ANTIBODY CONJUGATES IN ONCOLOGY
Over the past decade, protein-drug conjugates and more specifically antibody-drug conjugates (ADCs) have emerged as a core class of therapeutics, used primarily in oncology. This expansion is the result of an increased understanding of the factors influencing the efficacy and toxicity of immunoconjugates, improved antibody engineering, advances in coupling technologies to cytotoxic agents, as well as improved target and cytotoxic agent selection. However, the development and optimization of ADCs requires accurate determination of the plasma and tissue profiles of the protein and its drug conjugate because, due to their duality, determining the in vivo fate of the two components of the conjugate can be difficult and requires the use of multiple and complementary bioanalytical approaches.
PROMISING NEW DUAL RADIOLABELED CONJUGATES
In this context, the authors have developed an innovative and original bioanalytical approach based on a double 14C-3H isotopic labeling of an antibody-drug conjugate. The team produced several anti-MMP-14 (Matrix Metalloproteinase-14) antibody fragments (Fabs), which were then conjugated to monomethyl auristatin E (MMAE) using a cleavable or non-cleavable linker, in which the protein part (Fab) is labeled with carbon 14 and the drug part (MMAE) with tritium. By combining liquid scintillation counting and ex vivo dual-isotope digital radio-imaging, it was possible not only to follow both components simultaneously during their circulating phase in plasma, but also to accurately quantify their accumulated amount in different organs and tumors of mice (standard and preclinical breast cancer model). In particular, the concentration of both components could be accurately determined at the tumor site and the effective release of 3H-MMAE into the tumor was confirmed by high-performance liquid chromatography (HPLC).
This innovative strategy can be used to compare the stability and in vivo performance of protein-drug conjugates in preclinical models, thus facilitating the identification of high potential conjugates for future clinical evaluations.
Contact : Laurent Devel laurent.devel@cea.fr
ADCs (antibody-drug conjugates) are immunoconjugates composed of a
monoclonal antibody (or monoclonal antibody fragment, Fab) linked to a
cytotoxic drug by a chemical bond. A
Fab directed against MMP14 was recently shown to limit metastatic proliferation in a preclinical breast cancer model, validating the predominant role of MMP-14 in cancer cell invasion.
Monomethyl auristatin E (MMAE) is a synthetic anti-tumor agent that, due to its toxicity, cannot be used as a drug itself. It is therefore bound to an antibody that directs it to the cancer cells.
To label the team-developed anti-MMP-14 Fab component and track it during in vivo experiments, an original pegylated-
14C marker was designed. Tritium labeling of MMAE was performed by ruthenium-catalyzed hydrogen isotope exchange.
These 2 labelings were made possible thanks to the expertise and know-how of the SCBM chemists.