Chemopreventive effects of the aromatase inhibitor vorozole (R 83842) in the methylnitrosourea-induced mammary cancer model

The chemopreventive activity of the highly specific nonsteroidal aromatase inhibitor, vorozole, was examined in the methylnitrosourea (MNU)-induced rat model of mammary carcinogenesis. Various doses of vorozole (0.08-1.25 mg/kg body wt/day) were administered daily (by gavage) to female Sprague-Dawley rats starting at 43 days of age. Seven days later, the rats were given a single i.v. dose of MNU (50 mg/kg body wt). Rats were continually treated with vorozole until the end of the experiment (120 days post-MNU). Vorozole caused a dose dependent inhibition of mammary cancer multiplicity. The highest dose of vorozole (1.25 mg/kg body wt/day) decreased cancer multiplicity by approximately 90%, and simultaneously decreased cancer incidence from 100 to 44%. The next two highest doses of vorozole (0.63 and 0.31 mg/kg body wt/day) inhibited MNU-induced mammary cancer multiplicity by 70-80%. Even the two lowest doses of vorozole (0.16 and 0.08 mg/kg body wt/ day) decreased cancer multiplicity -50%. Serum level determinations were performed on a variety of endpoints at either 4 or 24 h following the last dose of vorozole. Insulin-like growth factor (IGF)-1 levels were slightly, but significantly, increased by vorozole treatment. Vorozole induced striking increases in serum testosterone levels at 4 h at all the dose levels employed. Testosterone levels were significantly elevated over controls at 24 h in rats given the lower doses of vorozole (0.08-0.31 mg/kg body wt/day), but were significantly lower than in rats administered the higher doses of vorozole (0.63 or 1.25 mg/kg body wt/ day). This result presumably reflects the limited half- life of vorozole in rats. In a second series of experiments, the effects of limited duration of dosing with vorozole (2.5 mg/kg body wt/day) or intermittent dosing with vorozole were determined. Treatment of rats with vorozole for limited time periods, from 3 days post-MNU administration until 30 or 60 days post-MNU treatment, resulted in significant delays in the time to appearance of palpable cancers. However, these limited treatments did not greatly affect the overall incidence or multiplicity of mammary cancers when compared with the MNU controls at the end of the study (150 days post-MNU). Finally, the effects of intermittent dosing with vorozole (2.5 mg/kg body wt/day) were examined. Rats were administered cycles of vorozole daily for a period of 3 weeks followed by treatment with the vorozole vehicle for the next 3 weeks (total of four cycles). Although this intermittent treatment did inhibit the appearance of new tumors during each of the periods that vorozole was administered, it did not cause regression of palpable cancers.      

Antitumoral and endocrine effects of (+)-vorozole in rats bearing dimethylbenzanthracene-induced mammary tumors.

The antitumoral activity of vorozole, a potent and specific nonsteroidal aromatase inhibitor, against 7,12-dimethylbenz(a)anthracene-induced estrogen-dependent mammary adenocarcinoma was evaluated in 257 Sprague-Dawley rats. Twice daily p.o. administration of 1 and 5 mg/kg of the racemate R 76713 for 42 days induced almost complete regression of tumors, inhibited the appearance of new tumors, and reduced multiplicity of the remaining tumors. Antitumoral effects observed after ovariectomy or treatment with 5 mg/kg twice a day were not significantly different. R 76713, the racemate, (+)-vorozole (both at 2.5 mg/kg twice a day), and ovariectomy all similarly reduced tumor growth at 42 days by 90% or more, lowered the number of existing tumors, and prevented the appearance of new tumors. The less active levo-enantiomer (-)-vorozole at the same dose did not alter tumor growth. Vorozole reduced serum estradiol to the levels measured in ovariectomized animals. Serum progesterone levels were lowered, but to a much lesser extent than after ovariectomy, while serum luteinizing hormone and follicle-stimulating hormone concentrations increased, but also much less than after ovariectomy. On the other hand, the androgen levels, which remained undetectable or decreased after ovariectomy, markedly rose after vorozole treatment. These endocrine changes, observed in intact female rats, were not detected in ovariectomized animals demonstrating the ovarian origin of the endocrine changes induced by vorozole.     

Comparison of the systemic and intratumoral effects of tamoxifen and the aromatase inhibitor vorozole in postmenopausal patients with primary breast cancer.

