A phase 1 and pharmacodynamic study of decitabine in combination with carboplatin in patients with recurrent, platinum-resistant, epithelial ovarian cancer

Abstract

Background: Aberrant DNA methylation is a hallmark of cancer, and DNA methyltransferase inhibitors have demonstrated clinical efficacy in hematologic malignancies. On the basis of preclinical studies indicating that hypomethylating agents can reverse platinum resistance in ovarian cancer cells, the authors conducted a phase 1 trial of low-dose decitabine combined with carboplatin in patients with recurrent, platinum-resistant ovarian cancer.

Methods: Decitabine was administered intravenously daily for 5 days, before carboplatin (area under the curve, 5) on Day 8 of a 28-day cycle. By using a standard 3 + 3 dose escalation, decitabine was tested at 2 dose levels: 10 mg/m(2) (7 patients) or 20 mg/m(2) (3 patients). Peripheral blood mononuclear cells (PBMCs) and plasma collected on Days 1 (pretreatment), 5, 8, and 15 were used to assess global (LINE-1 repetitive element) and gene-specific DNA methylation.

Results: Dose-limiting toxicity (DLT) at the 20-mg/m(2) dose was grade 4 neutropenia (2 patients), and no DLTs were observed at 10 mg/m(2). The most common toxicities were nausea, allergic reactions, neutropenia, fatigue, anorexia, vomiting, and abdominal pain, the majority being grades 1-2. One complete response was observed, and 3 additional patients had stable disease for >/=6 months. LINE-1 hypomethylation on Days 8 and 15 was detected in DNA from PBMCs. Of 5 ovarian cancer-associated methylated genes, HOXA11 and BRCA1 were demethylated in plasma on Days 8 and 15.

Conclusions: Repetitive low-dose decitabine is tolerated when combined with carboplatin in ovarian cancer patients, and demonstrates biological (ie, DNA-hypomethylating) activity, justifying further testing for clinical efficacy. Cancer 2010. (c) 2010 American Cancer Society.

Figure 1. Waterfall plot depicting maximal CA125 level decrease during treatment expressed as percentage of baseline level

CA125 levels were obtained prior to each cycle of therapy. Data are available for 8 of 10 enrolled patients. One patient was deceased prior to completing cycle 1 and one patient did not return for follow up after cycle 1.

Figure 2

In vivo biological activity of 10 mg/m² decitabine (dose level 1) in peripheral blood peripheral blood mononuclear cells (PBMCs) and plasma collected from patients on days 1, 5, 8, and 15 of each cycle (averaged over three replicates). A, methylation levels (expressed as PMR, percentage of fully methylated reference molecules, normalized by ALU-C4) of LINE-1 repetitive element levels in patient PBMCs during cycle 1. Seven specimens were analyzed from all patients enrolled at dose level 1 B, PBMC LINE-1 methylation levels for cycle 2. Six specimens were analyzed from patients enrolled at dose level 1, as one patient was discontinued before completing cycle 1. C, methylation of the tumor suppressor gene BRCA1, in patients' plasma, during cycle 1. D, plasma BRCA1 methylation levels for cycle 2. E,Scatter plot of gene-specific (plasma HOXA11, y axis) and global (PBMC LINE-1, x axis) DNA methylation levels (normalized by ALU-C4) for all subjects. Rho is the Pearson Correlation Coefficient estimate. For 1A – 1D, each symbol represents the same patient.

Figure 3

Changes in DNA methylation levels from blood collected from Patient 1 during the first two treatment cycles. A, percent of fully methylated reference (PMR) values for PBMC LINE-1 repetitive elements. B, PMR values of plasma BRCA1. C, PMR values for RASSF1A.

Figure 4

Changes in DNA methylation levels (expressed as percent of fully methylated reference molecules, PMR) from blood and ascites fluid collected from Patient 3 during the first two treatment cycles. PMR values of: A, PBMC LINE-1 elements. B, plasma BRCA1. C, plasma Wwox. D, LINE-1, BRCA1, RASSF1A, WWOX, and HOXA10 in DNA isolated from Patient 3's ascites fluid.

Figure 5

Changes in DNA methylation levels (i.e., PMR values) from blood and tumor biopsy tissue collected from Patient 5. PMR values of: A, plasma HOXA10. B, plasma HOXA11. C, plasma WWOX. D, LINE-1, WWOX, HOXA10, and HOXA11 in DNA isolated from biopsy tissue obtained from Patient 5.