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M. Padval



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    MINI 27 - Biology and Other Issues in SCLC (ID 152)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Small Cell Lung Cancer
    • Presentations: 1
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      MINI27.07 - Targeting Cancer Stem Cells in Small Cell Lung Cancer (ID 2727)

      16:45 - 18:15  |  Author(s): M. Padval

      • Abstract
      • Presentation
      • Slides

      Background:
      Small cell lung cancer (SCLC) is an extremely aggressive cancer with limited treatment options and poor outcome. The majority of SCLC patients respond to frontline chemotherapy, but experience rapid recurrence with metastasis, that may be attributed to the prevalence of cancer stem cells (CSCs). We previously demonstrated that PI3K/mTOR signaling is key for CSCs in cell culture and solid tumor models. As shown with a dual PI3K/mTOR inhibitor, VS-5584, inhibition of multiple PI3K isoforms and mTOR is necessary to achieve preferential targeting of CSCs.

      Methods:
      Antitumor activity of VS-5584 was assessed by in vitro proliferation assay as well as in multiple xenograft models in vivo, including patient-derived xenograft models. Anti-CSC activity was measured by the side-population CSC assay in vitro and in limiting dilution tumor initiation assay in vivo.

      Results:
      VS-5584 inhibited SCLC growth in vitro at sub-┬ÁM IC50, and was synergistic with cisplatin and etoposide in reducing the viability of SCLC cells. In vivo, single agent VS-5584 (20 mg/kg, 3 days per week dosing, MWF) demonstrated robust anti-CSC activity in the NCI-H841 SCLC model by reducing tumor initiating potential 70-fold (p=5x10[-6]). In tandem, VS-5584 partially reduced tumor growth of the NCI-H841 xenograft tumors. Furthermore, a VS-5584 dose dependency was evident, both for tumor initiating potential and tumor growth reduction. When VS-5584 was combined with cisplatin and etoposide, the standard of care agents for SCLC, an increased tumor growth inhibition was observed whether VS-5584 was concurrently administered or added sequentially following the dual chemotherapy. In the SCLC PDX model, combination treatment also suppressed the regrowth of the tumor following cessation of chemotherapy for extended duration. VS-5584 was found to preferentially induce apoptosis in CSCs in multiple cell lines, indicating that these cells are eliminated through cell death-related mechanism. Importantly, we demonstrated that for eradication of CSCs it is necessary to inhibit simultaneously multiple PI3K isoforms and mTOR pathways.

      Conclusion:
      The VS-5584 pre-clinical findings support the preferential targeting of CSCs in SCLC models and provide an important rationale for advancing clinical development of the compound. A phase 1 dose finding clinical trial is on-going to establish a Phase 2 dose of VS-5584 and explore target inhibition. VS-5584 alone or in combination with standard of care chemotherapy may lengthen the time to relapse and improve outcome for patients with small cell lung cancer.

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