Abstract A190: In vivo activity of SGI‐110, a novel hypomethylating agent for treatment in hematology and solid malignancies

SGI‐110 is a second generation hypomethylating agent being developed for treatment in myelodysplastic syndrome (MDS) and solid tumor malignancies. In previous work, SGI‐110 has demonstrated potent in vivo activity in a number of tumor types, including non‐hematological cell lines. Current efforts are underway to optimize formulation and delivery of SGI‐110 for first‐in‐human (FIH) studies. In animals, SGI‐110 is well‐tolerated across multiple species utilizing multiple routes of drug delivery. Tolerability studies have been performed in mouse, rat, and rabbit models with multiple dose routes and schedules. Myelosuppression is an observed toxicity endpoint for hypomethylating agents. Hence, myelotoxic effects were investigated by comparing RBCs and bone marrow cellularity of mice treated with and without SGI‐110. Mice dosed with SGI‐110 for five consecutive days showed a significant decrease in RBCs at the end of the dosing period and a continued decrease one week after dosing. Bone marrow cellularity also showed a decrease at the end of dosing, but recovered to near normal levels one week later. Interestingly, RBCs from SGI‐110 treated mice were elevated in the bone marrow after the dosing period. Pyrosequencing methylation analysis of colon samples was also evaluated in this study. A significant decrease in B1 methylation was observed in colon samples of treated mice, indicating global DNA methylation is being inhibited. Decreased levels in several hematology parameters and decreases in bone marrow cellularity were also observed in rat and rabbit studies after five consecutive days of SGI‐110 dosing. Increased dosing frequency, while maintaining the same total dose per week, appears to result in increased toxicity. Previous pharmacokinetic studies have shown that SGI‐110 rapidly metabolizes to decitabine, an FDA‐approved drug for MDS. Multiple formulations and different routes of delivery were examined to determine the optimal dose form to be used in FIH studies. Subcutaneous dosing results in bioavailability that is similar to that of intravenous dosing. Subcutaneous dosing appears to reduce the Cmax while maintaining similar AUC values when compared to intravenous dosing. Similar results in pharmacokinetic parameters are observed when the delivery vehicle is changed from an aqueous to non‐aqueous formulation. SGI‐110 is a novel hypomethylating agent that is well‐tolerated in rodent models, provides excellent PK exposure, and demonstrates inhibition of DNA methylation in a mouse model. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A190.