CT Perfusion Evaluation of Cerebral Haemodynamics before and after Cranioplasty.

CT Perfusion imaging is usually applied to assess perfusion abnormalities in acute stroke. This prospective study applied the technique to monitor cerebral haemodynamics before and after cranioplasty. Cranioplasty is the surgical correction of a skull defect using autologous or heterologous material to obtain cosmetic repair, restoration of brain protection and neurological improvement (1). As far as we know the effect of cranioplasty on cerebral haemodynamics flow has been analysed by CT perfusion only in one article (2). We tested the examination as method of monitoring intracranial haemodynamics in a larger number of patients evaluating its reliability and efficacy. We prospectively examined cerebral haemodynamics with Perfusion CT before and after (two weeks, three and six months) cranioplasty in ten patients. The data evaluation of dynamic CT was done by an application software package on a workstation (Leonardo) permitting the use of visual assessment combined with quantitative analysis with ROIs. There was a comparison of CBF, CBV and TTP values between the regions of interest and mirror-image control regions, and in the three different examinations for each patient. After cranioplasty there was clearly an improvement in neurological symptoms and CT perfusion in the majority of cases showed a slight increase in CBF, CBV and decrease of TTP in the cerebral parenchyma close to the cranioplasty, not only on the symptomatic side but also on the opposite side. Even though there was neurological improvement and improved cranial perfusion from the first to the last examinations, our data were not statistically significant. The method is easily reproducible, well tolerated by all patients but has several limitations related to data processing and radiation exposure.

Intravenous administration of 9-aminocamptothecin to dogs with lymphoma.

A colloidal dispersion formulation of 9-aminocamptothecin (9-AC) was administered intravenously to 10 dogs with previously untreated, spontaneously occurring, multicentric lymphoma. The dogs received a 72-h infusion of 9-AC at a rate of 46.5-51.25 microg m(-2) h(-1) (total dose range 3.35-3.69 mg m(-2)). This dose range was associated with myelosuppression, consisting principally of neutropenia with a nadir at 7 days following the start of infusion. Neutropenia and thrombocytopenia were the most common toxicoses and are most likely to be dose-limiting toxicities; low-grade gastrointestinal signs were rarely seen. Concentrations of 9-AC lactone, as well as clinical toxicities, compare favourably with those found in humans. Tumour responses were seen in all treated dogs. Response to other chemotherapy, following cessation of 9-AC treatment, was not obviously compromised even in dogs clinically resistant to 9-AC. 9-AC is a novel treatment drug for canine lymphoma, which appears to show great promise.

PNU-159548, a novel cytotoxic antitumor agent with a low cardiotoxic potential.

PURPOSE: PNU-159548 (4-demethoxy-3'-deamino-3'aziridinyl-4'-methylsulphonyl-daunorubicin), a derivative of the anticancer idarubicin, has a broad spectrum of antitumoral activity in vitro and in vivo attributable to its DNA intercalating and alkylating properties. The present study was conducted to determine the cardiotoxic activity of PNU-159548 relative to doxorubicin in a chronic rat model sensitive to anthracycline-induced cardiomyopathy. METHODS: Young adult male rats were allocated to the following treatment groups: group 1, PNU-159548 vehicle control (colloidal dispersion); group 2, doxorubicin control (saline); groups 3, 4, 5, 6, and 7, PNU-159548 at 0.12, 0.25, 0.50, 0.75, and 1.0 mg/kg, respectively; and group 8, 1.0 mg/kg doxorubicin. Treatments were administered intravenously once weekly for 4 weeks (first sacrifice time) or for 7 weeks (rats killed at weeks 8, 12, 22, 27, or 35). Body weights, organ weights, serum chemistry, hematology, serum troponin-T, and cardiac histopathology were followed throughout the study. RESULTS: Doxorubicin caused irreversible cardiomyopathy evident at week 4 in some rats and progressing in severity in all rats by week 8. There were also marked myelotoxicity, increased liver and kidney weights, testicular atrophy, and about 20% mortality by week 27 in doxorubicin-treated rats. The deaths were attributed to cardiomyopathy and/or nephropathy. PNU-159548 caused a dose-dependent myelotoxicity, with the dose of 0.5 mg/kg per week being equimyelotoxic to 1.0 mg/kg per week doxorubicin. PNU-159548 also caused an increase in liver weight that was reversible and a non-reversible testicular atrophy but, unlike doxorubicin, had no effect on kidney weight. At equimyelotoxic doses, the cardiotoxicity caused by PNU-159548, expressed as the mean total score, was less than one-twentieth of that induced by doxorubicin, and much less than that predicted on the basis of its content of idarubicin, which is in turn markedly less cardiotoxic than doxorubicin. CONCLUSIONS: The novel cytotoxic antitumor derivative, PNU-159548, is significantly less cardiotoxic than doxorubicin at equimyelosuppressive doses. The combination of intercalating and alkylating activities within the same molecule without the cardiotoxic side effects of anthracyclines makes PNU-159548 an excellent candidate for clinical development in oncology.

