2-acetylfuranonaphthoquinone and Adenocarcinoma

Napabucasin is a novel oral first-in-class cancer stemness inhibitor. Preclinical and early phase clinical trials showed promising antitumor efficacy signals for napabucasin in a variety of malignancies. In this article, we describe the design and rationale for the now completed BRIGHTER trial, a multicenter, randomized, placebo-controlled, Phase III study designed to determine the efficacy and safety of combining napabucasin with paclitaxel in previously treated patients with advanced gastric and gastroesophageal junction adenocarcinoma (NCT02178956). Patients were randomized in a 1:1 fashion to receive weekly paclitaxel with either napabucasin or placebo. The study failed to achieve its primary end point of overall survival in the intention to treat population. Ongoing analysis of the secondary end points includes progression-free survival, objective response rate, disease control rate, the safety of the combination therapy and evaluation of efficacy in the biomarker-positive subpopulation.

Topics: Adenocarcinoma; Antineoplastic Combined Chemotherapy Protocols; Benzofurans; Clinical Protocols; Disease-Free Survival; Double-Blind Method; Drug Administration Schedule; Esophageal Neoplasms; Humans; Immunohistochemistry; Kaplan-Meier Estimate; Naphthoquinones; Paclitaxel; Stomach Neoplasms; Survival Analysis; Treatment Outcome

Immunosuppressive myeloid-derived suppressor cells (MDSC) subvert antitumor immunity and limit the efficacy of chimeric antigen receptor T cells (CAR-T). Previously, we reported that the GM-CSF/JAK2/STAT3 axis drives liver-associated MDSC (L-MDSC) proliferation and blockade of this axis rescued antitumor immunity. We extended these findings in our murine liver metastasis (LM) model, by treating tumor-bearing mice with STAT3 inhibitors (STATTIC or BBI608) to further our understanding of how STAT3 drives L-MDSC suppressive function. STAT3 inhibition caused significant reduction of tumor burden as well as L-MDSC frequencies due to decrease in pSTAT3 levels. L-MDSC isolated from STATTIC or BBI608-treated mice had significantly reduced suppressive function. STAT3 inhibition of L-MDSC was associated with enhanced antitumor activity of CAR-T. Further investigation demonstrated activation of apoptotic signaling pathways in L-MDSC following STAT3 inhibition as evidenced by an upregulation of the pro-apoptotic proteins Bax, cleaved caspase-3, and downregulation of the anti-apoptotic protein Bcl-2. Accordingly, there was also a decrease of pro-survival markers, pErk and pAkt, and an increase in pro-death marker, Fas, with activation of downstream JNK and p38 MAPK. These findings represent a previously unrecognized link between STAT3 inhibition and Fas-induced apoptosis of MDSCs. Our findings suggest that inhibiting STAT3 has potential clinical application for enhancing the efficacy of CAR-T cells in LM through modulation of L-MDSC.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; Benzofurans; Cell Line, Tumor; Colorectal Neoplasms; Cyclic S-Oxides; Drug Screening Assays, Antitumor; fas Receptor; Gene Expression Regulation, Neoplastic; Immunotherapy; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Targeted Therapy; Myeloid-Derived Suppressor Cells; Naphthoquinones; Neoplasm Proteins; Signal Transduction; Specific Pathogen-Free Organisms; STAT3 Transcription Factor; Tumor Burden; Tumor Escape