Rational drug design solves the problem through the use of structural biology combined with many other disciplines to speed up the development process. The structure based drug involves the selection of target proteins based on their involvement in the biological pathway integral to the course of a disease, in-vitro/ in-vivo studies and uses the structural information as a blueprint to design drug candidate. Once the target molecule is characterized the specific ligands are required to be designed to interact with it for the inhibition of its function leading to the design of specific therapeutic agents. Peptides are usually highly specific and therefore exhibit relatively low systemic toxicity. They do not accumulate in the body as they have relatively short half lives. They are easily acceptable by body; side effects will be very low. We have targeted PLA2, COX-2, LOX, p38a p38b, for different cancers. The expression level of theses enzyme in the patients serum level were estimated and specific peptides against different enzymes were tested for inhibition studies. The biochemical assay was done for determining the Ki, IC50 and KD and very significant result were obtained which were comparable with the known drugs. The specific peptides also inhibited the proteins in serum in the presence of respective substrates, which were also confirmed on various cell lines. Hence, peptide can be considered to be potent therapeutic agent for different cancers.