Heat Shock Protein 70 (Hsp70) Peptide Activated Natural Killer (NK) Cells for the Treatment of Patients with Non-Small Cell Lung Cancer (NSCLC) after Radiochemotherapy (RCTx) - From Preclinical Studies to a Clinical Phase II Trial

Abstract

Heat shock protein 70 (Hsp70) is frequently overexpressed in tumor cells. An unusual cell surface localization could be demonstrated on a large variety of solid tumors including lung, colorectal, breast, squamous cell carcinomas of the head and neck, prostate and pancreatic carcinomas, glioblastomas, sarcomas and hematological malignancies, but not on corresponding normal tissues. A membrane (m)Hsp70-positive phenotype can be determined either directly on single cell suspensions of tumor biopsies by flow cytometry using cmHsp70.1 monoclonal antibody or indirectly in the serum of patients using a novel lipHsp70 ELISA. A mHsp70-positive tumor phenotype has been associated with highly aggressive tumors, causing invasion and metastases and resistance to cell death. However, natural killer (NK), but not T cells were found to kill mHsp70-positive tumor cells after activation with a naturally occurring Hsp70 peptide (TKD) plus low dose IL-2 (TKD/IL-2). Safety and tolerability of ex vivo TKD/IL-2 stimulated, autologous NK cells has been demonstrated in patients with metastasized colorectal and non-small cell lung cancer (NSCLC) in a phase I clinical trial. Based on promising clinical results of the previous study, a phase II randomized clinical study was initiated in 2014. The primary objective of this multicenter proof-of-concept trial is to examine whether an adjuvant treatment of NSCLC patients after platinum-based radiochemotherapy (RCTx) with TKD/IL-2 activated, autologous NK cells is clinically effective. As a mHsp70-positive tumor phenotype is associated with poor clinical outcome only mHsp70-positive tumor patients will be recruited into the trial. The primary endpoint of this study will be the comparison of the progression-free survival of patients treated with ex vivo activated NK cells compared to patients who were treated with RCTx alone. As secondary endpoints overall survival, toxicity, quality-of-life, and biological responses will be determined in both study groups.

Keywords: Hsp70-based immunotherapy; NK cells; NSCLC patients; clinical phase II; radiochemotherapy clinical trial.

Figure 1

Scheme of the NK cell activation in the clinical phase I trial. NSCLC patients after radiochemotherapy undergo leukapheresis and the immune phenotype (NK cell and T cell markers) is assessed by flow cytometry. Following erythrocyte depletion on a SEPAX system peripheral blood lymphocytes (PBLs) are stimulated ex vivo in a GMP laboratory with TKD/IL-2 for 3–5 days. After measuring of NK activation markers and sterility testing, the activated cells are washed and re-infused (i.v.) in the patient.

Figure 2

Scheme of the phase II clinical trial. In the pre-study part, the Hsp70 phenotype and the stage of the tumor disease is assessed. Only Hsp70-positive NSCLC patients in stage IIIA/B who received a radiochemotherapy (RCTx) and showed at least a stable disease are randomized into the trial. The interventional group receives four cycles of ex vivo TKD/IL-2 activated NK cells on a monthly basis; the control group gets best supportive care. Tumors will be assessed in the first year every 2–3 months by CT in both groups.