NCE (Year 5)
CFI-402257 was selected as the IND-development candidate for the TTK inhibitor program. During the past year this molecule has progressed through IND-enabling studies. ADME studies and in vitro mechanism of action characterization have been completed. The synthesis of the compound has been scaled up and batches of material have been produced for both formulation development and the toxicology program. A formulation suitable for dosing rats and dogs in the toxicology program was identified and all in-life activity in the toxicology program has been completed, with the study reports now being generated. Development of the clinical formulation (formulated powder-in-capsule) is well advanced and the GLP synthesis of the drug substance for use in the clinic is nearing completion.
In addition, we have performed in vivo combination studies with CFI-402257 and the PLK4-inhibitor CFI-400945. We designed a combination MTD for CFI-402257 and CFI-400945 to identify tolerable combination doses in non-tumor bearing mice. These data were used to inform the design of a combination efficacy study using the HCT116 colon cell line xenograft model. Significantly increased tumor growth inhibition was observed in the combination arm relative to either inhibitor alone. Even at single agent MTD, CFI-402257 and CFI-40945 induced tumor growth inhibitions of between 40-70% whereas the combination induced a tumor growth inhibition of >100%. These studies are being replicated with bisphosphate form of CFI-402257 and will then be tested in additional cell line xenograft models to test the potential efficacy of this combination therapy.
Finally, we have developed immunofluorescence assays to detect Plk4 and TTK in formalin-fixed, paraffin-embedded (FFPE) cancer cell lines as well as in FFPE tissue samples. Our Plk4 immunofluorescence methods localize either full-length Plk4 or cleaved phopho-Plk4 depending on the primary antibody used. We have shown a correlation between Plk4 expression levels measured per 500 tumor cells by immunofluorescence and responsiveness to Plk4 inhibitor in colorectal cancer cell lines. We consider Plk4 expression levels, determined by immunofluorescence, to be a potential predictive biomarker assay that we will evaluate in tissue samples from the phase I trial of CFI-400945 Plk4 inhibitor.