Milin R. Acharya

Phase I and Pharmacokinetic Study of MS-275, a Histone Deacetylase Inhibitor, in Patients With Advanced and Refractory Solid Tumors or Lymphoma

PURPOSE The objective of this study was to define the maximum-tolerated dose (MTD), the recommended phase II dose, the dose-limiting toxicity, and determine the pharmacokinetic (PK) and pharmacodynamic profiles of MS-275. PATIENTS AND METHODS Patients with advanced solid tumors or lymphoma were treated with MS-275 orally initially on a once daily x 28 every 6 weeks (daily) and later on once every-14-days (q14-day) schedules. The starting dose was 2 mg/m2 and the dose was escalated in three- to six-patient cohorts based on toxicity assessments. RESULTS With the daily schedule, the MTD was exceeded at the first dose level. Preliminary PK analysis suggested the half-life of MS-275 in humans was 39 to 80 hours, substantially longer than predicted by preclinical studies. With the q14-day schedule, 28 patients were treated. The MTD was 10 mg/m2 and dose-limiting toxicities were nausea, vomiting, anorexia, and fatigue. Exposure to MS-275 was dose dependent, suggesting linear PK. Increased histone H3 acetylation in peripheral-blood mononuclear-cells was apparent at all dose levels by immunofluorescence analysis. Ten of 29 patients remained on treatment for > or = 3 months. CONCLUSION The MS-275 oral formulation on the daily schedule was intolerable at a dose and schedule explored. The q14-day schedule is reasonably well tolerated. Histone deacetylase inhibition was observed in peripheral-blood mononuclear-cells. Based on PK data from the q14-day schedule, a more frequent dosing schedule, weekly x 4, repeated every 6 weeks is presently being evaluated.

Identification of OATP1B3 as a high-affinity hepatocellular transporter of paclitaxel

Interindividual variability in paclitaxel and docetaxel pharmacokinetics, toxicity and response is extensive, and largely unexplained. We hypothesized that this is due to affinity of taxanes for an uptake transporter that indirectly regulates elimination pathways. Here, we studied accumulation of [3H]docetaxel and [3H]paclitaxel in Xenopus laevis oocytes injected with cRNA of the liver-specific organic anion transporting polypeptide (OATP) family members OATP1B1 (OATP2) or OATP1B3 (OATP8). Taxane transport by OATP1B1 expressing oocytes was not significantly different from that by water-injected controls, whereas uptake by OATP1B3 was 2.2-fold higher for docetaxel (P=0.0007) and 3.3-fold higher for paclitaxel (P

Mechanisms of resistance to anticancer drugs: the role of the polymorphic ABC transporters ABCB1 and ABCG2.

ATP-binding cassette (ABC) genes play a role in the resistance of malignant cells to anticancer agents. The ABC gene products, including ABCB1 (P-glycoprotein) and ABCG2 (breast cancer-resistance protein [BCRP], mitoxantrone-resistance protein [MXR], or ABC transporter in placenta [ABCP]), are also known to influence oral absorption and disposition of a wide variety of drugs. As a result, the expression levels of these proteins in humans have important consequences for an individuals susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. Naturally occurring variants in ABC transporter genes have been identified that might affect the function and expression of the protein. This review focuses on recent advances in the pharmacogenetics of the ABC transporters ABCB1 and ABCG2, and discusses potential implications of genetic variants for the chemotherapeutic treatment of cancer.

Effects of α1-Acid Glycoprotein on the Clinical Pharmacokinetics of 7-Hydroxystaurosporine

Objective: UCN-01 (7-hydroxystaurosporine) is a small molecule cyclin-dependent kinase modulator currently under clinical development as an anticancer agent. In vitro studies have demonstrated that UCN-01 is strongly bound to the acute-phase reactant α 1-acid glycoprotein (AAG). Here, we examined the role of protein binding as a determinant of the pharmacokinetic behavior of UCN-01 in patients. Experimental Design: Pharmacokinetic data were obtained from a group of 41 patients with cancer receiving UCN-01 as a 72-hour i.v. infusion (dose, 3.6 to 53 mg/m2/day). Results: Over the tested dose range, total drug clearance was distinctly nonlinear (P = 0.0076) and increased exponentially from 4.33 mL/hour (at 3.6 mg/m2/day) to 24.1 mL/hour (at 54 mg/m2/day). As individual values for AAG increased, values for clearance decreased in a linear fashion (R2 = 0.264; P = 0.0008), although the relationship was shallow, and the data showed considerable scatter. Interestingly, no nonlinearity in the unbound concentration (P = 0.083) or fraction at the peak plasma concentration of UCN-01 was apparent (P = 0.744). Conclusion: The results suggest the following: (1) that extensive binding to AAG may explain, in part, the unique pharmacokinetic profile of UCN-01 described previously with a small volume of distribution and slow systemic clearance, and (2) that measurement of total UCN-01 concentrations in plasma is a poor surrogate for that of the pharmacologically active fraction unbound drug.

Histone deacetylase inhibitor enhances the anti-leukemic activity of an established nucleoside analogue.

Interest in histone deacetylase (HDAC) inhibitors as antineoplastic agents has been accelerating over the last several years and increasing number of compounds are in or entering clinical trials in humans. Recently, attention has been focused on the ability of HDAC inhibitors to induce perturbations in cell cycle regulatory proteins (e.g. p21CIP1), down regulation of survival signaling pathways (e.g. Raf/MAPkinase/ERK), and disruption of cellular redox state (e.g. reactive oxygen species, ROS). In April 2004 issue of Cancer Research, Maggio et al. report that pre-treatment of human leukemic cells with a histone deacetylase inhibitor, MS-275 significantly enhances the abrogative capacity of an established nucleoside analogue, fludarabine. The study indicates that apart from promoting acetylation of histones and regulation of genes involved in differentiation and apoptosis, MS-275 also induces multiple perturbations in signal transduction, survival and cell cycle regulatory pathways that increase the fludarabine-mediated cell death.