The present invention provides peptides of general formula (I) and salts thereof, wherein: R1 and R2, taken together, form a birradical linker； and R2′； is hydrogen； or, alternatively, R1 is selected from hydrogen, —；C(═；O)—；CH2—；NH—；C(═；O)—；(C1-C5)alkyl, and —；C(═；O)—；(C1-C20)alkyl； one of R2 and R2′； is hydrogen and the other is selected from —；C(═；O)NR3R4, and —；C(═；O)OH； and R3 and R4 are same or different and are selected from hydrogen and (C1-C10)alkyl. These peptides are highly efficient in binding and inhibiting FoxP3, being efficient in inhibiting and blocking Treg cell functionality, which make them useful in the treatment of cancer. The present invention also provides constructs comprising the peptide of formula (I) as well as combinations comprising the peptide of formula (I), the construct or both.
