Abstract CT309: Influencing the tumor microenvironment: A phase II study of copper-depletion using tetrathiomolybdate (TM) in patients (pts) with breast cancer (BC) at high risk for recurrence

Abstract

Abstract Background: Bone marrow derived endothelial progenitor cells (EPCs) and copper-dependent angiogenic pathways are critical to the metastatic process. Copper depletion (CD) therapy inhibits tumor metastases in preclinical models. We hypothesized that TM-associated CD would reduce EPCs in pts at high risk for BC recurrence, and we explored the relationship between CD and its effects on the tumor microenvironment in pre-clinical models. Methods: In this single arm, phase II study, BC pts at high risk for recurrence, defined as node positive triple negative (TN), stage 3 and 4 with no evidence of disease (NED) were enrolled on a trial of CD with TM. We CD’d to maintain ceruloplasmin (Cp) between 5-17 mg/dl for 2 years or until relapse. The primary endpoint was change in EPCs measured before and during treatment with TM. Secondary endpoints included tolerability, safety, and efficacy of CD. Laboratory studies: MDA-LM2-luciferase cells were implanted into CB17-SCID mice gavaged with water or TM. The tumors were quantified by bioluminescence images (BLI). We measured Cp oxidase to determine copper status. Western blots were used to assess LOX activity, and IHC was used to quantify collagen cross-linking and CD11b+ macrophage infiltration. Results: We enrolled 43 pts. Treatment duration was 24 cycles (each cycle is 28 days) for the primary study. A total of 752 cycles were completed in 2 years. The mean age was 49 (range 29-66). Mean Cp level decreased from 29 at baseline to 16 (p<0.001) at 4 weeks. 94% of pts achieved CD by cycle 2. TM was well tolerated in most pts and the only grade 3 and 4 toxicities were neutropenia (3.9%) and anemia (0.1%). CD was most effective in TNBC pts with significantly reduced time to CD (P=0.0153). At one year of analysis, TM reduced EPCs (p=0.044). The 2-year analysis of effect of TM on EPCs is ongoing. The 2 year PFS for the entire cohort from the start of TM treatment was 81%. The overall survival from the start of treatment was 90.6% with median follow up of 4.5 years. In pre-clinical models, TM had no effects on the primary tumor, but decreased secondary metastases as seen by BLI. Western blots demonstrated decreased LOX, and IHC showed reduced collagen cross-linking with less CD11b+ macrophage recruitment.Conclusion: TM is safe, well tolerated and effective in achieving CD in breast cancer patients, and appears to affect the tumor microenvironment in pre-clinical models. Molecular subtype may affect CD and TM may be most effective in TN patients. Citation Format: Nancy Chan, Naomi Kornhauser, Maureen Ward, Amy Willis, Tessa Cigler, Ellen Chuang, Anne Moore, Diana Donovan, Sarah E. Schneider, Christina Lam, David J. Warren, Anna Rubinchik, Sandra Hurtado Rua, Sharrell Lee, Maureen Lane, Vivek Mittal, Linda Vahdat. Influencing the tumor microenvironment: A phase II study of copper-depletion using tetrathiomolybdate (TM) in patients (pts) with breast cancer (BC) at high risk for recurrence. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT309. doi:10.1158/1538-7445.AM2014-CT309