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 KD 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.

hIMB1636-MMAE, a Novel TROP2-Targeting Antibody-Drug Conjugate Exerting Potent Antitumor Efficacy in Pancreatic Cancer.

Herein, we first prepared a novel anti-TROP2 antibody-drug conjugate (ADC) hIMB1636-MMAE using hIMB1636 antibody chemically coupled to monomethyl auristatin E (MMAE) via a Valine-Citrulline linker and then reported its characteristics and antitumor activity. With a DAR of 3.92, it binds specifically to both recombinant antigen (KD ∼ 0.687 nM) and cancer cells and could be internalized by target cells and selectively kill them with IC50 values at nanomolar/subnanomolar levels by inducing apoptosis and G2/M phase arrest. hIMB1636-MMAE also inhibited cell migration, induced ADCC effects, and had bystander effects. It displayed significant tumor-targeting ability and excellent tumor-suppressive effects in vivo, resulting in 5/8 tumor elimination at 12 mg/kg in the T3M4 xenograft model or complete tumor disappearance at 10 mg/kg in BxPc-3 xenografts in nude mice. Its half-life in mice was about 87 h. These data suggested that hIMB1636-MMAE was a promising candidate for the treatment of pancreatic cancer with TROP2 overexpression.

Elucidating the development, characterization, and antitumor potential of a novel humanized antibody against Trop2.

Trophoblast cell surface antigen 2 (Trop2) has emerged as a potential target for effective cancer therapy. In this study, we report a novel anti-Trop2 antibody IMB1636, developed using hybridoma technology. It exhibited high affinity and specificity (KD = 0.483 nM) in binding both antigens and cancer cells, as well as human tumor tissues. hIMB1636 could induce endocytosis, and enabled targeted delivery to the tumor site with an in vivo retention time of 264 h. The humanized antibody hIMB1636, acquired using CDR grafting, exhibited the potential to directly inhibit cancer cell proliferation and migration, and to induce ADCC effects. Moreover, hIMB1636 significantly inhibited the growth of MDA-MB-468 xenograft tumors in vivo. Mechanistically, hIMB1636 induced cell cycle arrest and apoptosis by regulating cyclin-related proteins and the caspase cascade. In comparison to commercialized sacituzumab, hIMB1636 recognized a conformational epitope instead of a linear one, bound to antigen and cancer cells with similar binding affinity, induced significantly more potent ADCC effects against cancer cells, and displayed superior antitumor activities both in vitro and in vivo. The data presented in this study highlights the potential of hIMB1636 as a carrier for the formulation of antibody-based conjugates, or as a promising candidate for anticancer therapy.