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S. Chakrabarti



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    MA 12 - Circumventing EGFR Resistance (ID 665)

    • Event: WCLC 2017
    • Type: Mini Oral
    • Track: Advanced NSCLC
    • Presentations: 1
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      MA 12.06 - Using Population Dynamics Mathematical Modeling to Optimize an Intermittent Dosing Regimen for Osimertinib in EGFR-Mutant NSCLC (ID 9110)

      11:00 - 12:30  |  Author(s): S. Chakrabarti

      • Abstract
      • Presentation
      • Slides

      Background:
      Acquired resistance to therapy occurs with both first- and newer-generation epidermal growth factor receptor (EGFR) inhibitors. One strategy to delay the emergence of resistance is to use the most active/least toxic inhibitor and replace the traditional daily dosing with a biologically-rational dosing approach. Osimertinib is a covalent mutation-specific EGFR tyrosine kinase inhibitor (TKI) with activity against common EGFR plus EGFR-T790M mutations and less activity against the wild-type receptor. This drug is poised to become a 1[st] line EGFR TKI for treatment-naïve EGFR mutated lung adenocarcinomas. Therefore, it is an ideal candidate to devise rationale dosing schemes to maximize its efficacy and minimize tumor adaptation.

      Method:
      We explored pulse dosing of osimertinib, to delay the emergence of acquired resistance. We applied population dynamics mathematical modeling to this question, using key parameters (“birth rate” and “death rate”), established through cellular assays. These parameters are presumed to be dose-dependent. First, we experimentally determined the “birth-rates” of PC9 lung cancer cells, PC9 cells bearing the T790M resistance mutation, and PC9 cells that were resistant to osimertinib, with increasing concentrations of osimertinib (0 - 10μM, total of eight doses at half log intervals) using cell viability assays (MTS assay). Next, we determined cellular “death-rates” using annexin V/propidium iodide (PI) fluorescence-activated cell sorting (FACS). We then applied those parameters to our population dynamics model and simulated various treatment conditions with different dosing strategies, to identify the most effective regimens at delaying or preventing the emergence of resistance to osimertinib.

      Result:
      Using our mathematical model, we predicted that high-dose weekly treatment of osimertinib with a low maintenance dose led to minimal cell proliferation in comparison to daily dosing. Following this in silico prediction of the superiority of pulse dose treatment, we experimentally compared the frequency of emergence of resistance with different treatment dosing regimens, using a long-term cell culture system. Indeed, weekly administration of 5uM osimertinib to PC9 cells, followed by a maintenance dose of 0.25uM, suppressed the emergence of resistance for up to 5-7 weeks in culture.

      Conclusion:
      We have established a population dynamics mathematical model to predict optimal dosing regimens for osimertinib in treatment-naïve EGFR mutated lung cancers. The model was experimentally validated using a long-term culture system. Future validation in additional preclinical models (cell lines, xenografts and genetically engineered mice) can lead to rationale development of pulse-maintenance clinical trials of osimertinib and eventually establish a novel paradigm for clinical use of EGFR TKIs.

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