Researchers are now suggesting that antisense oligonucleotides may inhibit cell growth in acute and chronic myelogenous leukaemia (AML and CML). Encouraging results have been achieved with a phosphorothioate-modifiedc-mybantisense oligonucleotide used as a bone marrow purging agent in patients with CML. In addition, the antisense oligonucleotide OL(1)p53 inhibited the growth of human AML blast cellsin vitro, and has now been administered to patients with AML or myelodysplastic syndrome (MDS). The latest progress with these agents, being developed in affiliation with Lynx Therapeutics, was discussed at the IIR Ltd conference, entitled‘Antisense Therapy: Efficacy and Delivery of Antisense & Ribozyme Oligonucleotides’[London, UK; February 1995].