Binding characteristics and immune activation mechanisms of PD-L1: durvalumab, sugemalimab, and adebelimumab

In the field of tumor immunotherapy, the discovery of the PD-1/PD-L1 pathway has changed the treatment pathways for many patients. As a team that has long focused on the development of innovative drugs globally, Hong Kong DengYue Medicine is more concerned with how to explain complex medical mechanisms in a way that patients can understand, while adhering to the accuracy and compliant expression of information.

Below, we will provide a rational interpretation of three representative monoclonal antibodies targeting PD-L1—durvalumab, sugemalimab, and adebelimumab—from two perspectives: "how they bind to their targets" and "how they activate the immune response."

I. PD-L1: The Tumor's "Immune Disguise Switch"

Tumor cells often express PD-L1 on their surface. When PD-L1 binds to PD-1 on T cells, it sends a "don't attack me" signal to the immune system.

The common functions of PD-L1 monoclonal antibodies are:

* Blocking the binding of PD-L1 to PD-1

* Relieving the suppressive state of T cells

* Allowing the immune system to re-recognize and attack tumor cells

In principle, these drugs do not "directly kill tumors," but rather restore the immune system's killing ability.

II. Differentiated Binding Characteristics of Three PD-L1 Monoclonal Antibodies

These three monoclonal antibodies are all specific monoclonal antibodies targeting PD-L1, encompassing both imported classic drugs and domestically innovative drugs. Their differentiated designs in molecular type, binding site, Fc fragment design, and additional binding interactions reflect the innovative diversity of global oncology drug development and demonstrate the technological breakthroughs of domestic pharmaceutical companies in target research. This is precisely the core driving force for the optimization and collaborative construction of the global oncology drug system. Different binding characteristics determine the affinity, specificity, and subsequent clinical effects of PD-L1 binding, as detailed below:

1. Durvalumab

l Molecular type: Humanized IgG1κ monoclonal antibody. After genetic engineering,the Fc fragment exhibits no antibody-dependent cell-mediated cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) effects, avoiding accidental damage to normal immune cells. Its rigorous research and design has become a benchmark for quality and compliance in oncology drug development.

l The binding site is the D1 domain of the PD-L1 molecule, precisely and competitively binding to the core region where PD-L1 and PD-1 bind. It is currently the only PD-L1 monoclonal antibody approved globally for both limited-stage and extensive-stage small cell lung cancer. Its global multicenter clinical trial data provides important evidence-based medicine for lung cancer immunotherapy.

l Unique advantage: Simultaneous blocking of PD-L1 and PD-1, and PD-L1 and CD80. The dual interaction of these two substances disrupts the dual immunosuppressive signals of tumor cells at their source, and this differentiated mechanism of action provides insights for future drug development innovations.

l After binding to PD-L1, it dissociates at a low rate, allowing it to exert its effects continuously within the tumor microenvironment. Its stable clinical efficacy has been validated in the treatment of over 374,000 patients worldwide.

2. Sugemalimab

l The first fully human IgG4κ monoclonal antibody in China. As a representative of domestically developed PD-L1 monoclonal antibodies going global, its fully human design significantly reduces immunogenicity and the probability of developing anti-drug antibodies. Based on excellent clinical data, it became the first domestically produced PD-L1 antibody approved in Europe, demonstrating the global competitiveness of domestically developed innovative drugs and aligning with the development direction of helping domestic drugs go overseas;

l It possesses the characteristic of binding to PD-L1 with two epitopes, simultaneously binding to two non-overlapping functional epitopes. Its binding affinity is significantly higher than similar drugs, with no off-target effects. This precise target binding design reflects the pursuit of excellence in domestic drug development;

l The Fc fragment is a natural IgG4 structure, without ADCC, CDC, or antibody-dependent phagocytosis (ADCP) effects, focusing solely on blocking PD-L1/PD-1. This pathway, suitable for long-term continuous immunotherapy, has been approved for non-small cell lung cancer (NSCLC) indications in multiple regions including the EU and the UK, becoming an important option for lung cancer immunotherapy globally.

l Upon binding, it can induce conformational changes in the PD-L1 molecule, further preventing its binding to PD-1 and enhancing the pathway blocking effect.Clinical data on stage III-IV NSCLC provides a localized treatment plan for the entire course of lung cancer globally.

