1. Zeneca Pharma, Centre de recherches, Z. I. La Pompelle, BP 401, 51064 Reims, France, Zeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG, England, and CRC Centre for Cancer Therapeutics at the Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey SM2 5NG, England