7501 Background: LBH589 is a novel histone deacetylase inhibitor in Phase I trials. Since other HDACi have induced disease regression in CTCL, we evaluated the activity of LBH589 and resulting changes in gene expression of LBH589 in CTCL patients (pts).
METHODS
Pts with advanced-stage CTCL, who had progressed following prior systemic therapy were entered into the DLT dose level 30mg M,W,F cohort (n = 1) or the subsequent MTD dose level 20mg M,W, F weekly (n = 10). LBH589 was continued until disease progression or unacceptable toxicity. The first three pts had 3mm punch biopsies from CTCL-involved skin lesions at 0, 4, 8 and 24h after administration, which were subjected to gene expression profiling using Affymetrix U133 plus 2.0 GeneChips with 47,000 probesets.
RESULTS
Eleven pts with CTCL have been entered to date. Two of the pts attained a complete response (CR), 3 attained a partial response (PR), 2 achieved stable disease (SD) with ongoing improvement, and 4 progressed on treatment (PD). Of particular interest, 2 pts who were initially SD required discontinuation because of toxicities (Grade III diarrhea at week 4, Grade II fatigue at week 12). Both had ongoing improvement in their disease achieving a CR and PR, respectively 3 months later. Of the 5 responding pts, one with a CR (discontinued after 10 doses due to Grade III diarrhea) progressed at 8m. Microarray data on the first 3 pts (2CR and 1PD) demonstrated distinct gene expression response profiles between the 3 pts. Surprisingly, the pt with PD showed the greatest transcriptional response with more than 16,000 genes activated or repressed over the 24 hr time course. Of these responsive genes, close to 60% were activated while 40% were repressed. In contrast, less than 1000 genes showed a 2-fold change in expression in the 2 pts with a CR with greater than 85% of the genes being repressed.
CONCLUSIONS
LBH589 induce CR's in CTCL pts. Regression of disease can occur some weeks after discontinuation of therapy. Preliminary microarray analysis of tumor samples indicated that LBH589 mediates changes in gene expression in vivo with an unexpected observed inverse relationship between the number of genes altered and clinical outcome. [Table: see text].