The Src Kinase inhibition platform refers to novel small molecule compounds that have differentiated mechanisms of actions (MOAs) including: (1) the inhibition of the activity of Src Kinase and (2) the inhibition of tubulin polymerization. We believe the combination of the two mechanisms of action provides a broader range of anticancer activity compared to either mechanism of action alone. Our three key clinical product candidates in this platform are tirbanibulin (formerly KX2-391 or KX-01) ointment for actinic keratosis, pre-cancerous lesions and psoriasis; tirbanibulin oral for solid and liquid tumors, and KX2-361 (formerly KX-02) oral for glioblastoma multiforme (GBM).
Tirbanibulin: An Ointment Formulation
Tirbanibulin is a small molecule developed under our Src Kinase Inhibition platform that, as a free base, has advantageous physical properties for topical ointment formulations.
Tirbanibulin ointment has shown promising results in actinic keratosis, or AK, a pre-cancerous skin lesion. AK is a common disease that affects more than 55 million patients in the United States. If left untreated, 10-15% of AK lesions will develop into skin cancers. Currently available treatments are limited by severe local skin reactions such as vesicultation, pustulation, erosion and ulceration, which compromise patient compliance. A new ointment product with good clinical activity and a favorable side effect profile is expected to provide benefit to a greater number of patients and capture new market share for treatment of this condition.
We have announced positive topline results from two Phase 3 studies of tirbanibulin ointment 1%, featured in a late breaker program at the March 2019 American Academy of Dermatology Annual Meeting. The filing of the U.S. NDA for Tirbanibulin Ointment in Actinic Keratosis has been accepted by the U.S. Food and Drug Administration (FDA).
Tirbanibulin is also being investigated for the treatment of psoriasis. The trial has already yielded positive early signals of clinical activity, as disclosed in June 2019. Preclinical research is underway to identify further indications for tirbanibulin, such as skin cancers and other dermatological hyperproliferative disorders.
Tirbanibulin: An Oral Formulation
Tirbanibulin is also being developed as an oral for the control of cancer and hyper-proliferative disorders. Src plays a demonstrated role in regulating multiple aspects of tumor development, growth, and metastases, and its inhibition limits such tumor activity. Interfering with tubulin polymerization activity is a clinically validated mechanism for treating cancer. For both targets, tirbanibulin binds at a novel binding site. Together, these two MOAs may provide a potent means of treating cancer and other hyper-proliferative disorders.
Tirbanibulin oral has been evaluated in several early dose finding studies against both solid and liquid tumors. Initial clinical results indicate activity against both solid and liquid tumors in patients. We are planning further probing studies to focus our evaluation on those indications where activity was observed.
KX2-361: An Oral Formulation
KX2-361 is a closely related structural analog of tirbanibulin and demonstrates similar dual MOAs of Src and microtubule polymerization inhibition. KX2-361 was designed to readily cross the blood-brain-barrier (BBB). KX2-361 levels in the mouse brain meet or exceed that in the plasma at the same time points after oral dosing, demonstrating that KX2-361 readily crosses the BBB. We believe that this ability to cross the BBB provides a rationale for investigating brain cancers and metastases in the brain as potential therapeutic applications for what is considered an unmet medical need.
KX2-361 was tested orally in a mouse GBM tumor model, wherein the mice with a fully competent immune system are implanted with mouse GBM tumor cells into the brain in order to simulate a human patient. When compared with the current standard of treatment, TMZ, KX2-361 produced long term survival mice, which extended survival but did not result in any long term survivors. Based on this data, the FDA to granted Orphan Drug Status to KX2-361 for the treatment of gliomas.
In 2012, we out-licensed KX2-361 to Xiangxue Pharmaceuticals for development and marketing in China. The China FDA has approved the IND application for KX2-361 and clinical trials are currently being planned.
This compound is currently in Phase 1 clinical studies.