Synthesis and Preliminary Biological Evaluations of Fluorescent or 149Promethium Labeled Trastuzumab-Polyethylenimine

Jonathan Fitzsimmons; Tapan Nayak; Cathy Cutler; Robert Atcher

doi:10.3390/biomedicines4010001

Synthesis and Preliminary Biological Evaluations of Fluorescent or ¹⁴⁹Promethium Labeled Trastuzumab-Polyethylenimine

Biomedicines. 2015 Dec 30;4(1):1. doi: 10.3390/biomedicines4010001.

Authors

Jonathan Fitzsimmons¹, Tapan Nayak^{2

3}, Cathy Cutler⁴, Robert Atcher^{5

6}

Affiliations

¹ Chemistry, Life, and Earth Sciences Directorate, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. jfitzsimmons@bnl.gov.
² Department of Cell Biology and Physiology, School of Medicine, University of New Mexico Health Science Center, Albuquerque, NM 87131, USA. tapann@gmail.com.
³ College of Pharmacy, Radiopharmaceutical Sciences Program, University of New Mexico Health Science Center, Albuquerque, NM 87131, USA. tapann@gmail.com.
⁴ University of Missouri Research Reactor (MURR), University of Missouri-Columbia, Columbia MO 65211, USA. ccutler@bnl.gov.
⁵ Chemistry, Life, and Earth Sciences Directorate, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. ratcher@lanl.gov.
⁶ College of Pharmacy, Radiopharmaceutical Sciences Program, University of New Mexico Health Science Center, Albuquerque, NM 87131, USA. ratcher@lanl.gov.

Abstract

Background: Radioimmunotherapy utilize a targeting antibody coupled to a therapeutic isotope to target and treat a tumor or disease. In this study we examine the synthesis and cell binding of a polymer scaffold containing a radiotherapeutic isotope and a targeting antibody.

Methods: The multistep synthesis of a fluorescent or ¹⁴⁹Promethium-labeled Trastuzumab-polyethyleneimine (PEI), Trastuzumab, or PEI is described. In vitro uptake, internalization and/or the binding affinity to the Her2/neu expressing human breast adenocarcinoma SKBr3 cells was investigated with the labeled compounds.

Results: Fluorescent-labeled Trastuzumab-PEI was internalized more into cells at 2 and 18 h than fluorescent-labeled Trastuzumab or PEI. The fluorescent-labeled Trastuzumab was concentrated on the cell surface at 2 and 18 h and the labeled PEI had minimal uptake. DOTA-PEI was prepared and contained an average of 16 chelates per PEI; the compound was radio-labeled with ¹⁴⁹Promethium and conjugated to Trastuzumab. The purified ¹⁴⁹Pm-DOTA-PEI-Trastuzumab had a radiochemical purity of 96.7% and a specific activity of 0.118 TBq/g. The compound demonstrated a dissociation constant for the Her2/neu receptor of 20.30 ± 6.91 nM.

Conclusion: The results indicate the DOTA-PEI-Trastuzumab compound has potential as a targeted therapeutic carrier, and future in vivo studies should be performed.

Keywords: Actinium-225; Promethium-149; Trastuzumab; polyethylenimine; radiotherapy; targeted therapy.