PURPOSE: To determine biologic differences, if any, between presurgical endocrine treatment with an aromatase inhibitor (vorozole) and tamoxifen in patients with postmenopausal primary breast cancer. PATIENTS AND METHODS: Randomization was to 12 weeks of 2.5 mg of vorozole per day or 20 mg of tamoxifen per day, both orally. Clinical response was assessed monthly together with serum sex hormone binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogens (E1, E2, and E1S), lipids, insulin-like growth factor-1 (IGF-1), and bone metabolites (CrossLaps CTx). Tissue samples for Ki67, apoptotic index (AI), estrogen receptor, and progesterone receptor were collected at 0, 2, and 12 weeks. RESULTS: Ki67 fell by 58% and 43% (means) at 2 weeks in the vorozole and tamoxifen patients, respectively (P =.13). In the vorozole group, the correlations of proportional changes in Ki67 at 2 weeks with tumor volume changes and clinical response at 12 weeks were not significant (P =.09) and marginally significant (P =.04), respectively. Serum lipids did not differ between groups. Serum levels of EI, E2, and E1S were suppressed markedly by vorozole, whereas levels of SHBG increased and LH and FSH fell significantly with tamoxifen. IGF-1 levels fell significantly with tamoxifen (P =.001) compared with the nonsignificant rise with vorozole. Twelve-week CTx values fell by 19% with tamoxifen (P =.006) and rose by 11% with vorozole (P =.15). CONCLUSION: The correlation with vorozole of Ki67 with volume and clinical response supports this as an intermediate marker. The nonsignificant effects on bone and lipid metabolism by the aromatase inhibitor may be important to consider for adjuvant and potential prevention strategies.     

Antitumor efficacy and pharmacokinetic analysis of 4-hydroperoxycyclophosphamide in comparison with cyclophosphamide±hepatic enzyme effectors

 4-Hydroperoxycyclophosphamide is an oxazaphosphorine which is readily converted without enzymatic involvement to 4-hydroxycyclophosphamide – a key intermediate in the antitumor activity of this class of drugs. The efficacy of 4-hydroperoxycyclophosphamide as a systemically administered antitumor drug was examined in mice bearing EMT-6 mammary carcinoma and in rats bearing 13762 mammary carcinoma in comparison with other oxazaphosphorines. 4-Hydroperoxycyclophosphamide was a more potent tumor cell killing agent than cyclophosphamide or ifosfamide in animals bearing the EMT-6 tumor. There were no significant differences in the toxicity to bone marrow amongst the three oxazaphosphorines. 4-Hydroperoxycyclophosphamide (90 mg/kg) on days 7, 9 and 11 produced 11.5 days of tumor growth delay compared with 10.4 days and 7.1 days for cyclophosphamide (150 mg/kg) and ifosfamide (150 mg/kg) administered on the same schedule, respectively. 4-Hydroperoxycyclophosphamide was tolerated at 90 mg/kg daily for 5 days and at 75 mg/kg twice daily for 4 days producing tumor growth delays of 14.4 days and 16.6 days, respectively. In rats bearing 13762 tumors, 4-hydroperoxycyclophosphamide (90 mg/kg) on days 8, 10 and 12 produced a tumor growth delay of 14.5 days compared with 8.9 days for cyclophosphamide (100 mg/kg) administered on the same schedule. Treatment of 13762 tumor-bearing rats with phenobarbital, pentobarbital or etanidazole increased the tumor growth delay produced by cyclophosphamide while treatment with cimetidine decreased the tumor growth delay produced by cyclophosphamide but not significantly. Administration of 4-hydroperoxycyclophosphamide (90 mg/kg) produced blood concentrations of 4-hydroxycyclophosphamide three-fold higher than those produced by administration of cyclophosphamide (100 mg/kg) at 15 min after drug injection. Treatment with phenobarbital or pentobarbital increased 4-hydroxycyclophosphamide blood concentration while pretreatment with cimetidine decreased 4-hydroxycyclophosphamide blood concentration from cyclophosphamide. 4-Hydroperoxycyclophosphamide is an effective antitumor agent worthy of further investigation. Received: 25 July 1995/Accepted: 29 January 1996     

Chemopreventive effects of the aromatase inhibitors vorozole (R-83842) and 4-hydroxyandrostenedione in the methylnitrosourea (MNU)-induced mammary tumor model in Sprague-Dawley rats

The chemopreventive activity of the aromatase inhibitors vorozoleand 4-hydroxyandrostenedione were determined in the methylnitrosourea(MNU)-induced model of rat mammary tumorigenesis. Vorozole (5and 2.5 mg/kg body wt) and 4-hydroxyandrostenedione (15 and6 mg/rat) were administered daily (by gavage) to virgin femaleSprague-Dawley rats starting at an age of 43 days. Seven dayslater animals were given a single dose of MNU. Following treatmentwith MNU, animals continued to be treated with vorozole and4-hydroxyandrostenedione daily until the end of the experiment(100 days post MNU treatment). Vorozole at either dose provedto be a profound inhibitor of MNU-Induced mammary tumors. Vorozoledecreased tumor incidence from 100% to 10%, while simultaneouslydecreasing tumor multiplicity from 5 tumors per annual to 0.1tumors per animal. This chemopreventive effect was accompaniedby significant increases In body weight gain in the animalstreated with vorozole when compared with control rats. In contrast,neither dose of 4-hydroxyandrostenedione had any effect on tumorincidence and only the higher dose slightly decreased tumormultiplicity.     

