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Molecular Cancer Therapeutics Jul 2022Exatecan and deruxtecan are antineoplastic camptothecin derivatives in development as tumor-targeted-delivery warheads in various formulations including peptides,...
Exatecan and deruxtecan are antineoplastic camptothecin derivatives in development as tumor-targeted-delivery warheads in various formulations including peptides, liposomes, polyethylene glycol nanoparticles, and antibody-drug conjugates. Here, we report the molecular pharmacology of exatecan compared with the clinically approved topoisomerase I (TOP1) inhibitors and preclinical models for validating biomarkers and the combination of exatecan with ataxia telangiectasia and Rad3-related kinase (ATR) inhibitors. Modeling exatecan binding at the interface of a TOP1 cleavage complex suggests two novel molecular interactions with the flanking DNA base and the TOP1 residue N352, in addition to the three known interactions of camptothecins with the TOP1 residues R364, D533, and N722. Accordingly, exatecan showed much stronger TOP1 trapping, higher DNA damage, and apoptotic cell death than the classical TOP1 inhibitors used clinically. We demonstrate the value of SLFN11 expression and homologous recombination (HR) deficiency (HRD) as predictive biomarkers of response to exatecan. We also show that exatecan kills cancer cells synergistically with the clinical ATR inhibitor ceralasertib (AZD6738). To establish the translational potential of this combination, we tested CBX-12, a clinically developed pH-sensitive peptide-exatecan conjugate that selectively targets cancer cells and is currently in clinical trials. The combination of CBX-12 with ceralasertib significantly suppressed tumor growth in mouse xenografts. Collectively, our results demonstrate the potency of exatecan as a TOP1 inhibitor and its clinical potential in combination with ATR inhibitors, using SLFN11 and HRD as predictive biomarkers.
Topics: Animals; Ataxia Telangiectasia Mutated Proteins; Camptothecin; DNA; DNA Topoisomerases, Type I; Humans; Mice; Neoplasms; Nuclear Proteins; Protein Kinase Inhibitors; Topoisomerase I Inhibitors
PubMed: 35439320
DOI: 10.1158/1535-7163.MCT-21-1000 -
Cancer Science Jul 2016Antibody-drug conjugates deliver anticancer agents selectively and efficiently to tumor tissue and have significant antitumor efficacy with a wide therapeutic window....
Bystander killing effect of DS-8201a, a novel anti-human epidermal growth factor receptor 2 antibody-drug conjugate, in tumors with human epidermal growth factor receptor 2 heterogeneity.
Antibody-drug conjugates deliver anticancer agents selectively and efficiently to tumor tissue and have significant antitumor efficacy with a wide therapeutic window. DS-8201a is a human epidermal growth factor receptor 2 (HER2)-targeting antibody-drug conjugate prepared using a novel linker-payload system with a potent topoisomerase I inhibitor, exatecan derivative (DX-8951 derivative, DXd). It was effective against trastuzumab emtansine (T-DM1)-insensitive patient-derived xenograft models with both high and low HER2 expression. In this study, the bystander killing effect of DS-8201a was evaluated and compared with that of T-DM1. We confirmed that the payload of DS-8201a, DXd (1), was highly membrane-permeable whereas that of T-DM1, Lys-SMCC-DM1, had a low level of permeability. Under a coculture condition of HER2-positive KPL-4 cells and negative MDA-MB-468 cells in vitro, DS-8201a killed both cells, whereas T-DM1 and an antibody-drug conjugate with a low permeable payload, anti-HER2-DXd (2), did not. In vivo evaluation was carried out using mice inoculated with a mixture of HER2-positive NCI-N87 cells and HER2-negative MDA-MB-468-Luc cells by using an in vivo imaging system. In vivo, DS-8201a reduced the luciferase signal of the mice, indicating suppression of the MDA-MB-468-Luc population; however, T-DM1 and anti-HER2-DXd (2) did not. Furthermore, it was confirmed that DS-8201a was not effective against MDA-MB-468-Luc tumors inoculated at the opposite side of the NCI-N87 tumor, suggesting that the bystander killing effect of DS-8201a is observed only in cells neighboring HER2-positive cells, indicating low concern in terms of systemic toxicity. These results indicated that DS-8201a has a potent bystander effect due to a highly membrane-permeable payload and is beneficial in treating tumors with HER2 heterogeneity that are unresponsive to T-DM1.
