / radiation effects
  • Cell Line, Tumor
  • Colonic Neoplasms / diagnostic imaging*
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Colonic Neoplasms / radiotherapy*
  • Female
  • HT29 Cells
  • Humans
  • Lutetium / therapeutic use*
  • Mice
  • Mice, Nude
  • Molecular Targeted Therapy / methods*
  • Radiopharmaceuticals / therapeutic use
  • Receptors, Neurotensin / antagonists & inhibitors*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Theranostic Nanomedicine / methods*
  • Treatment Outcome

Substances

  • Radiopharmaceuticals
  • Receptors, Neurotensin
  • neurotensin type 1 receptor
  • Lutetium