Validation of a predictive modeling approach to demonstrate the relative efficacy of three different schedules of the AKT inhibitor AZD5363.

PURPOSE: Intermittent dosing of inhibitors of the PI3K/AKT/mTOR network offers the potential to maximize the therapeutic margin. Here, we validate a predictive modeling approach to establish the relative efficacy of continuous and two intermittent dosing schedules of the AKT inhibitor AZD5363.

METHODS: A mathematical model of pharmacokinetics, pharmacodynamics and anti-tumor effect was constructed based upon experimental data from dosing regimens that give constant and transient inhibition of the AKT pathway.

RESULTS: Continuous and intermittent dosing of AZD5363 inhibited growth of BT474c xenografts and caused dose- and time-dependent inhibition of AKT substrate phosphorylation. Both dosing schedules inhibited proliferation, but a higher intermittent dose also induced apoptosis. The mathematical model described this pharmacodynamic and efficacy data well, for both monotherapy and combination dosing with docetaxel, and predicted that equivalent efficacy could be achieved at 1.3- and 1.7× continuous dose when AZD5363 was dosed intermittently for 4 and 2 days per week, respectively. These predictions were confirmed in two independent xenograft models. Moreover, the model also correctly predicted the relative efficacy of three different sequences of intermittent dosing of AZD5363 with docetaxel.

CONCLUSIONS: Equivalent anti-tumor activity to continuous dosing can be achieved at modestly increased intermittent doses of AZD5363. These intermittent dosing regimens may potentially overcome tolerability issues seen with continuous dosing and enable greater flexibility of dosing schedule in combination with other agents, including chemotherapy.