Families of repeated DNA in the oomycete Phytophthora infestans and their distribution within the genus

Paclitaxel (Taxol) is a new class of anti-tumor agents which act by promoting the assembly and inhibiting the disassembly of microtubules. Single-agent studies have shown its significant activity for advanced cancers in various organs including ovary, lung, breast, and head and neck. Combination therapies with other anticancer agents have been extensively investigated in these cancers. Paclitaxel combined with cisplatin is now considered to be the standard treatment for advanced ovarian cancer. In other cancers, promising results have been obtained in several studies of paclitaxel-based chemotherapy. Major toxicities of paclitaxel-monotherapy are hypersensitivity reaction, neutropenia, and peripheral neuropathy. Combination of other cytotoxic agents sometimes leads to severer toxicities such as neurotoxicity with cisplatin and cardiotoxicity with anthracycline. Although further evaluation is needed, paclitaxel will be a main agent in the treatment of advanced solid tumors.     

Paclitaxel with mitoxantrone, fluorouracil, and high-dose leucovorin in the treatment of metastatic breast cancer: a phase II trial

PURPOSE: Paclitaxel is a highly active single agent in the treatment of breast cancer. However, its optimal incorporation into combination regimens awaits definition. In this phase II study, we added paclitaxel, administered by 1-hour infusion, to a previously described combination regimen that included mitoxantrone, fluorouracil (5-FU), and high-dose leucovorin (NFL). PATIENTS AND METHODS: Forty-six patients with metastatic breast cancer received the following regimen as first- or second-line treatment: paclitaxel 135 mg/m2 by 1-hour intravenous (i.v.) infusion on day 1, mitoxantrone 10 mg/m2 by i.v. bolus on day 1, 5-FU 350 mg2/m by i.v. bolus on days 1, 2, and 3, and leucovorin 300 mg i.v. over 30 to 60 minutes immediately preceding 5-FU on days 1, 2, and 3. Courses were administered at 3-week intervals for a total of eight courses in responding patients. RESULTS: Twenty-three of 45 assessable patients (51%) had major responses. Previous chemotherapy, and in particular previous treatment with doxorubicin, did not affect response rate. The median response duration was 7.5 months. Myelosuppression was moderately severe, with 76% of courses resulting in grade 3 or 4 leukopenia. Hospitalization for treatment of fever during neutropenia was required in 13% of courses, and two patients died as a result of sepsis. Two patients developed severe congestive heart failure after a large cumulative anthracycline dose. CONCLUSION: This combination regimen was active as first- or second-line therapy for metastatic breast cancer, although its activity compared with other combination regimens or with paclitaxel alone is unclear. Myelosuppression was more severe than anticipated based on previous results with the NFL regimen or with paclitaxel administered at this dose and schedule as a single agent. The infrequent development of cardiotoxicity in these patients suggests that the paclitaxel/mitoxantrone combination may not share the problems previously reported with the paclitaxel/doxorubicin combination.     

5-Fluorouracil interferes with paclitaxel cytotoxicity against human solid tumor cells

Paclitaxel, a naturally occurring antimitotic agent, has shown efficacy in the treatment of certain solid tumors, particularly metastatic breast carcinoma and drug-refractory ovarian cancers. Recent studies have demonstrated that paclitaxel, in addition to its effects on microtubules and cell cycle arrest, possesses significant cell-killing activity in solid tumor cells by the induction of apoptosis. However, the mechanism by which paclitaxel leads to cell death and its relationship with paclitaxel-induced mitotic arrest is presently unclear. In this study, we attempted to determine whether pre-arresting tumor cells at other phases of the cell cycle could affect paclitaxel-induced apoptosis. We found that 5-fluorouracil (5-FU), another antineoplastic agent that usually arrests tumor cells at the G1-S phase of the cell cycle, could significantly repress the cell-killing activity of paclitaxel in solid tumor cells, even when it was added simultaneously with paclitaxel. Further studies indicated that 5-FU actually inhibits the cytotoxic effects of paclitaxel on both mitotic arrest and apoptotic cell death, suggesting that 5-FU might interfere with paclitaxel cytotoxicity at an early stage, probably by preventing tumor cells from entering G2-M phase. Because recent clinical trials have used a combination of paclitaxel and 5-FU in the treatment of metastatic breast cancers, our results also suggest that the combination of these two drugs might not be as valuable in clinical chemotherapy.     