Pharmacoeconomic analysis of adjuvant therapy with exemestane, anastrozole, letrozole or tamoxifen in postmenopausal women with operable and estrogen receptor-positive breast cancer

Objective To compare the efficiency of adjuvant therapy with aromatase inhibitors or with tamoxifen in postmenopausal women with operable breast cancer and positive estrogen receptors. Material and methods A cost-utility analysis was performed based on a Markov model, from the Spanish National Health Care System perspective, comparing the treatment with exemestane (EXE: 25 mg/day) or tamoxifen (TAM: 20 mg/day) after 2–3 years of monotherapy with TAM; anastrozole (ANA, 1 mg/day) or TAM (20 mg/day) without previous TAM therapy; and letrozole (LET: 2.5 mg/day) or placebo after 5 years of monotherapy with TAM. The follow-up of a hypothetical cohort of women starting treatment at 63 years of age was simulated during 10 and 20 years. The probabilities of transition between health states and quality adjusted life years (QALYs) were obtained from the literature, and the unit costs (∈ corresponding to 2004) from a Spanish database. Results After 10 and 20 years of follow-up, more QALYs per patient would be gained with the EXE scheme (0.230–0.286 and 0.566–0.708, respectively) than with ANA (0.114 and 0.285) and LET (0.176 and 0.474). The cost of gaining one QALY was lower with the EXE scheme (50,801–62,522 ∈ and 28,849–35,371 ∈ respectively) than with ANA (104,272 ∈ and 62,477 ∈) and LET (91,210 ∈ and 49,460 ∈). The result was stable for the cost per life-year gained (LYG) and in the sensitivity analysis. Conclusions The EXE scheme after TAM is more cost-effective than the ANA and LET schemes.     

Toremifene concentration and multidrug resistance in lung tumors

 In this pharmacokinetics study, concentrations of toremifene (TOR), a new antiestrogen, were measured after a 7-day oral treatment in serum, lung, and tumor tissue to determine the optimal dose of TOR for the modulation of clinical multidrug resistance in patients with lung cancer. Target levels of the antiestrogen were based on previous in vitro studies. Altogether, 18 patients with operable lung tumors were studied. TOR was given in an open, nonrandomized, phase I study at three different dose levels. The medication consisted of oral TOR given for 7 days at either 240, 480, or 600 mg/day before surgical removal of the tumor. At least five patients were scheduled to be included at each dose level, with all five receiving the full course of therapy before escalation of the dose. Blood samples for serum TOR concentration measurements were taken on days 0 and 7. Specimens of tumor and normal lung tissue of approximately 0.5 g were taken on day 7. The concentrations of TOR and its metabolites were determined in serum, lung, and tumor tissue at different dose levels. Altogether, 12 evaluable patients completed the scheduled treatment. The concentrations measured in serum, lung, and tumor tissue increased along with the dose used, such that the highest TOR values were achieved at 600 mg/day, with mean values being 4.9 μmol/l, 175.0 μmol/g, and 122.7 μmol/g, respectively. The concentrations of TOR and its metabolite N-demethyltoremifene were highest in lung tissue, but the values measured in tumor specimens were also well above the respective concentrations detected in serum samples. The TOR doses of 240 and 480 mg/day were well tolerated. One patient in the group treated at 600 mg/day had to discontinue the treatment because of headache and nausea. TOR given at doses ranging from 480 to 600 mg/day for 7 days will produce serum, lung, and tumor concentrations of the parent drug and its metabolites that have been shown to reverse multidrug resistance of cancer cells in vitro. As the 480-mg/day dose of TOR produced tumor concentrations high enough to reverse multidrug resistance without producing adverse drug reactions, the dose recommended for the foreseen clinical trials in the reversal of multidrug resistance would be 480 mg/day for 7 days. Received: 26 July 1995/Accepted: 15 May 1996     

A phase I study of irinotecan and infusional cisplatin for advanced non-small-cell lung cancer

 A phase I study was performed to establish the optimum dose for combination therapy with infusional cisplatin and irinotecan (CPT-11) in non-small-cell lung cancer (NSCLC). The subjects were 20 patients with a performance score of 0–2 with untreated advanced NSCLC. Cisplatin was administered by 5-day continuous intravenous infusion at 20–25 mg/m² per day. CPT-11 was administered by bolus infusion at a starting dose of 20 mg/m² on days 1 and 8 or 60 mg/m² per day on day 1 alone, followed by serial increments of 20 mg/m². Since grade 4 granulocytopenia was observed in two of the five patients receiving 20 mg/m² per day cisplatin (days 1–5) and 100 mg/m² CPT-11 (day 1), and since one of them developed severe pneumonia and sepsis associated with the granulocytopenia, the regimen was considered to be intolerable. In the same patient, grade 4 thrombocytopenia and grade 3 diarrhea were observed. Therefore, the optimum dose appeared to be 20 mg/m² per day (days 1–5) for cisplatin and 80 mg/m² (day 1) for CPT-11. The side effects were grade 2 diarrhea in one of three patients, and grade 2 vomiting in three patients, but grade ≥2 hemotoxicity was not observed. This combined regimen resulted in a partial response in 9 out of 19 assessable patients. The dose-limiting factor in this combination therapy was granulocytopenia, and a high efficacy rate was obtained. Received: 14 August 1995 / Accepted: 3 June 1996     

