Preparation And Evaluation Of Relugolix Nanosuspensions For Improved Oral Bioavailability

Relugolix(RLGL)is mainly used for the treatment of hormone dependent advanced prostate cancer and endometriosis,but its low water solubility and the role of P-glycoprotein(P-gp)affect its oral bioavailability.Therefore,this article adopted nanocrystalline technology to prepare relugolix nanosuspensions(RLGL-NS)to improve the oral bioavailability of relugolix.And RLGL-NS was evaluated in vitro and in vivo.Firstly,the suitable stabilizers was selected based on the stability of the nanosuspensions.Then,a single factor experiment was conducted to screen and optimize the prescription and technology to obtain a preliminary prescription.Based on this,the optimal prescription and technology were obtained through orthogonal experiments.The optimal formulation and technology of RLGL-NS consisted of Span85(33.3%w/w),TPGS(33.3%w/w),relugolix(33.3%w/w),and loading of relugolix(0.2 mg/mL).Pharmaceutical evaluation showed that RLGL-NS had a clear and transparent appearance with a light blue milky light.The average particle size was around 112 nm,the particle size polydispersity coefficient(PDI)was less than 0.3,and the Zeta potential was-12.51 mV.The morphology of the RLGL-NS can be observed to be spherical and uniform in size by transmission electron microscopy.The XRD and DSC analysis results indicated that the drugs in RLGL-NS mainly existed in an amorphous form.The stability test results showed that RLGL-NS had good thermodynamic stability with mini particle size change within 7 days under 4℃conditions.According to the solubility experiment results,the solubility of RLGL-NS in water(pH7)was 6.4 times higher than that of RLGL,significantly improving the water solubility of relugolix.The in vitro dissolution test results showed that in the buffer containing 0.05%SDS(sodium dodecyl sulfate)(pH1.2,pH6.8,pH7.4),the drug dissolution of RLGL-NS was higher than that of RLGL.In the dissolution medium at pH 6.8,the cumulative dissolution of RLGL-NS was 63%,and the cumulative drug dissolution of RLGL was 3.4%,significantly improving the drug dissolution.Secondly,the in vitro permeability of RLGL-NS and RLGL was evaluated through the parallel artificial membrane permeability assay(PAMPA).A single factor experiment was used to screen the formulation for preparing parallel artificial membranes.The formulation consisted of egg yolk lecithin:dodecane(2%m/v),DMSO(5%m/v),and 10 μL coating volume.Then,the successful establishment of the model was validated using propranolol hydrochloride,and the in vitro permeability of RLGL-NS was evaluated using the model.The experimental results indicated that the effective permeability coefficient(lgPe)of RLGL increased from-6.47±0.06 to5.15±0.04 after preparation of the nanosuspensions,improving from low permeability to medium permeability.Meanwhile,the influence of excipients on its permeability was not significant.Once again,the preliminary safety of RLGL-NS and RLGL,as well as the uptake of Caco-2 cells,were evaluated through in vitro cytological evaluation experiments.The results of the cytotoxicity experiment showed that within the concentration range of 0.5-20μg/mL,RLGL-NS and RLGL showed good safety after incubation with Caco-2 cells for 24 hours,with cell survival rates greater than 80%.The results of the cell uptake test showed that the preparation of RLGL into nanosuspensions could increase the uptake of Caco-2 cells from 1.5%to 6%,which was about four times higher.At the same time,excipients also had a certain promoting effect on uptake,increasing the uptake rate from 1.5%to 2.4%,approximately 60%.It might be that the inhibitory effect of TPGS on P-gp enhanced the uptake of RLGL by Caco-2 cells.This proved that the combination of RLGL nanoparticle and P-gp inhibitor could enhance the uptake efficiency of Caco-2 cells,which was beneficial for oral administration.Finally,the results of in vivo pharmacokinetic experiments in animals showed that the maximum blood drug concentration(Cmax)of the RLGL-NS administration group was 778.9 ± 269 μg/L,which was 2.5 times that of the RLGL suspension group and 1.8 times that of the RLGL physical mixture(suspension of RLGL and excipients)group.In addition,compared to the peak time of 2.0 hours in RLGL group,the RLGLNS group advanced by 1 hour.The the area under the concentration time curve(AUC(0t))of RLGL-NS group was 4283.664±61.795 μg/L·h,which was 1.34 times that of the physical mixing group and 1.73 times that of RLGL group,respectively.In summary,prepared relugolix nanosuspensions which has been demonstra-ted through in vitro and in vivo evaluations to improve the oral bioavailability of RLGLNS with low toxicity and side effects.