Conjugation Of Oxaliplatin With PEGylated-nanobody For Enhancing Tumor Targeting And Prolonging Circulation

Cancer is one of the most serious diseases that cause high mortality rate,and its morbidity rate and mortality rate are increasing year by year.At present,chemotherapy is the most important tumor treatment strategy.Platinum-base antitumor drugs,such as cisplatin,carboplatin and oxaliplatin,etc.can effectively inhibit the synthesis of DNA in tumor cells and induce cellular apoptosis.However,platinum-base drugs have many limitations in clinical application,such as high systemic toxicity,low effective accumulation and serious toxic side effects.These problems greatly limit the effective dose level and efficacy of platinum-base drugs.Using targeted therapy and extended circulation time strategies to solve the problems of platinum-base drugs and improve their pharmacokinetic properties are very important for achieving tumor therapy.In the first chapter,we introduced the development course,the mechanism and limitations of platinum-base antitumor drugs.Then the source,preparation process,structural characteristics and functions of nanobody as a new targeting agent were introduced.We also summarized the research and methods of nanobody-drug conjugation,and finally briefly introduced the strategy of extending the circulatory time and improving pharmacokinetic properties of nanobody in vivo.In the second chapter,the Pt(Ⅳ)prodrug of oxaliplatin was site-specifically conjugated to an anti-EGFR nanobody in order to achieve the specific tumor targeting.The nanobody-oxaliplatin prodrug conjugate(Pt@Nb)significantly increased the drug internalization in EGFR+cells,as well as reduced the non-specific uptake in EGFR’ cells.Therefore,the Pt@Nb can selectively kill EGFR+tumor cells with less toxicity to normal cells.In addition,a series of polyethylene glycol(PEG)with molecular weight from 10 K to 30 K was covalently attached to the nanobody in order to improve the pharmacokinetic profile of nanobody-drug-conjugate(NDC).Results indicated that the PEGylation prolonged the drug retention in vivo and improved the drug availability to different extent depending on the molecular size of PEG.Moreover,a fusion protein with anti-albumin nanobody(ALB1)was also constructed.The different behaves in prolonging drug retention have been investigated on the PEGylation and the ALB1-fusion.In the end,we took oxaliplatin,Pt@Nb and the selected Pt@NbP30K with the best pharmacokinetic properties as the research objects,and further explored the tumor inhibitory effect at the animal level.The suppressor effect of Pt@NbP30K to A431 tumor is obvious.This work provides important information for the design of platinum-based drug systems that can improve tumor-specific targeting,prolong circulation time in vivo,and achieve improved tumor treatment effects of drugs.