Effects of an Unlabeled Loading Dose on Tumor-Specific Uptake of a Fluorescently Labeled Antibody for Optical Surgical Navigation.
Intraoperative optical imaging to guide surgeons during oncologic resections offers a unique and promising solution to the ambiguity of cancer margins to tactile and visual assessment that results in devastatingly high rates of positive margins. Sequestering of labeled antibodies by normal tissues with high expression of the antibody target, or "antigen sinks", diminishes the efficacy of these probes to provide contrast between the tumor and background tissues by decreasing the amount of circulating probe available for uptake by the tumor and by increasing the fluorescence of non-tumor tissues. We hypothesized that administering a dose of unlabeled antibody prior to infusion of the near-infrared (NIR) fluorescently labeled antibody would improve tumor-specific uptake and contrast of the fluorescently labeled probe by occupying extra-tumoral binding sites, thereby increasing the amount of labeled probe available for uptake by the tumor.



In this study, we explore this concept by testing two different "pre-load" doses of unlabeled cetuximab (the standard 10-mg test dose, and a larger, experimental 100-mg test dose) in six patients receiving cetuximab conjugated to the fluorescent dye IRDye800CW (cetuximab-IRDye800CW) in a clinical trial, and compared the amount of fluorescent antibody in tumor and background tissues, as well as the tumor-specific contrast of each.



The patients receiving the larger preload (100 mg) of unlabeled cetuximab demonstrated significantly higher concentrations (9.5 vs. 0.1 μg) and a longer half-life (30.3 vs. 20.6 days) of the labeled cetuximab in plasma, as well as significantly greater tumor fluorescence (32.3 vs. 9.3 relative fluorescence units) and tumor to background ratios (TBRs) (5.5 vs. 1.7).



Administering a preload of unlabeled antibody prior to infusion of the fluorescently labeled drug may be a simple and effective way to improve the performance of antibody-based probes to guide surgical resection of solid malignancies.
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA.
Lindsay S
LS
Moore
Department of Otolaryngology, Stanford University, Stanford, CA, USA.
Eben L
EL
Rosenthal
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA.|Department of Surgery, University of Groningen, Groningen, the Netherlands.
Esther
E
de Boer
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA.
Andrew C
AC
Prince
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA.
Neel
N
Patel
Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
Joshua M
JM
Richman
Department of Oral & Maxillofacial Surgery, University of Alabama Birmingham, Birmingham, AL, USA.
Anthony B
AB
Morlandt
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA.
William R
WR
Carroll
Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, USA.
Kurt R
KR
Zinn
Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL, USA. mojack@uab.edu.|Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, USA. mojack@uab.edu.|Departments of Otolaryngology, Neurosurgery, and Radiology, The University of Alabama at Birmingham, 1670 University Blvd., Birmingham, AL, 35294, USA. mojack@uab.edu.
Jason M
JM
Warram
D000328:Adult; D000368:Aged; D000906:Antibodies / Q000378:metabolism*; D000068818:Cetuximab / Q000493:pharmacokinetics; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D061848:Optical Imaging / Q000379:methods*; D013194:Staining and Labeling; D013514:Surgical Procedures, Operative
D000906:Antibodies; D005456:Fluorescent Dyes; D000068818:Cetuximab
Cetuximab; Cetuximab-IRDye800CW; Fluorescence-guided surgery; Head and neck cancer; Loading dose; Optical surgical navigation; Unlabeled preload