Targeting anti-apoptotic Bcl-2 by AT-101 to increase radiation efficacy: data from in vitro and clinical pharmacokinetic studies in head and neck cancer.

BACKGROUND: Pro-survival Bcl-2 family members can promote cancer development and contribute to treatment resistance. Head and neck squamous cell carcinoma (HNSCC) is frequently characterized by overexpression of anti-apoptotic Bcl-2 family members. Increased levels of these anti-apoptotic proteins have been associated with radio- and chemoresistance and poor clinical outcome. Inhibition of anti-apoptotic Bcl-2 family members therefore represents an appealing strategy to overcome resistance to anti-cancer therapies. The aim of this study was to evaluate combined effects of radiation and the pan-Bcl-2 inhibitor AT-101 in HNSCC in vitro. In addition, we determined human plasma levels of AT-101 obtained from a phase I/II trial, and compared these with the effective in vitro concentrations to substantiate therapeutic opportunities. METHODS: We examined the effect of AT-101, radiation and the combination on apoptosis induction and clonogenic survival in two HNSCC cell lines that express the target proteins. Apoptosis was assessed by bis-benzimide staining to detect morphological nuclear changes and/or by propidium iodide staining and flow-cytometry analysis to quantify sub-diploid apoptotic nuclei. The type of interaction between AT-101 and radiation was evaluated by calculating the Combination Index (CI) and by performing isobolographic analysis. For the pharmacokinetic analysis, plasma AT-101 levels were measured by HPLC in blood samples collected from patients enrolled in our clinical phase I/II study. These patients with locally advanced HNSCC were treated with standard cisplatin-based chemoradiotherapy and received dose-escalating oral AT-101 in a 2-weeks daily schedule every 3 weeks. RESULTS: In vitro results showed that AT-101 enhances radiation-induced apoptosis with CI's below 1.0, indicating synergy. This effect was sequence-dependent. Clonogenic survival assays demonstrated a radiosensitizing effect with a DEF37 of 1.3 at sub-apoptotic concentrations of AT-101. Pharmacokinetic analysis of patient blood samples taken between 30 min and 24 h after intake of AT-101 showed a dose-dependent increase in plasma concentration with peak levels up to 300-700 ng/ml between 1.5 and 2.5 h after intake. CONCLUSION: AT-101 is a competent enhancer of radiation-induced apoptosis in HNSCC in vitro. In addition, in vitro radiosensitization was observed at clinically attainable plasma levels. These finding support further evaluation of the combination of AT-101 with radiation in Bcl-2-overexpressing tumors.

A phase I-II study of postoperative capecitabine-based chemoradiotherapy in gastric cancer.

BACKGROUND: The Intergroup 0116 randomized study showed that postoperative 5-fluorouracil-based chemoradiotherapy improved locoregional control and overall survival in patients with gastric cancer. We hypothesized that these results could be improved further by using a more effective, intensified, and convenient chemotherapy schedule. Therefore, this Phase I-II dose-escalation study was performed to determine the maximal tolerated dose and toxicity profile of postoperative radiotherapy combined with concurrent capecitabine. PATIENTS AND METHODS: After recovery from surgery for adenocarcinoma of the gastroesophageal junction or stomach, all patients were treated with capecitabine monotherapy, 1,000 mg/m2 twice daily for 2 weeks. After a 1-week treatment-free interval, patients received capecitabine (650-1,000 mg/m2 orally twice daily 5 days/week) in a dose-escalation schedule combined with radiotherapy on weekdays for 5 weeks. Radiotherapy was delivered to a total dose of 45 Gy in 25 fractions to the gastric bed, anastomoses, and regional lymph nodes. RESULTS: Sixty-six patients were treated accordingly. Two patients went off study before or shortly after the start of chemoradiotherapy because of progressive disease. Therefore, 64 patients completed treatment as planned. During the chemoradiotherapy phase, 4 patients developed four items of Grade III dose-limiting toxicity (3 patients in Dose Level II and 1 patient in Dose Level IV). The predefined highest dose of capecitabine, 1,000 mg/m2 twice daily orally, was tolerated well and, therefore, considered safe for further clinical evaluation. CONCLUSIONS: This Phase I-II study shows that intensified chemoradiotherapy with daily capecitabine is feasible in postoperative patients with gastroesophageal junction and gastric cancer.

Prospective study on late renal toxicity following postoperative chemoradiotherapy in gastric cancer.

