Phase I and clinical pharmacological evaluation of aphidicolin glycinate.

The toxicity profile and the pharmacokinetics of aphidicolin glycinate, a water-soluble analogue of aphidicolin, have been evaluated in two consecutive phase I clinical studies. In the first study, aphidicolin glycinate was given by 1-hour infusion for 5 consecutive days, every 3 weeks (daily x 5 study); in the second study, which was planned on the basis of the pharmacokinetic information obtained in the previous study, the drug was given by 24-hour continuous infusion. Treatment was repeated every 3 weeks. In the daily x 5 study, the daily dose was escalated from 12 mg/m2 to the maximum tolerated dose of 2250 mg/m2. Local toxicity was dose limiting. Elimination half-life was 2 +/- 0.2 hours (mean +/- SE) with aphidicolin being undetectable 6-8 hours after the end of the infusion. In the 24-hour continuous-infusion study, the dose was escalated from 435 mg/m2 to the maximum tolerated dose of 4500 mg/m2. Local toxicity was dose limiting, while other toxic effects were absent. The experimentally determined concentrations at the steady state were in agreement with those predicted on the basis of the available pharmacokinetic data. The targeted concentration at the steady state of 3 micrograms/mL was achieved at doses greater than or equal to 3000 mg/m2. Twenty-four-hour continuous infusion is the recommended schedule for clinical evaluations of aphidicolin glycinate as the synchronizing agent or in combination with cisplatin.

Phase II preclinical drug screening in human tumor xenografts: a first European multicenter collaborative study.

In a European joint project carried out in 6 laboratories a disease-oriented program was set up consisting of a panel of 7 tumor types, each represented by 4 to 8 different human tumor lines, for secondary screening of promising anticancer drugs. Human tumor lines were selected on the basis of differences in histology, growth rate, and sensitivity to conventional cytostatic agents. Xenografts were grown s.c. in nude mice, and treatment was started when tumors reached a mean diameter of 6 mm in groups of mice where at least 6 tumors were evaluable. Drugs were given at the maximum tolerated dose. For evaluation of drug efficacy, median tumor growth curves were drawn, and specific growth delay and treated/control x 100% were calculated. Doxorubicin (8 mg/kg i.v. days 1 and 8) was effective (treated/control < 50%, and specific growth delay > 1.0) in 0 of 2 breast cancers, 1 of 3 colorectal cancers, 2 of 5 head and neck cancers, 3 of 6 non-small cell lung cancers, 4 of 6 small cell lung cancers, 0 of 3 melanomas, and 3 of 6 ovarian cancer lines. Amsacrine (8 mg/kg i.v. days 1 and 8) was not effective, while datelliptium (35 mg/kg i.p. days 1 and 8) was active against 2 of 6 small cell lung cancer lines. Brequinar sodium (50 mg/kg i.p. days 1-5) showed efficacy in 4 of 5 head and neck cancers, 5 of 8 non-small cell lung cancers, and 4 of 5 small cell lung cancer lines. The project has been shown to be a feasible approach. Clinical activity for doxorubicin and inactivity for amsacrine against solid tumor types was confirmed in the human tumor xenograft panel. Additional anticancer drugs will be studied in the European joint project to further define the reliability of this novel, promising screening approach.

Comparative pharmacokinetics of cisplatin and three analogues in mice and humans.

Pharmacokinetics of cisplatin, spiroplatin, ethylenediaminemalonatoplatinum(II) (JM-40), and carboplatin was studied in BALB/c x DBA/2 F1 mice receiving 10% lethal doses of 15.5, 6.8, 100, and 165 mg/kg, respectively. Blood samples were collected for up to 5 days after a single i.v. bolus injection. Total platinum in plasma and non-protein-bound free platinum in plasma ultrafiltrate were determined by flameless atomic absorption spectrometry. Parent JM-40 and carboplatin were determined by high performance liquid chromatography. Calculated pharmacokinetic parameters (peak concentrations, half-lives, areas under the curve) were compared with the corresponding values in patients at the maximal tolerated dose. Peak plasma concentrations were 2.4- to 20-fold higher in mice than in humans. Initial and terminal half-lives in mice were up to 6 times shorter than in patients. However, the areas under the plasma concentration versus time curves (AUCs) were found to agree. The ratios of the AUCs of free platinum in patients (AUCp) and mice (AUCm) measured over the first part of the plasma concentration versus time curve were 1.2, 0.3, 1.1, and 0.9 for cisplatin, spiroplatin, JM-40, and carboplatin, respectively. These values changed to 1.3, 0.3, 2.5, and 1.0 when the time interval was extended to free platinum levels just above the detection limit. Ratios of the AUCs of total platinum in patients and mice measured over 5 days were 2.7, 2.6, 4.2, and 1.8, respectively. Using a ratio of 1 for free platinum originating from JM-40, the retrospectively calculated maximal tolerated dose from AUCp at low dosages was 1021 mg/m2 (n = 7; range, 836-1282), compared to 1200 mg/m2 as found in the phase I trial. This suggests that the AUCp/AUCm ratio of free platinum over the first part of the concentration versus time curve can possibly be used to predict the maximal tolerated dose of platinum analogues in humans, during the early stage of phase I studies.

