A new TROP2-targeting antibody-drug conjugate shows potent antitumor efficacy in breast and lung cancers

Trophoblast cell surface antigen 2 (TROP2) is considered to be an attractive therapeutic target in Cancer treatments. We previously generated a new humanized anti-Trop2 antibody named hIMB1636, and designated it as an ideal targeting carrier for Cancer therapy. Lidamycin (LDM) is a new antitumor Antibiotic, containing an active enediyne chromophore (AE) and a noncovalently bound apoprotein (LDP). AE and LDP can be separated and reassembled, and the reassembled LDM possesses cytotoxicity similar to that of native LDM; this has made LDM attractive in the preparation of gene-engineering drugs. We herein firstly prepared a new fusion protein hIMB1636-LDP composed of hIMB1636 and LDP by genetic engineering. This construct showed potent binding activities to recombinant antigen with a K_D value of 4.57 nM, exhibited binding to Trop2-positive Cancer cells and internalization and transport to lysosomes, and demonstrated powerful tumor-targeting ability in vivo. We then obtained the antibody-drug conjugate (ADC) hIMB1636-LDP-AE by molecular reconstitution. In vitro, hIMB1636-LDP-AE inhibited the proliferation, migration, and tumorsphere formation of tumor cells with half-maximal inhibitory concentration (IC₅₀) values at the sub-nanomolar level. Mechanistically, hIMB1636-LDP-AE induced Apoptosis and cell-cycle arrest. In vivo, hIMB1636-LDP-AE also inhibited the growth of breast and lung cancers in xenograft models. Moreover, compared to sacituzumab govitecan, hIMB1636-LDP-AE showed more potent antitumor activity and significantly lower myelotoxicity in tumors with moderate TROP2 expression. This study fully revealed the potent antitumor efficacy of hIMB1636-LDP-AE, and also provided a new preparation method for LDM-based ADC, as well as a promising candidate for breast Cancer and lung Cancer therapeutics.