Development of inhalational agents for oncologic use.

Because regional chemotherapy has been useful in treatment and palliation of many cancer types, the concept of delivering drugs by inhalation for the treatment of cancers in the lung is attractive. Much higher local drug exposure can be achieved with total doses considerably lower than those required for systemic administration, resulting in lower exposure of nonrespiratory tract tissues to potentially toxic drugs. Regional delivery of chemotherapy to the respiratory tract has been shown to have activity in preclinical and clinical studies. Technical improvements in delivery methods have now made it possible to conduct trials of inhalational agents, both to treat cancers affecting the respiratory tract and to deliver other drugs used in cancer patients. This review discusses the rationale of drug delivery by the inhalational route, its technical challenges, preclinical and clinical experiences, limitations, and promise.

Topical delivery of 13-cis-retinoic acid by inhalation up-regulates expression of rodent lung but not liver retinoic acid receptors.

Chemopreventive retinoids may be more effective if delivered to the lung epithelium by inhalation. 13-cis-Retinoic acid (13-cis-RA) was comparable to all-trans-retinoic acid (RA) in inducing transglutaminase II (TGase II) in cultured human cells. Inhaled 13-cis-RA had a significant stimulatory activity on TGase II in rat lung (P < 0.001) but not in liver tissue (P < 0.544). Furthermore, inhaled 13-cis-RA at daily deposited doses of 1.9 mg/kg/day up-regulated the expression of lung retinoic acid receptors (RARs) alpha, beta, and gamma at day 1 (RARalpha by 3.4-fold, RARbeta by 7.2-fold, and RARgamma by 9.7-fold) and at day 17 (RARalpha by 4.2-fold, RARbeta by 10.0-fold, and RARgamma by 12.9-fold). At a lower aerosol concentration, daily deposited doses of 0.6 mg/kg/day were also effective at 28 days. Lung RARalpha was induced by 4.7-fold, RARbeta by 8.0-fold, and RARgamma by 8.1-fold. Adjustment of dose by exposure duration was also effective; thus, inhalation of an aerosol concentration of 62.2 microg/liter, for durations from 5 to 240 min daily for 14 days, induced all RARs from 30.6- to 74-fold at the shortest exposure time. None of the animals exposed to 13-cis-RA aerosols showed RAR induction in livers. By contrast, a diet containing pharmacological RA (30 microg/g of diet) failed to induce RARs in SENCAR mouse lung, although it induced liver RARs (RARalpha, 21.8-fold; RARbeta, 13.5-fold; RARgamma, 12.5-fold); it also failed to induce lung TGase II. A striking increase of RARalpha expression was evident in the nuclei of hepatocytes. Pharmacological dietary RA stimulated RARalpha, RARbeta, and RARgamma as early as day 1 by 2-, 4-, and 2.1-fold, respectively, without effect on lung RARs. Therefore, 13-cis-RA delivered to lung tissue of rats is a potent stimulant of lung but not liver RARs. Conversely, dietary RA stimulates liver but not lung RARs. These data support the concept that epithelial delivery of chemopreventive retinoids to lung tissue is a more efficacious way to attain up-regulation of TGase II and the retinoid receptors and possibly to achieve chemoprevention.