PURPOSE: Postoperative chemoradiotherapy in gastric cancer improves locoregional control and survival. Reports on late toxicity, however, have been scarce thus far. Because renal toxicity is one of the most serious late complications in upper abdominal radiotherapy, we prospectively analyzed kidney function in patients who underwent postoperative chemoradiotherapy for gastric cancer. PATIENTS AND METHODS: In 44 patients, Tc99m-thiatide renography was performed before and at regular intervals after postoperative chemoradiotherapy. The left-to-right (L/R) ratio was used as an index of the relative kidney function. Mean L/R values were calculated for four follow-up time intervals. For all patients, kidney V20 (percentage of the volume of the kidney that received more than 20 Gy) and mean dose of both kidneys were retrieved from the three-dimensional dose-volume histograms. RESULTS: We observed a progressive decrease in left renal function of 11% (p = 0.012) after 6 months, up to 52% (p < 0.001) after >18 months. The V20 (left kidney) and mean left kidney dose were identified as parameters associated with decreased kidney function. Mean serum creatinine was increased from 74.6 micromol/L before treatment to 86.1 micromol/L at 1 year after chemoradiotherapy (p < 0.001). In patients with a follow-up of 18-28 months, one case of severe renovascular hypertension was observed. CONCLUSION: A progressive relative functional impairment of the left kidney in patients after postoperative chemoradiotherapy for gastric cancer is demonstrated. To optimize the survival benefit that can be established with adjuvant regimens, strategies to minimize the dose to the kidneys and other critical organs should be explored.

Phase I and pharmacokinetic study of combined treatment with perifosine and radiation in patients with advanced solid tumours.

PURPOSE: Perifosine is an orally applicable, membrane-targeted alkylphosphocholine analogue with antitumour activity and radiosensitising properties in preclinical models. The purpose of this phase I study was to determine the feasibility and tolerability of concurrent daily perifosine and radiation in patients with advanced cancer. PATIENTS AND METHODS: Starting dose of perifosine was 50 mg/day; dose escalation was in steps of 50mg. Daily administration commenced 2 days before radiotherapy and was continued throughout the radiation treatment. At least three patients were entered at each dose level; at the 150 mg/day level 10 patients were included. Pharmacokinetic sampling was performed weekly pre-dosing. Twenty-one patients were entered. Tumour types included NSCLC (n=17), prostate, oesophageal, colon and bladder cancer. Most patients (16/21) had received prior chemotherapy; none radiotherapy. Median number of daily perifosine administrations was 31 (range 24-53). Mean radiation dose (BED(10)) was 59.8 Gy (range 50.7-87.5 Gy in 13-28 fractions). RESULTS: Major drug-related toxicities according to CTC criteria were nausea in 57%, fatigue in 48%, vomiting in 38%, diarrhoea in 38% and anorexia in 19%. No bone marrow toxicity was observed. DLT (nausea/vomiting) was encountered in two of five patients at the 200mg/day dose level. Dose-dependent steady-state plasma levels were reached after 1 week. Major radiotherapy-related acute toxicity consisted of dysphagia in 38% and pneumonitis in 29%. CONCLUSION: Perifosine can be safely combined with fractionated radiotherapy. A dosage of 150 mg/day, to be started at least 1 week prior to radiotherapy, is recommended for phase II evaluation.

Urinary and fecal excretion of topotecan in patients with malignant solid tumours.

PURPOSE: The objectives of the study were to determine the pharmacokinetics and routes of excretion of topotecan following intravenous or oral administration to patients with refractory solid tumours. METHODS: Patients were randomized to receive either oral (2.3 mg/m(2)) or intravenous (1.5 mg/m(2)) topotecan once daily for 5 days in course 1. Patients who received in course 1 oral topotecan received in course 2 intravenous topotecan on day 1 followed by oral topotecan on days 2 to 5. Patients who received in course 1 intravenous topotecan received in course 2 oral topotecan once daily for 5 days. Plasma pharmacokinetics were performed on day 1 of course 1 (all patients) and course 2 (only patients receiving intravenous topotecan on that day). In course 1, urine and feces were collected for up to 9 days after the first dosage. The amounts of topotecan and N-desmethyl topotecan in plasma, urine and feces were determined by validated high-performance liquid chromatographic assays. RESULTS: A total of 11 patients were enrolled in the study. Nine patients were evaluable for pharmacokinetics. Plasma pharmacokinetics were similar to those previously reported. The principal route of excretion was the urine, with approximately 49% of the intravenously administered topotecan dose and 20% of the oral dose collected in the urine as parent drug. Approximately 18% and 33% of the intravenous and oral dose, respectively, were recovered unchanged in the feces. Only small amounts of N-desmethyl topotecan were found in the excreta. CONCLUSIONS: Fecal and urinary excretion of unchanged topotecan were the major routes of topotecan elimination. Approximately 28% of the intravenous dose and 43% of the oral dose of topotecan were unaccounted for and eliminated through other routes.