Chemotherapy in non-small cell lung cancer: a review

Lung cancer, of which non-small cell carcinoma is the most common, has been a significant therapeutic challenge for decades and will remain so for decades to come. Despite its prevalence, progress in the management of non-small cell lung cancer has been relatively slow. This is in part due to the pessimism of most physicians treating this disease, which has resulted in a relatively lackadaisical attitude with regards to clinical trials when compared to other solid tumours like breast or colorectal cancers. Nevertheless, the past decade has seen significant progress, specifically with regards to the management of locally advanced disease. Chemotherapy, though shown to be biologically active in non-small cell lung cancer, is considered an ineffective palliative tool in the setting of metastatic disease due to its toxicities and the "less than encouraging" response rates generated by the cisplatin-based combination regimen which is generally considered to be the most active currently available. The advent of new active agents such as paclitaxel and vinorelbine which are potentially less toxic may change this view. Conversely, the response rate of locally advanced disease to chemotherapy is significantly higher and this has resulted in numerous multimodality trials of neoadjuvant chemotherapy prior to surgery and/or radiation. To date, a number of randomised trials have shown that this approach can result in significant survival benefit for patients with locally advanced disease. An alternative approach makes use of the potential synergism between certain chemotherapeutic agents (such as cisplatin) and radiation when used concurrently. However, data on concurrent chemoradiotherapy in locally advanced disease have been largely based on single-arm studies and are inconclusive. Three randomised trials on concurrent chemoradiotherapy have been shown benefit for the use of combined modality in locally advanced disease. Hence, treatment of locally advanced disease should include chemotherapy as part of the combined modality approach. However, the optimal sequencing of these modalities would require well-designed randomised trials to determine.     

Comparative antitumor efficacy of docetaxel and paclitaxel in nude mice bearing human tumor xenografts that overexpress the multidrug resistance protein (MRP)

BACKGROUND: Multidrug resistance has been associated with expression of the multidrug resistance protein (MRP). Recently, MRP-expression has been detected in human tumor samples of patients with breast cancer and non-small-cell lung cancer. Since taxoids are the most active drugs in the treatment of both tumor entities, the antitumor efficacies of paclitaxel and docetaxel were compared in nude mice bearing human tumor xenografts that express MRP. MATERIALS AND METHODS: Athymic nude mice (nu/nu) bearing tumor xenografts of parental human sarcoma HT1080 or MRP-expressing HT1080/DR4 cells (as confirmed by Northern blot analysis) were treated with the maximum tolerated doses (MTD) of doxorubicin ([Dx] 10 mg/kg i.v. push), paclitaxel ([PC] 50 mg/kg three-hour i.v. infusion), or docetaxel ([DC] 40 mg/kg three-hour i.v. infusion). In vitro, the activity of doxorubicin, paclitaxel and docetaxel was evaluated by the sulphorhodamine B (SRB) assay using the pyridine analogue PAK-104P (5 microM), a potent inhibitor of MRP-function. RESULTS: At their MTDs both taxoids showed significant activity against MRP-negative HT1080 xenografts with response rates of 80% (40% CR) for PC and 100% (60% CR) for DC. In contrast, DC was significantly more active than PC in nude mice bearing doxorubicin resistant MRP-expressing HT1080/DR4 tumor xenografts (overall response rates: 100% (60% CR) for DC; 10% (0% CR) for PC; 0% for Dx). Since treatment of mice with the MTD of PC or DC yielded similar overall toxicity (maximum weight loss for HT1080: PC 8.6 +/- 2.2%; DC 7.5 +/- 2.2% and for HT1080/DR4: PC 11.6 +/- 3.0%; DC 7.6 +/- 1.8%, respectively), these results demonstrate the increase in the therapeutic index for docetaxel against MRP-expressing tumors. In vitro, HT1080/DR4 cells were 270-fold, 6.4-fold and 2.8-fold more resistant than parental cells to doxorubicin, PC and DC, respectively. Pyridine analogue PAK-104P completely restored drug sensitivity to PC and DC, while no effect of PAK-104P on parental HT1080 cells was observed. CONCLUSIONS: Both taxoids, when given at their MTDs, showed significant efficacy against parental HT1080 tumor xenografts. However, docetaxel at its MTD was significantly more active against MRP-expressing tumor xenografts than paclitaxel. Furthermore, in vitro resistance of HT1080/DR4 cells was higher for PC (6.4-fold) than for DC (2.8-fold). Since PAK-104P completely restored sensitivity to both taxoids, the observed resistance appears to be related to MRP. These data suggest, that docetaxel is not as readily transported by MRP as paclitaxel leading to an increased therapeutic ratio in MRP-expressing tumors in vivo. Therefore, docetaxel may have therapeutic advantages in the clinical treatment of MRP-expressing tumors.     

