Mechanism of Action Magnifier – 2016 Desk Reference
Panobinostat: a Histone Deacetylase Inhibitor
In the cell nucleus, DNA is maintained in a tightly coiled state around proteins called histones.1 During the process of DNA replication for cell division or during the synthesis of RNA and proteins, histone acetyltransferase adds acetyl groups onto the histones, enabling DNA to uncoil.1 By contrast, histone deacetylases (HDACs) catalyze the removal of acetyl groups from the lysine residues of histones and some nonhistone proteins.2 Removal of these acetyl groups results in tightly coiled DNA, which prevents cells from making proteins or dividing.1
HDACs control several vital cellular processes, including the expression of some genes.3 In cancer, HDACs are expressed differently between cells, resulting in gene expression changes that can favor a tumor’s ability to multiply, to avoid apoptosis, or to become resistant to chemotherapy.3-5
Panobinostat is an HDAC inhibitor that inhibits the enzymatic activity of HDACs at nanomolar concentrations.2 Inhibition of HDAC activity by panobinostat results in increased acetylation of histone proteins, an epigenetic alteration that results in a relaxing of chromatin, leading to transcriptional activation.2 In vitro, panobinostat caused the accumulation of acetylated histones and other proteins, inducing cell cycle arrest and/or apoptosis of some transformed cells.2 Increased levels of acetylated histones were observed in xenografts from mice that were treated with panobinostat.2 Panobinostat shows more cytotoxicity toward tumor cells than toward normal cells.2
- Marks PA, Richon VM, Rifkind RA. Histone deacetylase inhibitors: inducers of differentiation or apoptosis of transformed cells. J Natl Cancer Inst. 2000;92:1210-1216.
- Farydak [package insert]. East Hanover, NJ: Novartis Pharmaceuticals Corporation; 2015.
- Dokmanovic M, Clarke C, Marks PA. Histone deacetylase inhibitors: overview and perspectives. Mol Cancer Res. 2007;5:981-989.
- Buggy JJ, Cao ZA, Bass KE, et al. CRA-024781: a novel synthetic inhibitor of histone deacetylase enzymes with antitumor activity in vitro and in vivo. Mol Cancer Ther. 2006;5:1309-1317.
- Stiborová M, Eckschlager T, Poljaková J, et al. The synergistic effects of DNA-targeted chemotherapeutics and histone deacetylase inhibitors as therapeutic strategies for cancer treatment. Curr Med Chem. 2012;19:4218-4238.
At Johns Hopkins Hospital, each specialist in my practice sees approximately 8 to 10 patients with nonmetastatic NSCLC per month, some of whom are not candidates for surgery based on physiologic parameters. In most cases, we follow the NCCN Guidelines or ASCO clinical practice guidelines in our management of patients with early-stage NSCLC, except in clinical scenarios where the patient may not fit into a particular category within the guidelines, or when we enroll a patient in a clinical trial. For example, we may determine that a neoadjuvant clinical study is appropriate for a patient with stage IB NSCLC, whereas this recommendation is not concordant with the NCCN Guidelines. There are also instances in which we apply recently published clinical study data when managing our patients—even before the NCCN Guidelines have been updated to reflect the most recent findings.
Although the cost of care can have severe effects on patients with cancer and their families, oncologists rarely address financial toxicity, according to Hanna K. Sanoff, MD, MPH, Medical Director, University of North Carolina (UNC) NC Cancer Hospital Clinics.