The present invention relates to novel peptides which impair PBX dependent regulation of gene transcription and thus have utility in the treatment or prevention of disorders in which aberrant cell division occurs. In particular the invention provides a peptide comprising the amino acid sequence (I): Y1X1X2KWX3X4X5X6X7Y2 (I) wherein the sequence X1 to X7 is an amino acid sequence comprising at least 7 amino acids which may optionally be interrupted by one or two amino acid residues between one or more of the 9 amino acid positions defined herein X1 is selected from W T PE KQI W PQT H Rl and absent X2 is an amino acid with an aromatic side chain or cysteine X3 is a hydrophobic amino acid X4 is an amino acid with a charged side chain X5 is an amino acid with a basic side chain X6 is an amino acid or absent X7 is one or more amino acids or absent and Y1 and Y2 are each either absent or a peptide comprising a cationic polymer of basic amino acids provided that at least one of Y1 and Y2 is present.
