Effective penetration of the blood-brain barrierPLX3397 successfully crossed the blood brain barrier, with oral administration, enabling the kinase inhibitor to block the targeted kinase. Dramatic reduction of activated microglia in Alzheimer's Disease modelActivation of microglial cells was effectively prevented due to PLX3397's inhibition of the targeted kinase leading to a reduction in the number of activated microglia in the brain, while no effect on disease plaques was observed. Activated microglia appear in elevated numbers associated closely with the disease plaques present in brains of Alzheimer's patients, and are considered by some researchers to play a destructive role in the progression of disease, including neuronal loss and function. Unprecedented learning performanceAfter three months of treatment, the PLX3397-treated group in the Tg3x AD model in very old mice (22 months) demonstrated significantly improved learning performance compared to the untreated group, using the Morris Water Maze for the evaluation of learning and memory.
"PLX3397 has demonstrated the ability to cross the blood-brain barrier which presents a unique opportunity to treat diseases driven by the activation of microglia, such as Alzheimer's Disease, multiple sclerosis, glioblastoma and possibly other brain tumors," stated K. Peter Hirth, Ph.D., chief executive officer of Plexxikon. "PLX3397's selective targeting of the microglia, macrophages and osteoclasts has shown broad utility in a wide range of disease models, where activation or proliferation of these cell types is a key culprit. Plexxikon is developing a portfolio of these selective candidates, each with differentiating features, in order to specifically address not only Alzheimer's Disease, but also rheumatoid arthritis, multiple sclerosis and many cancers, such as metastatic breast cancer, glioblastoma and Hodgkin's lymphoma."
Rationale for PLX3397 as Treatment for Inflammatory Disorders and Cancer
PLX3397 selectively targets a number of cell types, including microglia, macrophages, osteoclasts and mast cells, cells that play key roles in the disease processes in various inflammatory disorders and cancers. Preclinical data have shown PLX3397 to be effective and disease-modifying in models of Alzheimer's Disease, cancer, rheumatoid arthritis, multiple sclerosis and lupus, among others. Macrophage colony stimulating factor 1 (CSF-1) controls an important signaling pathway in the activation of microglia, and offers a potential therapeutic target to treat neuro-inflammatory conditions including Alzheimer's Disease.
PLX3397 is already in early clinical trials in cancer patients. The company plans to evaluate PLX3397 in a number of cancers, where the activation or proliferation of the microglia and macrophage contribute to the invasiveness or metastatic spread of the tumor, including metastatic breast cancer, glioblastoma and Hodgkin's lymphoma. Data from the Phase 1 trial to date, indicate that PLX3397 is well tolerated, and has a half-life of about fifteen hours. Blood levels of PLX3397 have reached the targeted efficacy range with once daily dosing.
SOURCE Plexxikon Inc.