Empowering T and NK cells for adoptive cell transfer (ACT) through engineering with PD-1:4-1BB
The adoptive transfer of selected highly tumor-reactive T and NK cells and checkpoint inhibitors achieve remarkable tumor regression in patients. Also recently, viral-antigens as targets in infectious indications have shown high interest to use engineered T and NK cells. Experimentally generated high-affinity T cell receptors (TCR), CAR constructs and NK cells have been advantageous by boosting effector function and proliferation, but they may bear an increased risk of unwanted toxicities. Functional inactivation of T cells may occur due to inter alia blockade of TCR signaling and upregulated inhibitory checkpoint receptors on activated T cells and their respective ligands expressed on tumor or viral-infected cells. To break the immunosuppressive axis in ACT, co-stimulation and co-inhibition signals controlling the strength and duration of the T cell response should be considered to improve the efficacy and safety of ACT.
Costimulation can provide pivotal survival signals to the T cell and can prolong effector functions. Tailored costimulation, when and where it is required, can be achieved by engineered costimulatory proteins that are activated by locally expressed ligands. The object of the invention was therefore to provide a fusion construct comprising the native co-inhibitory PD-1 receptor extracellular domain and the transmembrane domain operably linked to the intracellular domain of the costimulatory 4-1BB (CD137) receptor. The PD-1:4-1BB chimeric protein is one those engineered proteins which is designed to turn the native PD-1 inhibitory signal into a costimulatory signal for T cell activation and optimal T cell function. The PD-1:4-1BB chimeric receptors upgraded low-avidity T cells and enhanced TCR-triggered cytokine secretion in a tumor cell model. In a second set of experiments, TCR and CAR engineered T cells have been successfully used to enhance IFNγ production and killing in a cell culture model against a viral target.
The features of 4-1BB signaling apparently apply in the context of CAR-T cell engineering and NK cells. With this respect, the costimulatory receptors may add a considerable improvement of CAR-T as well as NK cell therapies. In addition, checkpoint inhibition therapies may benefit from a combination with PD-1:4-1BB engineered T and NK cells. The supportive effect of PD-1:4-1BB on T and NK cell function make it an attractive tool for ACT.
The technology is open for licensing in the fields of CAR-T and NK cell therapies, further co-development is highly welcomed. The technology has been licensed in the field of TCR-engineered cell therapies.
The costimulating concept especially using PD-1:4-1BB has been tested in the context of TCR- and CAR-engineered T cells. Target cells expressing tumor- or viral-antigens have been used and killing experiments have been successfully performed. In an human melanoma xenograft model, PD-1:4-1BB fostered intratumoral T cell proliferation and enabled better tumor control with reduction of tumor volume.
Further costimulatory constructs consisting of PD-1:CD28 and CD40L:CD28 have also been developed and characterized.
Patents are pending in US, EP, CA, CN, JP, NZ and AU, with priority from March 2016.
Schlenker et al. (2017), Cancer Res. 77:3577-3590