Abstract 6310: Phylogenetic conservation of primate Trop-2 underscores favorable pharmacokinetics and lack of toxicity of the cancer-selective Hu2G10 anti-Trop-2
Authors: Alberti Saverio , Ceci Martina , Pantalone Ludovica , Trerotola Marco , Guerra Emanuela 
Published: June 2023

Abstract
Trop-2 is a transmembrane signal transducer that activates growth-signaling networks that converge on Akt, ERK, Cyclin D1, NFkB (1). We discovered that Trop-2 cleavage by ADAM10 is an activator switch of cancer growth and metastatic diffusion (2) and exposes novel target epitopes that are inaccessible in the unprocessed wtTrop-2. The Hu2G10 mAb selectively binds these epitopes with an affinity that is ≈10,000-fold higher than for the unprocessed molecule. To validate a reliable model for Hu2G10 binding in vivo, we explored Trop-2 phylogenetic conservation in primates. Pan troglodites (chimpanzee), Papio anubis (baboon), Macaca mulatta/fascicularis (Rhesus/Cynomolgous), Callithrix jaccus (marmoset) TROP2/TACSTD2 sequences were compared. The only difference between Pan troglodytes and human Trop-2 is one additional leucine in the Pan leader peptide, making the mature Trop-2 identical to that in man. The Macaca mulatta/fascicularis Trop-2 sequences are 97% identical, 100% similar to the human sequence. Three-dimensional modeling revealed polymorphic residues usage versus activation-driven structural rearrangement of Trop-2. COS-7 and HEK-293 cells transfected with individual primate Trop-2 showed efficient recognition by Hu2G10 in all tested species. Immunohistochemistry analysis of normal Macaca tissues showed Trop-2 expression patterns essentially corresponding to the human ones. IV injected Hu2G10 at doses of 5 to 10 mg/kg was well tolerated by Cynomolgous monkeys. No neurological, respiratory, digestive and urinary adverse effects were observed, and no body-weight loss occurred during the 28-day observation. No alterations of blood monocyte, neutrophil and basophil counts nor significant changes in biochemical parameters were detected. A pharmacokinetic (PK), study was carried out. Serum concentration of Hu2G10 was determined using anti-idiotypic antibody-based ELISA assays. At the higher dosing of 10 mg/kg Hu2G10 serum values reached a peak 2-hour after the injection (13281±4686 ng/ml). The concentration of Hu2G10 then diminished gradually, and reached baseline levels on day 21. The serum concentration peak of 5 mg/kg Hu2G10 was 5759±1729 ng/ml, and reached baseline levels on day 14. Thus, Hu2G10 is stable in plasma, and is detectable in the circulation up to three weeks after the infusion (t1/2=6.5 days). Taken together, these findings validate primate models as reliable for assessing Hu2G10 in vivo toxicity and PK. The lack of toxicity and favorable PK parameters candidate the cancer specific Hu2G10 as first-in-class anti-Trop-2 mAb. (1) Guerra E. et al., Oncogene 41:1795-1808 (2022).(2) Trerotola M. et al., Neoplasia 23: 415-428 (2021).
Citation Format: Saverio Alberti, Martina Ceci, Ludovica Pantalone, Marco Trerotola, Emanuela Guerra. Phylogenetic conservation of primate Trop-2 underscores favorable pharmacokinetics and lack of toxicity of the cancer-selective Hu2G10 anti-Trop-2. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6310.