Use of <i>Ex</i> <i>Vivo</i> Patient-Derived Tumor Organotypic Spheroids to Identify Combination Therapies for <i>HER2</i> Mutant Non-Small Cell Lung Cancer.

Abstract

Evaluating drug responses using primary patient-derived cells <i>ex vivo</i> represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in <i>HER2</i> mutant non-small cell lung cancer (NSCLC) patient <u>x</u>enograft-<u>d</u>erived <u>o</u>rganotypic <u>s</u>pheroids (XDOTS) using a short-term <i>ex vivo</i> system. We generated two <i>HER2-</i>mutant NSCLC PDX models [DFCI359 (<i>HER2</i> exon19 755_757LREdelinsRP) and DFCI315 (<i>HER2</i> exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated <i>ex vivo</i> with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious <i>ex vivo</i> combination was subsequently validated <i>in vivo</i> using the DFCI359 and DFCI315 PDXs and a <i>HER2</i> ^YVMA genetically engineered mouse model. Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab <i>in vivo</i> was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. The XDOTS platform can be used to evaluate therapies and therapeutic combinations <i>ex vivo</i> using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.