Inhaled isotretinoin (13-cis retinoic acid) is an effective lung cancer chemopreventive agent in A/J mice at low doses: a pilot study.

In previously treated head-and-neck cancer patients, p.o. administered isotretinoin (13-cis retinoic acid) reduced the occurrence of second aerodigestive tumors, including lung tumors, but side effects made chronic therapy problematic. We reasoned that inhaled isotretinoin might provide sufficient drug to the target cells for efficacy while avoiding systemic toxicity, and we proceeded with the pilot study reported here. Male A/J mice were given single i.p. doses of urethane, a common experimental lung carcinogen, or benzo[a]pyrene (BaP) or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), putative major carcinogens in tobacco smoke. The following day, exposures to isotretinoin aerosols for 45 min daily at 1.3, 20.7, or 481 microg/l were initiated. After 2 weeks, the high dose caused severe toxicity on the snout skin, necessitating a reduction of dose frequency to twice a week. As a precaution, the mid dose was reduced to three exposures per week. The weekly total deposited doses after the dose frequency reductions were calculated to be 0.24, 1.6, and 24.9 mg/kg for the low, mid, and high doses, of which 16% was estimated to be deposited in the lungs. The weekly deposited pulmonary drug doses were calculated to be 0.01, 0.07, and 1.1% of a previously reported ineffective oral dose in urethane-treated A/J mice. After 10-16 weeks, mice were sacrificed to count areas of pulmonary hyperplasia and adenomas. For all carcinogens, the mice exposed to the high isotretinoin dose showed reductions of tumor multiplicity ranging from 56 to 80% (P < 0.005). The mid dose was associated with reductions of tumor multiplicity by 67 and 88% (P < 0.005) in BaP- and NNK-treated mice, respectively, and was tolerated until approximately 12 weeks, when both these and the high-dose mice began losing weight. The low-dose mice had nonsignificant reductions of 30% (P < 0.13) and 16% (P < 0.30) for BaP- and NNK-treated mice, respectively without any evidence of side effects. For BaP- and NNK-treated mice, numbers of hyperplastic areas directly correlated to dose level and inversely to tumor number, suggesting arrested progression. Inhaled mid-dose isotretinoin caused up-regulation of lung tissue nuclear retinoic acid receptors (RARs) relative to vehicle-exposed mice, RARalpha (3.9-fold vehicle), RARbeta (3.3-fold), and RARgamma (3.7-fold), suggesting that these receptors may be useful biomarkers of retinoid activity in this system. The encouraging results from this pilot study suggest that inhaled isotretinoin merits evaluation in people at high risk for lung cancer.

Inhalation chemotherapy for macroscopic primary or metastatic lung tumors: proof of principle using dogs with spontaneously occurring tumors as a model.

