CJC-1004

Deacetylase (DAC) inhibitors are promising new anticancer drugs that have complex mechanisms of action, including induction of cell-cycle arrest and apoptosis, inhibition of angiogenesis and induction of a favorable anti-tumor immune response. Panobinostat, a potent inhibitor of DAC 1-11 enzymatic activity, has demonstrated a significant in vitro antiproliferative activity against classical Hodgkin's lymphoma (cHL) cell lines in addition to a promising clinical activity in early Phase I studies in patients with relapsed cHL. In a recently completed large Phase II study in patients with relapsed cHL, panobinostat reduced tumor measurements in 74% of patients, including 23% partial and 4% complete remissions. In this article, we review the status of panobinostat drug development and compare its activity to those of other DAC inhibitors in patients with relapsed cHL. Future investigations should focus on designing rational combination regimens and identifying predictive markers that will assist in selecting patients who are likely to benefit from this novel therapy.

While deacetylase (DAC) inhibitors show promise for the treatment of B-cell malignancies, those introduced to date are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have shown suboptimal activity or unacceptable toxicities. We therefore investigated the novel DAC inhibitor AR-42 to determine its efficacy in B-cell malignancies.

In mantle cell lymphoma (JeKo-1), Burkitt's lymphoma (Raji), and acute lymphoblastic leukemia (697) cell lines, the 48-hr IC(50) (50% growth inhibitory concentration) of AR-42 is 0.61 microM or less. In chronic lymphocytic leukemia (CLL) patient cells, the 48-hr LC(50) (concentration lethal to 50%) of AR-42 is 0.76 microM. AR-42 produces dose- and time-dependent acetylation both of histones and tubulin, and induces caspase-dependent apoptosis that is not reduced in the presence of stromal cells. AR-42 also sensitizes CLL cells to TNF-Related Apoptosis Inducing Ligand (TRAIL), potentially through reduction of c-FLIP. AR-42 significantly reduced leukocyte counts and/or prolonged survival in three separate mouse models of B-cell malignancy without evidence of toxicity.

Together, these data demonstrate that AR-42 has in vitro and in vivo efficacy at tolerable doses. These results strongly support upcoming phase I testing of AR-42 in B-cell malignancies.