Topics: Ado-Trastuzumab Emtansine; Animals; Antibodies, Monoclonal, Humanized; Breast Neoplasms; Bystander Effect; Camptothecin; Cell Line, Tumor; Cell Membrane Permeability; Cell Proliferation; Female; Humans; Immunoconjugates; Maytansine; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasms; Receptor, ErbB-2; Stomach Neoplasms; Topoisomerase I Inhibitors; Trastuzumab
PubMed: 27166974
DOI: 10.1111/cas.12966 -
Molecular Cancer Therapeutics Oct 2023Protein tyrosine kinase 7 (PTK7) is a Wnt signaling pathway protein implicated in cancer development and metastasis. When using a potent microtubule inhibitor (Aur0101),...
Protein tyrosine kinase 7 (PTK7) is a Wnt signaling pathway protein implicated in cancer development and metastasis. When using a potent microtubule inhibitor (Aur0101), PTK7-targeting antibody-drug conjugate (ADC), h6M24-vc0101 (PF-06647020/cofetuzumab pelidotin) is efficacious only in limited tumor types with low response rates in a phase I trial. To improve patient response and to expand responding tumor types, we designed MTX-13, a PTK7-targeting ADC consisting of a novel antibody (Ab13) conjugated to eight molecules of topoisomerase I inhibitor exatecan through T1000, a novel self-immolative moiety. MTX-13 exhibited PTK7-specific cell binding, efficient internalization, and exatecan release to cause cytotoxic activity through DNA damage and apoptosis induction, and a strong bystander killing. MTX-13 displayed potent antitumor activities on cell line-derived xenograft and patient-derived xenograft models from a wide range of solid tumors, significantly outperforming h6M24-vc0101. PTK7 was shown to be an actionable target in small cell lung cancer for which MTX-13 showed complete and durable responses. With a consistent overexpression of PTK7 in squamous cell carcinomas derived from diverse anatomic sites, strong potency of MTX-13 in this group of heterogenous tumors suggested a common treatment strategy. Finally, MTX-13 inhibited tumor growth and metastasis in an orthotopic colon cancer xenograft model. MTX-13 displayed a favorable pharmacokinetic and safety profile in monkeys with the highest non-severely toxic dose (HNSTD) of ≥30 mg/kg, significantly higher than 3-5 mg/kg of HNSTD for h6M24-vc0101. The higher therapeutic index of MTX-13 bodes well for its clinical translation with the potential to expand the responding patient population beyond that of current PTK7-targeting ADCs.
Topics: Humans; Immunoconjugates; Receptor Protein-Tyrosine Kinases; Cell Line, Tumor; Antibodies; Cell Adhesion Molecules
PubMed: 37352387
DOI: 10.1158/1535-7163.MCT-23-0164 -
Molecular Cancer Therapeutics Sep 2023HER3 is a unique member of the EGFR family of tyrosine kinases, which is broadly expressed in several cancers, including breast, lung, pancreatic, colorectal, gastric,...
HER3 is a unique member of the EGFR family of tyrosine kinases, which is broadly expressed in several cancers, including breast, lung, pancreatic, colorectal, gastric, prostate, and bladder cancers and is often associated with poor patient outcomes and therapeutic resistance. U3-1402/Patritumab-GGFG-DXd is the first successful HER3-targeting antibody-drug conjugate (ADC) with clinical efficacy in non-small cell lung cancer. However, over 60% of patients are nonresponsive to U3-1402 due to low target expression levels and responses tend to be in patients with higher target expression levels. U3-1402 is also ineffective in more challenging tumor types such as colorectal cancer. AMT-562 was generated by a novel anti-HER3 antibody Ab562 and a modified self-immolative PABC spacer (T800) to conjugate exatecan. Exatecan showed higher cytotoxic potency than its derivative DXd. Ab562 was selected because of its moderate affinity for minimizing potential toxicity and improving tumor penetration purposes. Both alone or in combination therapies, AMT-562 showed potent and durable antitumor response in low HER3 expression xenograft and heterogeneous patient-derived xenograft/organoid models, including digestive system and lung tumors representing of unmet needs. Combination therapies pairing AMT-562 with therapeutic antibodies, inhibitors of CHEK1, KRAS, and tyrosine kinase inhibitor showed higher synergistic efficacy than Patritumab-GGFG-DXd. Pharmacokinetic and safety profiles of AMT-562 were favorable and the highest dose lacking severe toxicity was 30 mg/kg in cynomolgus monkeys. AMT-562 has potential to be a superior HER3-targeting ADC with a higher therapeutic window that can overcome resistance to generate higher percentage and more durable responses in U3-1402-insensitive tumors.
