Mechanism of Action of Bispecific ADCs: Precise Targeting, Synergistic Internalization, and Efficient Tumor Killing

With the continuous advancement of antibody-drug conjugate (ADC) technology, bispecific antibody-drug conjugates (Bispecific ADCs) are emerging as an important innovation in the field of precision oncology. Unlike traditional ADCs that recognize only a single target, bispecific ADCs can simultaneously bind to two antigens, significantly enhancing tumor targeting specificity, internalization efficiency, and antitumor activity. This article systematically explains the core mechanisms of action of bispecific ADCs and their potential therapeutic advantages.

What Are Bispecific ADCs?

Bispecific ADCs are a novel class of targeted therapeutics composed of a bispecific antibody, a cleavable or non-cleavable linker, and a potent cytotoxic payload.

Their design aims to improve tumor cell selectivity through dual-target recognition, reduce off-target toxicity, and enhance tumor-killing efficacy, thereby expanding the clinical potential of ADCs in complex tumor settings.

Compared with conventional ADCs, bispecific ADCs demonstrate stronger adaptability in heterogeneous tumor environments, which is one of the key reasons they are receiving increasing global attention.

Core Mechanisms of Action of Bispecific ADCs

1️⃣ Dual-Target Recognition: Improving Tumor Selectivity

Bispecific ADCs can simultaneously recognize two tumor-associated antigens, for example:

● Targeting a tumor-driving antigen together with an internalization-enhancing antigen

● Targeting two tumor antigens with different expression profiles

This “AND-gate” binding mechanism provides multiple advantages:

● Increased binding strength to tumor cells (avidity effect)

● Reduced probability of binding to normal tissues with low antigen expression

● Overcoming tumor antigen heterogeneity

As a result, bispecific ADCs can maintain more stable targeting capability within complex tumor microenvironments.

2️⃣ Synergistic Internalization: Enhancing Drug Uptake Efficiency

The internalization efficiency of traditional ADCs is often limited by the endocytic capacity of a single antigen. In contrast, bispecific ADCs can enhance internalization through:

● Antigen cross-linking, which promotes receptor clustering

● Activation of stronger receptor-mediated endocytosis signaling

● Accelerated trafficking into lysosomal pathways

Studies have shown that simultaneous binding to two receptors can induce faster internalization rates and higher intracellular drug concentrations, thereby improving cytotoxic payload release efficiency—an important contributor to enhanced therapeutic efficacy.

3️⃣ Lysosomal Release: Precise Delivery of Cytotoxic Payloads

After entering tumor cells, bispecific ADCs undergo the following processes in lysosomes:

● Linker cleavage via enzymatic degradation or reduction

● Release of small-molecule cytotoxic drugs (such as microtubule inhibitors or DNA-damaging agents)

● Drug action on critical cellular structures or genetic material

This ultimately leads to:

● Cell cycle arrest

● DNA damage or strand breaks

● Apoptosis or immunogenic cell death

This “targeted delivery–intracellular release” mechanism enables bispecific ADCs to function like biological guided missiles, achieving precise tumor cell killing.

4️⃣ Bystander Effect: Expanding Antitumor Coverage

Some bispecific ADCs are designed with membrane-permeable payloads and cleavable linkers, enabling a bystander effect:

● Released drugs can diffuse into neighboring tumor cells

● Killing cells with low or even absent target antigen expression

● Helping overcome resistance caused by tumor heterogeneity

Therefore, bispecific ADCs can not only precisely eliminate target-positive cells but also generate a localized diffusion-mediated cytotoxic effect within the tumor microenvironment.

5️⃣ Potential Immune Synergy

Emerging research suggests that bispecific ADCs may also:

● Induce immunogenic cell death (ICD)

● Promote antigen presentation

● Enhance T-cell infiltration

When combined with immune checkpoint inhibitors, these effects may produce stronger antitumor synergy, making combination strategies an important direction for current clinical research.

Clinical Advantages of Bispecific ADCs

Compared with traditional ADCs, bispecific ADCs offer several potential advantages:

● ✅ Higher tumor specificity

● ✅ Stronger internalization efficiency

● ✅ Improved antitumor activity

● ✅ Lower risk of systemic toxicity

● ✅ Greater potential to overcome drug resistance

These characteristics position bispecific ADCs as a key trend in next-generation ADC development.

Future Development Trends

Currently, multiple bispecific ADC programs worldwide have entered clinical trials, with major indications focusing on high-unmet-need cancers such as non-small cell lung cancer, breast cancer, gastrointestinal malignancies, and hematological tumors. These diseases are often associated with strong tumor heterogeneity, high resistance risk, and frequent recurrence, creating an urgent demand for more precise and effective targeted therapies. Through mechanisms such as dual-target recognition, enhanced internalization, and the bystander effect, bispecific ADCs are expected to demonstrate superior therapeutic potential and clinical value in these tumor types.

Future R&D priorities include:

● Novel linker design

● Optimization of next-generation high drug-to-antibody ratio (DAR) structures

● Development of safer cytotoxic payloads

● Combination strategies with immunotherapy

As more bispecific ADC candidates progress into clinical stages, the demand for high-quality innovative drug supply and professional pharmaceutical services continues to grow. For example, companies such as Dengyue Pharma are supporting access to innovative targeted therapies by integrating international drug resources and strengthening supply chain capabilities, thereby contributing to the continuous improvement of the precision oncology ecosystem.

Conclusion

Through dual-target recognition, synergistic internalization, precise intracellular payload release, and the bystander effect, bispecific ADCs theoretically achieve stronger antitumor efficacy than conventional ADCs. They have the potential not only to deepen treatment responses but also to address drug resistance and tumor heterogeneity challenges, representing a major advancement in ADC drug development.

It is foreseeable that in the future precision oncology landscape, bispecific ADCs will become one of the most promising core innovative therapeutic strategies.