Magic bullets are drugs that can be administered on a micro local scale near the tumour by exploiting the different surface antigens that cancers expose. The drug attaches via an mAb (attached to the pro-drug) and then a conjugated enzyme cleaves or converts the pro drug to a drug. This would eliminate a lot of side effects from chemotherapy.
Use in clinical trials. Some mAbs have started to be used in clinical trials, almost 40 years after they were first proposed. My question is simply; have there been any cases of mAbs being used as a successful treatment for any disease? If not, what makes the R&D of this drug type so difficult?