Silicon-fluoride acceptor substituted radiopharmaceuticals and precursors thereof

A ligand-SiFA conjugate compound represented by formula (1)

• wherein:
• RL is a ligand moiety which is capable of binding to prostate-specific membrane antigen (PSMA) and which has a structure represented by formula (6):
• wherein
• r is an integer of 2 to 6;
• R1L is CH2, NH or O;
• R2L is C or P(OH);
• R3L is CH2, NH or O;
• R4L is a linear C1 to C7 alkanediyl group which carries a —COOH substituent;
• and wherein the dashed line marks the bond which attaches the moiety to the remainder of the conjugate compound;
• RSiFA has a structure represented by formula (7):
• wherein
• XS is F, OH or H;
• R1S and R2S are independently a linear or branched C3 to C10 alkyl group;
• R3S is a C1 to C20 hydrocarbon group, wherein up to 3 carbon atoms may be replaced by a heteroatom selected from N, O and S;
• and wherein the dashed line marks the bond which attaches the moiety to the remainder of the conjugate compound;
• L is a linking moiety;
• RH is a hydrophilic moiety which comprises
• (i) a linear or branched sequence of
• 2 to 10 hydrophilic amino acid units AH, each of which is independently derived from a natural or non-natural amino acid carrying a hydrophilic side chain,
• and optionally one amino acid unit AN derived from a natural or non-natural amino acid which is devoid of a hydrophilic side chain,
• wherein the hydrophilic amino acid units and, if present, the unit AN, are bound to each other via a direct covalent bond or via a coupling unit;
• and which optionally further comprises
• (ii) one or more hydrophilic residues RT, each of which may be bound to an amino group, a carboxylic acid group, or to a functional group of a hydrophilic side chain of an amino acid unit;
• or a pharmaceutically acceptable salt thereof.