Ab initio conformational study of the phenylisoserine side chain of paclitaxel

Paclitaxel (Taxol) and related compounds are important antitumor drugs, currently used for the treatment of several types of cancer. The flexible amino acidic C13 side chain is a key element of the taxoid pharmacophore, and the identification of the bioactive conformation is a top priority for a better understanding of the mode of action of these anticancer agents. The conformational features of the side chain have been investigated by Hartree-Fock ab initio and semiempirical PM3 calculations. To gain a better understanding of solvent effects, different molecular models of paclitaxel were used in the calculations. The gas-phase calculations confirm that only one conformation, named ch1 (very similar to the one found in the crystal structure of docetaxel), is present in apolar environments. The preference for this conformer has been rationalized in terms of its L shape, which minimizes steric and Coulombic interactions, and of a favorable arrangement of the glycolate moiety. When a polar solvent was simulated by different methods, a greater conformational variability was found, with different conformations differing by less than 1.5 kcal/mol. Among these conformations, only one (ch5', similar to molecule B of the crystal structure of paclitaxel) is particularly apt to interact with solvent molecules. In light of these data, it seems reasonable to assume that, when the drug is bound to the lipophilic pocket of the tubuline receptor, the C13 amino acidic side chain assumes a conformation close to ch1.     

Knowledge and attitudes among California dental care providers regarding child abuse and neglect

Combination chemotherapy with paclitaxel plus a platinum compound (carboplatin or cisplatin) is the current regimen of choice for the treatment of advanced epithelial ovarian cancer. The two most widely used combinations are paclitaxel (135 mg/m2, 24-hour infusion) plus cisplatin (75 mg/m2) or paclitaxel (175 mg/m2, 3-hour infusion) plus carboplating dosed to an area under curve of 7.5. Randomized trials are in progress comparing these two regimens. Numerous other clinical issues remain regarding how to maximize the effectiveness of this therapy, including dose and schedule, duration of treatment, route of administration, and incorporation of other agents with novel mechanisms of cytotoxicity. New agents currently undergoing evolution as part of novel induction regimens have been shown to have significant activity in recurrent ovarian cancer and include topotecan, gemcitabine, oral etoposide, and encapsulated doxorubicin.     

