Antibody–Drug Conjugates: A Novel Paradigm for Cancer Therapy

Chemotherapy is one of the most widely used cancer therapies; however, chemotherapy often causes serious side effects. Antibody-drug conjugates (ADCs) are promisingly emerging cancer therapies that combine the effective killing power of small molecule cytotoxins and the highly specific targeting ability of monoclonal antibodies (mAbs). Thus, ADCs precisely deliver cytotoxins to tumor cells, while minimally affecting normal cells. ADCs have become a hot spot for anticancer drug development1,2. The first-generation ADC, gemtuzumab ozogamicin, was approved by the U.S. Food and Drug Administration (FDA) in 2000. Since then, multiple ADCs have been approved worldwide, and more than 100 ADC candidates have entered the clinical phase. These new anticancer drugs are leading the way to a new cancer therapy phase. Table. 1 Currently approved ADCs on the market. www.sinobiological.com Sino Biological US Inc. (U.S.A.) +1-215-583-7898 order_us@sinobiologicalus.com Sino Biological Europe GmbH (Europe) +49(0)6196 9678656 order_eu@sinobiologicaleu.com Sino Biological, Inc. (Global) +86-400-890-9989 order@sinobiological.com 株式会社日本シノバイオロジカル (Japan) 044-400-1330 order@sinobiological.co.jp Targets Drugs Approval Indications CD33 Gemtuzumab ozogamicin 2000-FDA;2017-FDA Acute myeloid leukemia CD30 Brentuximab vedotin 2011-FDA Hodgkin lymphoma HER2 Trastuzumab emtansine 2013-FDA Breast cancer CD22 Inotuzumab ozogamicin 2017-FDA Acute myeloid leukemia CD22 Moxetumomab pasudotox 2018-FDA Hairy cell leukemia CD79 Polatuzumab vedotin 2019-FDA Diffuse large B-cell lymphoma Nectin4 Enfortumab vedotin 2019-FDA Advanced urothelial cancer HER2 Trastuzumab deruxtecan 2019-FDA Breast cancer TROP2 Sacituzumab govitecan 2020-FDA Triple-negative breast cancer EGFR Cetuximab Saratolacan 2020-MHLW Head and neck cancer BCMA Belantamab mafodotin 2020-FDA: Withdrawal in 2022 Multiple myeloma CD19 Loncastuximab tesirine 2021-FDA Large B-cell lymphoma Tissue factor Tisotumab vedotin-tftv 2021-FDA Cervical cancer HER2 Disitamab vedotin 2021-NMPA Gastric or gastroesophageal cancer FRα Mirvetuximab soravtansine 2022-FDA Ovarian Cancer Antibody-drug Conjugates: A Novel Paradigm for Cancer Therapy www.sinobiological.com Sino Biological US Inc. (U.S.A.) +1-215-583-7898 order_us@sinobiologicalus.com Sino Biological Europe GmbH (Europe) +49(0)6196 9678656 order_eu@sinobiologicaleu.com Sino Biological, Inc. (Global) +86-400-890-9989 order@sinobiological.com 株式会社日本シノバイオロジカル (Japan) 044-400-1330 order@sinobiological.co.jp Target antigens should be non-secretory, expressed mainly on the tumor cell surface, and expressed at low levels in normal tissues. In addition, target antigens should be internalized after binding to the corresponding antibodies to facilitate the entry of ADC-antigen complexes into tumor cells to release cytotoxic payloads via an appropriate intracellular translocation route4. At present, the target antigens for approved ADC drugs are specific proteins overexpressed in tumor cells, including HER2, Trop2, Nectin4, and EGFR in solid tumors, and CD19, CD22, CD33, CD30, BCMA, and CD79 in hematologic malignancies. Emerging targets, such as EpCAM, CD70, CD25, CD166, and others, are under development and showing promising results5. Sino Biological is at the forefront of the ADC therapy field, providing quality products for ADC target antigens. (1) Well-established targets: EGFR, HER2, and CD22 Target Antigens Figure 1. The general mechanism of action for antibody-drug conjugates (ADCs). Immobilized Human EGF (Cat#: 10605-H01H) can bind Human EGFR An ADC consists of a target-specific mAb, a cytotoxic payload, and a chemically synthesized linker that covalently links the toxin and the antibody. The mAb binds to specific antigens on the surface of tumor cells, and ADCs are internalized into tumor cells during the formation of antibody-antigen complexes. ADCs are typically transported from the endosome to the lysosome, where the linker is cleaved and the small molecule cytotoxins are released, leading to tumor cell death3. Overall, ADC development requires consideration of the target antigens, antibodies, cytotoxic payload, and linker (Figure 1). Key Components of ADCs 1. ADCs 2. Binding to antigen target 3. Receptor-mediated endocytosis 4. ADC in endosome 5. Drug released from ADC in lysosome 6. Free drug in cytosol 7. Cell death Linker Cytotoxin Antibody 0 0.5 1.5 2.0 2.5 1.0 EC50=60-480 ng/mL 1 10 100 1000 10000 Human EGFR Conc. (ng/mL) Abs.