Abstract
New drugs have recently been added that may eventually replace the two-decade dominance of cyclosporin in solid organ transplantation. This cornerstone of immunosuppression was introduced by Borel [1] and Calne [2] in the mid-70s. In 1989, Starzl et al., after 2 years of preclinical experimentation, introduced tacrolimus (originally designated as FK506 by the Fujisawa Pharmaceutical Company of Japan) as a potent immunosuppressant for liver transplants [3]. Also, in recent years, a variety of novel purine and pyrimidine biosynthesis inhibitors have been tested for transplantation therapy. The leading agent which appears to be replacing the 35-year position occupied by azathioprine is the semi-synthetic morpholinoethyl ester of mycophenolic acid (MPA), mycophenolate mofetil (MMF), introduced by Allison [4] and Sollinger [5], and developed by the Syntex Corporation (now Roche Pharmaceuticals). Others, affecting different intra- or intercellular messages amplifying immunity, are in the pipeline.