Chemotherapy for advanced non-small cell lung cancer: past, present, and future

Until recently, chemotherapeutic intervention in advanced and metastatic non-small cell lung cancer (NSCLC) has been viewed with a certain degree of nihilism. Although meta-analysis of randomized clinical studies from the 1970s and 1980s comparing cisplatin-based chemotherapy to best supportive care in metastatic NSCLC showed improvement in survival, it was modest at best. A number of novel agents have been developed with significant activity against NSCLC in the past 5 to 6 years and are being incorporated into the therapy of this disease. These agents include paclitaxel, docetaxel, vinorelbine, gemcitabine, and irinotecan. Clearly there has been improvement in response rates, and in some cases the responses have been durable with an increase in the number of 1- and 2-year survivors. The next generation of studies has evaluated combinations of these novel agents with either cisplatin or carboplatin for patients with NSCLC and the results have been provocative, with 1-year survival rates as high as 54%. A randomized phase III study of the Eastern Cooperative Oncology Group has shown the superiority of paclitaxel-cisplatin regimens over etoposide-cisplatin for patients with advanced and metastatic NSCLC. The vinorelbine-cisplatin regimen has also proven to have significant, albeit modest benefit in survival when compared with cisplatin alone. These combination regimens have now become the reference regimens in ongoing randomized studies. There is continued interest in developing new agents, or selective approaches that effect novel targets with the hope of showing improved therapeutic activity. Some of these approaches include gene therapy, monoclonal antibodies, and introduction of antisense oligodeoxynucleotides. With better understanding of the molecular and cellular biology of lung cancer, the hope for the future is to combine the mechanistic approaches with new drug development to define an effective, optimal, and definitive regimen for NSCLC.     

Molecular etiology of colorectal carcinogenesis, clinical manifestations and therapy]

The metabolism of paclitaxel and docetaxel by human liver microsomes was investigated in vitro. The main metabolite of paclitaxel formed in vitro was the 6 alpha-hydroxypaclitaxel: its formation largely exceeded the formation of other metabolites hydroxylated on the lateral chain by rat liver microsomes and initially characterized in rat bile. In contrast, in vitro studied showed that the initial metabolite of docetaxel resulted from the hydroxylation of the tert-butyl of the lateral chain at C13 and that the same metabolites were formed in human and animal models. Comparison of individual CYP protein content of human microsomes and catalytic activities with taxoid biotransformation, showed that 2 distinct isoforms were assigned to the 6 alpha-hydroxylation (CYP2C) and to the hydroxylation of the lateral chain (CYP3A4). Chemical and immunological inhibitions confirmed these assumptions. The effect of antineoplastic drugs potentially associated with taxoids during chemotherapy has been tested in vitro on paclitaxel and docetaxel biotransformations. In the therapeutic range, vincristine, vinblastine, doxorubicine and cisplatin elicited a moderate or no inhibition of paclitaxel and docetaxel metabolism, as well as cimetidine, ranitidine and diphenylhydramine used to prevent major side effects associated with taxoid therapy. In patients given barbiturates, the hydroxylation on the lateral chain of paclitaxel and docetaxel was markedly stimulated and resulted from the induction of CYP3A isoforms. These results clearly demonstrated that the biotransformation of paclitaxel and docetaxel by human liver microsomes was supported by 2 distinct CYP proteins and that drug interactions could modify the therapeutic efficiency of taxoids during chemotherapy.     

Paclitaxel (Taxol)

The paclitaxel (TAXOL); Bristol-Myers Squibb Company) represents first agent from novel class of antineoplastic drugs--taxanes to enter routine clinical practice. Paclitaxel interferes with microtubular polymerization by promoting abnormal assembly of microtubules and inhibiting their subsequent disassembly. Pharmacokinetics of paclitaxel has been intensively studied. There are indications for nonlinear pharmacokinetics when paclitaxel is administered as a short infusion and at higher doses. Neurotoxicity, mucositis, and leukopenia correlate with some pharmacokinetic parameters. The clinical development of paclitaxel was initially hampered by hypersensitivity reactions. Current dosage regiments with premedication reduced the incidence of these events to 3%. The major dose-limiting adverse effect of paclitaxel is neutropenia. Significant activities were reported especially in patients with advanced ovarian, breast, non-small cell lung cancer (NSCLC), head and neck cancer and in other types of tumours. Long-term follow-up will also allow the effects of the drug on patient survival to be determined. At present combination of Taxol (paclitaxel) with cisplatin clearly improves the duration of progression-free survival and of overall survival compared with cyclophosphamide and cisplatin in women ovarian cancer. Recently was TAXOL (paclitaxel) registered in Czech republic for treatment of patients with advanced metastatic ovarian carcinoma and in patients with metastatic breast cancer after failure of the standard therapy.     

