With more than 130 antibodies in clini-cal development, designer antibodiesconstitute the most rapidly advancingdrug class in the pharmaceutical indus-try and the second largest drug classafter vaccines. Monoclonal antibodieshave shown the best track record (17marketed out of the 18 approved since1990). Currently, their use is also wide-spread, encompassing diverse clinicalsettings, including oncology and trans-plantation. They have also found a veryrich niche in certain conditions relatedto inflammatory, infectious and cardio-vascular diseases. The success rate ofdrug approval by the US FDA for chi-meric and humanized antibodiesremains well above 20% compared withthat of small molecular drugs at 11%