Anti-cancer agent comprising a tumour homing peptide having arsenic bonded to cysteine residues

A pharmaceutical composition comprising an anti-cancer agent and a pharmaceutically acceptable carrier, diluent and/or excipient wherein the anti-cancer agent comprises a cyclised tumour homing peptide having an arsenic atom bonded to two cysteine residues,

• wherein the anti-cancer agent has a structure as shown in formula I or formula II:
• wherein, in formula I:
• the sulfur atoms shown and to which the arsenic is bonded are thiol sulfurs of the two cysteine residues;
• the two cysteine residues in formula I are separated by between 2 and 20 amino acid residues represented by the curved line;
• and
• R is a stabilizing group selected from the group consisting of hydroxyl, C1 to C6 alkyl, C2 to C6 alkenyl, C2 to C6 alkynyl, C1 to C6 alkoxy, aryl, cycloalkyl, heterocyclic, and short chain peptides, each of which groups may be substituted or unsubstituted;
• and
• wherein, in formula II:
• the atoms and groups are as described for formula I;
• the capping group is formed from an amino reactive compound;
• and
• W is between 2 and 20 amino acid residues.

A process for producing an anti-cancer agent including the steps of:

• (a) contacting a tumour homing peptide comprising two cysteine residues with an arsenic compound;
• and
• (b) allowing the arsenic to become bound to each of the two cysteine residues to form a cyclised tumour homing peptide comprising a bound arsenic atom;
• to thereby produce the anti-cancer agent;
• wherein the arsenic compound is an oxide of arsenic;
• wherein the anti-cancer agent comprises a cyclised tumour homing peptide having an arsenic atom bonded to two cysteine residues,
• wherein the anti-cancer agent has a structure as shown in formula I or formula II:
• wherein, in formula I:
• the sulfur atoms shown and to which the arsenic is bonded are thiol sulfurs of the two cysteine residues;
• the two cysteine residues in formula I are separated by between 2 and 20 amino acid residues represented by the curved line;
• and
• R is a stabilizing group selected from the group consisting of hydroxyl, C1 to C6 alkyl, C2 to C6 alkenyl, C2 to C6 alkynyl, C1 to C6 alkoxy, aryl, cycloalkyl, heterocyclic, and short chain peptides, each of which groups may be substituted or unsubstituted;
• and
• wherein, in formula II:
• the atoms and groups are as described for formula the capping group is formed from an amino reactive compound;
• and
• W is between 2 and 20 amino acid residues.

A method of diagnosing a cancer including the steps of:

• administering an anti-cancer agent to a patient;
• (ii) allowing the anti-cancer agent to become localised to the cancer;
• and
• (iii) detecting the presence of the at least one radiolabelled atom of the anti-cancer agent, to thereby diagnose the cancer;
• wherein the anti-cancer agent comprises at least one radiolabelled atom, and comprises a cyclised tumour homing peptide having an arsenic atom bonded to two cysteine residues,
• wherein the anti-cancer agent has a structure as shown in formula I or formula II:
• wherein, in formula I:
• the sulfur atoms shown and to which the arsenic is bonded are thiol sulfurs of the two cysteine residues;
• the two cysteine residues in formula I are separated by between 2 and 20 amino acid residues represented by the curved line;
• and
• R is a stabilizing group selected from the group consisting of hydroxyl, C1 to C6 alkyl, C2 to C6 alkenyl, C2 to C6 alkynyl, C1 to C6 alkoxy, aryl, cycloalkyl, heterocyclic, and short chain peptides, each of which groups may be substituted or unsubstituted;
• and
• wherein, in formula II:
• the atoms and groups are as described for formula I;
• the capping group is formed from an amino reactive compound;
• and
• W is between 2 and 20 amino acid residues.

An anti-cancer agent comprising a cyclised tumour homing peptide having an arsenic atom bonded to two cysteine residues,

• wherein the anti-cancer agent has a structure as shown in formula I or formula II:
• wherein, in formula I:
• the sulfur atoms shown and to which the arsenic is bonded are thiol sulfurs of the two cysteine residues;
• the two cysteine residues in formula I are separated by between 2 and 20 amino acid residues represented by the curved line;
• and
• R is a stabilizing group selected from the group consisting of hydroxyl, C1 to C6 alkyl, C2 to C6 alkenyl, C2 to C6 alkynyl, C1 to C6 alkoxy, aryl, cycloalkyl, heterocyclic, and short chain peptides, each of which groups may be substituted or unsubstituted;
• and
• wherein, in formula II:
• the atoms and groups are as described for formula I;
• the capping group is formed from an amino reactive compound;
• and
• W is between 2 and 20 amino acid residues;
• wherein the capping group is an alkanoyl group which is optionally substituted.