With advanced technology and years of experience, BOC Sciences provides multiple ADCs cytotoxin with linkers products to support your ADCs development and research. We also provide the service in a customizable fashion to suit our customers' specific research goals. We are known to our customers as a professional and attentive partner who delivers quality results.
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Antibody-drug conjugates (ADCs) are targeted therapeutic systems that precisely connect monoclonal antibodies with potent cytotoxins through linkers. In the ADC structure, the cytotoxin with linker refers to the complex composed of the cytotoxic agent and the linker, serving as the core module for achieving precise treatment. This system is designed to ensure the stability of the payload during circulation and to guarantee its activation and release only within target cells, balancing maximum efficacy with minimal systemic toxicity. BOC Sciences offers a variety of pre-linked ADC cytotoxin-linker products, widely used in drug discovery, preclinical research, and process development projects.
In ADCs, the cytotoxin is responsible for inducing cancer cell death, while the linker controls the timing and location of its release. The functionality of ADC cytotoxin with linker is reflected in the following aspects:
Compared to the traditional approach of introducing toxins and linkers separately during conjugation, pre-linked payload-linker systems (cytotoxin with linker) offer multiple advantages:
In ADC design, selecting the appropriate combination of cytotoxin and linker is critical for therapeutic efficacy, safety, and CMC development. Different types of cytotoxins have distinct mechanisms of action, while the linker type directly influences drug release pathways and systemic stability.
In the ADC field, selected cytotoxins must possess extremely high potency, low IC50 values, and conjugatability. These cytotoxins exhibit ultra-high cytotoxicity, often inducing tumor cell death at sub-nanomolar concentrations, and therefore require precise release control via linkers. The current mainstream types of cytotoxins can be categorized into the following groups:
| Type | Representative Molecules | Mechanism of Action | Representative Drugs |
| Microtubule Inhibitors | MMAE, MMAF, DM1, DM4 | Inhibit mitosis. | Adcetris, Kadcyla |
| DNA Damaging Agents | Calicheamicin, PBD dimers | Induce DNA cleavage and crosslinking. | Mylotarg, Zynlonta |
| RNA Polymerase Inhibitors | α-Amanitin | Block transcription. | Research stage |
| Protein Degraders | Proteolysis Targeting Chimeras (PROTACs), Molecular Glues | Promote selective degradation of target proteins via ubiquitin-proteasome system. | Emerging ADCs and targeted therapies |
The design of linkers directly determines the drug release pathway and stability of ADCs, making it a critical element for precise drug delivery. Based on whether they can be cleaved intracellularly, linkers are classified into ADC cleavable linkers and ADC non-cleavable linkers. Cleavable linker ADC structures enable rapid release of cytotoxins under specific conditions (such as lysosomal enzymes, acidic environments, or reductive states), making them suitable for fast-acting anticancer drugs. In contrast, ADC non-cleavable linkers rely on the degradation of antibody proteins within cells to release the active component, offering stronger plasma stability and more controlled pharmacokinetics.
| Linker Type | Representative Molecules | Cleavage Mechanism | Application Features |
| Acid Cleavable Linker/Hydrazone Linker | Hydrazone derivatives | Cleaved in acidic environments (pH ~5–6) within tumor cells. | Rapid release in acidic compartments. |
| Disulfide Linker | Disulfide bonds (–S–S–) | Reduced by intracellular glutathione in tumor cells. | Selective release in reductive environments. |
| Cathepsin B Cleavable Linker/Peptide Linker | Val-Cit, Phe-Lys | Cleaved by Cathepsin B in lysosomes. | High specificity and stability. |
| Phosphatase Cleavable Linker | Phosphorylated esters | Cleaved by phosphatases in tumor cells. | Tumor-selective activation. |
| Sulfatase Cleavable Linker | Sulfate ester-based linkers | Cleaved by sulfatases in disease tissues. | Site-specific payload release. |
| β-Galactosidase Cleavable Linker | β-galactoside conjugates | Cleaved by β-galactosidase in lysosomes. | Enzyme-specific activation. |
| β-Glucuronidases Cleavable Linker | Glucuronide conjugates | Cleaved by β-glucuronidases in necrotic tumor areas. | Release in necrotic tumor regions. |
In several FDA-approved ADC drugs, the rationality of payload-linker combinations has been clinically validated. For example, MMAE with cleavable linker (such as Val-Cit) is a widely used combination, featuring both high potency and controlled release characteristics, and has become the core structural design of multiple commercialized ADCs. The following are common successful combination cases, demonstrating the profound impact of structural choices in ADC design on efficacy and safety:
| Drug Name | Payload | Linker | Type | Pharmacological Features |
| Adcetris | MMAE | Val-Cit-PABC | Cleavable Linker | Rapid release, strong cytotoxicity. |
| Kadcyla | DM1 | SMCC | Non-Cleavable Linker | Stability, high safety profile. |
| Polivy | MMAE | mc-Val-Cit-PABC | Cleavable Linker | Potent against CD79b-positive B-cell lymphomas. |
| Zynlonta | SG3199 (PBD) | Enzyme-sensitive Linker | Cleavable Linker | Extremely strong DNA crosslinking capability. |
| Trodelvy | SN-38 | CL2A | Cleavable Linker | Targets Trop-2 breast cancer cells. |
BOC Sciences leverages cutting-edge technologies and extensive expertise to accelerate your ADC development. From cytotoxins and linkers to custom synthesis and comprehensive ADC services, we are committed to empowering your next breakthrough.
