Biomarker Correlation with Outcomes in Patients with Relapsed or Refractory Multiple Myeloma on a Phase I Study of Everolimus in Combination with Lenalidomide

Abstract 3966 Background. Lenalidomide plus dexamethasone is approved for the treatment of relapsed and/or refractory multiple myeloma following prior therapy. Everolimus, an oral mTOR inhibitor, has been studied as a single agent in multiple myeloma but does not have significant activity. Based on previous preclinical studies showing synergistic anti-myeloma activity of mTOR inhibitors when combined with lenalidomide, we studied this combination as a non-steroid containing oral regimen in advanced multiple myeloma. In order to help determine the molecular mechanisms of response, we comprehensively assessed patient samples using gene expression analysis, western blotting, and immunohistochemistry of the mTOR pathway as well as cytokine analysis and measurement of T cell subsets. Methods. Patients with relapsed and refractory multiple myeloma were assigned to lenalidomide and everolimus for 21 days out of a 28 day cycle until disease progression or unacceptable toxicity (NCT00729638). We measured levels of p70S6K phosphorylated protein in peripheral blood mononuclear cells by western blotting before and during treatment. Immunohistochemical analysis for target proteins of the mTOR/AKT pathway was performed on bone marrow (BM) aspirates. Gene expression of CD138+ selected BM aspirates was analyzed on Affymetrix expression arrays prior to treatment. IGF-1 and IL-6 cytokine levels were determined by ELISA. T cell subsets were defined immunophenotypically over the course of treatment. Results. Twenty-six patients were evaluable for toxicity. The MTD was lenalidomide 15 mg and everolimus 5 mg for 21 days with a 7 day rest period. Nineteen patients finished at least two cycles of treatment and were evaluable for response. The overall response (OR) was 58% (1 CR + 3 PR + 7 MR). Three patients had SD and 5 patients had PD. The median progression free survival was 6.3 month at a median follow-up of 8.2 months. Biomarker data demonstrated that treatment with everolimus and lenalidomide consistently downregulated protein expression of phosphorylated p70S6K, a downstream target of mTOR. Microarray gene expression data was available for 12 patients, including 9 responders (MR, PR, SD) and 3 non-responders (PD). Gene set enrichment analysis showed enrichment for genes in the mTOR pathway gene set among the responders (p = 0.033, FDR 0.026). At the individual gene level, expression of members of the mTOR pathway, e.g. IGF1 (p = 0.034, FDR = 0.20) and RICTOR (p = 0.016, FDR = 0.15) was significantly higher in responding patients than non-responding patients. IHC for p-Akt (Ser 473) was evaluable in 10 patients, and 7 patients scored positively for pAkt expression. Given the small numbers, we were unable to correlate pAkt expression with response. DEPTOR was evaluable in 12 cases and strongly expressed in the majority of tumors. Quantification of T cell subsets was available for 25 patients. Treatment with everolimus and lenalidomide did not affect populations of CD4+ or CD8+ T cells or NK cells. Of the patients where IGF-1 levels were available, IGF-1 levels rose in the non-responding patients (N = 2) over the course of treatment; conversely, IGF-1 levels had an initial peak followed by decrease at time of best response in 4 of 5 responders. There was no difference in IL-6 levels between responders and non-responders. Conclusions. The combination of lenalidomide and everolimus showed durable responses in a heavily pretreated population. The doses of lenalidomide and everolimus used in this phase I study inhibited the downstream target of mTOR, p70S6K; was active in cases of constitutive mTOR activation; did not alter T cell subsets; and modulated IGF-1, but not IL-6 levels. With confirmation in larger patient numbers, this analysis may serve as a framework for guiding patient selection for future clinical trials investigating the role of mTOR inhibition in multiple myeloma. Disclosures: Off Label Use: The combination of everolimus and lenalidmoide is an off-label use for multiple myeloma. Richardson:Millennium Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy; Johnson & Johnson: Consultancy. Hideshima:Acetylon: Consultancy. Ghobrial:Noxxon: Research Funding; Bristol-Myers Squibb: Research Funding; Millennium: Research Funding; Noxxon: ; Millennium: ; Celegene: ; Novartis:. Munshi:Celgene: Consultancy; Millenium: Consultancy; Novartis: Consultancy; Onyx: Consultancy. Anderson:Celgene: Membership on an entity9s Board of Directors or advisory committees; Millennium: Membership on an entity9s Board of Directors or advisory committees; Onyx: Membership on an entity9s Board of Directors or advisory committees; Merck: Membership on an entity9s Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity9s Board of Directors or advisory committees; Novartis: Membership on an entity9s Board of Directors or advisory committees; Acetylon: Membership on an entity9s Board of Directors or advisory committees. Raje:Celgene: Membership on an entity9s Board of Directors or advisory committees; Novartis: Membership on an entity9s Board of Directors or advisory committees; Millenium: Membership on an entity9s Board of Directors or advisory committees; Astra Zeneca: Research Funding; Amgen: Membership on an entity9s Board of Directors or advisory committees; Acetylon: Research Funding.