The effects of aromatase inhibitors and antiestrogens in the nude mouse model

The effects of antiestrogens, tamoxifen and ICI 182,780, and aromatase inhibitors, arimidex (anastrozole ZD1033) and letrozole (CGS 20,267), on the growth of tumors were studied in nude mice. In this model, estrogen dependent MCF-7 human breast cancer cells stably transfected with the aromatase gene were inoculated in four sites per mouse. Sufficient estrogen is produced from aromatization of androstenedione supplement (0.1 mg/mouse/day) by the cells to stimulate their proliferation, tumor formation, and maintain the uterus similar to that of the intact mouse. Once the tumors reached a measurable size, the mice were injected with antiestrogen or inhibitor for 35–56 days. Tumor volumes were measured weekly. At autopsy, the tumors were removed, cleaned, and weighed. Statistical data was determined from tumor weights. Both antiestrogens were effective in reducing tumor growth in these mice. Tamoxifen appears to be more effective than ICI 182,780, although the former stimulated the uterine weight whereas the pure antiestrogen did not. However, both aromatase inhibitors were more effective than the antiestrogens. Tumor regression was observed with letrozole. Thus, after-treatment tumor weights were less than those of a group of mice at the start of treatment. The aromatase inhibitors also reduced the weight of the uterus, suggesting that these compounds, as well as the pure antiestrogen, may not cause endometrial proliferation, unlike tamoxifen. These aromatase inhibitors may not only benefit patients who have relapsed from tamoxifen, but may be more effective in patients as first line agents for suppressing the effects of estrogen.     

Erythropoietin and granulocyte-macrophage colony-stimulating factor allow acceleration and dose escalation of cyclophosphamide/epidoxorubicin/5-fluorouracil chemotherapy: a dose-finding study in patients with advanced breast cancer

 To verify whether the association of granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (EPO) would allow both the acceleration and the dose escalation of the cyclophosphamide/epidoxorubicin/5-fluorouracil (CEF) regimen as first-line therapy in advanced breast cancer patients, we conducted a dose-finding study. Cohorts of three consecutive patients received cyclophosphamide (Ctx, dose range 800 –1400 mg/m²), epidoxorubicin (Epidx, dose range 70–100 mg/m²), and 5-fluorouracil (5-Fu, 600 mg/m², fixed dose) given as an intravenous bolus on day 1 every 14 days; GM-CSF at 5 μg/kg given as a subcutaneous injection from day 4 to day 11; and EPO at 150 IU/kg given as a subcutaneous injection three times a week. In no single patient was any dose escalation allowed. A total of 14 patients entered the study. At the 4th dose level (Ctx 1400 mg/m², Epidx 100 mg/m², 5-Fu 600 mg/m²), two patients had dose-limiting mucositis and one patient developed dose-limiting neutropenia. Therefore, the 3rd cohort received the maximum tolerated dose, i.e. Ctx at 1200 mg/m², Epidx at 90 mg/m², and 5-Fu at 600 mg/m², given every 18.5 (±2.5) days. Toxicity was moderate and manageable in an outpatient setting. Only 1 admission at the 4th dose level was required. Throughout the 4 dose levels there was no toxicity-related death; grade IV leukopenia ranged from 24% to 75% of cycles and grade IV thrombocytopenia ranged from 6% to 8%. No grade IV anemia was recorded. Increasing the doses of Ctx and Epidx while maintaining a fixed dose of 5-Fu with the support of both EPO and GM-CSF allows safe acceleration and dose escalation of CEF chemotherapy. Further controlled studies will evaluate the activity and efficacy of this strategy. Received: 8 October 1995/Accepted: 1 March 1996     

Antitumor activity and low intestinal toxicity of S-1, a new formulation of oral tegafur,in experimental tumor models in rats