Dose-dense therapy with weekly 1-hour paclitaxel infusions in the treatment of metastatic breast cancer

PURPOSE: To evaluate the efficacy and toxicity of paclitaxel administered as a 1-hour infusion on weekly basis, without interruption, to patients with metastatic breast cancer who had received prior therapy. PATIENTS AND METHODS: Thirty patients with metastatic breast cancer received sustained weekly paclitaxel therapy at an initial dose of 100 mg/m2 until disease progression. Prior therapy included adjuvant only (n=17), metastatic only (n=7), or both (n=6). Eighteen patients had received prior anthracycline therapy, 12 of whom had demonstrated progression of disease within 12 months of it. All patients were assessable for efficacy; 29 patients were assessable for toxicity. Pharmacokinetic studies of paclitaxel were also performed. RESULTS: A total of 469 weekly paclitaxel infusions were administered to 30 patients (median, 14 infusions/patient). The median delivered dose-intensity was 91 mg/m2/wk (range, 80 to 108). The overall response rate was 53% (95% confidence interval [CI], 34% to 72%), with 10% complete responses (CRs) and 43% partial responses (PRs). Median response duration was 7.5 months (range, 2 to 11+). Responses were observed in nine of 18 (50%) patients with prior anthracycline therapy, including six of 12 (50%) with disease progression on anthracycline within 1 year (three of four within 6 months). Therapy was well tolerated and remarkable for a lack of overall and cumulative myelosuppression. Grade 3/4 neutropenia occurred in four patients; febrile neutropenia was not observed. Peripheral neuropathy prohibited dose escalation above 100 mg/m2, and grade 3 neuropathy was observed in two of 21 patients at < or = 100 mg/m2. CONCLUSION: Weekly paclitaxel therapy is active and well tolerated in patients with metastatic breast cancer. Weekly therapy should be considered as a current clinical option for these patients and should be incorporated into future comparative clinical trials.     

Paclitaxel enhances in vitro radiosensitivity of squamous carcinoma cell lines of the head and neck

Squamous cell carcinoma of the head and neck is the fourth most common cancer in the United States, and therapy for very advanced cases is relatively ineffective. Paclitaxel has activity against cancers of the breast, lung, prostate, cervix, and ovary. The activity of paclitaxel for squamous cell carcinoma of the head and neck is less certain, and results of its radiosensitization properties have been variable. The radiation responses of two squamous carcinomas, SCC-9 (oropharynx) and HEP-2 (larynx), were examined to determine the radiosensitizing potential of paclitaxel. In vitro exposures for 24 and 48 h with paclitaxel concentrations of 10(-4) to 6 x 10(-2) microg/ml were followed by irradiation of 0.1-10 Gy. Percent survival was calculated by colony count, and the paclitaxel-radiation interaction was quantitated by the median effect principle and the combination index method of Chou and Talalay. The paclitaxel-radiation combination resulted in multiphasic interactions in both 24 and 48 h paclitaxel pretreatment in SCC-9 and HEP-2 cell lines. In general there was slight synergism [combination index (CI) <1] at low dose-low effect levels (e.g., at a paclitaxel concentration of 0.002 microg/ml or lower and radiation of 0.1-0.3 Gy), moderate antagonism (CI >1) at median dose ranges and strong synergism (CI <1) at high dose ranges (e.g., at a paclitaxel concentration of 0.012-0.06 microg/ml and radiation doses of 3-10 Gy), especially at a surviving fraction of <0.1, which is therapeutically relevant. The median effect principle and combination index method provided a simple way to quantitate the synergism or antagonism of a paclitaxel-radiation interaction under various conditions. This analysis demonstrated that paclitaxel-radiation synergy exists at doses that are readily achievable in the clinical scenario for both agents and that greater synergy occurred at high dose-high effect levels. These results suggest that the combination of both therapies should be explored further in clinical trials assessing the treatment of squamous cell carcinomas of the head and neck.     

