‘Unmasking’ of the anti-CD3 targeting moiety by cleavage by active proteases in the TME led to selective killing of FOLR1-expressing tumour cells in vitro and in vivo, while sparing normal cells with low FOLR1 expression.74 Next-generation designs of masked antibodies that are capable of being selectively unmasked at tumour sites have been optimised. The gene discussed is FOLR1; the disease is neoplasm.