A compound of formula (I) is described, wherein Y represents a macrocycle, the ring of which has 9 to 36 atoms, and is functionalized by three amine or COOH functions Rc represents a group of formula H—Xa—Xb—Xc—Xd—Xe—(Xf)i—, i represents 0 or 1, Xa is in particular lysine, arginine, or ornithine residues, Xb is in particular glycine, asparagine, L-proline or D-proline residues, Xc and Xd are in particular tyrosine, phenylalanine or 3-nitrotyrosine residues, Xe and Xf are in particular amino acid residues: NH2—(CH2)n—COOH, n ranging from 1 to 10, or NH2—(CH2—CH2—O)m—CH2CH2COOH, m ranging from 3 to 6, provided that at least one of the amino acid residues Xa, Xb, Xc and Xd is different from the corresponding amino acid in the sequence of the natural CD40 143Lys-Gly-Tyr-Tyr146 fragment(SEQ ID NO: 1).