This study represents part of an effort to determine the safety and efficacy of inhaled antineoplastic drugs, using pet dogs with spontaneously arising primary and metastatic lung cancers (including sarcoma, carcinoma, and malignant melanoma) as a model. Dogs received new formulations of either paclitaxel (PTX) or doxorubicin (DOX) by the inhalation route every 2 weeks using a specially designed aerosol device. Response was assessed radiographically using the indices of tumor nodule number and volume measurement of discrete pulmonary nodules. Dogs experiencing progressive disease after two consecutive treatments were crossed over to receive the alternate compound. In 24 dogs, 6 (25%) responses were noted including 5 partial responses (PR) and 1 complete response. These include 4 (22.2%) of 18 responses to DOX and 2 (13.3%) of 15 responses to PTX. Responses were noted with osteosarcoma (including three dogs with metastatic osteosarcoma that had failed prior systemic chemotherapy), liposarcoma, hemangiosarcoma, and undifferentiated sarcoma. One dog with mammary carcinoma experienced a 47% reduction in volume after PTX inhalation, just shy of PR criteria. One dog with liposarcoma is experiencing a long-term (>12 months) stabilization of disease on PTX. To date, no systemic toxicities have been observed with either PTX or DOX inhalations. Local (pulmonary) toxicity was not observed with PTX; however, changes consistent with pneumonitis/fibrosis were observed in some dogs receiving DOX. Only one of these dogs showed clinical signs, which were responsive to steroid and antitussive therapy. These data represent "proof of principle" for the avoidance of systemic toxicity while delivering efficacious local drug levels by the inhalation route.

Cardioprotection by dexrazoxane in rats treated with doxorubicin and paclitaxel.

PURPOSE: Results of several clinical studies suggest that the combination of doxorubicin (DOX) and paclitaxel (PTX) is highly active against solid tumors. Both drugs are known to cause adverse cardiac effects, cardiomyopathy in the case of DOX and acute changes in cardiac rhythm in the case of PTX. It has been suggested that the addition of dexrazoxane (DZR) to this regimen may reduce the risk of cardiotoxicity. A model of chronic cardiomyopathy in the rat was used to determine whether DZR was tolerated and cardioprotective in a DOX + PTX combination. METHODS: Male rats were treated once weekly for 7 weeks with one of the following vehicle and/or drug sequences: Group A, M/6 sodium lactate/saline/Cremophor EL (CEL); Group B, lactate/DOX/CEL; Group C, DZR/DOX/CEL; Group D, lactate/DOX/PTX; and Group E, DZR/DOX/PTX. DZR and DOX or their respective vehicles were given i.v. whilst PTX or CEL were given i.p. DZR, DOX and PTX were administered at 16 mg/kg, 0.8 mg/kg and 2.4 mg/kg, respectively, doses which caused minimal noncardiac toxicities. The hearts were examined histologically 5 weeks following the last treatment. RESULTS: There were no deaths and no signs of overt toxicity during the 12 weeks of study. There was a significant decrease (P < 0.01) in white blood cell count in rats treated with DZR + DOX, DOX + PTX or DZR + DOX + PTX but not in those given DOX alone. Liver and kidney weights were increased in rats given DOX (P < 0.05) but not in those given DZR + DOX. PTX had no effect on the DOX-induced liver and kidney changes and did not interfere with the protective effect of DZR on the kidney. The severity and extent of cardiomyopathy expressed as the mean total score (MTS) for each treatment group, was similar for DOX and DOX + PTX (4.6 and 4.2, respectively). DZR provided significant cardioprotection (P < 0.01) when added to either DOX (MTS 2.0) or to DOX + PTX (MTS 2.1). CONCLUSIONS: The results suggest that PTX does not exacerbate the chronic cardiomyopathy caused by DOX and when added to the DOX + PTX combination, DZR retains its protective activity against DOX-induced cardiotoxicity without increasing noncardiac toxicity.

Protection against doxorubicin-induced cardiotoxicity in weanling rats by dexrazoxane.

