Intracranial injection of natural killer cells engineered with a HER2-targeted chimeric antigen receptor in patients with recurrent glioblastoma

BACKGROUND

Glioblastoma (GB) is incurable at present without established treatment options for recurrent disease. In this phase I first-in-human clinical trial we investigated safety and feasibility of adoptive transfer of clonal chimeric antigen receptor (CAR)-NK cells (NK-92/5.28.z) targeting HER2, which is expressed at elevated levels by a subset of glioblastomas.

METHODS

Nine patients with recurrent HER2-positive GB were treated with single doses of 1 × 107, 3 × 107, or 1 × 108 irradiated CAR-NK cells injected into the margins of the surgical cavity during relapse surgery. Imaging at baseline and follow-up, peripheral blood lymphocyte phenotyping and analyses of the immune architecture by multiplex immunohistochemistry and spatial digital profiling were performed.

RESULTS

There were no dose-limiting toxicities, and none of the patients developed a cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome. Five patients showed stable disease after relapse surgery and CAR-NK injection that lasted 7 to 37 weeks. Four patients had progressive disease. Pseudoprogression was found at injection sites in 2 patients, suggestive of a treatment-induced immune response. For all patients, median progression-free survival was 7 weeks, and median overall survival was 31 weeks. Furthermore, the level of CD8+ T-cell infiltration in recurrent tumor tissue prior to CAR-NK cell injection positively correlated with time to progression.

CONCLUSIONS

Intracranial injection of HER2-targeted CAR-NK cells is feasible and safe in patients with recurrent GB. 1 × 108 NK-92/5.28.z cells was determined as the maximum feasible dose for a subsequent expansion cohort with repetitive local injections of CAR-NK cells.

OS12.6.A Combination therapy of CAR-NK-cells and anti-PD-1 results in high efficacy against advanced-stage glioblastoma in a syngeneic mouse model and induces protective anti-tumor immunity in vivo

INTRODUCTION

Checkpoint inhibitors as well as adoptive cell therapy hold promise for cancer therapy and encouraging treatment responses have already been demonstrated in different cancer indications. Glioblastoma (GB) is the most common and aggressive primary brain tumor. Standard therapy has very limited efficacy in the majority of patients. Analysis of the GB microenvironment (TME) has shown prominent immunosuppressive features, including expression of PD-L1 on tumor cells and increased frequency of FOXP3-positive regulatory T cells. While the surrounding brain is HER2-negative, GB are frequently HER2-positive, suggesting HER2 as a promising target for adoptive immunotherapy. Previous results from mouse glioma models showed efficacy of CAR-NK cells (NK-92/5.28.z) targeted against HER2 as monotherapy with early stage but not with advanced-stage tumors.

MATERIALS AND METHODS

The murine glioma cell line GL261 was transfected with human HER2. Tumor cells were implanted either subcutaneously or orthotopically into C57BL/6 mice and treated either with HER2-specific NK-92/5.28.z cells alone or in combination with an anti-PD-1 antibody. Effects on tumor growth and survival were determined. Lymphocyte infiltration and immunosuppressive TME were characterized via highplex multi-color flow cytometry (FACS Symphony) and IHC (Phenoptics). Furthermore, gene expression profiles of tumor-infiltrating cells were determined via bulk RNAseq (NanoString).

RESULTS

Combined treatment with NK-92/5.28.z cells and anti-PD-1 checkpoint blockade resulted in synergistic effects, with tumor regression and long-term survival observed even in advanced-stage tumor bearing mice. Analysis of the TME showed changes in lymphocyte infiltration and increased expression of exhaustion markers in tumor and immune upon combined treatment with NK-92/5.28.z cells and anti-PD-1 antibody resulting in an altered TME. Both, PD-1 and Lag-3 expression are highly upregulated on tumor infiltrating T cells. Total infiltrating lymphocytes show a rather cytotoxic phenotype up combination treatment with NK-92/5.28.z cells and anti-PD-1 antibody

CONCLUSION

Our data demonstrate that efficacy of NK-92/5.28.z cells can be enhanced by combination with checkpoint blockade, resulting in successful treatment of advanced tumors refractory to NK-92/5.28.z monotherapy. Furthermore, the combination therapy induced a cytotoxic rather than immunosuppressive TME, leading to a primed immune system. To translate the concept of CAR-NK-cell therapy plus checkpoint inhibition to a clinical setting, we are adding a combination therapy cohort to our ongoing phase I clinical study (CAR2BRAIN; NCT03383978).

OS06.2A Local immunotherapy of glioblastoma via AAV-mediated gene transfer of checkpoint inhibitors in combination with CAR-NK cells

BACKGROUND

Glioblastoma (GB) is the most common primary brain tumor which is characterized by low immunogenicity of tumor cells and prevalent immunosuppression in the tumor microenvironment (TME). Since expression of PD-L1 on GB cells has been described, immunotherapy with checkpoint inhibitors (CIs) may be a promising approach for GB treatment. However, systemic administration of CIs bears the risk of autoimmune-like side effects, while the intratumoral drug concentration reached may not be sufficient.

