2024 EHA | Prof. Chunrui Li: Focusing on China's original research power, the field of EBV-associated hematological oncology therapeutics is revitalized

Question 1: According to current research findings, through which mechanisms may EBV induce hematological tumorigenesis and malignant transformation? For EBV-positive hematological tumors, what are the key aspects that the KSD-101 vaccine mainly acts on and how does it bring potential therapeutic benefits?

The interactions between EBV and host cells are complex, and after decades of research, the exact mechanisms by which it promotes tumorigenesis and malignant transformation are still not fully understood. It has been found that EBV can employ different strategies to evade host immune responses and compromise intrinsic and adaptive immunity during its life cycle, involving mechanisms includingGenetic and epigenetic alterations, inhibition of apoptosis, enhancement of cell proliferationas well asInhibition of immune recognition of EBV-infected cellset al. (and other authors)^1-2The

In recent years, more and more studies have focused on the roles of the tumor microenvironment and immune escape mechanisms in EBV-induced malignant tumors, from which potential therapeutic approaches for EBV-associated malignant tumors have been explored. The immune system plays an important role in the control of EBV-associated malignant tumors.EBV can promote tumor growth by altering the number and infiltration of immune cells in the tumor microenvironment, regulating the expression of immune checkpoints as well as specific cytokines, and forming an immunosuppressive microenvironment.

Currently, immune-based tumor-specific therapies are being evaluated in clinical studies¹. The KSD-101 vaccine used in the current study is an immune cell therapy, theKSD-101 is an autologous dendritic cell (DC) vaccine loaded with EBV-associated antigens, which can inhibit tumor growth and proliferation by inducing the specific immune function of DC against tumors and enhancing the body's ability to attack tumor cells.

On March 30, 2024, KSD-101 was granted clinical investigational new drug (IND) clearance by the U.S. Food and Drug Administration (FDA). The tolerability, safety and associated immune response of KSD-101 for the treatment of patients with EBV-associated hematologic neoplasms has been preliminarily demonstrated in the Phase I exploratory clinical trial announced at this EHA Congress³, which provides a valid basis for further subsequent clinical development and exploration.

Question 2: What are the key scientific questions that this clinical trial on KSD-101 was conducted to answer? To this end, what are the respective observables of the study and how are they assessed in an integrated manner to find a suitable dosing regimen for the clinical trial?

This study is a phase I exploratory trial, the first human study of KSD-101 for the treatment of EBV-associated hematologic neoplasms, with the primary objective of evaluating the safety and preliminary efficacy of KSD-101 as a novel cellular drug and providing an important basis for dosing regimens, etc., in subsequent studies.

In the trial, enrolled patients received KSD-101 monotherapy by subcutaneous injection once every 2 weeks for a total of 3 to 5 doses. A 3+3 dose-climbing design was used in the study to assess dose-limiting toxicity (DLT) in each dose group and to determine the maximum tolerated dose (MTD). Two dose level groups were successively set in the trial (5.0 × 10⁶cells/dose and 7.5 × 10⁶cells/dose), based on safety, preliminary efficacy, and feasibility assessments, eliminated dose group 3 levels and amplified 5.0 × 10⁶Dose group samples.

current studyPrimary endpointsFor tolerability, safety, DLT and MTD for each dose group, the type and incidence of adverse events (AEs) and serious adverse events (SAEs) were observed for the different dose groups, including adverse events occurring after injection, adverse events related to the study drug, or events leading to withdrawal from the study.secondary endpointTo determine the clinical efficacy of KSD-101, including EBV-DNA load, objective remission rate (ORR), disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), and overall survival (OS) 1 year after DC vaccine injection, as well as the immune response after injection, and to monitor the peripheral blood EBV-specific CD8⁺ Changes in the levels of T cells, B cells, NK cells, and immunosuppressive regulatory T cells (Tregs). The results of this published test were observed within 84 days after vaccination.

Question 3: What are the main key core data obtained in this study? Do you think the results of this trial met expectations in terms of the study's pre-determined endpoint indicators?

As of October 30, 2023, 9 patients have received at least 3 doses of KSD-101 treatment. At dose increments, 3 patients received 5.0 x 10⁶cells/dose, and 2 patients received 7.5 × 10⁶cells/agents.The vaccine was well tolerated by all patients.Adverse events associated with KSD-101 consisted primarily of grade 1-2 fever, grade 1 injection site reactions, enlarged lymph nodes, and increased lymphocyte counts, all of which were mild.No drug-related grade 3 or higher adverse reactions or DLTs were identified.

In terms of clinical efficacy, of the nine patients, all but one were excluded because of early disease recurrence, one was not included because the diagnosis was unknown, and two had not yet reached the time for efficacy assessment.The remaining 5 patients with assessable efficacy all achieved clinical complete remission (CR) during the 12-week period of KSD-101 vaccination with a CR and ORR of 100%.

The results of this trial are in line with expectations - KSD-101 has been preliminarily shown to have a favorable safety and efficacy profile and is a very promising treatment for EBV-related hematological tumors.

Question 4: It is noted that the study also took a closer look at changes in peripheral blood lymphocyte levels in patients before and after vaccination. How do you think the discovery of this result will help to understand the therapeutic effect of KSD-101 on EBV-related hematologic tumors?