Balancing ADC potency, safety, and CMC stability relies on systematic design of the linker and payload. Rational structural combinations not only influence in vivo release kinetics but also directly impact targeted killing efficiency and clinical translation potential. BOC Sciences has extensive experience in ADC linker chemistry and toxin derivative development, supporting end-to-end services from molecular design to synthesis validation.
In modern ADC development, ADC linker chemistry is regarded as a key variable determining drug efficacy and safety margins. The structure of the linker affects drug stability, plasma half-life, endocytosis efficiency, and payload release pathways. Current mainstream ADC linker design focuses on highly selective release mechanisms, hydrophilicity optimization, and precise control of conjugation sites. BOC Sciences provides clients with various solutions based on Val-Cit, Gly-Phe-Phe, PEG chain structures, supporting the entire ADC linker development process. In addition, the team actively tracks current ADC linker chemistry advances, developing innovative designs such as self-assembling linkers and enzyme-cleavable linkers to meet next-generation ADC construction needs.
The cytotoxin and linker in ADCs do not exist in isolation but as a synergistic system that must be scientifically matched for optimal efficacy. Specifically, cytotoxin examples (such as MMAE, DM1, PBD, etc.) differ significantly in physicochemical properties, conjugation capabilities, and water solubility, requiring appropriate ADC linker-payload combinations. For instance, highly hydrophobic toxins are better suited to linkers with hydrophilic modifications to reduce ADC aggregation; whereas unstable toxins require milder ADC payload linker systems to ensure complete delivery. BOC Sciences offers a wide range of toxin and linker components and can optimize structural matching based on target characteristics and mechanisms of action, enhancing the development success rate of candidate molecules.
As the core active component of ADCs, cytotoxins determine the ultimate killing power and therapeutic effect of the drug. Selecting suitable toxins requires consideration not only of their mechanism and potency but also compatibility with linkers and antibodies, as well as manufacturability. BOC Sciences provides a variety of potent cytotoxins and derivatives, supporting ADC projects from early screening to IND development.
In the ADC system, cytotoxins are highly potent small-molecule drugs capable of inducing rapid cancer cell death at nanomolar or picomolar concentrations. The key to cytotoxins' function lies in their ability to disrupt cell division, DNA integrity, or protein synthesis, thereby achieving efficient targeted killing. Regarding how cytotoxins work, they are typically released after antibody-mediated internalization into target cells, rapidly initiating lethal mechanisms intracellularly. Only when combined with precise linker systems can cytotoxins achieve selective delivery rather than systemic toxicity.
Selecting appropriate cytotoxins for ADC development requires a comprehensive evaluation of both chemical and biological properties, extending beyond mere potency. Critical factors include the IC50 value, which measures the minimum effective concentration of the cytotoxin and serves as a fundamental indicator of activity. Hydrophobicity must also be considered, as it affects the in vivo stability of the ADC and its tendency to aggregate. Membrane permeability plays a key role in determining the potential for a bystander effect, allowing the toxin to diffuse and impact neighboring cells. Finally, site-specificity is essential to ensure the toxin is precisely released within target cells via the linker, minimizing systemic diffusion and off-target toxicity.
Linkers are an indispensable component of ADC structures, positioned between the antibody and cytotoxin, serving as both a "bridge" and a "switch." Through linkers of different structures and chemical mechanisms, drug developers can achieve precise toxin delivery and controlled release.
In ADC structures, an ADC linker is not merely a physical connection unit; its chemical nature and configuration directly determine the therapeutic performance of the drug. Understanding ADC linker function involves grasping its mechanisms at multiple levels: it must first ensure plasma stability of the ADC during systemic circulation to avoid premature toxin release that could cause off-target toxicity; secondly, after the ADC is specifically recognized and internalized by target cells, the linker must precisely cleave in specific intracellular environments (such as lysosomal enzyme activity, acidic pH, or reductive states) to release the active drug component; additionally, the linker regulates the overall metabolic process of the ADC, influencing in vivo distribution, clearance rates, and forms of active metabolites. BOC Sciences offers flexible and controllable linker chemistry strategies based on various cleavage mechanisms and structural platforms to enable precise toxin delivery.