Phase I study of ethylenediamine platinum(II) malonate (NSC 146 068), a second generation platinum analogue.

Ethylenediamine platinum(II) malonate [JM-40 (NSC 146 068)] has been selected for clinical studies because of its favorable preclinical toxicity profile as a "second generation" platinum analogue. When compared to cisplatin, JM-40 was less emetic in the ferret and less nephrotoxic in the dog, while its antitumor activity approached that of cisplatin. Twenty-nine patients received 86 courses of JM-40 as a single dose every 3-4 wk. After 13 dose escalation steps the maximum tolerable dose was reached at 1200 mg/m2. The dose limiting toxicities were nausea, vomiting, and nephrotoxicity. The renal damage seemed reversible up to a dose level of 1000 mg/m2 and consisted of a glomerular and tubular dysfunction. JM-40 did not cause any other dose related side effect or myelo-suppression. Pharmacokinetic studies at a dose of 1000 mg/m2 revealed mean terminal half-lives of 5.0 and 1.9 days for platinum in plasma and plasma ultrafiltrate, respectively. The mean cumulative excretion of platinum in urine accounted for 57% of the dose up to day 5. Two partial responses were observed in a patient with a large cell carcinoma of the lung and in one with a carcinoma of the lacrimal gland. Limited evaluation of JM-40 in phase II studies is warranted. The recommended dose is 1000 mg/m2 every 4 wk and 800 mg/m2 for patients pretreated with platinum analogues.

Etoposide bioavailability after oral administration of the prodrug etoposide phosphate in cancer patients during a phase I study.

PURPOSE: The purpose of this study was to determine the bioavailability (F) of etoposide (E;VP-16) after oral administration of the water-soluble prodrug etoposide phosphate (EP;BMY-40481) during a phase I trial in cancer patients. PATIENTS AND METHODS: Twenty-nine patients received oral EP (capsules, 50 to 150 mg/m2/d of E equivalent) for 5 days in week 1 (course 1), followed every 3 weeks thereafter by a daily intravenous (i.v.) infusion for 5 days of E (80 mg/m2, 1-hour i.v. infusion; course 2); in three patients, the i.v. E course was given before oral EP. Plasma and urine E pharmacokinetics (high-performance liquid chromatography [HPLC]) were performed on the first day of oral EP administration and on the first day of i.v. E. RESULTS: Twenty-six of 29 patients completed two courses or more, whereas three patients received only one course due to toxicity. Myelosuppression was dose-dependent and dose-limiting, with grade 4 leukoneutropenia in four of 15 patients at 125 mg/m2 and in five of seven patients at 150 mg/m2. One patient died of meningeal hemorrhage related to grade 4 thrombocytopenia. Other toxicities were infrequent and/or manageable. No objective response was observed. The maximum-tolerated dose (MTD) is therefore 150 mg/m2, and the recommended oral dose of EP for phase II trials in this poor-risk patient population is 125 mg/m2. Twenty-six patients had pharmacokinetic data for both oral EP and i.v. E, whereas three had pharmacokinetic data on the i.v. E course only. After oral administration of EP, the pharmacokinetics of E were as follows: mean absorption rate constant (Ka), 1.7 +/- 1.7 h-1 (mean +/- SD); lag time, 0.3 +/- 0.2 hours; time of maximum concentration (t(max)), 1.6 +/- 0.8 hours; and mean half-lives (t1/2), 1.6 +/- 0.2 (first) and 10.3 +/- 5.8 hours (terminal); the increase in the area under the plasma concentration-versus-time curve (AUC) of E was proportional to the EP dose. After the 1-hour i.v. infusion of E, maximum concentration (C(max)) was 15 +/- 3 micrograms/mL; mean AUC, 88.0 +/- 22.0 micrograms.h/mL; mean total-body clearance (CL), 0.97 +/- 0.24 L/h/m2 (16.2 mL/min/m2); and mean t1/2, 0.9 +/- 0.6 (first) and 8.1 +/- 4.1 hours (terminal). The 24-hour urinary excretion of E after i.v. E was significantly higher (33%) compared with that of oral EP (17%) (P < .001). Significant correlation was observed between the neutropenia at nadir and the AUC of E after oral EP administration (r = .58, P < .01, sigmoid maximum effect [E(max)] model). The mean F of E after oral administration of EP in 26 patients was 68.0 +/- 17.9% (coefficient of variation [CV], 26.3%; F range, 35.5% to 111.8%). In this study, tumor type, as well as EP dose, did not significantly influence the F in E. There was no difference in F of E, whether oral EP was administered before or after i.v. E. Compared with literature data on oral E, the percent F in E after oral prodrug EP administration was 19% higher at either low ( < or = 100 mg/m2) or high ( > 100 mg/m2) doses. CONCLUSION: Similarly to E, the main toxicity of the prodrug EP is dose-dependent leukoneutropenia, which is dose-limiting at the oral MTD of 150 mg/m2/d for 5 days. The recommended oral dose of EP is 125 mg/m2/d for 5 days every 3 weeks in poor-risk patients. Compared with literature data, oral EP has a 19% higher F value compared with oral E either at low or high doses. This higher F in E from oral prodrug EP appears to be a pharmacologic advantage that could be of potential pharmacodynamic importance for this drug.

