In addition to our SINE compounds, we also investigate XPO1 cargo proteins and their role in the cell cycle and cell division. As part of this investigation, we have identified several XPO1 cargo proteins whose inhibition leads to the selective death of cancer cells. One of the XPO1 cargo proteins that we identified was p21-activated kinase 4, or PAK4. PAK4 is member of the PAK family of kinases that includes 6 proteins, PAK1-6. PAK4-6 belong to a growth-promoting sub-family. PAK4 is a signaling protein regulating numerous fundamental cellular processes, including intracellular transport, cellular division, cell shape and motility, cell survival, immune defense and the development of cancer. PAK4 interacts with many key signaling molecules involved in cancer such as beta-catenin, CDC42, Raf-1, BAD and myosin light chain. Based on this biology, we used our drug discovery and optimization expertise to identify small molecule modulators of PAK4. Our PAK4 allosteric modulators have shown broad evidence of anti-cancer activity against hematological and solid tumor malignant cells while showing minimal toxicity to normal cells in vitro. In mouse and rat xenograft studies, our PAK4 inhibitors given orally have shown evidence of anti-cancer activity and tolerability. To our knowledge, we are the only company with a pre-IND allosteric, PAK4 specific inhibitor.
Recently, we identified an additional target for our clinical candidate KPT-9274 known as NAMPT (Nicotinamide phosphoribosyltransferase; also known as PBEF or Visfatin). NAMPT is a pleiotropic protein with intra- and extra-cellular functions as an enzyme, cytokine, growth factor, and hormone that can be found in complex with PAK4 in the cell. NAMPT is of interest as an oncology target because it catalyzes the rate-limiting step in one of the two intracellular salvage pathways that generate nicotinamide adenine dinucleotide, or NAD. NAD is a universal energy- and signal-carrying molecule involved in mitochondrial function, energy metabolism, calcium homeostasis, antioxidation, and paradoxically generation of oxidative stress, gene expression, immunological functions, aging, and cell death.
KPT-9274 is a first-in-class orally bioavailable small molecule that is a non-competitive dual modulator of PAK4 and NAMPT. Co-inhibition of these targets leads to synergistic anti-tumor effects through energy depletion, inhibition of DNA repair, cell cycle arrest, inhibition of proliferation, and ultimately apoptosis. Normal cells are more resistant to inhibition by KPT-9274 due in part to their relative genomic stability and lower metabolic rates. Hematologic and solid tumor cells become dependent on both PAK4 and NAMPT pathways and are therefore susceptible to single-agent cytotoxicity by KPT-9274. We are planning to develop
KPT-9274 for a variety of neoplastic disease indications. We have completed IND-enabling toxicology studies and filed an IND in February 2016 to facilitate a first-in-humans open-label Phase 1 clinical trial of the safety, tolerability, and efficacy of KPT-9274 in patients with advanced solid malignancies or non-Hodgkin’s lymphoma. The first patient was dosed with KPT-9274 in June 2016.