The epidermal growth factor receptor（EGFR）—tyrosine kinase inhibitors（TKIs） monotherapies have limited efficacy in the treatment of EGFR mutation-negative non-small cell lung cancers（NSCLCs）. In the present study, we aimed to investigate the combined effect of erlotinib（ER） and cabozantinib（CAB） on NSCLC cell lines harboring wild-type EGFR and to optimize the dosage regimens using pharmacodynamic（PD） modeling and simulation. Therefore, we examined the combined effect of ER and CAB on cell viability, cloning, apoptosis induction, migration and growth dynamics in H1299 and A549 cells. PD modeling and simulation were also performed to quantitatively describe the H1299 cells growth dynamics and to optimize the dosage regimens as well. Our results showed that CAB effectively enhanced the sensitivity of both cell lines to ER. The PD models fitted the data well, and some important parameters were obtained. The exponential（λ_0） and linear（λ_1） growth rates of H1299 cells were 0.0241 h^（–1） and 360 cells？h^（–1）, respectively. The Emax of ER and CAB was 0.0091 h^（–1） and 0.0085 h^（–1）, and the EC50 was 0.812 μM and 1.16 μM, respectively. The synergistic effect observed in the experiments was further confirmed by the estimated combination index φ（1.37）,（95% confidence interval： 1.24–1.50）, obtained from PD modeling. Furthermore, the dosage regimens were optimized using simulations. In summary, both the experimental and modeling results demonstrated the synergistic interaction between ER and CAB in NSCLCs without EGFR mutations. Sequential combinations of ER and CAB provided an option for the therapy of the NSCLCs with wild-type EGFR, which would provide some references for preclinical study and translational research as well.
A sensitive, rapid, and simple liquid chromatography tandem mass spectrometry（LC-MS/MS） method for simultaneous determination of sunitinib and its active metabolites in plasma of BABL/c nude mice was developed and validated. Plasma samples were pre-treated by protein precipitation with pazopanib and used as an internal standard. Separation was performed on a reversed phase C18 column with a mobile phase composing of 10 m M ammonium formate p H 3.25（adjusted with formic acid） and acetonitrile（65：35, v/v） at a flow rate of 0.5 mL /min. Triple quadrupole tandem mass in multiple reaction monitoring（MRM） mode with electrospray positive ionization was used to monitor all the compounds. The current LC-MS/MS method was highly selective and sensitive with lowest limit of quantitation（LLOQ） of 0.5 ng/mL for both analytes and reliable intra- and inter-day precision and accuracy validated by relative error（RE%） and relative standard deviation（RSD%）. Linearity of calibration curve was excellent（r0.99） within a concentration range of 0.5–1000 ng/mL. This method was successfully applied to a pharmacokinetics study on BABL/c nude mice given with single dose of oral administration of sunitinib at 20 mg/kg.
