Abstract
Introduction: Currently bio-distribution of biologic drugs is evaluated by PET imaging, autoradioraphy using radio-labeled molecules or ex vivo methods. Advances in optical probes and non-invasive imaging technologies have given us an opportunity to conduct such studies without the use of radio-labeled materials or by traditional pharmacokinetic (PK) studies. 5T4 (also known as TPBG or oncofetal antigen) is a transmembrane glycoprotein expressed highly on tumor-initiating cells. Anti-5T4-mcMMAF used in these studies is an anti-5T4-antibody drug conjugate (ADC) that reacts to human, cyno and marmoset orthologs of 5T4. Previously, we showed the efficacy of anti-5T4-ADC in pre-clinical models (Sapra et al.,). In this study we show the utility of Fluorescence Molecular Tomography (FMT) imaging in bio-distribution studies with this ADC using a H1975 non-small cell lung cancer (NSCLC) xenograft model.
Methods: For the H1975 xenograft model, five million cells in 50% matrigel were injected into the subcutaneous flanks of the female nu/nu mice, and a biodistribution study was initiated when the tumors reached ∼500 mm3. The anti-5T4-ADC and a control ADC (non-binding) were conjugated with near-IR fluorophore VivoTag680XL. The labeling efficiency and quality was determined by Nanodrop-8000 spectrophotometer and binding assays. FMT imaging was performed longitudinally at 5min, 6hr, 24hr, 48hr, 96hr and 240hrs post injection of labeled ADCs. Ex vivo imaging of organs was performed at intermittent time points after perfusing with PBS. Data was analyzed using TrueQuant software. Plasma and tissues were collected at various time points and analyzed by GyrolabTM workstation and LCMS methods.
Results: VivoTag680XL conjugation was efficient and achieved degree of labeling between 2-3. Three-dimensional quantitative analysis of FMT data showed significant specific targeting of anti-5T4-ADC to the tumors (ex vivo and in vivo comparison), relative to the control non-binding ADC. The peak accumulation in tumor was observed at 48hrs post injection and the concentration decreased in later time points. Liver was the major organ for the non-specific accumulation of these antibodies/ADCs, followed by kidneys and lung. Both 5T4-ADC and Control-ADC showed similar accumulation at 48hrs and 96hrs in liver, whereas it decreased significantly at 240hrs. The FMT imaging data was comparative and correlated with the traditional plasma PK profile data.
Conclusion: These results show that anti-5T4-ADC targets the tumor better than non-binding ADC. This study also shows the utility of FMT in bio-distribution studies of biologics. Since the fluorophore can be conjugated to any protein/peptide, this novel approach can become a platform technology in conducting biodistribution studies of all biologic drugs.
Citation Format: Anand Giddabasappa, Rand Norberg, Mauricio Leal, David Paterson, Kush Lalwani, Ted Levkoff, Stella Rapa, Puja Sapra, Michael Ritche, Joann Wentland, Brian Rago, Jeetendra Eswaraka. Whole-body bio-distribution of anti-5T4-mcMMAF (anti-5T4-ADC) using fluorescence molecular tomography (FMT) imaging in a non-small cell lung cancer mice model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4293. doi:10.1158/1538-7445.AM2014-4293
- ©2014 American Association for Cancer Research.
Volume 74, Issue 19 Supplement