Multicenter, randomized comparative study of two doses of paclitaxel in patients with metastatic breast cancer.

PURPOSE AND METHODS: The objective of this multicenter study was to compare the therapeutic index of two different doses of paclitaxel given as a 3-hour infusion in patients with metastatic breast cancer (MBC), who had failed to respond to previous chemotherapy. A total of 471 patients with MBC were randomized to receive intravenous paclitaxel at a dose of 175 or 135 mg/m2 every 3 weeks. RESULTS: Better treatment results were achieved with high-dose (HD) versus low-dose (LD) paclitaxel: overall response rate, 29% versus 22% (P = .108); complete response (CR) rate, 5% versus 2% (P = .088); median time to disease progression, 4.2 versus 3.0 months (P = .027); and median survival time, 11.7 versus 10.5 months (P = .321). Patients previously exposed or resistant to anthracyclines were as likely to respond as those without such prior exposure. Treatment was well tolerated, as documented by the number of administered treatment courses (median, six v five; range, one 17 v one to 18), the low frequency of dose reductions (14% v 7%, P = .024), and the small number of patients (n = 9 or 4% vn = 5 or 2%) who required treatment discontinuation for adverse reactions. The incidence and severity of neutropenia and peripheral neuropathy were dose-related. After quality-of-life-adjusted time-to-progression analysis, the HD arm (175 mg/m2) retained its advantage over the LD arm (135 mg/m2). CONCLUSION: The results of this trial substantiate the activity of paclitaxel in the treatment of MBC. The observed superior efficacy with a dose of 175 mg/m2 over 135 mg/m2 suggests a dose-effect relationship. The clinical activity in anthracycline-resistant patients is particularly noteworthy. Paclitaxel in breast cancer needs further evaluation in large trials that use combination chemotherapy and involve earlier disease stages.

Paclitaxel is safe and effective in the treatment of advanced AIDS-related Kaposi's sarcoma.

