Natural Killer (NK) cells are lymphocytes with intrinsic cytotoxic activity and are core components of innate immunity. Studies have shown that NK cells play important roles in combating tumors, fighting viral infections, and regulating sub-health conditions.

Sources of NK Cells

NK cells can be obtained from various sources, such as peripheral blood, umbilical cord blood, and the NK-92 cell line, among others. NK cells from different sources exhibit varying biological functions.

(Figure 1: Sources of NK cells)

(Table 1: Comparison of NK cells from different sources)

Although NK cells have multiple sources, considering cost and safety, NK cells derived from peripheral blood and umbilical cord blood are currently considered more suitable for clinical application.

Application Scenarios of NK Cell Therapy

NK cell-based immunotherapy has emerged as a new major force in the field. Current application scenarios for NK cell therapy include:

1. Immune Enhancement and Anti-Aging: NK cells are a major subset of innate lymphoid cells, mediating various responses including surveillance and elimination of senescent cells.

As early as 2021, researchers at the University of Minnesota Medical School published in Nature confirming the link between aging and immune cell senescence. Multiple studies have confirmed that NK cells are key participants in immune surveillance of senescent cells, and their numbers increase with age. However, studies also confirm that NK cell cytotoxicity and function decline with age, with reduced cytokine release affecting their ability to interact with other immune cells and target cells [1].

(Figure 2: Nature article: "An aged immune system drives senescence and ageing of solid organs")

Researchers used specific ERCC-1 knockout to induce premature immune aging in mice. The knockout mice exhibited immune characteristics similar to normal aged mice, confirming that immune cells in the mouse model indeed showed signs of senescence. When immune cells from ERCC-1 knockout mice were transferred into aged mice, the recipients aged faster and had shorter lifespans.

Conversely, when immune cells from young healthy mice were transferred into aged mice, testing one month later revealed significantly reduced levels of aging-related markers, and senescence was reversed in multiple tissues and organs. This confirmed that young immune cells can reverse aging in aged mice to a certain extent.

(Figure 3: Multiple tissues in gene-knockout mice show senescence markers)

(Figure 4: Senescence characteristics significantly decreased in aged mice after receiving young mouse immune cells)

2. Consolidation Therapy After Hematopoietic Stem Cell Transplantation: Clinical anti-tumor regimens often select NK cell immunotherapy as a post-remission consolidation strategy or in combination with other treatments.

Researchers from West China Hospital of Sichuan University and the Sichuan Cord Blood Bank jointly completed a pioneering study exploring the feasibility and efficacy of cord blood-derived NK cells as maintenance therapy after autologous hematopoietic stem cell transplantation [2].

(Figure 5: Annals of Hematology article: "A pilot study of cord blood-derived natural killer cells as maintenance therapy after autologous hematopoietic stem cell transplantation")

The research team selected 31 patients with acute myeloid leukemia (AML) and high-risk lymphoma as the study group, and 90 patients who did not receive NK cell therapy as controls. All patients had undergone autologous hematopoietic stem cell transplantation. Cord blood-derived NK cells were expanded in vitro and infused as maintenance therapy post-transplant.

After observation, the researchers found that the relapse rate in the cord blood NK cell maintenance group was 9.7%, compared to 24.4% in the control group. Patients in the NK cell treatment group had better progression-free survival (PFS) and overall survival (OS), with 4-year PFS and OS rates of 84.4% and 100%, respectively, significantly higher than the control group's 73.5% and 78.1%.

(Figure 6: Comparison of PFS and OS between patients with and without CBNK cell infusion)

The results indicate that multiple cord blood NK cell infusions can effectively reduce tumor recurrence rates and improve patient survival. Cord blood NK cells show high clinical application potential in reducing relapse and improving long-term survival in AML and high-risk lymphoma patients after autologous hematopoietic stem cell transplantation.

4.Combination Therapy for Solid Tumors: NK cells combined with monoclonal antibodies, chemotherapy, and other modalities for treating solid tumors.

(Figure 7: Research article: "Pembrolizumab plus allogeneic NK cells in advanced non-small cell lung cancer patients")

This study, conducted by Professor Jiang Yong's team at the Guangdong Provincial Key Laboratory of Proteomics, found that PD-1 inhibitors are active against non-small cell lung cancer (NSCLC) and that, beyond T cells, NK cells also express PD-L1 and have the potential to extend survival in advanced NSCLC patients.

109 PD-L1-positive advanced NSCLC patients were randomized into two groups: Group A (55 patients) received allogeneic NK cell infusion plus Keytruda (pembrolizumab), while Group B (54 patients) received Keytruda alone.

Results showed that Group A patients had longer survival than Group B (median OS: 15.5 months vs. 13.3 months; median PFS: 6.5 months vs. 4.3 months; P < 0.05). In Group A patients with TPS ≥ 50%, median OS and PFS were significantly longer. Furthermore, patients receiving multiple NK cell infusions had better OS (18.5 months) than those receiving a single infusion (13.5 months) [3].

4.Treatment of Hematological Malignancies: CD19-positive malignancies, including non-Hodgkin lymphoma, chronic lymphocytic leukemia, and diffuse large B-cell lymphoma.

(Figure 8: Research article: "Phase I Study of Random Healthy Donor-Derived Allogeneic Natural Killer Cell Therapy in Patients with Malignant Lymphoma or Advanced Solid Tumors")

As early as 2016, researchers used allogeneic NK cells in clinical studies for malignant lymphoma. Ex vivo-expanded and highly activated NK cells (MG4101) showed potent anticancer activity in preclinical studies.