 S-1, a new oral antitumor agent, is composed of 1-(2-tetrahydrofuryl)-5-fluorouracil (Tegafur, FT), 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo) in a molar ratio of 1 : 0.4 : 1. FT which is a masked compound of 5-fluorouracil (5-FU) acts as an effector, while both CDHP and Oxo which do not have antitumor activity themselves act as modulators. In this study, the antitumor activity and intestinal toxicity of S-1 were investigated using experimental tumor models in rats, and compared with those of other oral fluoropyrimidines, namely 5-FU, FT, FCD (1 M FT/0.4 M CDHP) and UFT (combination of FT and uracil). In rats bearing subcutaneous Yoshida sarcoma, S-1 inhibited tumor growth at the lowest dose (ED₅₀ value: S-1 5, UFT 22, FT 82, FCD 5, and 5-FU 19 mg/kg per day), and induced the least host body weight suppression, leading to the highest therapeutic index (TI) (S-1 4.5, UFT 1.4, FT 1.8, FCD 2.0, and 5-FU 1.4). S-1 also showed a higher therapeutic effect than UFT against AH-130 and Sato lung carcinoma. After administration of S-1 and UFT at equitoxic doses, S-1 showed a higher and more prolonged concentration of 5-FU than UFT both in plasma (AUC_0-∞: S-1 28 nmol h/ml, UFT 15 nmol⋅h/ml) and in tumor tissue (AUC_0-∞: S-1 95 nmol h/g tissue, UFT 52 nmol h/g tissue), leading to a higher 5-FU level incorporated into the RNA fraction (F-RNA level) in tumor tissue (AUC_0-24: S-1 7.0 nmol h/mg RNA, UFT 4.3 nmol h/mg RNA) and 5–8% higher thymidylate synthase (TS) inhibition in tumor tissue at every time-point through 24 h. Compared with other oral fluoropyrimidines after administration of the maximal tolerable dose (MTD), S-1 caused the lowest rates of intestinal toxicities, such as diarrhea and occult blood in feces. S-1 also showed a higher antitumor effect on Yoshida sarcoma implanted intracolonically than UFT at an equitoxic dose (tumor weight: S-1 64±30 mg, UFT 133±52 mg; P<0.05). These results suggest that CDHP, which is a potent inhibitor of 5-FU degradation, increases the antitumor activity of FT, and that Oxo, which is an inhibitor of 5-FU phosphorylation, locally protects the gastrointestinal tract from 5-FU-induced toxicity without decreasing the antitumor activity. Received: 13 October 1996/Accepted: 18 May 1996     

Intraarterial O6-benzylguanine enables the specific therapy of nitrosourea-resistant intracranial human glioma xenografts in athymic rats with 1,3-bis(2-chloroethyl)-1-nitrosourea

 The prognosis for patients with malignant gliomas continues to be dismal. The high degree of resistance of gliomas to nitrosourea-based chemotherapy is one major factor in poor treatment outcome. The identification of O ⁶-alkylguanine-DNA alkyltransferase (AGAT) as a major determinant of nitrosourea resistance has resulted in the development of several agents to inactivate this repair protein and counteract tumor cell resistance. However, a major problem in preclinical trials has been the marked nitrosourea dose limitations imposed by the prior administration of AGAT-depleting agents. We investigated the AGAT depletion and selective enhancement of BCNU activity of intraarterial (i.a.) O ⁶-benzylguanine (O ⁶BG) in the human malignant glioma xenograft D-456 MG growing intracranially (i.c.) in athymic rats. Whereas i.a. O ⁶BG at 2.5 mg/kg produced 100% inhibition of D-456 MG AGAT i.c. activity 8 h after administration, intraperitoneal (i.p.) O ⁶BG at this dose produced only 40% inhibition, requiring dose escalation to 10 mg/kg to produce 100% AGAT depletion. Prior administration of i.p. O ⁶BG (10 mg/kg) and i.a. O ⁶BG (2.5 mg/kg) limited maximum tolerated intravenous (i.v.) BCNU doses (37.5 mg/kg when given alone) to 6.25 and 25 mg/kg, respectively. Higher doses of BCNU alone or in combination with O ⁶BG produced histopathologic evidence of cerebral and hepatic toxicity. Therapy experiments revealed a significantly improved median survival for rats treated with O ⁶BG i.a. (2.5 mg/kg) plus BCNU i.v. (25 mg/kg, days 61 and 59 in duplicate experiments) compared with saline (day 21, P=0.001), O ⁶BG i.a. or i.p. (days 22 and 23, P=0.001), BCNU i.v. (37.5 mg/kg, day 29, P=0.001), and O ⁶BG i.p. (10 mg/kg) plus BCNU i.v. (6.25 mg/kg, day 37, P<0.001). Therefore, O ⁶BG i.a., by virtue of rapid AGAT depletion and selective uptake into i.c. tumors, offers significant potential for regional chemomodulation of AGAT-mediated nitrosourea resistance in malignant human gliomas with concomitant reduction of systemic toxicity. Received: 30 January 1996/Accepted: 16 June 1996     

Response of sensitive and resistant IgM immunocytomas to cis-diamminedichloroplatinum(II) does not correlate with the platination level or with the formation or removal of DNA adducts

