2567 Background: MLN0128 (INK128) is an investigational oral, potent, and highly selective inhibitor of mammalian target of rapamycin complex 1 and 2 (mTORC1/2) currently in clinical investigation. In the phase1 study INK128-001, MLN0128 was administered once daily (QD), once weekly (QW), QDx3D/week, and QDx5D/week, with respective MTDs of 6, 40, 16, and 10 mg. To guide selection of dose/schedule for further investigation, PD modulation in skin (pS6, p4EBP1, pNDRG1, pPRAS40) was put into context of clinical PK in INK128-001. A preclinical translational dynamic-PK efficacy model was used to describe the relationship and determine PK drivers of efficacy in tumor xenograft models. This model was implemented using human PK parameters to predict tumor volume-time curves, which was utilized to help determine the optimal MLN0128 dose/schedule. Methods: Phoenix NLME v1.1 was used for compartmental modeling of clinical and preclinical PK data, and modeling the preclinical PK-efficacy relationship of MLN0128. PD activity in skin was measured by immunohistochemistry, reported as H scores. Tumor growth curves were simulated using NONMEM v7.2; predicted tumor growth curves were plotted in S-Plus v8.1. Results: Clinical skin PD data suggests exposure dependent inhibition of pS6, and p4EBP1. A two compartment PK model adequately described the PK characteristics of MLN0128 [mean (%CV) ka: ~5.305 h-1 (114), k12: ~0.490 h-1(85), k21: ~0.67 h-1(69), V/F: ~180 L (44), Tlag: 0.317 h (73)]. Simulation of human tumor volume-time curves suggest efficacy is dependent on schedule and that MLN0128 administered in more frequent schedules (QD, QDx5D) provides stronger antitumor effect vs less frequent schedules (QW, QDx3D). Conclusions: The results indicate that per unit MLN0128 plasma exposure, QD and QDx5D may be optimal in comparison with QDx3D and QW dosing. However, these results will also need to be put into context with the overall safety profile and respective MTDs and RP2Ds for each schedule with their resultant achievable total cycle dose by schedule. Clinical trial information: NCT01058707.
Inhibition of human tumor growth in nude mice by a conjugate of doxorubicin with monoclonal antibodies to epidermal growth factor receptor.