Results showed that among 17 uable patients, 8 (47.1%) had stable disease and 9 (52.9%) had progressive disease [4].

5. Autoimmune Diseases: Compared to other innovative cell therapy products, NK cell therapy significantly reduces patient financial burden and is readily available. With their inherent safety advantages, NK therapies are poised to stand out in the autoimmune disease field.

Autoimmune diseases typically arise from loss of self-tolerance (the immune system's inability to distinguish self from non-self), characterized by autoantibody production and overactivation of T cells, leading to damage in specific or multiple organs. Systemic lupus erythematosus (SLE) is a classic systemic autoimmune disease, often called the "incurable cancer," and currently has no cure.

In 2023, the U.S. FDA approved Artiva Biotherapeutics' Investigational New Drug (IND) application for its allogeneic NK therapy AlloNK® (also known as AB-101) in combination with rituximab for the treatment of SLE in patients with active lupus nephritis (LN). This IND approval marked the first time an allogeneic, off-the-shelf NK or CAR-T cell therapy was approved for autoimmune disease.

(Figure 9: AlloNK® investigational new drug preparation and use)

6. Neurological Disorders: NK cell therapies for Alzheimer's disease and Parkinson's disease have received FDA IND approval.

On April 29, 2024, NKGen Biotech, a biotechnology company focused on developing autologous, allogeneic, and CAR-NK/NK cell therapies, announced that its NK cell therapy SNK01 for Parkinson's disease had received FDA IND approval.

Previously, SNK01 had shown positive results in a Phase I trial in Alzheimer's patients, with data indicating the therapy may reduce blood levels of Alzheimer's biomarker Aβ42/40 amyloid and alleviate neuroinflammation.

(Figure 10: Alzheimer's disease – image source online)

7. Improving Sub-Health Conditions: NK cells kill infected cells, clear aging and necrotic cells, prevent infected cells from becoming viral reservoirs, and block further viral replication. Unlike over 150 other types of white blood cells, NK cells do not require special instructions from the immune system or cooperation from other cells; they can independently recognize and attack foreign cells, cancer cells, and viruses.

In 32 sub-healthy patients treated with autologous NK cells for 4 cycles and followed for 6 months, peripheral blood CD8⁺ T cells decreased, while CD3⁺, CD4⁺, and the CD4⁺/CD8⁺ ratio increased significantly compared to baseline. Fatigue levels were significantly reduced after 4 cycles and 6 months. Autologous NK cell immunotherapy can alleviate fatigue symptoms in sub-healthy individuals, enhance cellular immune function, and improve quality of life [5].

(Figure 11: Changes in T lymphocyte subsets before and after NK cell infusion in sub-healthy patients)

Shenzhen Cell Valley – APUNK™

APUNK™ (Allogeneic PB/UCB Natural Killer) is a series of non-engineered allogeneic NK cell therapy products developed and launched by Shenzhen Cell Valley. The product line is named after the company's breakthrough NK cell SDAP (Screening, Detection, Amplification, Purification) technology.

(Figure 12: Shenzhen Cell Valley APUNK™)

APUNK™ cells can be expanded more than 10,000-fold in vitro (feeder-free system), meeting the cell numbers required for clinical infusion. The prepared NK cells have >99% purity with T cells <1%, far exceeding the allogeneic transplantation standards recognized by the U.S. FDA (NK cells >90%, T cells <5%) [6][7].

The PB-NK products in the APUNK™ series are prepared from peripheral blood of "super donors" – individuals with excellent lifestyle habits and physiological parameters well above average. PB-NK derived from such donors shows higher yield, higher expansion fold, and stronger killing activity. Additionally, APUNK™ cells have robust proliferative capacity, achieving 15,000-50,000-fold expansion by day 32, with NK cell purity consistently >99% throughout the expansion.

Shenzhen Cell Valley APUNK™ Quality Control Standards:

CD3⁻CD56⁺ ≥ 99%

CD3⁻CD56⁺CD16⁺ ≥ 80%

CD3⁻CD56⁺NKG2D⁺ ≥ 95%

(Figure 12: Flow cytometry results of Shenzhen Cell Valley NK cell products)

Shenzhen Cell Valley is committed to providing high-quality cell products for clinical use. We welcome collaboration to benefit patients!

References:

[1] Yousefzadeh MJ, Flores RR, Zhu Y, et al. An aged immune system drives senescence and ageing of solid organs. Nature. 2021 Jun;594(7861):100-105.

[2] Wu Y, Wang Y, Ji J, et al. A pilot study of cord bloodderived natural killer cells as maintenance therapy after autologous hematopoietic stem cell transplantation. Ann Hematol. 2023;102:3229-3237.

[3] Lin M, Luo H, Liang S, et al. Pembrolizumab plus allogeneic NK cells in advanced non-small cell lung cancer patients. J Clin Invest. 2020 May 1;130(5):2560-2569.

[4] Yang Y, Lim O, Kim TM, et al. Phase I Study of Random Healthy Donor-Derived Allogeneic Natural Killer Cell Therapy in Patients with Malignant Lymphoma or Advanced Solid Tumors. Cancer Immunol Res. 2016 Mar;4(3):215-24.

[5] Biochem Biophys Rep. 2022 Nov 11;32:101380.

[6] Phase I study of cord blood-derived natural killer cells combined with autologous stem cell transplantation in multiple myeloma. Br J Haematol. 2017 May;177(3):457-466.

[7] Pembrolizumab plus allogeneic NK cells in advanced non-small cell lung cancer patients. J Clin Invest. 2020 May 1;130(5):2560-2569.