 An IgM immunocytoma cell line sensitive to cis-diamminedichloroplatinum(II) (CDDP) and a subline with acquired resistance were grown in LOU/M rats. In a previous study with such rats that had been treated with a high dose of CDDP (10 mg/kg) the tumors did not show differences in cellular platinum content or DNA-adduct levels, either immediately after treatment or 24 h later. Recently, this high dose was found to overcome resistance. Therefore, the study was repeated with a 10-fold lower dose (1 mg/kg, i.v.). At 1 and 24 h after treatment, tumor and kidney tissue were assayed for cellular platinum (atomic absorption spectroscopy, AAS) and DNA platination (immunochemical detection of the four CDDP-DNA adducts). The results were compared with previous data. All tissues showed a linear response to dose with regard to platinum uptake as well as adduct formation, with no quantitative difference being seen between the tumors. Also the relative occurrence of the four adducts was very similar. Between 1 and 24 h, in tumors a substantial decrease occurred in both platinum content and adduct level; the kidneys showed little reduction, if any. At the lower CDDP dose a somewhat larger loss of platinum and removal of DNA adducts was observed for the resistant tumor, but these differences could be explained by “dilution”, as this tumor continues to grow after low-dose treatment (about 20% within 24 h). Since the strong difference observed between the tumors in sensitivity to CDDP cannot be attributed to differences in CDDP uptake, efficiency of adduct formation, or repair capability, other mechanisms are held responsible. Received 10 August 1995 / Accepted: 14 August 1996     

Antitumor activity of the aromatase inhibitor FCE 24928 on DMBA-induced mammary tumors in ovariectomized rats treated with testosterone

Summary The antitumor activity of the irreversible aromatase inhibitor FCE 24928 (4-aminoandrosta-1,4,6-triene-3,17-dione) was studied in ovariectomized and testosterone propionate (TP)-treated rats bearing 7,12-dimethylbenzanthracene (DMBA)-induced mammary tumors. This experimental condition was used as a model of postmenopausal breast cancer. TP was given s.c. three times per week for 4 weeks at a dose of 20 mg/kg per day, a treatment that is effective in maintaining tumor growth in ovariectomized rats (89% growing tumors). FCE 24928 given s.c. twice daily 6 days/week for 4 weeks at doses of 10 and 30 mg/kg per day inhibited the tumor growth-promoting effect of TP as shown by 81% and 80% tumor-regression rates. When FCE 24928 was given at various dose levels either s.c. (3, 10, and 30 mg/kg daily) or orally (10, 30, and 100 mg/kg per day), tumor regression were observed at all doses, amounting to 63%–93% and 63%–72%, respectively. In addition, FCE 24928 given alone (30 mg/kg daily s.c.) to ovariectomized rats did not affect ovariectomy-induced tumor regression. In conclusion, following both s.c. and oral administration, FCE 24928 was effective against DMBA-induced mammary tumors in ovariectomized TP-treated rats, a postmenopausal mammary tumor model.     

Combined treatment of Dunning R3327 rat prostatic tumor with the 5α-reductase inhibitor PNU 157706 and the antiandrogen bicalutamide

 PNU 157706 [N-(1,1,1,3,3,3-hexafluorophenyl- propyl)-3-oxo-4-aza-5α-androst-1-ene-17β-carboxamide], a novel, potent and selective dual 5α-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. Purpose: We investigated the efficacy of treatment with PNU 157706 in combination with the antiandrogen bicalutamide in this prostatic tumor model. Methods: Rats with tumor diameters of about 1 cm were treated orally 6 days a week for 9 weeks with PNU 157706 (10 mg/kg per day) alone or in combination with bicalutamide (0.2 and 1 mg/kg per day). Animals were killed 24 h after the last treatment, and ventral prostates were removed for testosterone (T) and dihydrotestosterone (DHT) determination. Results: PNU 157706 reduced the growth of established tumors by 39%; bicalutamide proved ineffective at 0.2 mg/kg per day, but reduced tumor growth by 45% at a dose of 1 mg/kg per day. The combination of PNU 157706 with both doses of bicalutamide caused an additive tumor growth inhibition (50% and 64%). Castration resulted in marked tumor growth inhibition (72%). Ventral prostate weight was markedly reduced by PNU 157706 (78%) treatment and by bicalutamide (59% and 77%); combined treatment was as effective as castration. Prostatic DHT content was markedly reduced by PNU 157706 (88%), whereas prostatic T increased slightly (60%). Concomitant treatment with bicalutamide antagonized the T increase induced by PNU 157706 and did not modify the already remarkable suppression of DHT. Conclusions: These data show that the inhibitory effect of PNU 157706 and bicalutamide on Dunning prostatic tumor growth is additive, thus suggesting a possible role of PNU 157706 in the therapy of advanced prostate cancer, in combination with antiandrogens, to provide an effective peripheral androgen ablation therapy with minimal side effects. Received: 1 February 1999 / Accepted: 8 June 1999     

