Scaffold for bifunctional molecules comprising pd-1 or cd28 and sirp binding domains

A bifunctional molecule comprising a single antigen binding domain that binds to a target specifically expressed on immune cells surface and a single immune-stimulating moiety,

• wherein the molecule comprises a first monomer comprising an antigen-binding domain covalently linked via C-terminal end to N-terminal end of a first Fc chain, optionally via a peptide linker, and a second monomer comprising a complementary second Fc chain devoid of antigen-binding domain and of the immune-stimulating moiety;
• wherein either i) the immune-stimulating moiety is covalently linked to the C-terminal end of said first Fc chain, optionally via a peptide linker;
• or ii) the single antigen binding domain comprises a heavy variable chain and a light variable chain and the immune-stimulating moiety is covalently linked to the C-terminal end of the light chain;
• wherein the target specifically expressed on immune cells surface is selected from the group consisting of PD-1, CD28, CTLA-4, BTLA, TIGIT, CD160, CD40L, ICOS, CD27, OX40, 4-1BB, GITR, HVEM, Tim-1, LFA-1, TIM3, CD39, CD30, NKG2D, LAG3, B7-1, 2B4, DR3, CD101, CD44, SIRPG, CD28H, CD38, CD3, PDL2, and PDL1;
• and
• wherein the immune-stimulating moiety is selected from the group consisting of SIRPγ, SIRPα, SIRPβ, CD80, CD86, LIGHT, CTLA-4, TIGIT, CD40L, OX40L, APRIL and GITRL or a fragment thereof comprising the extracellular part thereof or a variant thereof having at least 80% of identity with the wildtype protein or the extracellular part thereof.