Efficacy of T-DM1 in the Brain Microenvironment(preclinical)

[Lani]

just in mice so far, but hopeful!

J Natl Cancer Inst. 2015 Nov 7;108(2). pii: djv313. doi: 10.1093/jnci/djv313. Print 2016 Feb.
Preclinical Efficacy of Ado-trastuzumab Emtansine in the Brain Microenvironment.
Askoxylakis V1, Ferraro GB1, Kodack DP1, Badeaux M1, Shankaraiah RC1, Seano G1, Kloepper J1, Vardam T1, Martin JD1, Naxerova K1, Bezwada D1, Qi X1, Selig MK1, Brachtel E1, Duda DG1, Huang P1, Fukumura D1, Engelman JA1, Jain RK2.


Abstract
BACKGROUND:
Central nervous system (CNS) metastases represent a major problem in the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer because of the disappointing efficacy of HER2-targeted therapies against brain lesions. The antibody-drug conjugate ado-trastuzumab emtansine (T-DM1) has shown efficacy in trastuzumab-resistant systemic breast cancer. Here, we tested the hypothesis that T-DM1 could overcome trastuzumab resistance in murine models of brain metastases.
METHODS:
We treated female nude mice bearing BT474 or MDA-MB-361 brain metastases (n = 9-11 per group) or cancer cells grown in organotypic brain slice cultures with trastuzumab or T-DM1 at equivalent or equipotent doses. Using intravital imaging, molecular techniques and histological analysis we determined tumor growth, mouse survival, cancer cell apoptosis and proliferation, tumor drug distribution, and HER2 signaling. Data were analyzed with one-way analysis of variance (ANOVA), Kaplan-Meier analysis, and Coefficient of Determination. All statistical tests were two-sided.
RESULTS:
T-DM1 delayed the growth of HER2-positive breast cancer brain metastases compared with trastuzumab. These findings were consistent between HER2-driven and PI3K-driven tumors. The activity of T-DM1 resulted in a survival benefit (median survival for BT474 tumors: 28 days for trastuzumab vs 112 days for T-DM1, hazard ratio = 6.2, 95% confidence interval = 6.1 to 85.84, P < .001). No difference in drug distribution or HER2-signaling was revealed between the two groups. However, T-DM1 led to a statistically significant increase in tumor cell apoptosis (one-way ANOVA for ApopTag, P < .001), which was associated with mitotic catastrophe.
CONCLUSIONS:
T-DM1 can overcome resistance to trastuzumab therapy in HER2-driven or PI3K-driven breast cancer brain lesions due to the cytotoxicity of the DM1 component. Clinical investigation of T-DM1 for patients with CNS metastases from HER2-positive breast cancer is warranted.
© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
PMID: 26547932 [PubMed - in process]