The ZD1839 concentration samples were vortexed

and centrifuged at 1,600 g for 15 min at room temperature, 50 μL of the supernatant was diluted with 150 μL of water, and 5 μL of the solution was injected onto a Kinetex XB C-18 (30 × 2.1 mm, 2.6 μm) analytical column (Phenomenex, Torrance, CA, USA). An Agilent 1290 Infinity HPLC system (Agilent, Santa Clara, CA, USA) was equipped with a controller, two pumps, a column compartment, and a degasser. The column was maintained at 40°C by the column compartment. This system was coupled to an API 5500 Qtrap mass spectrometer (AB Sciex, Foster City, CA, USA) equipped with a turbo-electrospray interface in positive ionization mode. The aqueous mobile phase was water with 0.1% formic acid (A), and the organic mobile phase was acetonitrile with 0.1% formic acid (B). The gradient was as follows: starting at 15% B and increased to 95% B for 0.6 min, MK0683 maintained at 95% B for 0.1 min, then decreased to 15% B within 0.1 min. The total flow rate was 1.4 mL/min. Data was collected using multiple reaction monitoring (MRM) with transitions m/z 854.4 → 104.9 for paclitaxel and m/z 808.5 → 527.2 for docetaxel (internal standard). The calibration curve, which ranged from 0.03 to 24 μM for paclitaxel, was fitted to a 1/x weighted quadratic regression model. This calibration curve was used to quantitate paclitaxel concentration

levels in the plasma, tumor, liver, and spleen samples. Data analysis Pharmacokinetic parameters were estimated by non-compartmental methods as described by Gibaldi and Perrier [35] using WinNonlin

version 3.2 (Pharsight Corporation, Mountain View, CA, USA). Tissue to plasma ratios were determined by dividing the AUC0-8 (area under the concentration-time profile from 0 to 8 h) of the tissue of interest by the AUC0-8 of plasma. Myosin The percent tumor growth inhibition (%TGI) was calculated on the last day of the study (day 17) using the following formula as previously described [36]: (2) TVvehicle is the tumor volume for the vehicle-treated animals on day 17, TVinitial is the initial tumor volume at the start of the treatment, and TVtreatment is the tumor volume of the treatment 4SC-202 nmr groups on day 17. Normalized efficacy was determined with respect to plasma and tumor exposures for both Cremophor EL:ethanol and nanosuspension delivery. Normalized efficacy was determined by dividing TGI by either plasma or tumor AUC0-8. Results Formulation preparation for paclitaxel IV crystalline nanosuspension and stability evaluation A theoretical calculation was performed to estimate the target particle size at which a nanoparticle should rapidly dissolve in the bloodstream (i.e., < 10 s under non-stirred condition) upon intravenous administration.