Efficient ADC design depends on the rational construction of linker structures. An excellent ADC linker design must achieve the optimal balance between "high plasma stability" and "high intracellular release efficiency." This goal relies on the fine-tuning of ADC payload linker structures. Introducing hydrophilic fragments such as PEG can effectively enhance ADC solubility and stability in the circulatory system, reducing aggregation and non-specific binding. At the same time, the cleavage mechanism of the linker must align with the intracellular environment of the target cells, for example, using enzyme-sensitive structures like Val-Cit or acid-sensitive bonds like hydrazone to ensure highly precise timing and location of toxin release. Another key design aspect is site-specific conjugation to improve DAR uniformity and process controllability. BOC Sciences has a modular synthesis platform and structural library for linker design, enabling highly customized payload-linker combinations to support the construction of high-performance ADC molecules.
With the continuous advancement of ADC technology, current ADC linker chemistry is rapidly evolving toward smarter and highly tunable designs. Traditional linkers can no longer fully meet the complex clinical demands of tumor microenvironments and multi-mechanism actions. Current research focuses on developing linkers with multi-trigger response capabilities, such as dual-mechanism linker structures responsive to both enzymes and pH changes, to enhance selective release at tumor sites. Meanwhile, novel dynamic linker structures that regulate release rates are emerging, allowing precise tailoring of drug exposure profiles for different indications. To improve plasma performance of ADCs, scientists are also incorporating polarity modifications or hydrophilic fragments into linkers to reduce off-target toxicity and enhance tissue penetration. In addition, multifunctional linkers combined with immunomodulatory molecules are being explored to construct next-generation ADCs with both cytotoxic and immune-activating effects.
With the rapid global development of ADC drugs, the payload-linker system composed of cytotoxins and linkers has become a technological core of precision therapy and new drug development. Its flexible structural designs and targeted control mechanisms have driven ADCs to demonstrate excellent clinical performance across multiple indications and continue to expand into more complex therapeutic areas. BOC Sciences provides diversified ADC cytotoxins with linkers products and customized solutions to help clients establish differentiated ADC pipelines and accelerate progression from laboratory to clinic.
The most mature and widespread application of ADC cytotoxin-linker technology remains the targeted treatment of various malignancies. To date, more than ten marketed ADC products have demonstrated clear therapeutic advantages in cancers such as breast cancer, non-Hodgkin lymphoma, and bladder cancer. These success stories prove that, by leveraging antibodies for specific tumor antigen recognition, potent cytotoxins, and controlled release through linkers, ADCs can significantly improve killing efficiency while minimizing toxic side effects.
With increasing diversity of molecular targets, deeper research into immune mechanisms, and the growing challenge of tumor heterogeneity, ADC technology is rapidly evolving toward next-generation formats. In these new ADCs, the payload-linker system carries more versatile functions, such as dual payloads enabling multi-mechanism killing, linkers assisting in the release of immunomodulators to activate the microenvironment, and even integration of imaging capabilities for combined therapy and diagnostics (theranostics). Moreover, emerging targets such as TROP2, HER3, and Nectin-4 require even more precise matching of linker chemistry.
An ADC Cytotoxin with Linker refers to a structural module where a potent cytotoxin is covalently pre-conjugated to a linker for building Antibody-Drug Conjugates (ADCs). The cytotoxin kills tumor cells, while the linker controls the timing and location of its release. This pre-conjugated system enhances conjugation efficiency, improves batch consistency, and helps achieve precise control of the Drug-to-Antibody Ratio (DAR), making it an essential component in current ADC design.
The selection of cytotoxins and linkers requires comprehensive consideration of potency, release mechanisms, biocompatibility, and target indications. Common cytotoxins (such as MMAE, DM1, and PBD) must exhibit high cytotoxicity and have suitable conjugation sites; linkers are selected based on release mechanisms (e.g., enzyme-sensitive, acid-sensitive, or non-cleavable) to ensure precise intracellular toxin release. The structural and physicochemical properties of both must be highly matched to achieve optimal stability and efficacy.
Integrated Payload-Linker Solutions—pre-assembled toxin-linker modules—offer significant advantages: they simplify the conjugation process, improve reaction reproducibility, optimize quality control, and accelerate the development of candidate ADC molecules. Compared to stepwise loading, this approach facilitates DAR control and product consistency, making it highly suitable for full-cycle development needs from early screening to GMP scale-up and IND submission. It is a key strategy for driving efficient ADC translation and industrialization.
Pre-linked cytotoxin-linker systems simplify ADC synthesis, improve conjugation efficiency, enhance batch consistency, and allow precise control of the Drug-to-Antibody Ratio (DAR), which is critical for therapeutic efficacy and safety.
Common cytotoxins include microtubule inhibitors (MMAE, DM1), DNA-damaging agents (PBD dimers, Calicheamicin), topoisomerase inhibitors (SN-38, Exatecan), and RNA polymerase inhibitors (α-Amanitin). Each requires compatible linkers for stable delivery and controlled intracellular release.
Selection is based on factors such as cytotoxin potency (IC50), hydrophobicity, membrane permeability for potential bystander effects, and the target's microenvironment, ensuring optimal pairing for therapeutic effectiveness.
Yes, BOC Sciences offers fully customizable ADC cytotoxin-linker solutions, including a wide range of toxins and linker chemistries tailored to specific targets, mechanisms of action, and development stage needs.
