A Phase I Safety, Pharmacokinetic, and Pharmacodynamic Presurgical Trial of Vitamin E δ-tocotrienol in Patients with Pancreatic Ductal Neoplasia

Abstract

Background: Vitamin E δ-tocotrienol (VEDT), a natural vitamin E from plants, has shown anti-neoplastic and chemoprevention activity in preclinical models of pancreatic cancer. Here, we investigated VEDT in patients with pancreatic ductal neoplasia in a window-of-opportunity preoperative clinical trial to assess its safety, tolerability, pharmacokinetics, and apoptotic activity.

Methods: Patients received oral VEDT at escalating doses (from 200 to 3200 mg) daily for 13 days before surgery and one dose on the day of surgery. Dose escalation followed a three-plus-three trial design. Our primary endpoints were safety, VEDT pharmacokinetics, and monitoring of VEDT-induced neoplastic cell apoptosis (ClinicalTrials.gov number NCT00985777).

Findings: In 25 treated patients, no dose-limiting toxicity was encountered; thus no maximum-tolerated dose was reached. One patient had a drug-related adverse event (diarrhea) at a 3200-mg daily dose level. The effective half-life of VEDT was ~ 4 h. VEDT concentrations in plasma and exposure profiles were quite variable but reached levels that are bioactive in preclinical models. Biological activity, defined as significant induction of apoptosis in neoplastic cells as measured by increased cleaved caspase-3 levels, was seen in the majority of patients at the 400-mg to 1600-mg daily dose levels.

Interpretation: VEDT from 200 to 1600 mg daily taken orally for 2 weeks before pancreatic surgery was well tolerated, reached bioactive levels in blood, and significantly induced apoptosis in the neoplastic cells of patients with pancreatic ductal neoplasia. These promising results warrant further clinical investigation of VEDT for chemoprevention and/or therapy of pancreatic cancer.

Keywords: Chemoprevention; Pancreatic cancer; Presurgical trial; Tocotrienols; Vitamin E.

Figures

Fig. 1

Chemical structures of tocopherols and tocotrienols are similar in that they both contain an aromatic ring chromanol ring to which the free radical scavenging hydroxyl moiety is attached. The main difference between tocopherols and tocotrienols is in the saturation of the aliphatic side chain attached to the chromanol ring. The aliphatic side chain is saturated in tocopherols and unsaturated in tocotrienols. The 4 isomers (alpha, beta, gamma, delta) are named for specific methyl group substitutions at positions 5, 7, and 8 of the chromanol ring.

Fig. 2

VEDT reaches bioactive levels in human serum. a: Large variability in pharmacokinetic parameters is shown, with peak VEDT serum levels (Cmax) of up to 18 μM and AUC up to 170 μM. b: MTT assay of VEDT treatment of MiaPaCa-2 and L3.6 pl human PDAC cells in vitro demonstrates IC50 of 5 and 10 μM with 5-day treatment.

Fig. 3

Apoptosis in untreated control pancreatic ductal malignant cells compared with VEDT-treated pancreatic ductal normal and neoplastic (dysplastic or malignant) cells. The apoptotic index, as measured by % cells staining positive for caspase-3 in untreated control malignant cells in patients (n = 20) with PDAC operated on by the same surgeon who operated on the VEDT-treated patients on the same period of time was low. Moreover, the apoptotic index of these malignant cells was not statistically different from the apoptotic index of the normal ductal epithelial cells in VEDT-treated patients (P = 0.725). In contrast, the apoptotic index of the VEDT-treated neoplastic cells (Dysplastic and Malignant) were significantly higher than those of the untreated control malignant cells (P = 0.005). Moreover, the apoptotic index of the VEDT-treated neoplastic cells was also significantly higher than the VEDT-treated normal epithelial cells (P = 0.011). These findings strongly suggest selective induction of apoptosis in neoplastic cells by VEDT treatment.

Fig. 4

Biologic evidence of tumor response. a: Waterfall plot of the best biologic response to VEDT at different doses in patients at the escalation doses. Red line represents statistically calculated threshold of significant induction of apoptosis (7.6%). b: Immunohistochemistry sections from pancreatectomy specimens stained with hematoxylin and eosin (× 20 magnification), as well as for cleaved caspase-3 (× 20 magnification), highlighting biologic responses in representative patients. Both invasive mucinous adenocarcinoma and adjacent normal specimens are shown at two VEDT dose levels: 100 mg (Patient 1) and 200 mg (Patient 4). Arrows in normal specimens indicate normal duct or normal duct cells negative for caspase-3. For Patient 1, arrows in invasive specimens indicate mucinous adenocarcinoma (H&E slide) or carcinomatous epithelium (caspase-3 slide). For Patient 4, arrows in invasive specimens indicate malignant gland (H&E slide) or cells undergoing apoptosis based on caspase-3 expression (caspase-3 slide).

Fig. 5

Biologic response in the expansion cohort. Apoptotic index as measured by % cells staining positive for caspase-3 was used to assess biologic response in the expansion cohort. Ten patients (including three patients in the dose-escalation cohort) were treated at the 800-mg dose level; 80% (8/10) patients had significant induction of apoptosis in their dysplastic or malignant tissue. Red line indicates threshold of biological response (7.6%).

Fig. 6

Pairwise comparison of apoptotic index in untreated control versus VEDT-treated patient in both the dose-escalation and expansion cohorts. Untreated control tumor tissues had comparable percentage of caspase-3-positive cells to the “treated normal” tissues (adjusted P = 0.985), with a statistically significant difference (lower) versus treated dysplastic or malignant tissues (adjusted P = 0.044). Treated dysplastic or treated malignant tissues had a higher percentage of caspase-3-positive cells than treated normal tissues (adjusted P = 0.044). Both treated dysplastic and treated malignant tissues had a similar higher percentage of caspase-3-positive cells (P = 0.985).