Systemic therapy for breast cancer

Currently available information suggests that the optimal duration of adjuvant therapy for breast cancer patients with no involved axillary nodes is 5 years, though controversy about this recommendation persists. In postmenopausal patients, disease-free survival appears to be improved by the addition of combination chemotherapy to tamoxifen. Recently reported studies indicate that there is no benefit to dose escalation of cyclophosphamide in adjuvant therapy and that the risk of secondary leukemia may be increased. The combination of paclitaxel and doxorubicin has been reported in single-institution studies to produce high response rates but may also be cardiotoxic. Recent reports indicate that a pharmacokinetic interaction between these two drugs may cause these clinical findings. New agents that may be of utility in the management of advanced or primary breast cancer include novel hormonal agents, notably the aromatase inhibitors, and the bisphosphonates.     

Phase II trials of docetaxel (Taxotere) in advanced ovarian cancer--an updated overview

Docetaxel (Taxotere) has been studied at a dose of 100 mg/m2 i.v. as a one hour infusion every 3 weeks, in four phase II trials in patients with extensively pretreated ovarian cancer. A total of 340 patients were treated, including 256 patients in two separate EORTC (European Organization for Research and Treatment of Cancer) trials and 84 patients in two trials in the U.S.A. All patients had received prior cisplatin or carboplatin therapy and the treatment-free interval was less than 4 months in 155 patients. The overall response rate using conventional UICC criteria was 30% among 315 evaluable cases (95% confidence interval: 24-36%). Among 155 patients whose disease was most refractory (i.e. treatment-free interval was less than 4 months), the overall response rate was 28% (95% confidence interval: 19-36%). Response duration ranged from 4 to 17 months. Grade IV neutropenia was a common finding and fluid retention was observed. The incidence of febrile neutropenia ranged from 8 to 44% of patients with two deaths (i.e. 0.6% of the total treated) related to neutropenic sepsis. Docetaxel and paclitaxel (Taxol) have comparable activities in ovarian cancer. Ongoing studies with docetaxel include its use in patients as part of first-line therapy, as well as in patients refractory to paclitaxel. To prevent the development of fluid retention, these now involve the routine use of steroid prophylaxis. It is expected that docetaxel will prove to be an important addition to the drugs available for the treatment of ovarian cancer.     

A guinea pig''s view on prostate cancer screening trials

Although the combination of paclitaxel with doxorubicin has yielded high response rates in metastatic breast cancer, severe cardiotoxic events have been reported in several patients. The rationale for our study was to evaluate the activity of paclitaxel/doxorubicin combination in patients with this disease but to avoid excessive cardiotoxicity. Therefore, we administered 4 cycles of doxorubicin/paclitaxel followed by 6 cycles of standard cyclophosphamide, methotrexate and 5-fluorouracil (CMF) regimen. Study medication consisted of doxorubicin 60 mg/m2 as a 15-min intravenous infusion followed by paclitaxel 175 mg/m2 as a 3-hour infusion. CMF regimen consisted of cyclophosphamide 600 mg/m2 as 1-hour intravenous infusion followed by methotrexate 40 mg/m2 and 5-fluorouracil 600 mg/m2 bolus injection. The main toxicity of doxorubicin/paclitaxel treatment phase was neutropenia (WHO grade 3/4, 58%), but we observed only one cardiac adverse event. Toxicities of the CMF treatment phase were not significant. Of 24 patients evaluable for response, 2 (8%) had complete responses and 11 (46%) achieved partial response. Ten additional patients (42%) had stable disease. The median time to progression was 12 months and the median overall survival was 18.5 months. The sequential administration of doxorubicin and paclitaxel followed by CMF appeared active and well tolerated in patients with metastatic breast cancer.     