METHODS

We studied delivery of CIs through targeted Adeno-associated viral vectors (AAVs) encoding an anti PD-1 immunoadhesin (aPD-1) as a novel approach towards local immunotherapy in the syngeneic GL261-HER2 glioma model. Tumor cell-specific delivery was achieved by targeting HER2 via a specific designed ankyrin repeat protein (DARPin). We investigated the effects of this strategy alone and in combination with local injection of HER2-specific CAR-NK cells (NK-92/5.28.z), which have already shown efficacy in preclinical GB models and are currently under investigation in the CAR2BRAIN phase I clinical trial. Furthermore, aPD-1 functionality and cellular response to viral transduction as well as compatibility of both therapy approaches has been evaluated in various in vitro models.

RESULTS

HER2-AAV transduction efficacy of GB cells correlated with HER2 expression level, while target cells did not show anti-viral responses upon transduction. After transduction with aPD-1 HER2-AAVs, aPD-1 immunoadhesin was secreted in a time-dependent manner, bound its target on PD-1-expressing cells and was able to re-activate T-cells due to PD-1 blockade. AAV-transduction did not interfere with CAR-NK cell mediated tumor cell lysis. Biodistribution studies in mice revealed the presence of aPD-1 up to 10 days after a single HER2-AAV injection. In subcutaneous GL261-HER2 tumors, local treatment with HER2-AAVaPD-1 or HER2-AAVIgG-Fc+ NK-92/5.28.z therapy had no significant effect, whereas combination therapy profoundly delayed tumor growth.

CONCLUSIONS

Local therapy with aPD-1 encoding HER2-AAVs in combination with NK-92/5.28.z cells is a promising novel strategy for GB immunotherapy with the potential to enhance efficacy and reduce side effects.

AMPK activation protects astrocytes from hypoxia‑induced cell death

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a major cellular energy sensor that is activated by an increase in the AMP/adenosine triphosphate (ATP) ratio. This causes the initiation of adaptive cellular programs, leading to the inhibition of anabolic pathways and increasing ATP synthesis. AMPK indirectly inhibits mammalian target of rapamycin (mTOR) complex 1 (mTORC1), a serine/threonine kinase and central regulator of cell growth and metabolism, which integrates various growth inhibitory signals, such as the depletion of glucose, amino acids, ATP and oxygen. While neuroprotective approaches by definition focus on neurons, that are more sensitive under cell stress conditions, astrocytes play an important role in the cerebral energy homeostasis during ischemia. Therefore, the protection of astrocytic cells or other glial cells may contribute to the preservation of neuronal integrity and function. In the present study, it was thus hypothesized that a preventive induction of energy deprivation-activated signaling pathways via AMPK may protect astrocytes from hypoxia and glucose deprivation. Hypoxia-induced cell death was measured in a paradigm of hypoxia and partial glucose deprivation in vitro in the immortalized human astrocytic cell line SVG. Both the glycolysis inhibitor 2-deoxy-d-glucose (2DG) and the AMPK activator A-769662 induced the phosphorylation of AMPK, resulting in mTORC1 inhibition, as evidenced by a decrease in the phosphorylation of the target ribosomal protein S6 (RPS6). Treatment with both 2DG and A-769662 also decreased glucose consumption and lactate production. Furthermore, A-769662, but not 2DG induced an increase in oxygen consumption, possibly indicating a more efficient glucose utilization through oxidative phosphorylation. Hypoxia-induced cell death was profoundly reduced by treatment with 2DG or A-769662. On the whole, the findings of the present study demonstrate, that AMPK activation via 2DG or A-769662 protects astrocytes under hypoxic and glucose-depleted conditions.

P12.04 Synergistic effects of combination therapy of CAR-NK cells and anti-PD-1 antibody result in high efficacy against advanced stage orthotopic glioblastoma grafts in a syngeneic mouse model and induce protective anti-tumor immunity in vivo

BACKGROUND

Checkpoint inhibitors as well as adoptive cell therapy hold great promise for cancer treatment and encouraging treatment responses have already been demonstrated in different cancer indications. Glioblastoma (GB) is the most common and aggressive primary brain tumor. Standard therapy has very limited efficacy in the majority of patients. Analysis of the GB tumor microenvironment (TME) has shown prominent immunosuppressive features including expression of PD-L1 on tumor cells and increased frequency of FOX-P3 positive regulatory T cells. While the surrounding brain is HER2-negative, GB tumors are frequently HER2-positive, suggesting HER2 as a promising target for adoptive immunotherapy.

MATERIALS AND METHODS

The murine glioma cell line GL261 was transfected with HER2. Tumor cells were orthotopically implanted into C57BL/6 mice and treated either with HER2-specific NK-92/5.28.z cells alone or in combination with an anti-PD-1 antibody. Effects on tumor growth and survival were determined, lymphocyte infiltration and immunosuppressive TME were characterized.

RESULTS

Combined treatment with NK-92/5.28.z cells and anti-PD-1 antibody resulted in synergistic tumor regression and long-term survival of advanced-stage tumor bearing mice. Analysis of TME showed enhanced cytotoxic lymphocyte infiltration and altered profiles of exhaustion markers in tumor and immune cells.

CONCLUSION

These data demonstrate that efficacy of NK-92/5.28.z cells can be enhanced by co-therapy with checkpoint inhibitors, resulting in successful treatment of advanced tumors refractory to mono-therapy. Furthermore, this combination therapy induces a cytotoxic rather than immunosuppressive TME, leading to a primed immune system. To address this question in a clinical setting, we are planning a phase I clinical study (CAR2BRAIN-CHECK).