Topics: Male; Humans; Carcinoma, Non-Small-Cell Lung; Lung Neoplasms; Immunoconjugates; Receptor, ErbB-3; ErbB Receptors; Cell Line, Tumor
PubMed: 37302522
DOI: 10.1158/1535-7163.MCT-23-0198 -
Pharmaceuticals (Basel, Switzerland) Mar 2021We herein report the development and evaluation of a novel HER2-targeting antibody-drug conjugate (ADC) based on the topoisomerase I inhibitor payload exatecan, using...
We herein report the development and evaluation of a novel HER2-targeting antibody-drug conjugate (ADC) based on the topoisomerase I inhibitor payload exatecan, using our hydrophilic monodisperse polysarcosine (PSAR) drug-linker platform (PSARlink). In vitro and in vivo experiments were conducted in breast and gastric cancer models to characterize this original ADC and gain insight about the drug-linker structure-activity relationship. The inclusion of the PSAR hydrophobicity masking entity efficiently reduced the overall hydrophobicity of the conjugate and yielded an ADC sharing the same pharmacokinetic profile as the unconjugated antibody despite the high drug-load of the camptothecin-derived payload (drug-antibody ratio of 8). Tra-Exa-PSAR10 demonstrated strong anti-tumor activity at 1 mg/kg in an NCI-N87 xenograft model, outperforming the FDA-approved ADC DS-8201a (Enhertu), while being well tolerated in mice at a dose of 100 mg/kg. In vitro experiments showed that this exatecan-based ADC demonstrated higher bystander killing effect than DS-8201a and overcame resistance to T-DM1 (Kadcyla) in preclinical HER2+ breast and esophageal models, suggesting potential activity in heterogeneous and resistant tumors. In summary, the polysarcosine-based hydrophobicity masking approach allowsfor the generation of highly conjugated exatecan-based ADCs having excellent physicochemical properties, an improved pharmacokinetic profile, and potent in vivo anti-tumor activity.
PubMed: 33803327
DOI: 10.3390/ph14030247 -
International Journal of Cancer Oct 2017Anti-HER2 therapies are beneficial for patients with HER2-positive breast or gastric cancer. T-DM1 is a HER2-targeting antibody-drug conjugate (ADC) comprising the...
Anti-HER2 therapies are beneficial for patients with HER2-positive breast or gastric cancer. T-DM1 is a HER2-targeting antibody-drug conjugate (ADC) comprising the antibody trastuzumab, a linker, and the tubulin inhibitor DM1. Although effective in treating advanced breast cancer, all patients eventually develop T-DM1 resistance. DS-8201a is a new ADC incorporating an anti-HER2 antibody, a newly developed, enzymatically cleavable peptide linker, and a novel, potent, exatecan-derivative topoisomerase I inhibitor (DXd). DS-8201a has a drug-to-antibody-ratio (DAR) of 8, which is higher than that of T-DM1 (3.5). Owing to these unique characteristics and unlike T-DM1, DS-8201a is effective against cancers with low-HER2 expression. In the present work, T-DM1-resistant cells (N87-TDMR), established using the HER2-positive gastric cancer line NCI-N87 and continuous T-DM1 exposure, were shown to be susceptible to DS-8201a. The ATP-binding cassette (ABC) transporters ABCC2 and ABCG2 were upregulated in N87-TDMR cells, but HER2 overexpression was retained. Furthermore, inhibition of ABCC2 and ABCG2 by MK571 restored T-DM1 sensitivity. Therefore, resistance to T-DM1 is caused by efflux of its payload DM1, due to aberrant expression of ABC transporters. In contrast to DM1, DXd payload of DS-8201a inhibited the growth of N87-TDMR cells in vitro. This suggests that either DXd may be a poor substrate of ABCC2 and ABCG2 in comparison to DM1, or the high DAR of DS-8201a relative to T-DM1 compensates for increased efflux. Notably, N87-TDMR xenograft tumor growth was prevented by DS-8201a. In conclusion, the efficacy of DS-8201a as a treatment for patients with T-DM1-resistant breast or gastric cancer merits investigation.