Phase I and pharmacologic study of weekly doxorubicin and 1 h infusional paclitaxel in patients with advanced breast cancer

Doxorubicin and paclitaxel both display strong antitumor activity in the treatment of breast cancer. The optimal schedule of this combination, however, remains undefined. In this phase I and pharmacologic study, we administered weekly 12 mg/m2 doxorubicin as a bolus infusion immediately followed by a 1 h 80 mg/m2 paclitaxel infusion to patients with metastatic breast cancer. A total of 119 weekly courses were delivered to seven patients. Grade IV neutropenia was observed in two patients at the first dose level, thus already defining the maximum tolerated dose. Pronounced non-hematologic toxicities were mild neuropathy (grade I: 39%) and stomatitis (grade I: 19%, grade II: 8%). No signs of cardiac toxicity were observed with this dose schedule. Three partial responses were achieved in this group of heavily pretreated patients. The pharmacokinetics of paclitaxel, doxorubicin and Cremophor EL with this schedule were analyzed. Overall, the schedule was well tolerated and combined with its preliminary response rate justifies further evaluation in phase II studies.     

Therapy of anthracycline-resistant metastatic breast carcinoma

Treatment of anthracycline-resistant metastatic breast cancer with new antineoplastic agents remains a challenge for the next future. The 5-year survival for this disease is only 15%, and hormonal and chemotherapeutic options remain essentially palliative. New treatment drugs or drug combinations are urgently needed to improve the prospects for patients with metastatic breast cancer, particularly for those with disease characteristics indicating a particularly poor prognosis. Taxanes are promising new drugs and have shown encouraging activity in patients with disease resistant to anthracyclines and in patients with visceral metastases, both with a poor prognosis. Paclitaxel (taxol) is applied with a dose of 175 mg/m2 in a 3 hour infusion and docetaxel (taxotere) with a dose of 100 mg/m2 q 3 weeks. Remission rates are expected between 6-30% for taxol and between 29-48% for docetaxel. Highly active in patients with anthracycline-resistant disease appears to be the vinca-alkaloid vinorelbine too. In patients treated with adriamycin objective remissions between 15-33% can be obtained. The long time known 5-fluorouracil comes to the third place of the effective drugs. Continuous infusion or addition of folic acid increases the intracellular efficacy and results in 5-53% objective remissions. In second-line chemotherapy platin-analogues together with etoposide, vincristine and 5-FU achieve partial or complete remissions between 19-37% for cisplatin containing and 5-12 for carboplatin containing combinations. This may eventually play a role especially if three drug combinations containing paclitaxel, epirubicin and vinorelbine will be used, which are reported to result in 20-33% complete response rates and 66% objective response. The indication for other new drugs like tomudex, topoisomerase-I-inhibitor and gemcitabine for anthracycline-resistant breast cancer remains to be established in multicenter studies.     

A phase II trial of paclitaxel in refractory germ cell tumors

BACKGROUND: A significant percentage of patients with refractory germ cell tumors will not respond to standard salvage regimens. Thus there is a need for new active agents. Paclitaxel has demonstrated activity against a variety of solid tumors in both laboratory and clinical studies. METHODS: Eighteen patients with refractory germ cell tumors who failed initial cisplatin-based chemotherapy and a maximum of 2 salvage regimens were enrolled into a Phase II trial of paclitaxel at a dose of 170 mg/m2 by intravenous infusion over 24 hours every 21 days without growth factor support. The median age of the patients was 32.5 years (range, 18-49 years). The testis was the primary site of tumor for 13 patients (72%) and the tumor was extragonadal in 5 patients (28%). Six patients (33%) were late recurrences. Twelve patients (67%) had > or = 2 metastatic sites. The median number of previous chemotherapy cycles was six (range, four to nine). Three patients (17%) previously had undergone autologous bone marrow transplantation. RESULTS: Two patients (11%) responded to paclitaxel. Major toxicities were Grade 3-4 neutropenia (55% of patients) and Grade 3-4 neurotoxicity (2 patients). Neutropenic fever occurred in 3 patients (17%). CONCLUSIONS: Paclitaxel demonstrated minimal activity in heavily pretreated patients with multiple, poor risk clinical features. These results in part may be due to the unfavorable characteristics of the patients in the current study, specifically the high percentage of patients with late recurrences and extragonadal primary tumors, both of which are known to respond poorly to salvage therapy. Other trials with different patient populations and doses of paclitaxel reported response rates ranging from 13.3%-26%. The role of paclitaxel in the treatment of patients with refractory germ cell tumors remains to be defined in future studies.     