PURPOSE: Liposomal anthracyclines are the present standard treatment for advanced AIDS-related Kaposi's sarcoma (KS). No effective therapies have been defined for use after treatment failure of these agents. A phase II trial was thus conducted with paclitaxel in patients with advanced KS to assess safety and antitumor activity. MATERIALS AND METHODS: A regimen of paclitaxel at a dose of 100 mg/m(2) was given every 2 weeks to patients with advanced AIDS-related KS. Patients were treated until complete remission, disease progression, or unacceptable toxicity occurred. RESULTS: Fifty-six patients with advanced AIDS-related KS were accrued. Tumor-associated edema was present in 70% of patients and visceral involvement in 45%. Forty patients (71%) had received prior systemic therapy; 31 of these were resistant to an anthracycline. The median entry CD4(+) lymphocyte count was 20 cells/mm(3) (range, 0 to 358). A median of 10 cycles (range, 1 to 54+) of paclitaxel was administered. Fifty-nine percent of patients showed complete (n = 1) or partial response (n = 32) to paclitaxel. The median duration of response was 10.4 months (range, 2.8 to 26.7+ months) and the median survival was 15.4 months. The main side effects of therapy were grade 3 or 4 neutropenia in 61% of patients and mild-to-moderate alopecia in 87%. CONCLUSION: Paclitaxel at 100 mg/m(2) given every 2 weeks is active and well tolerated in the treatment of advanced and previously treated AIDS-related KS. The median duration of response is among the longest observed for any regimen or single agent reported for AIDS-related KS. Paclitaxel at this dosage and schedule is a treatment option for patients with advanced AIDS-related KS, including those who have experienced treatment failure of prior systemic therapy.

Overview of Taxol safety.

The safety profile of Taxol administered intravenously as a single agent has been established based on the experience of 655 patients. Of these patients, 253 were treated in nine phase I studies, and 402 were treated in eight disease-oriented phase II studies. Myelosuppression, specifically neutropenia, was the dose-limiting toxicity in all studies conducted in patients with solid tumors. Neutropenia was schedule dependent and was less severe when Taxol was administered via a 3-hour infusion. Severe hypersensitivity reactions were controlled in the phase II program with a premedication regimen consisting of dexamethasone, an antihistamine, and an H2 blocker. Cardiovascular toxicities were minimal and do not indicate constant electrocardiographic monitoring during Taxol infusions. Peripheral neuropathy was usually mild to moderate and dose related; however, it rarely caused treatment discontinuation. Additional adverse events associated with Taxol include arthralgia/myalgia, mucositis, nausea and vomiting, and alopecia.

Cytotoxic effects of anticancer agents on subconfluent and multilayered postconfluent cultures.

The cytotoxic effects of conventional (doxorubicin, 5-fluorouracil, cisplatin) and investigational (2',2'-difluorodeoxycytidine, hexadecylphosphocholine, EO9, rhizoxin) anticancer drugs were studied in subconfluent and multilayered postconfluent cultures of human colon and ovarian carcinoma cell lines. Chemosensitivity was assessed 4 days after a 24-h drug exposure with the sulphorhodamine B assay. Except for rhizoxin, all drugs tested yielded an EC50 (drug concentration producing absorbance readings 50% lower than those of non-treated wells) in postconfluent cultures that were higher than an EC50 obtained with subconfluent cultures. Compared with subconfluent cultures, postconfluent cultures showed decreased cellular nucleotide concentrations and ATP/ADP ratios, in addition to an increased percentage of G0/G1 cells. The activity of DT-diaphorase, a reductase involved in the bioactivation of EO9, was similar in sub- and postconfluent cultures. These results indicate similarity of the postconfluent model presented with those obtained with in vivo models and more complex in vitro techniques.

Comparison of the sulforhodamine B protein and tetrazolium (MTT) assays for in vitro chemosensitivity testing.

The sulforhodamine B (SRB) protein stain assay was compared with the tetrazolium (MTT) colorimetric assay for in vitro chemosensitivity testing of various human tumour cell lines. The SRB assay provided a better linearity with cell number and a higher sensitivity, and its staining was not cell-line dependent. In contrast to the MTT assay, the SRB assay stained recently lysed cells. Cell debris, however, was not stained by SRB and therefore the drug sensitivity data were not affected.

Drug discovery and development in the pharmaceutical industry.

The discovery and development of new anticancer drugs is a complex and largely empirical process. New compounds can be discovered by screening, modification of existing compounds, rational drug design, and serendipitous basic research observations. Selection of compounds for clinical trials depends on assays of uncertain predictive value. In the pharmaceutical industry, priorities for development of potentially active entities are set and available resources allocated based on the availability and cost of supplies, patent status, potential spectrum of activity, ability to meet regulatory requirements, and market assessments. Competition for resources also occurs from noncancer drugs, eg, cardiovascular agents. Clinical development (testing and approval for commercial distribution) requires close attention to the requirements of national regulatory agencies such as the United States Food and Drug Administration. The arbitrary nature by which compounds with antitumor potential are chosen for development means that some that would be useful never reach clinical trial and others are never made generally available. This article reviews the decision making process in the pharmaceutical industry by which compounds are identified and selected for clinical trial, the regulations in the United States that govern such trials, and what is required to have the drug approved for commercial distribution.