Topics: Ado-Trastuzumab Emtansine; Animals; Antibodies, Monoclonal, Humanized; Camptothecin; Cell Line, Tumor; Drug Resistance, Neoplasm; Female; Humans; Immunoconjugates; Maytansine; Mice; Mice, Inbred BALB C; Mice, Nude; Multidrug Resistance-Associated Protein 2; Random Allocation; Receptor, ErbB-2; Stomach Neoplasms; Topoisomerase I Inhibitors; Trastuzumab
PubMed: 28677116
DOI: 10.1002/ijc.30870 -
Cancer Science Dec 2020Trastuzumab deruxtecan (T-DXd: DS-8201a) is an anti-human epidermal growth factor receptor 2 (HER2) Ab-drug conjugated with deruxtecan (DXd), a derivative of exatecan....
Trastuzumab deruxtecan (T-DXd: DS-8201a) is an anti-human epidermal growth factor receptor 2 (HER2) Ab-drug conjugated with deruxtecan (DXd), a derivative of exatecan. The objective of this study was to characterize T-DXd-induced lung toxicity in cynomolgus monkeys. Trastuzumab deruxtecan was injected i.v. into monkeys once every 3 weeks for 6 weeks (10, 30, and 78.8 mg/kg) or for 3 months (3, 10, and 30 mg/kg). To evaluate the involvement of DXd alone in T-DXd-induced toxicity, DXd monohydrate was given i.v. to monkeys once a week for 4 weeks (1, 3, and 12 mg/kg). Interstitial pneumonitis was observed in monkeys given T-DXd at 30 mg/kg or more. The histopathological features of diffuse lymphocytic infiltrates and slight fibrosis were similar to interstitial lung diseases (ILD)/pneumonitis related to anticancer drugs in patients, with an incidence that was dose-dependent and dose-frequency-dependent. Monkeys receiving DXd monohydrate did not suffer lung toxicity, although the DXd exposure level was higher than that of DXd in the monkeys given T-DXd. The HER2 expression in monkey lungs was limited to the bronchial level, although the lesions were found at the alveolar level. Immunohistochemical analysis confirmed that T-DXd localization was mainly in alveolar macrophages, but not pulmonary epithelial cells. These findings indicate that monkeys are an appropriate model for investigating T-DXd-related ILD/pneumonitis. The results are also valuable for hypothesis generation regarding the possible mechanism of T-DXd-induced ILD/pneumonitis in which target-independent uptake of T-DXd into alveolar macrophages could be involved. Further evaluation is necessary to clarify the mechanism of ILD/pneumonitis in patients with T-DXd therapy.
Topics: Animals; Camptothecin; Cathepsin B; Drug Administration Schedule; Female; Immunoconjugates; Lung; Lung Diseases, Interstitial; Macaca fascicularis; Male; Receptor, ErbB-2; Time Factors; Trastuzumab
PubMed: 33051938
DOI: 10.1111/cas.14686 -
Cancer Research Nov 2023Recent advances in targeted therapy and immunotherapy have substantially improved the treatment of melanoma. However, therapeutic strategies are still needed for...
UNLABELLED
Recent advances in targeted therapy and immunotherapy have substantially improved the treatment of melanoma. However, therapeutic strategies are still needed for unresponsive or treatment-relapsed patients with melanoma. To discover antibody-drug conjugate (ADC)-tractable cell surface targets for melanoma, we developed an atlas of melanoma cell surface-binding antibodies (pAb) using a proteome-scale antibody array platform. Target identification of pAbs led to development of melanoma cell killing ADCs against LGR6, TRPM1, ASAP1, and MUC18, among others. MUC18 was overexpressed in both tumor cells and tumor-infiltrating blood vessels across major melanoma subtypes, making it a potential dual-compartment and universal melanoma therapeutic target. AMT-253, an MUC18-directed ADC based on topoisomerase I inhibitor exatecan and a self-immolative T moiety, had a higher therapeutic index compared with its microtubule inhibitor-based counterpart and favorable pharmacokinetics and tolerability in monkeys. AMT-253 exhibited MUC18-specific cytotoxicity through DNA damage and apoptosis and a strong bystander killing effect, leading to potent antitumor activities against melanoma cell line and patient-derived xenograft models. Tumor vasculature targeting by a mouse MUC18-specific antibody-T1000-exatecan conjugate inhibited tumor growth in human melanoma xenografts. Combination therapy of AMT-253 with an antiangiogenic agent generated higher efficacy than single agent in a mucosal melanoma model. Beyond melanoma, AMT-253 was also efficacious in a wide range of MUC18-expressing solid tumors. Efficient target/antibody discovery in combination with the T moiety-exatecan linker-payload exemplified here may facilitate discovery of new ADC to improve cancer treatment.