PURPOSE: Dexrazoxane (DZR) protects against anthracycline-induced cardiotoxicity in several laboratory animal species and in patients with breast cancer. Encouraging results have also been obtained in a limited number of pediatric oncology patients. We conducted studies to determine the safety and cardioprotective activity of DZR in the doxorubicin (DOX)-treated weanling rat simulating the rapidly growing immature child. METHODS: Male weanling rats and young adult rats, 20 days old and 7 weeks old, respectively, were given 1 mg/kg DOX i.v., either alone or with 20 mg/kg DZR, once weekly for 7 weeks. Rats were sacrificed at weeks 8, 12 or 26 following blood collection for hematology and serum chemistry. Hearts were weighed and examined histologically. RESULTS: DOX, either alone or with DZR, inhibited growth, and body weight remained below that of controls throughout the 26 weeks of study. There were no biologically significant hematologic changes in either the DOX- or DZR + DOX-treated young rats. DOX caused a slight increase in liver and kidney weights relative to body weight and a slight increase in serum cholesterol and triglycerides in the young rats. These effects were ameliorated or delayed by DZR. DOX, either alone or with DZR, caused a marked atrophy of the testes in the young rats which had recovered by week 26. In the mature rats, DOX caused a significant decrease in the WBC 1 week after the last treatment, and the WBC was significantly lower in the rats given DZR + DOX compared to those given DOX alone. There were marked increases in liver and kidney weight, serum cholesterol and triglycerides in the mature rats given DOX alone but not in those given DZR + DOX. There was also a marked testicular atrophy in the mature rats given either DOX or DZR + DOX but, unlike that observed in the young rats, this had not returned to normal by week 26. DOX-induced cardiotoxicity was less severe in the younger rats than in the mature rats but in both age groups, the lesion progressed rapidly until week 12, 5 weeks after the last dose, and remained relatively stable or progressed slightly thereafter. DZR provided significant cardioprotection in both age groups at all time points examined. Moreover, in both age groups, the severity of the cardiomyopathy in the DZR-treated rats was somewhat less at week 26 than it was at week 12. CONCLUSIONS: The results indicate that the pharmacologic effects of DZR, including its ability to protect against cardiotoxicity, are similar in immature and adult male animals treated with DOX.

Preclinical models of cardiac protection and testing for effects of dexrazoxane on doxorubicin antitumor effects.

The ability of dexrazoxane (DEX) to protect against doxorubicin (DOX)-induced cardiomyopathy has been demonstrated in mice, normotensive and hypertensive rats, rabbits, dogs, swine, and humans. These animal models of DOX-induced cardiomyopathy were found to be highly predictive of DEX activity clinically. In mice administered maximally tolerated doses of DOX over a period of 7 weeks, the optimum dose of DEX was from 10:1 to 20:1 (DEX:DOX) given from 30 minutes before to 15 minutes after DOX. The dose ratio required to reduce the incidence of moderate to severe cardiomyopathy by 90% in the mouse was more than 20:1 for DOX and 10:1, 5:1, and 5:1 for epirubicin, daunorubicin, and idarubicin, respectively. Dexrazoxane was most effective in rats when treatment commenced with the first and third doses of DOX, but also provided cardioprotection when started with the sixth of 10 doses of DOX. The cardioprotective activity of DEX in rats was evident for more than 6 months after completion of DOX dosing. Results of antitumor studies in several experimental tumor models indicate that DEX does not interfere with the antineoplastic activity of DOX or other antitumor drugs. In some case, especially cyclophosphamide, there was a markedly synergistic antitumor effect when combined with DEX.

9-Aminocamptothecin: a topoisomerase I inhibitor with preclinical activity in prostate cancer.

