Lorus Therapeutics has reported data demonstrating decreased expression of the molecular target for its antisense drug, GTI-2040, in a Phase II breast cancer clinical trial.
Rapid and dramatic reduction in expression of the gene for the R2 component of ribonucleotide reductase was demonstrated in tumor biopsy tissue following treatment with GTI-2040 in combination with capecitabine.
An approximately 25-fold decrease in R2 was seen as early as one day after the start of GTI-2040 treatment. This finding, in conjunction with an observed clinical response of six months duration, was paralleled by an observed reduction of the R2 target in circulating white blood cells (WBCs). This decrease suggests a potential utility of WBCs as a "surrogate" tissue for measuring this malignant determinant, and may also be useful for evaluating the activity of GTI-2040 in down regulating target gene expression in patients for whom tumor biopsy is not possible.