Study protocol for THINK: a multinational open-label phase I study to assess the safety and clinical activity of multiple administrations of NKR-2 in patients with different metastatic tumour types

Abstract

Introduction: NKR-2 are autologous T cells genetically modified to express a chimeric antigen receptor (CAR) comprising a fusion of the natural killer group 2D (NKG2D) receptor with the CD3ζ signalling domain, which associates with the adaptor molecule DNAX-activating protein of 10 kDa (DAP10) to provide co-stimulatory signal upon ligand binding. NKG2D binds eight different ligands expressed on the cell surface of many tumour cells and which are normally absent on non-neoplastic cells. In preclinical studies, NKR-2 demonstrated long-term antitumour activity towards a breadth of tumour indications, with maximum efficacy observed after multiple NKR-2 administrations. Importantly, NKR-2 targeted tumour cells and tumour neovasculature and the local tumour immunosuppressive microenvironment and this mechanism of action of NKR-2 was established in the absence of preconditioning.

Methods and analysis: This open-label phase I study will assess the safety and clinical activity of NKR-2 treatment administered three times, with a 2-week interval between each administration in different tumour types. The study will contain two consecutive segments: a dose escalation phase followed by an expansion phase. The dose escalation study involves two arms, one in solid tumours (five specific indications) and one in haematological tumours (two specific indications) and will include three dose levels in each arm: 3×10⁸, 1×10⁹ and 3×10⁹ NKR-2 per injection. On the identification of the recommended dose in the first segment, based on dose-limiting toxicity occurrences, the study will expand to seven different cohorts examining the seven different tumour types separately. Clinical responses will be determined according to standard Response Evaluation Criteria In Solid Tumors (RECIST) criteria for solid tumours or international working group response criteria in haematological tumours.

Ethics approval and dissemination: Ethical approval has been obtained at all sites. Written informed consent will be taken from all participants. The results of this study will be disseminated through presentation at international scientific conferences and reported in peer-reviewed scientific journals.

Trial registration number: NCT03018405, EudraCT 2016-003312-12; Pre-result.

Keywords: car-t; chimeric antigen receptor; multiple injections; nkg2d; nkr-2; solid tumours.

Figure 1

The NKR-2 construct. NKR-2 design contains the full-length human natural killer group 2D (NKG2D) receptor linked to the signalling domain of CD3ζ that provides primary signalling (signal 1) to activate T cells upon ligand binding. The naturally expressed adaptor molecule DNAX-activating protein of 10 kDa (DAP10) provides secondary signalling (signal 2) which allows NKR-2 to work as a second-generation CAR.

Figure 2

NKR-2 different mechanisms of action. Apart from direct cytotoxicity against cancer cells, NKR-2 mode of action also involves reduction of blood vessel density indicative of an antiangiogenic activity, modulation of the immunosuppressive tumour microenvironment (TME) and induction of a long-term antitumour-specific memory immune response. MDSC, myeloid-derived suppressor cell.

Figure 3

Overview of the study design. AML, acute myeloid leukaemia; CRC, colorectal cancer; MDS, higher risk myelodysplastic syndrome; MM, multiple myeloma; ORR, objective response rate; RecD, recommended dose; TNBC, triple-negative breast cancer.

Figure 4

Overview of study phases. NKR-2 will be infused on days 1, 15 and 29. Tumour assessment will be done by tumour imaging and blood sampling for solid tumours and tumour imaging, blood, urine and bone marrow sampling for haematological tumours. BM, bone marrow; D, day; ICF, Informed Consent Form; M, month.