Dual-Isotope Cryoimaging Quantitative Autoradiography: Investigating Antibody–Drug Conjugate Distribution and Payload Delivery Through Imaging

Abstract

In vitro properties of antibody-drug conjugates (ADCs) such as binding, internalization, and cytotoxicity are often well characterized before in vivo studies. Interpretation of in vivo studies might be significantly enhanced by molecular imaging tools. We present here a dual-isotope cryoimaging quantitative autoradiography (CIQA) methodology combined with advanced 3-dimensional imaging and analysis allowing for the simultaneous study of both antibody and payload distribution in tissues of interest in a preclinical setting. TAK-264, an investigational ADC targeting anti-guanylyl cyclase C (GCC), was synthesized using tritiated monomethyl auristatin E. The tritiated ADC was then conjugated to diethylenetriaminepentaacetic acid, labeled withIn, and evaluated in vivo in animals bearing GCC-positive and GCC-negative tumors. CIQA revealed the time course of drug release from ADC and its distribution into various tumor regions that are less accessible to the antibody. For GCC-positive tumors, a representative section obtained 96 h after tracer injection showed only 0.8% of the voxels to have colocalized signal, versus over 15% of the voxels for a GCC-negative tumor section, suggesting successful and specific cleaving of the toxin in the GCC-positive lesions. The combination of a veteran established autoradiography technology with advanced image analysis methodologies affords an experimental tool that can support detailed characterization of ADC tumor penetration and pharmacokinetics.

Co-administered antibody improves penetration of antibody–dye conjugate into human cancers with implications for antibody–drug conjugates

“…Autoradiography is another way to study the biodistribution of radiolabeled antibodies in biological samples. However, it has several limitations for measuring antibody microdistribution compared with fluorescently labeled antibodies [47][48][49][50][51][52] . These include the lack of cellular resolution (at typical specific activities and relevant antibody doses), the risk of exposing patients to radioactivity, challenges in quantification due to artifacts, and extremely long exposure times (e.g., for tritiated samples) required to accumulate enough signal (on the orders of days to months), etc.…”

Biodistribution and efficacy of an anti-TENB2 antibody-drug conjugate in a patient-derived model of prostate cancer

“…, 111 In-DOTA catabolites tend to get entrapped within cells (possibly within lysosomes to an extent) following internalization and degradation of the antibody to which it was originally conjugated [30, 31]. Recent efforts have examined the colocalization (or lack thereof) of 3 H-labeled MMAE versus the 111 In-DTPA-labeled antibody for a dual labeled ADC in tumor-bearing mice [32]. The two signals diverged as time progressed, suggesting evidence of the ‘bystander effect’ wherein a given hydrophobic MMAE molecule is able to diffuse across cell membranes beyond the cell in which it was originally released.…”

111In-DANBIRT In Vivo Molecular Imaging of Inflammatory Cells in Atherosclerosis

“…Correlation of SPECT/CT imaging 24 hours with autoradiography showed increased uptake in the resident-leukocyte-rich thymus, confirming functional and morphological distribution of 111In-DANBIRT. 3D autoradiography was critical, allowing radioligand localization in areas difficult for identification using plain CT or SPECT/CT because of the interference in the signal coming from small vessels, and the limits of detector sensitivity and specificity [ 46 ].…”