We demonstrate herein that daily administration of PBT-3 for 8 days to NU/NU mice bearing solid tumours derived from the s.c. administration of the leukemic cell line K562 results in inhibition of growth of the tumours in vivo, and this inhibition lasts for 60 days after stopping treatment with PBT-3 before recovery of tumour growth is re-established. Similar findings were observed when the mice were treated with Gleevec (STI-571). These results provide new evidence that PBT-3 is effective in controlling solid tumour growth in vivo and suggest that the PBT family may be useful in the development of new drugs in cancer therapy. (c) 2005 Elsevier Inc. All rights reserved.