9-Aminocamptothecin (9-AC) is a topoisomerase I inhibitor currently being developed as an antineoplastic agent. The aim of these preclinical studies was to assess the activity of 9-AC against prostate cancer, a malignancy notoriously insensitive to most cytotoxic agents in the clinic. The activity of 9-AC was first tested in vitro against one hormone-sensitive (LNCaP) and three hormone-resistant (PC-3, PC-3M, and DU145) human prostate cancer cell lines. After 96 h of drug exposure, concentrations required to inhibit cell viability to 50% of control values (IC50s) were 34.1, 10, 6.5, and 8.9 nm for PC-3, PC-3M, DU145, and LNCaP, respectively. Because 9-AC is known to undergo rapid hydrolysis, we assayed lactone levels in tissue culture medium over 24 h and found that the half-life was 20 min, with only 15%of the drug remaining as lactone at steady state. Consequently, the IC50s calculated from a single dose of the drug may represent overestimates. Subsequently, we tested the activity of a colloidal dispersion formulation of 9-AC against PC-3 implanted into flanks of nude mice. 9-AC was given for a total of 3 weeks by daily oral gavage (excluding weekends) or by twice weekly s.c. injections. 9-AC inhibited tumor growth at the lowest oral dose (0.35 mg/kg/day), whereas higher oral doses (0.75 and 1 mg/kg/day) and s.c. administration (4 mg/kg/week) caused tumor regression. 9-AC was well tolerated at all doses, with no toxic death or weight loss of more than 10% observed in any group. Finally, we considered that the activity of 9-AC seen in the mouse xenograft model might be explained, in part, by the relatively acidic tumor microenvironment, which would favor the formation of the more potent lactone. Simultaneous determination of plasma and tumor 9-AC lactone concentrations confirmed this hypothesis. Taken together, these studies suggest that 9-AC should be submitted for clinical trials in patients with prostate cancer.

Dose-response relationship of dexrazoxane for prevention of doxorubicin-induced cardiotoxicity in mice, rats, and dogs.

Dexrazoxane [(DZR), ADR 529, ICRF-187] ameliorates doxorubicin (DOX)-induced cardiotoxicity in animals, and is recommended as a cardioprotectant in patients receiving cumulative doses of DOX above 300 mg/m2. A DZR:DOX dose ratio of 10:1 is recommended based on studies in patients receiving 50 mg/m2. Since DOX may be used at much higher doses in certain clinical settings, we evaluated the ability of DZR to protect against cardiomyopathy in animals given bolus doses of DOX at varying dose levels. The severity and extent of the cardiomyopathy were evaluated histologically and expressed as the mean total score (MTS). Mice were given 10 doses of DOX (2 or 4 mg/kg) over a 7-week period. Without DZR, the MTS 4 weeks after the last treatment was 3.7 with 4 mg/kg DOX and 1.3 with 2 mg/kg DOX. DZR at 5:1, 10:1, and 20:1 dose ratios caused a dose-dependent decrease in the MTS but was less efficacious with the higher, more cardiotoxic dose of DOX. Rats were given DOX at 0.2, 0.4, and 0.8 mg/kg with a 20:1 ratio of DZR weekly for 13 weeks. Cardiomyopathy was most severe with the highest dose of DOX in the absence of DZR, especially in males, and progressed during the 6 weeks following the last treatment. DZR reduced the MTS in both sexes but in the males given the highest dose of DOX, there was still a significant amount of cardiac damage compared to vehicle-treated controls. Dogs were given 0.1, 0.3, and 0.8 mg/kg DOX with 20:1 DZR for 13 weeks. DZR reduced the MTS significantly (P < 0.05) in males and females but cardiac lesions were still present in each of the DZR-treated dogs. The results indicate that although DZR is highly effective in attenuating the cardiomyopathy caused by DOX, dose ratios of DZR:DOX capable of providing total or nearly complete cardioprotection at low doses of DOX are less efficacious at higher doses of DOX. One possible explanation for this effect is the marked pharmacokinetic difference between DZR and DOX, with DZR undergoing a much more rapid rate of elimination from the body compared to DOX. These findings point to the need for further studies to optimize the dose scheduling of DZR before using it clinically with bolus doses of DOX above those currently recommended.

Anthracyclines.

