Design, Synthesis, and Bioevaluation of a Novel Hybrid Molecular Pyrrolobenzodiazepine-Anthracenecarboxyimide as a Payload for Antibody-Drug Conjugate.

A novel series of hybrid molecules combining pyrrolobenzodiazepine (PBD) and anthracenecarboxyimide pharmacophores were designed, synthesized, and tested for in vitro cytotoxicity against various cancer cell lines. The most potent compound from this series, 37b3, exhibited a subnanomolar level of cytotoxicity with an IC50 of 0.17-0.94 nM. 37b3 induced DNA damage and led to tumor cell cycle arrest and apoptosis. We employed 37b3 as a payload to conjugate with trastuzumab to obtain the antibody-drug conjugate (ADC) T-PBA. T-PBA maintained its mode of target and internalization ability of trastuzumab. We demonstrated that T-PBA could be degraded through the lysosomal pathway to release the payload 37b3 after internalization. T-PBA showed a powerful killing effect on Her2-positive cancer cells in vitro. Furthermore, T-PBA significantly inhibited tumor growth in gastric and ovarian cancer xenograft mouse models without overt toxicity. Collectively, these studies suggest that T-PBA represents a promising new ADC that deserves further investigation.

Cryptophycin-55/52 based antibody-drug conjugates: Synthesis, efficacy, and mode of action studies.

Cryptophycin-52 (CR52), a tubulin inhibitor, exhibits promising antitumor activity in vitro (picomolar level) and in mouse xenograft models. However, the narrow therapeutic window in clinical trials limits its further development. Antibody-drug conjugate (ADC), formed by coupling cytotoxic compound (payload) to an antibody via a linker, can deliver drug to tumor locations in a targeted manner by antibody, enhancing the therapeutic effects and reducing toxic and side effects. In this study, we aim to explore the possibility of CR52-based ADC for tumor targeted therapy. Due to the lack of a coupling site in CR52, its prodrug cryptophycin-55 (CR55) containing a free hydroxyl was synthesized and conjugated to the model antibody trastuzumab (anti-HER2 antibody drug approved by FDA for breast cancer therapy) via the linkers based on Mc-NHS and Mc-Val-Cit-PAB-PNP. The average drug-to-antibody ratios (DARs) of trastuzumab-CR55 conjugates (named T-L1-CR55, T-L2-CR55, and T-L3-CR55) were 3.50, 3.29, and 3.35, respectively. These conjugates exhibited potent cytotoxicity in HER2-positive tumor cell lines with IC50 values at low nanomolar levels (0.58-1.19 nM). Further, they displayed significant antitumor activities at the doses of 10 mg/kg in established ovarian cancer (SKOV3) and gastric cancer (NCI-N87) xenograft models without overt toxicities. Finally, the drug releases were analyzed and the results indicated that T-L3-CR55 was able to effectively release CR55 and further epoxidized to CR52, which may be responsible for its best performance in antitumor activities. In conclusion, our results demonstrated that these conjugates have the potential for tumor targeted therapy, which provides insights to further research the CR55/CR52-based ADC for tumor therapy.

Effective antitumor activity of 5T4-specific CAR-T cells against ovarian cancer cells in vitro and xenotransplanted tumors in vivo.

Ovarian cancer is considered to be the most lethal gynecologic malignancy, and despite the development of conventional therapies and new therapeutic approaches, the patient's survival time remains short because of tumor recurrence and metastasis. Therefore, effective methods to control tumor progression are urgently needed. The oncofetal tumor-associated antigen 5T4 (trophoblast glycoprotein, TPBG) represents an appealing target for adoptive T-cell immunotherapy as it is highly expressed on the surface of various tumor cells, has very limited expression in normal tissues, and spreads widely in malignant tumors throughout their development. In this study, we generated second-generation human chimeric antigen receptor (CAR) T cells with redirected specificity to 5T4 (5T4 CAR-T) and demonstrated that these CAR-T cells can elicit lytic cytotoxicity in targeted tumor cells, in addition to the secretion of cytotoxic cytokines, including IFN-γ, IL-2, and GM-CSF. Furthermore, adoptive transfer of 5T4 CAR-T cells significantly delayed tumor formation in xenografts of peritoneal and subcutaneous animal models. These results demonstrate the potential efficacy and feasibility of 5T4 CAR-T cell immunotherapy and provide a theoretical basis for the clinical study of future immunotherapies targeting 5T4 for ovarian cancer.

Targeting of DDR1 with antibody-drug conjugates has antitumor effects in a mouse model of colon carcinoma.

DDR1 has been identified as a cancer-associated receptor tyrosine kinase that is highly expressed in several malignancies relative to normal tissues. Clinically approved multi-kinase inhibitors, such as nilotinib, inhibit DDR1-mediated tumor growth in xenograft models, suggesting DDR1 might be a potential target for cancer treatments. Here, we employed an antibody-based strategy with a novel anti-DDR1 antibody-drug conjugate (ADC) for colon carcinoma treatment. We developed T4 H11 -DM4, an ADC targeting DDR1 which carries the tubulin inhibitor payload DM4. Immunohistochemical analysis of a tissue microarray containing 100 colon cancer specimens revealed that DDR1 was highly expressed in 81% of tumor tissues. Meanwhile, high expression of DDR1 was associated with poor survival in patients. In vitro, T4 H11 -DM4 exhibited potent anti-proliferative activity with half maximal inhibitory concentration (IC50 ) values in the nanomolar range in a panel of colon cancer cell lines. In vivo, the antitumor efficacy of T4 H11 -DM4 was evaluated in three colon cancer cell lines expressing different levels of DDR1. T4 H11 -DM4 achieved complete tumor regression at doses of 5 and 10 mg·kg-1 in HT-29 and HCT116 tumor models. Moreover, a correlation between in vivo efficacy of T4 H11 -DM4 and the levels of DDR1 expression on the cell surface was observed. Tumor cell proliferation was caused by the induction of mitotic arrest, indicating that the antitumor effect in vivo was mediated by DM4. In addition, T4 H11 -DM4 was efficacious in oxaliplatin-resistant colon cancer models. In exploratory safety studies, T4 H11 -DM4 exhibited no overt toxicities when multi-doses were administered at 10 mg·kg-1 into BALB/c nude mice or when a single dose up to 50 mg·kg-1 was administered into BALB/c mice. Overall, our findings highlight the potential of DDR1-targeted ADC and may facilitate the development of a new effective therapeutic strategy for colon cancer.

