The intracellular histamine antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy] ethamine.HCL, may potentiate doxorubicin in the treatment of metastatic breast cancer: Results of a pilot study.

N,N-diethyl-2-[4-(phenylmethyl)phenoxy] ethanamine.HCl (DPPE) is a diphenylmethane analog of tamoxifen that antagonizes the intracellular binding of histamine to growth-regulatory sites, a proportion of which represents P450 enzymes, in microsomes and nuclei. We previously reported increased response rates and decreased myelotoxicity in patients with prostate and other cancers who received an intensive dose/schedule of DPPE plus single-agent chemotherapy. We now report the results of a study of DPPE combined with a standard dose/schedule of doxorubicin in twenty-three patients with metastatic breast cancer, sixteen of whom had received prior non-anthracycline chemotherapy. DPPE (6 mg/kg) was infused intravenously (i.v.) over 80 minutes. Doxorubicin (60 mg/m2) was administered i.v. over the last 20 minutes of the DPPE infusion. Treatment was repeated every 3 weeks (maximum, 7 cycles). Patients achieving complete response (CR) were followed off treatment until relapse. All patients were evaluable for toxicities and efficacy. Sixteen patients (69%; 95% C.I. = 47-87%) responded (7 CR and 9 PR). Eleven responders, including 6 with CR, had prior chemotherapy. Five responders (2CR, 3PR) had a poor (ECOG 3/4) performance status pre-treatment. Median CR duration was 11 (range 5-18) months. Hematological toxicity was low; GI toxicity (nausea/vomiting/dyspepsia) appeared somewhat higher than historical experience, but responded well to anti-emetics, ranitidine, and/or dexamethasone in most patients; a mean absolute drop in left ventricular ejection fraction of 8% occurred in 17 patients who received = or > 300 mg/m2 doxorubicin. The observed response rate in DPPE/doxorubicin-treated patients appeared to be higher than historically reported for doxorubicin alone in this setting, suggesting a chemopotentiating effect of DPPE. A multi-centre trial of this regimen in an additional 32 patients with early metastatic breast cancer has been conducted by the Clinical Trials Group, National Cancer Institute of Canada, and a phase 3 study is planned.

N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine in combination with cyclophosphamide: an active, low-toxicity regimen for metastatic hormonally unresponsive prostate cancer.

PURPOSE: The intracellular histamine antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine. HCl (DPPE), potentiates chemotherapy cytotoxicity to malignant cells but protects normal tissue, including bone marrow, gut, and hair. We assessed the response to and clinical toxicity of DPPE/cyclophosphamide therapy in 20 patients with advanced hormonally unresponsive prostate cancer, 19 of whom were symptomatic. PATIENTS AND METHODS: Subjects received a maximally tolerated dose of DPPE (6 mg/kg) intravenously (IV) over 80 minutes. Cyclophosphamide (600 to 800 mg/m2; maximum dose, 1,500 mg) was administered over the last 20 minutes of DPPE infusion. Treatments (usually outpatient) were given once weekly for 4 weeks, followed by a 1-week delay, and then 2 of every 3 weeks as long as the patient was deemed to benefit. RESULTS: Five of seven patients (71%) with measurable soft tissue disease had a partial remission (PR). Three of 16 (19%) with assessable bone disease responded (one complete remission [CR] and two PRs). Nine of 18 (50%) with an elevated serum level of prostate-specific antigen (PSA) had more than a 50% (mean +/- SD, 78% +/- 14%) decrease. Eleven of 13 (85%) with bone pain had partial or complete resolution of this symptom; the PSA level and bone scan improved in six and two of these subjects, respectively. Acute treatment toxicity consisted of nausea/vomiting (six of 20) and ataxia (20 of 20), which correlated with peak serum levels of DPPE. Delayed effects (24 to 48 hours) consisted mainly of tiredness and mild nausea; one patient developed hemorrhagic cystitis. Bone marrow and hair follicle toxicity was negligible in 14 and 15 patients, respectively. CONCLUSION: DPPE/cyclophosphamide appears to be an active regimen for metastatic prostate cancer, with the added benefit of relatively low toxicity.

Results of a clinical trial in humans with refractory cancer of the intracellular histamine antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine-HCl, in combination with various single antineoplastic agents.

PURPOSE: We assessed N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine-HCl (DPPE) potentiation of chemotherapy in vitro and performed a pharmacokinetic study and phase I/II trial of DPPE, combined with various single agents, in patients with advanced refractory cancer. PATIENTS AND METHODS: In vitro chemopotentiation by DPPE was assessed in drug-sensitive and -resistant (multidrug resistant-positive [MDR+]) human tumor cells using a colony survival assay. The effect of DPPE and verapamil on the intracellular concentration of daunorubicin in MDR+ cells was compared. For the clinical study, subjects with progressive malignancy received a weekly infusion of a maximally tolerated dose of DPPE (240 mg/m2) over 80 or 440 minutes, in conjunction with a single chemotherapy drug to which, in most cases, the patient's tumor was previously resistant. Concentrations of DPPE in blood and urine were determined by high-performance liquid chromatography (HPLC). RESULTS: In vitro, micromolar concentrations of DPPE potentiated (fivefold to 10-fold) chemotherapy cytotoxicity to both drug-sensitive and -resistant cells, but did not inhibit the p-glycoprotein pump; in vivo, serum levels of DPPE were 3 to 5 mumol/L at the end of 80 minutes and 1 to 2 mumol/L after 440 minutes of infusion. Of 48 patients monitored for a minimum of four DPPE/chemotherapy treatment cycles, 16 (33%) progressed, 12 (25%) stabilized, 12 (25%) improved, and eight (17%) responded (one complete and seven partial remissions). Four of 11 subjects who did not respond to the 80-minute infusion regimen improved with the 440-minute infusion; one had a partial remission of melanoma. In more than 600 patient-treatments, bone marrow toxicity was negligible (mean absolute neutrophil count [ANC] > 2.0 x 10(9)/L). Acute CNS symptoms associated with DPPE infusions were of relatively short duration (1 to 4 hours); delayed toxicity attributable to DPPE consisted of mild nausea and/or fatigue (1 to 2 days). CONCLUSION: Although preliminary, the results suggest that more structured trials should be performed to determine whether DPPE may increase the therapeutic index of certain chemotherapy drugs.