Paclitaxel plus carboplatin in the treatment of ovarian cancer.

Second-line treatment with paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) may achieve remissions in patients suffering from ovarian cancer who have failed primary chemotherapy with cisplatin- or carboplatin-based regimens. Introduction of paclitaxel in combination with cisplatin into the first-line treatment strategy was therefore the next logical step in the development of chemotherapy against ovarian cancer. Data already have shown that this may result in better survival. Since carboplatin may replace cisplatin, the combination of paclitaxel with carboplatin seemed a further necessary step. We therefore embarked on a dose-finding study of paclitaxel and carboplatin. Fourteen patients with International Federal of Gynecology and Obstetrics stage III and IV ovarian cancer with a median age of 55.5 years entered this study of escalating doses of either carboplatin or paclitaxel. Doses of carboplatin could be escalated from 300 to 450 mg/m2 and paclitaxel could be escalated from 125 to 175 mg/m2 without dose-limiting myelosuppression. At the highest dose level reported here, only transient short-lived leukopenia was observed. Other toxicities consisted of nausea and vomiting, peripheral neurotoxicity, and arthralgia, all mild. In the first 14 patients, 10 of whom are evaluable, complete remissions were seen in two patients and partial remissions in six. This study will escalate the doses of paclitaxel and carboplatin further. This treatment is well tolerated and yields satisfactory antitumor results.

Carboplatin and paclitaxel in patients with advanced ovarian cancer: a dose-finding study.

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) combined with cisplatin seems the new standard of care for ovarian cancer patients. Since carboplatin lacks the neurotoxicity of cisplatin with an equal antitumor activity against ovarian cancer, it was chosen as the next logical step for combination chemotherapy with paclitaxel. In 46 patients an alternating dose-escalation trial has been performed. The maximum tolerated doses are carboplatin 500 mg (area under the concentration-time curve of 9) and paclitaxel 200 mg/m2 given every 3 weeks. The dose-limiting toxicity is thrombocytopenia, which emerges in the later stages of the treatment. A true platelet-sparing effect of the combination seems highly probable. The antitumor activity of the combination equals that reported for the new standard paclitaxel/cisplatin treatment. Further phase III studies are warranted.

Etoposide phosphate infusion with therapeutic drug monitoring in combination with carboplatin dosed by area under the curve: a cancer research campaign phase I/II committee study.

The area under the plasma concentration-time curve (AUC) following an intravenous dose of etoposide varies considerably among patients, which in part contributes to the unpredictability of toxicity and response seen in individual patients. This study evaluated the utility of therapeutic drug monitoring of etoposide in reducing the interpatient variability of etoposide steady-state concentrations during prolonged infusion. The etoposide prodrug etoposide phosphate (Etopophos; Bristol-Myers Squibb Company, Princeton, NJ) was administered by infusion using an adaptive dosing strategy. It was given in combination with carboplatin, which was dosed on an AUC basis. Patients with histologically or cytologically proven small cell lung cancer were treated with etoposide phosphate by continuous 120-hour infusion and carboplatin at a dose calculated by the Calvert formula to give an AUC of 5 mg/ mL.min. Blood samples were taken on days 2 through 5 of each treatment cycle, and high-performance liquid chromatography was used to measure the plasma etoposide concentration. The resultant concentrations were compared with target concentrations of 1 or 2 micrograms/mL and these data were used to calculate the rate of infusion for the following 24 hours. In the first cohort, the target etoposide concentration was 1 microgram/mL, and this was achieved (mean +/- SD = 1.05 +/- 0.24 micrograms/mL) by infusing etoposide phosphate doses of 21 to 109 mg (15 to 68 mg/m2) per day. In the second cohort, the target concentration of 2.0 micrograms/mL was achieved (mean +/- SD = 2.05 +/- 0.31 micrograms/mL) with infused etoposide phosphate doses of 69 to 193 mg (41 to 114 mg/m2) per day. This technique reduced the variation in plasma levels and resulted in predictable hematologic toxicity. Cumulative hematologic toxicity necessitated an extension of the treatment cycle from 3 to 4 weeks, however. Of six evaluable patients, two had a complete response and one had a partial response. Therapeutic drug monitoring was shown to reduce the interpatient variation in the plasma etoposide concentration by half and shows promise for individualizing treatment with combination chemotherapy. Exploiting the known relationships between the pharmacokinetics and pharmacodynamics of these two drugs by using therapeutic drug monitoring may lead to better therapeutic safety and efficacy.

