A peptide which comprises a N-terminal fragment of SEQ ID NO 1 of up to 19 amino acids in length. This peptide could for example have the amino acid sequence of SEQ ID NO 2 (Sar1a1) or SEQ ID NO 6 (Sar1a2). Both SEQ ID NO 2 and SEQ ID NO 6 are demonstrated to kill human lung carcinoma cells (A549, ATCC) in cell death assays. Also disclosed is a biologically active complex comprising a peptide which comprises a truncated form of SEQ ID NO 1 of up to 19 amino acids in length in combination with oleic acid or a salt thereof. The complexes may be uses in therapy or the treatment of cancer. The oleate salt may be water soluble and may be an alkali metal salt such as sodium oleate or potassium oleate. MAGWDIFGWFRDVLASLGLWNKH (SEQ ID NO 1) MAGWDIFGWFRDVLA (SEQ ID NO 2) WFRDVLASLGLWNKH (SEQ ID NO 6)