KSD-101 is a patient-administered DC vaccine, in which mononuclear cells are extracted from the peripheral blood of patients, cultured in vitro and stimulated by specific cytokines to differentiate into mature DCs, loaded with EBV-associated antigens, and then infused back into the patients by subcutaneous injection.DCs are the most powerful antigen presenting cells (APCs) in the human immune system and play a key role in triggering and regulating innate and acquired immune responses. DCs are the most powerful antigen-presenting cells (APCs) in the human immune system, and play a key role in triggering and regulating innate and acquired immune responses.DCs have a strong antigen uptake and processing capacity, and are able to present tumor antigens to the initial T-cells, stimulate antigen-specific cytotoxic T-lymphocytes (CTLs) to proliferate, and use the cytotoxic activity of the intrinsic immune cells (e.g., NK-cells) to initiate a specific immune response against tumor cells. DC cells loaded with EBV-associated antigens have the ability to efficiently recognize EBV-infected cells and tumor cells, and in vivo are able to communicate the characteristics of EBV-infected cells and tumor cells to the attacking immune cells (e.g., killer T cells), which can be activated to inhibit viral replication and tumor progression, and ultimately remove the tumor load in the organism. Thus.KSD-101 is able to activate its own specific immune response against specific tumors, simultaneously exerting both anti-viral and anti-tumor therapeutic effects.

From the specific findings, patients showed a significant increase in the percentage of peak EBV-specific CTLs in the peripheral blood after KSD-101 vaccination (baseline mean 0.301 TP3T vs. 12-week treatment mean 2.471 TP3T, P < 0.05); and an increase in the peak number of immune cells, such as B-cells (mean up-regulated by 27.51-fold, P < 0.05), NK-cells (mean 1.68-fold upregulation, P < 0.01) and CD8⁺T cells (mean up-regulation of 2.38-fold, P < 0.05), while the proportion of Treg cells was significantly reduced (mean decrease of 53.05%, P < 0.001). The results suggest that.After the injection of KSD-101 vaccine, the number of many kinds of immune cells in the body changed significantly, and the anti-tumor immune response was enhanced, and the trend of this change was highly consistent with its clinical efficacy.

Therefore, combining the clinical efficacy of KSD-101 and the results of immune response monitoring in the study, the potential mechanism of action of KSD-101 vaccine can be basically deduced - i.e., activation of the autoimmune system, enhancement of the body's ability to respond to the immune response to viral infections and tumors, and exerting antiviral and anti-tumor effects. This further demonstrates the therapeutic potential of this therapy in EBV-related hematological tumors, which will help us in subsequent R&D optimization and research monitoring.

Question 5: Based on the KSD-101 R&D design principles and the preliminary results of this clinical trial, what application advantages do you believe the KSD-101 vaccine has over other available treatments for the treatment of EBV-associated hematologic neoplasms?

There is no specific treatment for EBV-associated hematologic malignancies. To date, classical regimens such as radiotherapy and/or chemotherapy remain the main options in their clinical management, but these therapies are still insufficient to completely treat EBV-positive malignancies or eradicate EBV-infected cells¹The

Compared to other treatments (e.g., radiotherapy, CAR-T cell therapy), DC immunotherapy uses the body's inherent immunity (immune cells) to fight tumors and has aActive immunity, high specificity, long duration(Establishment of immune protection, e.g., vaccination promotes a shift in the systemic immune microenvironment towards an anti-tumor state, creating favorable conditions for subsequent immune clearance of tumors) andfew side effectsand other advantages.

The ability of DCs loaded with EBV-associated antigens to migrate to lymph nodes in the tumor drainage area is critical for vaccine efficacy and depends in part on the route of vaccine administration⁴. Currently.The recommended frequency and route of administration of KSD-101 is 1 subcutaneous injection every 2 weeks, which is shorter in frequency compared to chemotherapy cycles, and easier and safer to administer than intravenous inputs, and can be done by patients at home.Avoiding the risk of deterioration due to repeated hospitalizations contributes to their treatment adherence.

Question 6: Based on the results of the Phase I clinical trial, what are your ideas and plans for the subsequent development and optimization of KSD-101 vaccine products and the conduct of clinical trials? For the exploration of the application of KSD-101 in EBV-associated hematological tumors, what do you think are the directions that can be focused on or researched in the future?

Scientific studies have shown that the efficacy of DC vaccines can be influenced by a variety of factors, such as the type of DCs, the selection and loading of EBV-associated antigen types, and the process of maturation and activation of DCs in vitro⁴, finding room for optimization from all aspects of the preparation process and through standardized mass production is the basis for achieving high quality vaccines for clinical use.

Phase I clinical trials have achieved relatively satisfactory results, but larger prospective studies and longer follow-up are needed to further validate the long-term clinical benefit and safety of KSD-101, and on this basis, to explore the dose range, dose selection, and quantitative-effective relationship characteristics of vaccination in greater depth, and to determine the appropriate dosage and dosing regimen. In subsequent clinical trials, in addition to expanding the sample size, it is also necessary to establish reasonable endpoints and treatment regimens (including co-administration) according to the specific research objectives, and refine the target population (including tumor type, severity, and other evaluative considerations), so as to adequately assess the clinical value of KSD-101 and accelerate its industrialization.

For the application of KSD-101 vaccine in EBV-associated hematological tumors, in addition to accelerating the confirmation of its efficacy and safety, exploring its potential synergistic effects with established therapeutic approaches is also an important research direction to explore its therapeutic potential. For example, combination with immune checkpoint inhibitors, or combination with certain low-dose radiotherapy methods to induce the release of tumor-associated antigens through immunogenic cell death may help to improve the efficacy of DC vaccines.