The genotoxicity and carcinogenicity data from in vitro and in vivo studies conducted during preclinical safety assessment of doxorubicin (DOXO), epirubicin (EPI) and idarubicin (IDA), are reviewed. The genotoxicity assays included a) gene mutation in Salmonella typhimurium with 5 tester strains; b) gene mutation in the V79 mammalian (lung) cell line; c) chromosome aberrations in human lymphocytes cultured in vitro; and d) chromosome aberrations in mouse bone marrow cells after intravenous (i.v.) administration in vivo. The long-term toxicity studies in the rat included a) single dose administration (3 mg/kg DOXO, 3.6 EPI and 0.75 IDA) to female rats of two different age groups, i.e. younger (7 weeks old at dosing) and older (13 weeks old), followed by one-year observation; and b) multiple dose administration to male and female rats (7 weeks old at dosing), consisting of i.v. administration of 0.25, 0.5 and 1 mg/kg DOXO or EPI and 0.06, 0.125 and 0.25 mg/kg IDA, once every 3 weeks for 10 cycles, followed by 18 months of observation. The genotoxicity studies revealed activity in gene mutation assays in bacterial and mammalian cells, and in chromosome aberration assays in human lymphocytes in vitro and in mouse bone marrow in vivo. In the two long-term studies in the rat, only mammary tumors were present. This finding was expected and, according to the literature, can be considered as species specific and not directly compound-related. The lack of tumor induction at the usual target organs for DNA reactive compounds, which are almost the same as those considered as target organs in anthracycline-exposed animals, indicates that the type and the extent of DNA damage precludes stimulation for proliferation and induction of neoplasia. Although an epigenetic mechanism can be hypothesized, support for such a mechanism is lacking.

Anthracyclines - a review of general and special toxicity studies.

Preclinical safety assessment data on doxorubicin (DOXO), epirubicin (EPI), idarubicin (IDA) and methoxymorpholinodoxorubicin (MORPHO), from mouse, rat and dog studies are reviewed. These data are put into perspective allowing for extrapolations across species, doses and dose regimens with recommendations for proper human use. The compounds were administered intravenously or intraperitoneally in studies ranging from single dose to multiple dose studies of different durations. The compounds were given once, daily, weekly or cyclically. In the cyclic administration studies, DOXO, EPI, and IDA were given for 3 consecutive days a week for 6 or 13 weeks; MORPHO was given for 3 consecutive days a week every three weeks for a total of 9 cycles. The duration of the cyclic studies was from 6-26 weeks. Daily dose studies lasted from 4-26 weeks. In the single dose studies the recovery ranged from 4 weeks to one year; in the multiple dose studies from 4 to 8 weeks. A few special studies were also considered. In all studies reviewed, 2 different types of toxicity were observed. These toxicities occur also in man. The first is the acute toxicity, which is the consequence of cytotoxicity and expresses the exaggerated pharmacological activity of the compounds. The target sites in all 3 species and in man include the hemolymphopoietic system (HLPS), the gastrointestinal (GI) tract, skin and testes; all renewing cell types. The second type of toxicity is the chronic progressive toxicity. This toxicity is the expression and result of sustained disruption of cytoplasmic homeostasis and occurs in non-renewing cell types. The target sites include the heart (both animals and man), kidneys (rodents) and peripheral nervous system (PNS) (rodents). From single administration animal data, chronicity, site and magnitude of toxicities can be predicted in man. Despite strong mitogenic stimuli in the rat, there is no evidence that there is a potential for hemolympho- or hepatocarcinogenicity with these compounds.

Major difference in the hepatocarcinogenicity and DNA adduct forming ability between toremifene and tamoxifen in female Crl:CD(BR) rats.

