ICOS and cancer: BiTEs could be conjugated to different checkpoint inhibitors (for example, CTLA-4 or ICOS) or cytokines (for example, interleukin-2)28, the selectivity of the construct could be improved by targeting two separate tumour-associated receptors in addition to CD3, or target-independent immune activators could be developed to reactivate exhausted T cells, regardless of cancer indication29.