A phase I study of 5-fluorouracil, leucovorin and levamisole

 Purpose: The activity of 5-fluorouracil (5-FU) against colon cancer is enhanced by leucovorin and the combination of 5-FU and levamisole has activity in the adjuvant treatment of colonic malignancies. The combination of 5-FU with both leucovorin and levamisole may provide additional benefit in the treatment of colon cancer. Methods: A phase I study to assess qualitative and quantitative toxicities of this three-drug combination and to determine a dose for further phase II testing was undertaken. The role of levamisole as an immunomodulator was also assessed. Results: A group of 38 patients with incurable etastatic malignancies received 119 cycles of treatment at eight dose levels. 5-FU (375 mg/m² per day) and leucovorin (200 mg/m² per day) were administered intravenously (days 1–5). Levamisole was administered orally (days 1–3 and 15–17) at doses from 30 to 470 mg/m² per day. Patients received both 5FU/leucovorin and 5-FU/leucovorin/levamisole in random order for their initial two cycles. All subsequent treatments were with the three-drug combination. Toxicities included nausea, vomiting, stomatitis, thrombocytopenia and granulocytopenia. Diarrhea was the dose-limiting toxicity at 470 mg/m² per day levamisole. The addition of levamisole resulted in more toxicity than 5-FU and leucovorin alone. No clinical responses were seen with this regimen. The addition of levamisole resulted in more immunomodulation than 5-FU and leucovorin alone as evidenced by release of neopterin from monocytes. Conclusion: With this schedule and dose of 5-FU and leucovorin, the maximum tolerated dose of levamisole was 354 mg/m². However, given the lack of response and the absence of dose-dependent immunomodulation, this may not be the appropriate dose for further phase 11 studies. Received: 20 October 1995 / Accepted: 16 June 1996     

Quantitative relationship between pharmacokinetics of unchanged cisplatin and nephrotoxicity in rats: importance of area under the concentration-time curve (AUC) as the major toxicodynamic determinant in vivo

 Purpose: The major pharmacokinetic parameters of unchanged cisplatin (CDDP) related to nephrotoxicity were evaluated in rats in vivo using a pharmacodynamic model. Methods: CDDP was administered according to various dosing schedules (single bolus, intermittent bolus, or continuous infusion). Unchanged CDDP in plasma and urine was quantified using high-performance liquid chromatography (HPLC). The pharmacokinetics were assessed by model-independent methods. The relationship between pharmacokinetics and BUN levels was evaluated using a sigmoid maximum response (E_max) model. Results: Unchanged CDDP showed linear pharmacokinetics after single bolus injections of 1 to 5 mg/kg CDDP. Nephrotoxicity was ameliorated following intermittent bolus injection (1 mg/kg per day for 5 days) and continuous infusions (over 2 and 3 h) of the same CDDP doses (5 mg/kg), although these dosing schedules did not change the area under the concentration-time curve (AUC), total clearance (Clt), urinary excretion of unchanged CDDP or kidney platinum levels significantly. The maximum BUN level, as a nephrotoxicity marker, showed dose-related increases after single bolus injection of 1 to 5 mg/kg CDDP and after 3-h infusion of 5 to 25 mg/kg. The pharmacodynamic relationship between the maximum BUN level and C_max and between the maximum BUN level and AUC were apparently different between single bolus injection and 3-h infusion. The maximum BUN level was related to the AUC calculated by plasma concentrations of unchanged CDDP greater than the threshold level (AUC_>Cmin), a relationship most successfully described by the signoid E_max model, regardless of CDDP dose and schedule. The plasma threshold level of unchanged CDDP was determined as 0.9 μgPt/ml in rats. Conclusions: The present results substantiated the importance of C×T (AUC) value as an indicator of CDDP-induced nephrotoxicity in vivo as well as of tumor cell-killing effect of CDDP in vitro. The AUC_>Cmin of unchanged CDDP was found to be an important pharmacokinetic parameter predicting CDDP nephrotoxicity. Received: 12 February 1996 / Accepted: 5 September 1996     

A new irreversible aromatase inhibitor, 6-methylenandrosta-1,4-diene-3,17-dione (FCE 24304): antitumor activity and endocrine effects in rats with DMBA-induced mammary tumors

