The Synthesis And Antitumor Effect Of Docetaxel-DHA-dextran Conjugates

Cancer is still one of the major diseases faced by human beings,causing serious adverse effects in both human health and social development.The established treatment strategies for cancer can be divided into four categories:surgery,radio-therapy,chemotherapy and immunotherapy.Among them,chemotherapy is still the main way to treat cancer.Taxanes,including paclitaxel and docetaxel,are the most commonly first-line drugs used for cancer treatment.Docetaxel is a semi-synthetic paclitaxel derivative whose anti-tumor mechanism is similar to that of paclitaxel.Docetaxel's anti-tumor mechanism is similar to paclitaxel.It binds to tubulin,which keeps cell division in G2/M phases,causing it to fail to replicate,and eventually causing cancer cell death.Studies showed that docetaxel has a broad spectrum of activity against a variety of tumors,such as breast cancer,ovarian cancer and non-small lung cancer and its antitumor effect is better than paclitaxel.However,its water solubility is extremely poor,and Tween 80 is needed as a co-solvent.The co-solvent can cause hypersensitivity and patients should take dexamethasone and diphenhydramine for 3 consecutive days to prevent hypersensitivity before injecting docetaxel.The lack of targeted distribution in normal tissues and tumor tissues is another clinical challenge.Therefore,the purpose of this paper is to improve the solubility of docetaxel in water by modifying the chemical structure of docetaxel,and try to improve the characteristics of its targeting tumor tissue.Development of polysaccharide drug conjugates has increased in the recent years due to the demonstrated biocompatibility,biodegradability,safety and low cost of the biopolymers.Compared with normal tissues,solid tumor tissue has abundant blood vessels,wide vascular wall gap,poor structural integrity,and lack of lymphatic drainage,resulting in high permeability and retention of macromolecular substances.This phenomenon is called the enhanced permeability and retention effect of tumors,referred to as EPR effect.Based on the existence of this phenomenon,we designed to couple docetaxel and water-soluble polysaccharide dextran and prepared into a polysaccharide-drugs conjugate,which can improve the water solubility of docetaxel,and can increase the accumulation of drugs in the tumor site,reducing its systemic toxicity.Dextran(Dex)is a kind of common polysaccharide and it is used as the plasma volume dilator clinically.It has the advantages of low cost,established safety profiles,good water solubility,and narrow molecular weight distribution range.Therefore,we chose different molecular weight dextran as the carrier of docetaxel.Docosahexaenoic acid(DHA),an omega-3 C22 natural fatty acid serving as a precursor for metabolic and biochemical pathways.Studies have reported that DHA can inhibit the activity of a variety of cancer cells and paclitaxel-fatty acid conjugate(DHA-paclitaxel)can improve the activity of antitumor effect in vivo.So we used DHA as an active targeting and synergist for polymers to further verify whether DHA can improve the antitumor effect of docetaxel.Firstly,based on the above explanation,we synthesized functionalized dextran with different molecular weights(70K,100K and 250K)as a drug carrier,including CDex7,Dex10,CDex10 and CDex25;synthesized linker LLG2 with lysine as the connecting arm base structure and connected the linker to DHA;synthesized the 2'hydroxyl-exposed docetaxel DTX-3.Finally we synthesized four dextran-DHA-docetaxel conjugates and the structure of the compound was confirmed by 1H NMR.Then,the DTX-Linker-Dex conjugates were dissolved in DMSO-d6 with the internal standard p-dimethoxybenzene,and the drug loading was analyzed by 1H NMR.The drug loadings of DTX-DHA-CDex7,DTX-DHA-CDex10,DTX-DHA-Dex10 and DTX-DHA-CDex25 conjugates were 11.3%,10.7%,12,5%and 9.3%,respectively.The solubility of the four conjugates in saline was tested to be>55 mg/ml.The nanometer diameter meter showed that the size of the above four conjugates were 334 nm,281 nm,194 nm,and 588 nm,and the polydispersity was all less than 0.25.The zeta potentials were-28.9 mV,-24.5 mV,-13.7 mV,and-36.6 mV,respectivelyWe established tumor model bearing lung cancer cells H460 for anti-tumor evaluation in vivo,the dose was 10 mg/kg,the tail vein was injected once a week,and the mice were sacrificed on the 27th day after the administration.The tumor inhibition rates of DTX-DHA-CDex7,DTX-DHA-CDex10,DTX-DHA-Dex10,DTX-DHA-CDex25 and DTX were 51.0%,51.9%,47.7%,56.0%and 61.7%,respectively.Compared with the control group,the mice weight loss of DTX-DHA-CDex7,DTX-DHA-CDex10,DTX-DHA-Dex 10,DTX-DHA-CDex25 and DTX were 28.8%,23.7%,17.5%,22.6%and 56.2%,respectively.The results showed that there was no significant difference in the tumor inhibition rate between the conjugates and DTX,but it can be seen from the change in the body weight of the mice that the conjugates can significantly reduce its toxic and side effects.In addition,the results also showed that the different molecular weight conjugates of tumor inhibition rate have no significant difference.In conclusion,we improved the water solubility of docetaxel by synthetic conjugates and decreased its toxicity,which provided an important basis for further screening of different linkers.