SGI-110 is a second generation hypomethylating agent (HMA) formulated as a dinucleotide of decitabine (DAC) and deoxyguanosine that prolongs the in vivo exposure of decitabine by protecting it from deamination. It gets injected subcutaneously as a small volume, allowing longer half-life and more extended decitabine exposure than DAC IV infusion. SGI-110’s differentiated pharmacokinetic profile resulted in potent hypomethylation and clinical responses in previously treated MDS and AML patients in a phase 1 trial (Kantarjian H et al. 2012).
Here, we have identified novel DNA-methylation biomarker candidates that may be predictive of response to SGI-110 using Differential Methylation Hybridisation (DMH) profiling of the NCI-60 cell line panel (Fassbender A et al, 2010). Cell lines were stratified based on SGI-110 EC50 values from Colony Forming Assays and the degree of LINE-1 (Long Interspersed Nucleotide Elements) demethylation post-SGI-110 treatment. Both stratification data sets were used to classify cell lines into either SGI-110 sensitive or resistant, and to generate 249 genomic methylation sites as candidate biomarkers of response to SGI-110. Fifty genomic fragments that characterized sensitivity and resistance to SGI-110 in cancer cell lines were selected for further validation. These candidate markers were tested in DNA samples from whole blood from 44 treatment naïve and relapsed/refractory AML patients that were classified into responders and non-responders following treatment with SGI-110 in our phase 2 clinical study.
We have identified DNA methylation patterns associated with sensitivity and resistance to SGI-110 in vitro. The validated methylation biomarker discovery process based on DMH and DBS approaches may help to identify and characterise specific subgroups of AML patients that could preferentially respond to SGI-110.
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2014:ASH Identification of Methylation Biomarkers to Predict Clinical Response to SGI-110 in AML pts