High-dose paclitaxel with granulocyte colony-stimulating factor in patients with advanced breast cancer refractory to anthracycline therapy: a European Cancer Center trial.

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is a novel cytostatic agent that has shown interesting antitumor activity in patients with advanced breast cancer. Depending on variable patient characteristics and amount and type of prior therapy, as well as the applied dose and schedule of paclitaxel, response rates have varied from 13% to 62%. However, optimal dose and schedule are still unknown. We studied a high-dose (250 to 300 mg/m2) 3-hour paclitaxel infusion schedule in a poor prognostic group of breast cancer patients who progressed or relapsed while taking anthracyclines. This regimen was given every 3 weeks. Twenty-one of the 36 patients studied had increased liver enzymes and 18 had documented liver metastases. The objective response rate was only 6%, but response rate by disease site indicated that soft tissue lesions responded in 30% of cases. For a better comparison with other reported data a uniform definition of "anthracycline refractory" is needed. Neuropathy, which was found to be dose limiting, and arthralgia/myalgia syndrome were the most frequently occurring toxicities. Both severe myelosuppression (and infections) and severe diarrhea and mucositis were reported more frequently in patients with liver dysfunction. As higher peak levels, increased areas under the concentration time curves, and longer times during which plasma concentrations were above the threshold level of 0.1 mumol/L were found in patients with elevated liver enzymes, a correlation with the observed toxicities is assumed. Further pharmacodynamic studies in such patients receiving a 3-hour infusion seem warranted.

The main steps in the development of anticancer agents.

The development of new anticancer agents is a long-term process, which involves the acquisition of new compounds, screening for antitumor activity, production and formulation, animal toxicology and finally, evaluation of toxicity and antitumor activity of the compound in man (Table I). In this paper, the main steps in the early development of new cytotoxic agents up to phase II clinical studies will be discussed. However, clinical phase III-IV trails, where the efficacy of the drug has been proven, should be dealt with separately.

Promising new developments in cancer chemotherapy.

The positive impact on survival of traditional chemotherapeutic agents has renewed interest in developing newer cytotoxic agents and orally active compounds with improved therapeutic indices. In addition, new insights into the pathways of human tumorigenesis have led to novel approaches aimed at specific mechanism-based targets. The taxane class, of which paclitaxel was the first member, has the unique ability to promote and stabilize microtubule function directly, thereby inhibiting mitotic progression and inducing apoptotic cell death. Paclitaxel provides treatment benefit in a broad range of solid tumors including breast, ovarian, and lung cancer. The success with paclitaxel stimulated interest in the microtubule as a new therapeutic target. Taxane analogues with improved preclinical efficacy have been identified and are entering clinical trials. The enthusiasm for oral anticancer agents and the therapeutic importance of platinum compounds has led to the development of JM216 (satraplatin), a novel platinum IV coordination complex with oral activity in cisplatin-resistant cell lines, which is now in phase III trials in prostate cancer. Another compound in late development is DPPE, a chemopotentiator that enhances the in vivo antitumor effects of cytotoxic agents such as doxorubicin, cyclophosphamide, and cisplatin. Agents that inhibit topoisomerase I and II have also been of interest. TAS-103 is a dual topoisomerase I and II inhibitor with preclinical efficacy in a broad spectrum of tumors and in multidrug-resistant tumor cell lines. Vaccination strategies represent a rational therapeutic approach in the minimal residual disease or high-risk adjuvant therapy setting. The GMK and MGV vaccines utilizing ganglioside antigens overexpressed on human tumors such as melanoma and small cell lung cancer appear to induce antibody production reliably at tolerable doses and are under further clinical investigation. Inhibition of matrix metalloproteinases (MMPs) is another attractive target for intervention in several aspects of tumor progression. Local production of MMPs with subsequent degradation of the extracellular matrix is implicated in supporting tumor growth, invasion, and angiogenesis. The development of orally active, nontoxic MMP inhibitors is critical since these compounds will likely require chronic administration in conjunction with other therapies. Oncogenes and tumor suppressor genes are appealing targets for therapy since they are thought to be responsible for a significant number of cancers. Mutations in the Ras oncogene occur with great frequency in a number of human cancers including lung, pancreas, and colon cancer. Clinical development of potent and selective inhibitors of farnesyltransferase, the Ras-processing enzyme, is ongoing. These compounds uncouple Ras activity, affect tumor growth, and have demonstrated significant antitumor activity against experimental models of human cancer. The exciting compounds and novel therapeutic approaches currently under investigation by Bristol-Myers Squibb Pharmaceutical Research Institute offer great potential as effective cancer chemotherapy agents for the near future.