SIGNIFICANCE
Discovery of melanoma-targeting antibodies using a proteome-scale array and use of a cutting-edge linker-payload system led to development of a MUC18-targeting antibody-exatecan conjugate with clinical potential for treating major melanoma subtypes.
Topics: Humans; Mice; Animals; Immunoconjugates; Proteome; Melanoma; Topoisomerase I Inhibitors; Immunotherapy; Xenograft Model Antitumor Assays; Cell Line, Tumor; TRPM Cation Channels
PubMed: 37668527
DOI: 10.1158/0008-5472.CAN-23-1356 -
Cancer Research Communications May 2023Exatecan (Exa) is a very potent inhibitor of topoisomerase I and anticancer agent. It has been intensively studied as a single agent, a large macromolecular conjugate...
UNLABELLED
Exatecan (Exa) is a very potent inhibitor of topoisomerase I and anticancer agent. It has been intensively studied as a single agent, a large macromolecular conjugate and as the payload component of antigen-dependent antibody-drug conjugates. The current work describes an antigen-independent conjugate of Exa with polyethylene glycol (PEG) that slowly releases free Exa. Exa was conjugated to a 4-arm 40 kDa PEG through a β-eliminative cleavable linker. Pharmacokinetic studies in mice showed that the conjugate has an apparent circulating half-life of 12 hours, which reflects a composite of both the rate of renal elimination (half-life ∼18 hours) and release of Exa (half-life ∼40 hours). Remarkably, a single low dose of 10 μmol/kg PEG-Exa-only approximately 0.2 μmol/mouse-caused complete suppression of tumor growth of BRCA1-deficient MX-1 xenografts lasting over 40 days. A single low dose of 2.5 μmol/kg PEG-Exa administered with low but efficacious doses of the PARP inhibitor talazoparib showed strong synergy and caused significant tumor regression. Furthermore, the same low, single dose of PEG-Exa administered with the ATR inhibitor VX970 at doses of the DNA damage response inhibitor that do not affect tumor growth show high tumor regression, strong synergy, and synthetic lethality.
SIGNIFICANCE
A circulating conjugate that slowly releases Exa is described. It is efficacious after a single dose and synergistic with ATR and PARP inhibitors.
Topics: Humans; Animals; Mice; Camptothecin; Antineoplastic Agents; Neoplasms; Polyethylene Glycols; Poly(ADP-ribose) Polymerase Inhibitors; DNA Damage
PubMed: 37377899
DOI: 10.1158/2767-9764.CRC-22-0517 -
Molecular Cancer Therapeutics Feb 2024Topoisomerase I (TOP1) Inhibitors constitute an emerging payload class to engineer antibody-drug conjugates (ADC) as next-generation biopharmaceutical for cancer...
Topoisomerase I (TOP1) Inhibitors constitute an emerging payload class to engineer antibody-drug conjugates (ADC) as next-generation biopharmaceutical for cancer treatment. Existing ADCs are using camptothecin payloads with lower potency and suffer from limited stability in circulation. With this study, we introduce a novel camptothecin-based linker-payload platform based on the highly potent camptothecin derivative exatecan. First, we describe general challenges that arise from the hydrophobic combination of exatecan and established dipeptidyl p-aminobenzyl-carbamate (PAB) cleavage sites such as reduced antibody conjugation yields and ADC aggregation. After evaluating several linker-payload structures, we identified ethynyl-phosphonamidates in combination with a discrete PEG24 chain to compensate for the hydrophobic PAB-exatecan moiety. Furthermore, we demonstrate that the identified linker-payload structure enables the construction of highly loaded DAR8 ADCs with excellent solubility properties. Head-to-head comparison with Enhertu, an approved camptothecin-based ADC, revealed improved target-mediated killing of tumor cells, excellent bystander killing, drastically improved linker stability in vitro and in vivo and superior in vivo efficacy over four tested dose levels in a xenograft model. Moreover, we show that ADCs based on the novel exatecan linker-payload platform exhibit antibody-like pharmacokinetic properties, even when the ADCs are highly loaded with eight drug molecules per antibody. This ADC platform constitutes a new and general solution to deliver TOP1 inhibitors with highest efficiency to the site of the tumor, independent of the antibody and its target, and is thereby broadly applicable to various cancer indications.
Topics: Humans; Camptothecin; Immunoconjugates; Neoplasms; Antibodies; Antineoplastic Agents
PubMed: 37828728
DOI: 10.1158/1535-7163.MCT-23-0359