In vitro to clinical translation of combinatorial effects of doxorubicin and dexrazoxane in breast cancer: a mechanism-based pharmacokinetic/pharmacodynamic modeling approach

FIGURE 1. Concentration-response curves for DOX (top; blue) and DEX (bottom; red) as single agents in JIMT-1 (left) and MDA-MB-468 (right) cancer cell lines. All observed data are represented by solid circles while the smooth lines are model fittings.

FIGURE 2. 3D response surface plots using a competitive interaction model from the effects of single agent (DOX or DEX) and drug combination data in JIMT-1 and MDA-MB-468 cells. The concentrations used for single agents, DOX (0.005–1 µM) or DEX (6.25–200 µM) and their combinations are summarized in (A). The 3D response surface plots represent model simulations under the assumption of an additive interaction (ψ = 1) and the circles represent observed cell viability data for JIMT-1 (B, top) and MDA-MB-468 (B, bottom), respectively. Circles above the surface are red in color and indicate antagonistic interactions while circles at or below the surface are blue in color and indicate additive or synergistic interactions between DOX and DEX. ψ = 1.11 and ψ = 0.84 indicate interaction parameters estimated using a competitive interaction model for JIMT-1 and MDA-MB-468 cells, respectively, and are consistent with the patterns of observed data relative to the additive 3D surfaces as described in the Results section.

FIGURE 3. Schematic of the in vitro cellular-level pharmacodynamic model (PD) for the single and combinatorial effects of Doxorubicin (DOX) and Dexrazoxane (DEX) on human breast cancer cell lines (JIMT-1 and MDA-MB-468). Definitions of parameters for the model are listed in Table 2. The solid lines with arrows denote turnover of the indicated response. The green circle represents cell viability, the blue or red boxes represent transit compartments to describe the delay in the effects of DOX or DEX, respectively and the open solid rectangles represent the stimulation of death induced by DOX and/or DEX as single agents or combination and as indicated by dashed black arrows. The interactions of DOX and DEX on the stimulation of death of breast cancer cells is captured by ψ with ψ = 1, ψ < 1, or ψ > 1 indicating additive, synergistic, or antagonistic interactions, respectively.

FIGURE 4. (A) Simulated degradation kinetics of DOX (top) and DEX (bottom) at indicated concentrations in a cell culture media. The first-order degradation rate (Kdeg) for DOX and DEX were estimated and assumed to be constant at indicated concentrations. (B,C) Model fittings (using PD model) for the in vitro effects of the single agents, DOX (top) or DEX (bottom) at indicated concentrations over time on the cell viability of human breast cancer cell lines, JIMT-1 (B) and MDA-MB-468 (C). All observed data are represented by solid circles while the smooth lines are model fittings or simulations.

FIGURE 5. (A) Model fittings (using PD model) for the in vitro effects of the single agents, DOX, DEX or their combination at indicated concentrations over time on the cell viability of human breast cancer cell line, JIMT-1. All observed data are represented by solid circles while the smooth lines are model fittings or simulations. Black, Control; Blue, DOX; Red, DEX; Green, DOX + DEX. The concentrations used are indicated at the top of each graph for single agents and combinations. (B) Model fittings (using PD model) for the in vitro effects of the single agents, DOX, DEX or their combination at indicated concentrations over time on the cell viability of human breast cancer cell line, MDA-MB-468. All observed data are represented by solid circles while the smooth lines are model fittings or simulations. Black, Control; Blue, DOX; Red, DEX; Green, DOX + DEX. The concentrations used are indicated at the top of each graph for single agents and combinations.

FIGURE 6. (A) Model structure of clinical pharmacokinetics for doxorubicin (DOX) (3-compartment; Left, Top) and for Dexrazoxane (DEX) (2-compartment; Left, Bottom). Schematic of the in vitro cellular level pharmacodynamic model (PD) for the single and combinatorial effects of Doxorubicin (DOX) and Dexrazoxane (DEX) (Right) on breast cancer cells. Time-varying concentrations were utilized to drive the DOX + DEX TD model as represented by the green dashed arrow (B). Area under the effect curves for JIMT-1 (left) and MDA-MB-468 (right) % cell viability. 50 mg/m2 doxorubicin was administered alone or in combination with 500 mg/m2 dexrazoxane once every 3 weeks (Q3W) for three dosing cycles. DEX 0.1X, 1X and 10X represent scenarios where tumor concentrations of dexrazoxane were assumed to be 0.1, 1 and 10-fold of plasma concentrations, respectively.