Phase I Study of TTI-101, an Oral Inhibitor of Signal Transducer and Activator of Transcription (STAT) 3, in Patients with Advanced Cancers

Signal transducer and activator of transcription 3 (STAT3) is a member of a family of seven closely related proteins responsible for transmission of peptide hormone signals from the extracellular surface of cells to the nucleus. STAT3 is a master regulator of most key hallmarks and enablers of cancer, including cell proliferation, resistance to apoptosis, metastasis, immune evasion, tumor angiogenesis, epithelial mesenchymal transition (EMT), response to DNA damage, and the Warburg effect. STAT3 also is a key mediator of oncogene addiction and supports the self-renewal of tumor-initiating cancer stem cells that contribute to cancer initiation, cancer maintenance, and relapse in several types of tumors. STAT3 activity is increased in ~50% of all cancers, due either to naturally occurring STAT3 mutations, as have been demonstrated in human inflammatory hepatocellular adenomas and large granular lymphocytic leukemia, or, more commonly as a result of activation of signaling molecules upstream of STAT3, including receptor tyrosine kinases (RTK; e.g. epidermal growth factor receptor, EGFR), tyrosine kinase-associated receptors (e.g. the family of IL-6 cytokine receptors or G-protein coupled receptors, GPCR), and Src kinases (e.g. Src, Lck, Hck, Lyn, Fyn, or Fgr). Thus, STAT3 is an attractive target for drug development to treat many types of cancer including breast cancer, head and neck squamous cell carcinoma (HNSCC), non-small cell lung cancer (NSCLC), hepatocellular carcinoma (HCC), colorectal cancer (CRC), gastric adenocarcinoma and melanoma.