(OD450nm-Blank) Human EGFR Protein Cat#: 10001-H27H-B Immobilized Anti-Erbb2 Antibody can bind Human HER2 / ErbB2 Protein 0.0 -0.5 0.5 2.5 2.0 3.0 3.5 4.0 1.5 1.0 EC50=1.25-3.75 ng/mL 0.01 0.1 1 10 100 Anti-HER2 Antibody Conc. (ng/mL) Abs.(OD450nm-Blank) Human HER2/ERBB2 Protein Cat#: 10004-H27H2-B Immobilized human CD22 can bind anti-human CD22 Mab 0.5 0.0 1.0 2.0 3.0 2.5 3.5 1.5 EC50=0.2-50 ng/mL 10 100 Anti-CD22Antibody Conc. (ng/mL) Abs.(OD450nm-Blank) Human CD22 Protein Cat#: 11958-H08H (2) Emerging targets: CD70, CD166, and CD25 Immunoglobulins (IgGs) and their derivatives are commonly used in clinical studies. IgG1, IgG2, and IgG4 are mainly used for ADCs because of their specificity, affinity for the target antigen, and long circulating half-life. In addition, the antibodies should possess effective internalization ability and low immunogenicity6. In early ADC drug development, predominantly mouse antibodies were used. However, these antibodies elicited a significant immune response, resulting in reduced therapeutic efficacy. With the advent of recombinant technology, mouse antibodies have been replaced with chimeric and humanized antibodies. Currently, ADCs increasingly use fully humanized antibodies with significantly lower immunogenicity7 . Sino Biological provides high-quality mAb humanization services using complementarity-determining region (CDR) grafting technology and computer-aided molecular modeling. In addition, Sino Biological possesses the high-throughput and scale-up capabilities to produce highly efficient antibodies in HEK293 and CHO cells in as fast as 2 weeks, with over 1000 Abs expression per batch. Antibodies Cytotoxins should have high toxicity, low immunogenicity, and high stability. In addition, the cytotoxin should have a modifiable functional group or a site where a functional group can be introduced to link the mAb. The most commonly used cytotoxins for ADC drugs on the market or in clinical trials are microtubule protein inhibitors or DNA-damaging agents8. Additionally, the drug-antibody ratio (DAR), i.e. the number of drug molecules attached to the antibody by the linker, is a key factor in ADC development. A low DAR may reduce ADC efficacy, while a high DAR may cause instability, leading to off-target toxicity8,9. Cytotoxic Payload Figure 2. High-quality target antigen products. Figure 3. The process of antibody humanization and complementarity-determining region (CDR) grafting technology. www.sinobiological.com Sino Biological US Inc. (U.S.A.) +1-215-583-7898 order_us@sinobiologicalus.com Sino Biological Europe GmbH (Europe) +49(0)6196 9678656 order_eu@sinobiologicaleu.com Sino Biological, Inc. (Global) +86-400-890-9989 order@sinobiological.com 株式会社日本シノバイオロジカル (Japan) 044-400-1330 order@sinobiological.co.jp Immobilized Human CD27 (Cat#: 10039-H08B1) can bind Human CD70 Human CD70 Protein Cat#: 10780-H01H Immobilized human CD166 can bind mouse CD6 Human CD166/ALCAM Protein Cat#: 10045-H08H Ability to inhibit IL2-induced proliferation of M07e cells Human CD25/IL2R alpha Protein Cat#: 10165-H08H 0 2 3 4 1 EC50=15-60 ng/mL 1 10 100 1000 10000 Human CD70 Conc. (ng/mL) Abs.(OD450nm-Blank) 0 1 3 4 5 2 EC50=0.1-0.22 µg/mL 0.1 1 10 100 1000 10000 Mouse CD6 Conc. (ng/mL) Abs.(OD450nm-Blank) -20 0 40 60 80 100 20 ED50=0.2-1.2 µg/mL 1E-3 0.01 0.1 1 10 Human IL2Rα Conc. (µg/mL) Inhibition,% Mouse Antibody Humanized Antibody Mouse Antibody Human Framework Region Humanized Antibody CDR Identification & 3D Structural Modeling CDR Grafting Back Mutations FR1 CDR1 FR2 CDR2 FR3 CDR3 FR4 FR1 CDR1 FR2 CDR2 FR3 CDR3 FR4 FR1 CDR1 FR2 CDR2 FR3 CDR3 FR4 The linker ensures that the cytotoxic payload remains firmly attached to the antibody in the plasma during circulation, avoiding premature release that would damage normal tissues or cells and ensuring the effective release within the target tumor cells. Linkers can be classified as cleavable and non-cleavable. Cleavable linkers take advantage of the environmental differences between the circulation and tumor cells to accurately release free cytotoxins. Non-cleavable linkers depend on lysosomal degradation of the entire antibody-linker structure, which results in the retention of charged amino acids in the payload10,11. Linker