Summary The antitumor activity of the new irreversible aromatase inhibitor 6-methylenandrosta-1,4-diene-3,17-dione (FCE 24304) was studied in rats with 7,12-dimethylbenzanthracene (DMBA)-induced tumors; several endocrine parameters were evaluated in these animals. The compound was given s.c. and p.o. twice daily, 6 days/week, for 4 weeks. The control group showed 13% tumor regressions (0% complete remission, CR; 13% partial remission, PR). FCE 24304 given s.c. induced 44% (22+22) regressions at the dose of 3 mg/kg per day, 70% (40+30) at 10 mg/kg per day, 73% (27+46) at 30 mg/kg per day, and 70% (50+20) at 100 mg/kg per day. FCE 24304 given orally induced 25% (17+8) tumor regressions at 30 mg/kg per day and 50% (17+33) at 100 mg/kg per day. Rats were killed 4 h after the last dose and the aromatase activity of ovarian microsomes (OAA) was evaluated. OAA was reduced by 56% after s.c. treatment with 3 mg/kg per day FCE 24304; complete OAA suppression (96%) was obtained starting at 10 mg/kg per day s.c. Oral treatment slightly reduced OAA only at a dose of 100 mg/kg per day (36%). Body weight increased in all the groups s.c. treated with FCE 24304 but not in those treated orally. The weights of the pituitary, adrenals, and uterus were reduced in rats treated s.c. with 10 and 30 mg/kg per day; at 100 mg/kg per day, a decrease in ovarian weight was observed while uterus weight was similar to that of controls. Oral FCE 24304 increased ovarian weight at a dose of 30 mg/kg per day but not at 100 mg/kg per day. Serum prolactin (PRL) and luteinizing hormone (LH) levels did not change. In conclusion, FCE 24304 given s.c. proved highly effective against DMBA-induced tumors in rats but had less activity when given orally. Its intrinsic androgenic activity, higher after s.c. than after oral treatment, could contribute to the antitumor effect in the intact (premenopausal) rat model.     

Phase I and pharmacologic study of 7- and 21-day continuous etoposide infusion in patients with advanced cancer

 Purpose. This phase I study was undertaken to evaluate the safety and tolerability of prolonged infusional etoposide, and to evaluate its pharmacokinetic/pharmacodynamic profile in patients with advanced cancer. Methods. A group of 17 patients received a 7-day infusion of etoposide (schedule A) every 21 days at doses from 30 to 75 mg/m² per day, and a second group of 37 patients a 21-day infusion (schedule B) every 28 days at doses from 18 to 40 mg/m² per day. Patients had a median Karnofsky performance status (PS) of 80%, and 34 patients had no prior chemotherapy. Etoposide concentrations at steady state (Css) and other pharmacokinetic parameters (plasma clearance, CLp; area under the curve, AUC) were determined during the first treatment cycle. Correlation coefficients were calculated to measure the relationship between variables. Results. Myelosuppression was the major toxicity, and was associated with three deaths. The maximum tolerated dose due to neutropenia was 75 mg/m² per day for schedule A and 40 mg/m² per day for schedule B. There was significant interpatient pharmacokinetic variability in both infusional schedules. Even though etoposide dose levels did not significantly correlate with plasma levels, the Css was ≥1 μg/ml in the majority of the patients. A significant correlation between AUC and neutrophil absolute decrease was noted only in schedule B (r=0.56,  P=0.003). There were several marginal relationships in schedule B: PS versus Css (r=0.31,  P=0.058), PS versus AUC (r=−0.38; P= 0.058) and age versus CLp (r=−0.31, P=0.057). Conclusion. Overall, significant correlations were found for several hematologic variables and etoposide dose levels, but not with the Css values. One major problem with the application of pharmacodynamic models to predict hematologic toxicity in clinical practice is the presence of significant interpatient variability. Received: 3 April 1995/Accepted: 6 December 1995     

Development of a novel aromatase inhibitor, anastrozole (Arimidex)--its basic and clinical studies

Anastrozole (JAN), developed by Zeneca UK (presently AstraZeneca UK), is a new aromatase inhibitor which belongs to triazole. Anastrozole shows selective aromatase inhibition and negligible effects on other steroid hormone biosyntheses. The daily dose of 3 mg/kg anastrozole inhibited the growth of DMBA mammary tumours significantly. Anastrozole inhibited the tumor growth at 5 micrograms/mouse/day (s.c.) in androstenedione-treated ovariectomized nude mice inoculated with MCF-7CA cells transfected with aromatase gene. In the Japanese Phase IIa study, the response rate was 27.8% (10/36) in the 0.5 mg group, and 38.2% (13/34) in the 1 mg group. The most common adverse drug reactions were leucopenia in the 0.5 mg group, and LDH increased and leucopenia in the 1 mg group. There were no early deaths, other serious adverse events, or adverse drug reactions of grade 3 or above in this trial; anastrozole was well tolerated. In the Japanese Phase IIb study, the response rates were 33.3% (117/351 patients) and 32.8% (114/348 patients) for anastrozole and tamoxifen, respectively, showing non-inferiority of anastrozole. The median time to disease progression (TTP) was 251 days and 252 days for anastrozole and tamoxifen, respectively. Group comparison using a Cox regression model revealed non-inferiority of anastrozole. Therefore, anastrozole was found to be at least as effective as tamoxifen (in the response rate and TTP). In US study compared anastrozole with tamoxifen, TTP with anastrozole is a significantly longer than that of tamoxifen (p = 0.005, two-sides). Anastrozole has shown to be at least as effective as tamoxifen, standard endocrine therapy for breast cancer, with good safety profiles. Thus, anastrozole is a promising first-line endocrine therapy in the treatment of postmenopausal breast cancer.