177Lu-Lilotomab Satetraxetan Has the Potential to Counteract Resistance to Rituximab in Non-Hodgkin Lymphoma

J Nucl Med. 2020 Oct;61(10):1468-1475. doi: 10.2967/jnumed.119.237230. Epub 2020 Apr 3.


Patients with non-Hodgkin lymphoma (NHL) who are treated with rituximab may develop resistant disease, often associated with changes in expression of CD20. The next-generation β-particle-emitting radioimmunoconjugate 177Lu-lilotomab-satetraxetan (Betalutin) was shown to up-regulate CD20 expression in different rituximab-sensitive NHL cell lines and to act synergistically with rituximab in a rituximab-sensitive NHL animal model. We hypothesized that 177Lu-lilotomab-satetraxetan may be used to reverse rituximab resistance in NHL. Methods: The rituximab-resistant Raji2R and the parental Raji cell lines were used. CD20 expression was measured by flow cytometry. Antibody-dependent cellular cytotoxicity (ADCC) was measured by a bioluminescence reporter assay. The efficacies of combined treatments with 177Lu-lilotomab-satetraxetan (150 or 350 MBq/kg) and rituximab (4 × 10 mg/kg) were compared with those of single agents or phosphate-buffered saline in a Raji2R-xenograft model. Cox regression and the Bliss independence model were used to assess synergism. Results: Rituximab binding in Raji2R cells was 36% ± 5% of that in the rituximab-sensitive Raji cells. 177Lu-lilotomab-satetraxetan treatment of Raji2R cells increased the binding to 53% ± 3% of the parental cell line. Rituximab ADCC induction in Raji2R cells was 20% ± 2% of that induced in Raji cells, whereas treatment with 177Lu-lilotomab-satetraxetan increased the ADCC induction to 30% ± 3% of that in Raji cells, representing a 50% increase (P < 0.05). The combination of rituximab with 350 MBq/kg 177Lu-lilotomab-satetraxetan synergistically suppressed Raji2R tumor growth in athymic Foxn1nu mice. Conclusion:177Lu-lilotomab-satetraxetan has the potential to reverse rituximab resistance; it can increase rituximab binding and ADCC activity in vitro and can synergistically improve antitumor efficacy in vivo.

Keywords: 177Lu; NHL; radioimmunotherapy; rituximab resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / therapeutic use*
  • Antibody-Dependent Cell Cytotoxicity
  • Apoptosis / drug effects
  • Apoptosis / radiation effects
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm
  • Humans
  • Immunoconjugates / therapeutic use*
  • Lymphoma, Non-Hodgkin / drug therapy
  • Lymphoma, Non-Hodgkin / mortality
  • Lymphoma, Non-Hodgkin / pathology
  • Lymphoma, Non-Hodgkin / radiotherapy*
  • Mice
  • Radioimmunotherapy*
  • Rituximab / metabolism
  • Rituximab / therapeutic use*
  • Xenograft Model Antitumor Assays


  • (177)Lu-lilotomab satetraxetan
  • Antibodies, Monoclonal
  • Immunoconjugates
  • Rituximab