New treatments based on stem cell technology moved nearer to becoming a realistic possibility, with a UK research group reporting last week that it had successfully cloned a human blastocyst and South Korean researchers reporting that they had created stem cells to match individuals for the first time.

Researchers from the University of Newcastle upon Tyne's Centre for Life reported that they had removed the nuclei from oocytes obtained from 11 women and replaced them with DNA from embryonic stem cells.

Three of the resulting clones lived and grew in the laboratory for three days, and one survived for five days. The blastocyst had identical DNA to the stem cell line, proving that it had resulted from cloning. The study was published on 19 May in Reproductive and BioMedicine Online (http://www.rbmonline.com/, search for article number 1872).

The critical factor for successful cloning seemed to …