Figure 4. Sino Biological bispecific antibody production service highlights. Many challenges remain in ADC development. The biggest challenge is the toxic effects of ADCs, including neutropenia, thrombocytopenia, leukopenia, anemia, and gastrointestinal effects4. Another challenge is tumor resistance to ADCs, as evidenced by reduced antigen expression levels, altered intracellular transport pathways, and payload resistance. In addition, payload release is a challenge. The ADCs are much larger than traditional cytotoxic drugs, and the efficiency of cytotoxin penetration into tumors is limited. To overcome these challenges, future ADC development should focus on the following: (1) improvements in ADC design to reduce toxicity, including payload platforms, linkers, and coupling strategies; (2) use of two cytotoxic agents as payloads to reduce ADC resistance; and (3) enhancing ADC internalization and lysosomal delivery through bispecific antibodies to improve antitumor specificity. Sino Biological utilizes an optimized mammalian cell expression platform to provide fast and efficient bispecific antibody expression services for clients worldwide12. Challenges and Perspectives References 1. Fu Z, Li S, Han S, et al. Antibody drug conjugate: the “biological missile” for targeted cancer therapy. Signal Transduction and Targeted Therapy. 2022;7(1):93. doi: 10.1038/s41392-022-00947-7 2. Schwach J, Abdellatif M, Stengl A. More than Toxins—Current Prospects in Designing the Next Generation of Antibody Drug Conjugates. Frontiers in Bioscience-Landmark. 2022;27(8):240. doi: 10.31083/j.fbl2708240 3. Tang H, Liu Y, Yu Z, et al. The analysis of key factors related to ADCs structural design. Frontiers in Pharmacology. 2019;10:373. doi: 10.3389/fphar.2019.00373 4. Zhao P, Zhang Y, Li W, et al. Recent advances of antibody drug conjugates for clinical applications. Acta Pharmaceutica Sinica B. 2020;10(9):1589-1600. doi: 10.1016/j.apsb.2020.04.012 5. Hafeez U, Parakh S, Gan HK, et al. Antibody–drug conjugates for cancer therapy. Molecules. 2020;25(20):4764. doi: 10.3390/molecules25204764 6. Zhang X, Huang AC, Chen F, et al. Novel development strategies and challenges for anti-Her2 antibody-drug conjugates. Antibody Therapeutics. 2022;5(1):18-29. doi: 10.1093/abt/tbac001 7. Khongorzul P, Ling CJ, Khan FU, et al. Antibody–Drug Conjugates: A Comprehensive ReviewAntibody–Drug Conjugates in Cancer Immunotherapy. Molecular Cancer Research. 2020;18(1):3-19. doi: 10.1158/1541-7786.MCR-19-0582 8. Ziad A, Abdurahman A, Misako N. A comprehensive review on antibody-drug conjugates (ADCs) in the treatment landscape of non-small cell lung cancer (NSCLC). Cancer Treatment Reviews. 2022;102393. doi: 10.1016/j.ctrv.2022.102393 9. Sheyi R, de la Torre BG, Albericio F. Linkers: An Assurance for Controlled Delivery of antibody-drug conjugate. Pharmaceutics. 2022;14(2):396. doi: 10.3390/pharmaceutics14020396 10. Tong JTW, Harris PWR, Brimble MA, et al. An insight into FDA approved antibody-drug conjugates for cancer therapy. Molecules. 2021;26(19):5847. doi: 10.3390/molecules26195847 11. Ungaro A, Tucci M, Audisio A, et al. Antibody-drug conjugates in urothelial carcinoma: a new therapeutic opportunity moves from bench to bedside. Cells. 2022;11(5):803. doi: 10.3390/cells11050803 12. Yu J, Fang T, Yun C, et al. Antibody-drug conjugates targeting the human epidermal growth factor receptor family in cancers. Frontiers in Molecular Biosciences. 2022;9:184. doi: 10.3389/fmolb.2022.847835 www.sinobiological.com Sino Biological US Inc. (U.S.A.) +1-215-583-7898 order_us@sinobiologicalus.com Sino Biological Europe GmbH (Europe) +49(0)6196 9678656 order_eu@sinobiologicaleu.com Sino Biological, Inc. (Global) +86-400-890-9989 order@sinobiological.com 株式会社日本シノバイオロジカル (Japan) 044-400-1330 order@sinobiological.co.jp ADC therapy has benefited many cancer patients. In the future, the therapeutic efficacy of ADC will be improved by reducing ADC toxicity and drug resistance. Sino Biological will continue to be at the forefront of the ADC therapy field, providing researchers and pharmaceutical companies with high-quality products and one-stop services. Optimized HEK293/ CHO Platforms Completed numerous bsAb production projects with >90% of overall success rates 1. Better post-translational modifications 2. Easier to scale up production >90% Success Rate Expression Systems