Design, synthesis and biological evaluation of a novel tubulin inhibitor 7a3 targeting the colchicine binding site.

Tubulin inhibitors that target the colchicine binding site continue to emerge as promising anticancer agents. In this study, based on the anti-proliferative activities, a novel tubulin inhibitor 7a3 targeting the colchicine binding site was designed, synthesized, and optimized from a series of novel cis-restricted pyrazole analogues of combretastatin A-4. The structure-activity relationships (SARs) of these newly synthesized compounds are summarized indicating that the methyl substituent at the N1 position and deamination were significantly important for the anti-proliferative efficacy. The optimized compound 7a3 exhibited the ability to arrest the cell cycle in the G2/M phase, induce cell apoptosis, and inhibit cell migration in tumour cells. The results of the immunofluorescence analysis using confocal microscopy and the tubulin polymerization assay revealed that tubulin assembly was disrupted by 7a3 in vitro. Furthermore, the targeting identification of 7a3 was illuminated by solving the crystal structure of 7a3 in complex with tubulin at a resolution of 3.2 Š(PDB code 5Z4U), which confirmed the result of molecular docking and further demonstrated that 7a3 binds to the site of colchicine. Moreover, the pharmacokinetic analysis in mouse plasma showed that 7a3 rapidly reached a peak concentration at 0.25 h after intraperitoneal administration, and the T1/2, Cmax, and AUC0-inf were 1.67 ±â€¯0.28 h, 882 ±â€¯71 ng mL-1, and 1166 ±â€¯129 h ng·mL-1, respectively, after a single-dose administration analysed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). In addition, the in vivo study indicated that 7a3 significantly inhibited the tumour growth of the SK-OV-3 xenograft in a nude mouse model. In conclusion, our study proved 7a3 to be a potential microtubule-targeting drug for cancer therapy. The SARs and mechanism of action studies of 7a3 based on the X-ray co-crystal structure provided insights into the next-generation tubulin inhibitors for cancer therapy.

A novel 5T4-targeting antibody-drug conjugate H6-DM4 exhibits potent therapeutic efficacy in gastrointestinal tumor xenograft models.

5T4, also named as trophoblast glycoprotein, is often upregulated in some cancer cells. Here, we demonstrated that 5T4 was highly expressed in gastric, colorectal, and pancreatic cancer, associated with significantly poor prognosis of gastrointestinal (GI) cancer patients. To search for new targeting drugs for GI cancer, we developed a novel anti-5T4 monoclonal antibody with high affinity and robust internalization ability and conjugated it to the potent microtubule inhibitor DM4 to produce conjugate H6-DM4. This antibody-drug conjugate (ADC) displayed significant cytotoxicity in a panel of GI cancer cell lines with IC50 values in the nanomolar range. H6-DM4 eradicated established GI tumor xenograft models at 2.5 mg/kg or 10 mg/kg without observable toxicity. Further, 5T4 was highly expressed in cancer-initiating cells (CICs) compared with non-CICs in colorectal cancer. In vitro and in vivo, treatment with H6-DM4 exhibited a powerful efficacy on colorectal CICs. Additionally, colorectal cancer cells resistant to platinum were effectively eliminated by H6-DM4. Taken together, our results showed 5T4-positive GI cancer cells, colorectal cancer-initiating cells, and platinum-resistant colorectal cancer cells were potently eliminated by H6-DM4, indicating H6-DM4 may be a potential candidate drug for GI cancer treatment.

Therapeutic potential of an anti-HER2 single chain antibody-DM1 conjugates for the treatment of HER2-positive cancer.

Antibody-drug conjugates (ADCs) take the advantage of monoclonal antibodies to selectively deliver highly potent cytotoxic drugs to tumor cells, which have become a powerful measure for cancer treatment in recent years. To develop a more effective therapy for human epidermal growth factor receptor 2 (HER2)-positive cancer, we explored a novel ADCs composed of anti-HER2 scFv-HSA fusion antibodies conjugates with a potent cytotoxic drug DM1. The resulting ADCs, T-SA1-DM1 and T-SA2-DM1 (drug-to-antibody ratio in the range of 3.2-3.5) displayed efficient inhibition in the growth of HER2-positive tumor cell lines and the half-maximal inhibitory concentration on SKBR-3 and SKOV3 cells were both at the nanomolar levels in vitro. In HER2-positive human ovarian cancer xenograft models, T-SA1-DM1 and T-SA2-DM1 also showed remarkable antitumor activity. Importantly, three out of six mice exhibited complete remission without regrowth in the high-dose group of T-SA1-DM1. On the basis of the analysis of luminescence imaging, anti-HER2 scFv-HSA fusion antibodies, especially T-SA1, showed strong and rapid tumor tissue penetrability and distribution compared with trastuzumab. Collectively, the novel type of ADCs is effective and selective targeting to HER2-positive cancer, and may be a promising antitumor drug candidate for further studies.