Pharmacokinetics and toxicology of sparsomycin in beagle dogs.

Sparsomycin is a cytotoxic drug exhibiting a broad spectrum of in vitro activity against murine tumors and many tumor cell lines. It also appears to be a potent stimulator of the antitumor activity of cisplatin against L1210 leukemia in vivo. However, because of its toxicity, the antitumor activity of sparsomycin on murine tumors in vivo has been disappointing. The purpose of our study was to investigate the pharmacokinetics of this drug as well as the possible mechanisms that produce sparsomycin toxicity. Tests on beagle dogs revealed that about 60% of the drug is eliminated by metabolic clearance, while 40% is eliminated by the kidneys. After a single bolus injection of 0.1 mg/kg sparsomycin without narcosis, sparsomycin was eliminated with a t beta 1/2 of 0.6-0.7 h, the AUC being 0.32-0.38 mg.h.l-1, and the volume of distribution (Vd) 0.26 l/kg. In addition to being subject to glomerular filtration, sparsomycin is probably also actively excreted and actively reabsorbed by the renal tubuli. Sparsomycin itself may inhibit its active tubular excretion, thus resulting in a decrease in the drug's renal clearance and its accumulation in the plasma. Sparsomycin appeared to be toxic primarily in the liver, disturbing its function and the synthesis of plasma proteins. Two out of five dogs developed hemorrhagic diathesis due to hypofibrinogenemia and deficiency of other blood-coagulation factors. Sparsomycin was not toxic to the bone marrow.

Phase I study of Brequinar sodium (NSC 368390) in patients with solid malignancies.

Brequinar sodium (DUP 785, NSC 368390) is a novel quinoline-carboxylic acid derivative that has been selected for clinical evaluation because of its broad spectrum of antitumor activity in animal models and its novel chemical structure. This compound inhibits the mitochondrial enzyme dihydroorotate dehydrogenase (DHO-DH), which catalyzes the conversion of dihydroorotate to orotate, leading to a blockage in the pyrimidine de novo biosynthesis. A total of 43 patients received 110 courses of Brequinar sodium by short-term intravenous (i.v.) infusion, which was repeated every 3 weeks. Dose escalation was initially based on a modified Fibonacci scheme. After pharmacokinetic data from mice and man became available, a pharmacologically guided dose escalation was used; at toxic levels, dose escalation was applied on the basis of clinical judgement. The dose-limiting toxicities were myelosuppression, mucositis, skin rash, nausea and vomiting. The maximum tolerable doses for poor- and good-risk patients were 1,500 and 2,250 mg/m2, respectively. One mixed response was observed in a patient with papillary carcinoma of the thyroid. The recommended doses for phase II studies are 1,200 and 1,800 mg/m2 Brequinar sodium, given by a 1-h i.v. infusion every 3 weeks to poor- and good-risk patients, respectively.

In vitro chemosensitivity testing of multilayered microcultures.

A potential limitation of in vitro microtiter cytotoxicity assays as compared to in vivo antitumor studies is that the complex three-dimensional structure of the solid tumor is lost in monolayer cultures in vitro. We investigated whether more in vivo like cell-cell interactions could be easily and reproducibly obtained in an in vitro cytotoxicity assay. HT29 human colon adenocarcinoma cells were seeded in 96-well microtiter plates with "V"-shaped wells and allowed to form postconfluent multilayered cultures. Cross-sections of microcultures fixed after 2 and 3 weeks following plating revealed approximately 7 and 35 cell layers, respectively. Using a tetrazolium assay to assess cytotoxicity, the EC50 (drug concentration which gives absorbance readings 50% lower than those of non-treated wells) of multilayered cultures exposed to doxorubicin for 24 h was 12 times higher (p less than 0.05) than that determined for subconfluent monolayered cells simultaneously exposed to the drug. This system offers an alternative to study the chemosensitivity of three-dimensionally organized cells using semiautomated microtiter plate technology.