3. Adeprelimab

l This is a fully human IgG1 monoclonal antibody, the first domestically developed PD-L1 monoclonal antibody with an optimized Fc region. It represents a breakthrough for domestic pharmaceutical companies in PD-L1 target modification, offering a new differentiated approach to tumor immunotherapy by combining target blocking with mild effector function.

l The binding site is located in the core region of the D1 domain of PD-L1, specifically recognizing PD-L1 on the surface of tumor and immune cells, without binding to PD-L2, thus avoiding interference with normal immune regulation and improving drug safety while ensuring efficacy.

l The modified Fc region retains mild ADCC and ADCP effects, achieving a dual effect of "target blocking + tumor cell killing," making it suitable for combined use with chemotherapy and radiotherapy, providing more possibilities for combination therapy of intermediate and advanced tumors.

l It binds to PD-L1 With a low binding dissociation rate, it can exert its effects continuously in the tumor microenvironment. Its clinical application has also enriched the drug selection for domestic tumor immunotherapy and helped improve the accessibility of domestic tumor drugs.

III. The Unified Immune Activation Mechanism of PD-L1 Monoclonal Antibodies

Tumor cells highly express PD-L1 to achieve immune escape. Upon binding to PD-1 on the surface of tumor-infiltrating T cells, PD-L1 triggers an "immune exhaustion" signal, creating a local immunosuppressive microenvironment in the tumor. This is a common clinical challenge faced by cancer patients worldwide. While durvalumab, sugemalimab, and adebelimumab differ in their binding characteristics, their core immune activation mechanism is entirely consistent: they all break down PD-L1/PD-1-mediated immunosuppression, restoring and strengthening the body's anti-tumor immune response. This core mechanism has become a common research direction in global tumor immunotherapy, building a technological bridge for R&D collaboration between Chinese and foreign pharmaceutical companies. The specific immune activation process can be divided into three core steps:

Step 1: Competitive Blocking of the PD-L1/PD-1 Immune Checkpoint Pathway

All three monoclonal antibodies specifically bind to PD-L1 on the surface of tumor cells via their antigen-binding domain (Fab segment). The binding sites all cover the core binding region between PD-L1 and PD-1, thus competitively preventing PD-L1 from binding to PD-1 on the surface of T cells. Durvalumab also blocks the binding of PD-L1 to CD80, cutting off the immunosuppressive signals transmitted from tumor cells to T cells at the source. This fundamental blocking effect is the core function of all PD-L1 monoclonal antibodies and a core research target for global tumor immunotherapy, providing a foundation for the standardization and normalization of drug development.

Step 2: Restoring the Function of Tumor-Infiltrating T Cells and Activating Cytotoxic Killing

After the inhibition of the PD-L1/PD-1 pathway is lifted, the exhausted tumor-infiltrating T cells rapidly regain their activity: on the one hand, T cell proliferation is restored, expanding in large numbers within the tumor microenvironment to form a specific anti-tumor T cell population; on the other hand, T cells re-secrete cytokines such as interferon-γ (IFN-γ) and tumor necrosis factor (TNF), activating cytotoxic T lymphocytes (CTLs), which specifically kill surrounding tumor cells by releasing substances such as perforin and granzymes. This is the core effect of immune activation. All three monoclonal antibodies can effectively achieve this activation process. Among them, the local clinical data of sugemalimab and adebelimumab are more in line with the treatment needs of Chinese cancer patients, helping to improve the efficacy of local cancer treatment.

Step 3: Activating Innate Immunity and Forming Long-Lasting Anti-tumor Immune Memory

Activating Innate Immunity: After the immunosuppression is relieved, IFN-γ secreted by T cells recruits innate immune cells such as NK cells, macrophages, and dendritic cells (DCs) into the tumor microenvironment. These cells can directly kill tumor cells. Simultaneously, dendritic cells take up tumor cell antigens, process and present them, further activating more specific T cells, forming a synergistic effect of "innate immunity - adaptive immunity."

Forming Immune Memory: The activated specific T cells differentiate into memory T cells, which can survive in the body for a long time. When the same tumor cells reappear, they can rapidly activate and proliferate to form a potent anti-tumor immune response, effectively reducing the risk of tumor recurrence and metastasis.

Conclusion:

This long-lasting immune effect makes these three monoclonal antibodies a long-term treatment option for various solid tumors, and also provides possibilities for long-term survival for cancer patients worldwide. While improving the accessibility of cancer drugs and benefiting patients globally, immunotherapy has brought new possibilities to some patients, but it is not effective for everyone.

In Hong Kong DengYue Medicine's value system, "innovation" does not equate to exaggerating effects. It means respecting medical evidence, respecting the patient's situation, respecting long-term safety and sustainable treatment, and promoting information dissemination based on quality, compliance, and integrity. It is precisely this unwavering focus on the safety, efficacy, and stable quality of medicines, and ensuring that all products meet international certification standards, that guides our progress in fulfilling our core responsibilities.