Adenovirus-mediated p53 gene therapy and paclitaxel have synergistic efficacy in models of human head and neck, ovarian, prostate, and breast cancer

Synergy (or antagonism) between two chemical agents is an in vitro empirical phenomenon, in which the observed effect of the combination is more (or less) than what would be predicted from the effects of each agent working alone. Although mathematical synergy is not directly provable in the clinical setting, it does predict a favorable outcome when the two therapeutics are combined in vivo and strongly suggests the presence of in vivo synergy. In contrast, overt antagonism warns of future problems. Sophisticated three-dimensional statistical modeling was used to evaluate the presence of synergistic, additive, or antagonistic efficacy between adenovirus (Ad)-mediated p53 gene therapy (p53 Ad) and paclitaxel (Taxol) in a panel of human tumor cell lines. Cells were either pretreated with paclitaxel 24 h before p53 Ad or treated with both agents simultaneously. Cell proliferation was measured 3 days later. Paclitaxel had synergistic or additive efficacy with p53 gene therapy. In no case was the interaction antagonistic. Cell cycle analysis demonstrated that p53 Ad arrested cells in G0/G1 prior to apoptotic cell death, whereas paclitaxel arrested cells in G2-M prior to apoptotic cell death. When combined, the relative concentration of each agent determined the dominant cellular response. These results are consistent with the previously reported cell cycle effects of p53 or paclitaxel, respectively; however, these data fail to explain the observed drug synergy. We found that low concentrations of paclitaxel (1-14 nM) increased the number of cells transduced by recombinant Ad 3-35% in a dose-dependent manner, which is one possible mechanism for the observed synergy. Of particular note, the concentrations of paclitaxel responsible for increased Ad transduction were lower than the concentrations required for microtubule condensation. The efficacy of combination therapy was also evaluated in vivo. In the p53null SK-OV-3 xenograft model of ovarian cancer, a dosing schedule of p53 Ad that, by itself, had a relatively minimal effect on tumor burden (16%) caused a much greater decrease in tumor burden (55%) when combined with paclitaxel. Greater combined efficacy was also observed in the p53mut DU-145 prostate, p53mut MDA-MB-468 breast, and p53mut MDA-MB-231 breast cancer xenograft models in vivo. In summary, p53 Ad for cancer shows enhanced efficacy when combined with paclitaxel. This combination is recommended for clinical cancer trials.     

Short-term and long-term memory in elderly patients with NIDDM

The new lipophilic anthracycline N-benzyl-adriamycin-14-valerate (AD198) was evaluated for its activity in comparison to doxorubicin in P-glycoprotein (Pgp)-positive and -negative cell lines. AD198 and doxorubicin showed comparable antitumor activity in the Pgp-negative breast cancer cell line MCF-7 and the Pgp-negative ovarian carcinoma cell line A2780. By contrast, AD198 was significantly more active than doxorubicin in the Pgp-positive breast cancer cell line MCF7AD (IC50 values 2.5 and 0.15 microM for 96 h continuous exposure) and the Pgp-positive ovarian carcinoma cell line A2780 DX5 (IC50 values 0.6 and 0.07 microM, respectively). Unlike doxorubicin, the activity of AD198 was not increased by concommittant application of cyclosporin A in cell line MCF7AD. Flow cytometry studies showed that, in contrast to doxorubicin, AD198 was not transported by Pgp and that verapamil did not change the intracellular pharmacokinetics of this new anthracycline. These data provide evidence that AD198 possesses high activity in human solid tumor cell lines expressing the classical multidrug resistant phenotype. Its further clinical development appears to be warranted.