The hepatoproliferative effects of 2 antiestrogens, tamoxifen and toremifene, were compared in a sequential 15-month study in which 2 doses of each compound were administered by daily gavage to female Sprague-Dawley rats for up to 12 months. The doses were 11.3 and 22.6 mg/kg for tamoxifen and 12 and 24 mg/kg for toremifene. There were scheduled sacrifices at 3, 6, 12, and 15 months, the latter including a 3-month recovery period from the 12th through the 14th month. In the chronic toxicity study, tamoxifen at 22.6 mg/kg produced 100% incidence of hepatocellular carcinoma at the 12- and 15-month sacrifice intervals and 67% and 71% incidences at the 11.3-mg/kg dose. Sequential observations showed an increased incidence of glutathione S-transferase-positive foci of hepatocellular alteration by 3 months with tamoxifen in the absence of hepatotoxicity, with the first liver carcinoma appearing by 6 months of treatment. Unscheduled deaths occurring beyond 7.5 months in the tamoxifen treated groups were due in almost all cases to liver cancer. In striking contrast, toremifene did not produce any hepatoproliferative effects at 12- and 24-mg/kg dose levels, nor in a pilot study at 48 mg/kg. The 24-mg/kg dose of toremifene exerted an inhibiting effect on foci of hepatocellular alteration in rat liver detectable by glutathione S-transferase immunohistochemistry at 3 months and by conventional histology at 12 months. An antiproliferative effect was also evident in mammary gland and anterior pituitary where both toremifene and tamoxifen suppressed tumor incidence in comparison to the control group. The ability of these drugs to modify rat liver DNA after p.o. administration was investigated using the 32P-postlabeling assay. Administration of tamoxifen at 45 mg/kg for 7 days produced liver DNA nucleoside modifications represented by 7 spots on the autoradiogram. Unlike tamoxifen, toremifene did not produce any modified bases in rat liver DNA detectable by the 32P-postlabeling technique. The dose levels of tamoxifen that are strongly hepatocarcinogenic in the rat are compared with doses used in humans in various applications. Taking internal drug exposure into account, we conclude that the margin of safety for use of tamoxifen as an endocrine prophylactic agent for healthy, but breast cancer prone, women is questionable.

Penetration of trolamine salicylate into the skeletal muscle of the pig.

Studies to determine the extent of local tissue penetration of topically applied trolamine [14C]salicylate were conducted in domestic pigs. The preparation was applied onto a 100-cm2 shaved area of skin overlying the biceps femoris at a concentration of 0.7 mg of salicylate/cm2 to closely approximate the actual use in humans. At least 82% of the topically applied trolamine salicylate was absorbed over a 2-h period. Based on blood and muscle salicylate levels, a localization of the absorbed drug occurred in muscle underlying the treated area within 120 min. Muscle from the treated area had a concentration of salicylate that was 13 times that of blood and 49 times that of muscle taken from untreated areas. Blood samples taken from the treated area at 10, 20, and 30 min showed that salicylate levels ranged from 15.8 to 5.3 micrograms/g. Less than 0.5% of the applied drug was excreted in the urine during the 2-h period.

Myocardial effects of mitoxantrone and doxorubicin in the mouse and guinea pig.

Mitoxantrone (DHAQ) was compared to doxorubicin for myocardial effects in the mouse and the guinea pig. Histologically, DHAQ induced a high incidence of focal myocardial damage in mice, similar to that observed with doxorubicin. Functionally, like doxorubicin, DHAQ significantly reduced the rate of contraction and histamine responsiveness of guinea pig right atria in vitro. Additionally, long-term ip administration of either DHAQ or doxorubicin reduced the atrial response to histamine in vitro. These data suggest that DHAQ may have a spectrum of myocardial activity similar to that of doxorubicin.

Isolation, identification, and synthesis of the major sulpiride metabolite in primates.

The major metabolite of sulpiride, N-[(1-ethyl-2-pyrrolidinyl)methyl]-5-sulfamoyl-2-anisamide (I), in the monkey is N-[(1-ethyl-5-oxo-2-pyrrolidinyl)methyl]-5-sulfamoyl-2-anisamide (II). It is also a metabolite in other laboratory animal species and possibly at very low levels in humans. Treatment of the urine from a monkey dosed orally with 14C-I by dry column chromatography and high-pressure liquid chromatography (HPLC) produced the major metabolite in pure form. Characterization of the purified 14C-radiolabeled metabolite by proton NMR, TLC, HPLC, and chemical ionization mass spectroscopy, along with subsequent comparison of a synthetically prepared sample, gave unequivocal structural confirmation.