Biomedical subjects

E K Rowinsky

Publications and source records attributed to E K Rowinsky.

At least 109 records · Page 6Linked to original sources

PubMed1996

Murine and human in vivo penclomedine metabolism.

Penclomedine is a multichlorinated alpha-picoline derivative which has shown prominent activity in murine breast cancer models and is currently undergoing clinical development. Previous in vitro research has identified several penclomedine metabolites. In this study, human and murine in vivo penclomedine metabolism was examined. Upon i.v. administration to mice, no penclomedine was detectable in plasma at time points as early as 1 h postinfusion. The principle metabolite was demethyl-penclomedine [3, 5-dichloro-2-methoxy-4-hydroxy-6-(trichloromethyl)pyridine]. Both penclomedine and demethyl-penclomedine could be recovered from tissues. Greater than 60% of the penclomedine dose remaining in the body at 22 h was indelibly bound to tissue and plasma proteins. Urinary metabolites of penclomedine consisted mainly of penclomic acid and additional polar metabolites. The results obtained after p. o. administration were nearly identical to i.v. administration with respect to the extent, level, and type of metabolites found in the plasma, tissues, and urine and with respect to the extent of protein binding. In human subjects administered penclomedine daily for 5 consecutive days, demethyl-penclomedine could be detected in plasma and accumulated with successive doses of penclomedine, reaching peak plasma concentrations of up to 10 times that of penclomedine itself and plasma exposures of nearly 400 times that of the parent drug. It appears that patients eliminate penclomedine largely through metabolism and that this drug may be amenable to p.o. administration.

Animals↗

PubMed1995

Paclitaxel (taxol)

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Arrhythmias, Cardiac↗

PubMed1995

Vinorelbine and the topoisomerase 1 inhibitors: current and potential roles in breast cancer chemotherapy.

Vinorelbine is a semi-synthetic vinca alkaloid which was initially developed in France in the 1980's. Due to its unique structure it is considerably less neurotoxic than vincristine. Several phase II studies have shown that vinorelbine is active in metastatic breast cancer therapy with response rates of 20-30% in pretreated and 40-50% in nonpretreated patients respectively. Higher response rates have been noted when vinorelbine is used in combination regimens. The main dose-limiting toxicity seen with this agent has been neutropenia; neurotoxicity manifest as symptomatic paresthesia can be seen in 10% of treated patients. Oral and implantable forms of the drug have also been investigated. The topoisomerase 1 inhibitors topotecan and camptothecin 11 (CPT-11) have been less extensively evaluated in breast cancer therapy. Preclinical studies have indicated that both of these agents are active against breast cancer and some responses have been seen in phase 1 trials of topotecan. An 8% response rate was noted in a phase II trial of CPT-11 in patients with pretreated metastatic breast cancer. Further phase II trials are ongoing at present with both agents.

Antineoplastic Agents↗

PubMed1995

The distribution of systemically administered [3H]-paclitaxel in rats: a quantitative autoradiographic study.

Paclitaxel is an important agent in the treatment of many common malignancies. Although the symptomatic peripheral neuropathy caused by this drug is its principal nonhematologic toxicity, little is known about the distribution of paclitaxel within the peripheral or central nervous system following systemic administration. In order to study paclitaxel's distribution in neural and extraneural tissues, adult Sprague-Dawley rats were sacrificed 2 h after a tail vein injection of [3H]-paclitaxel (0.03 mg/kg, 250 microC/rat). Samples of lung, heart, liver, spleen, kidney, skeletal muscle, brain, spinal cord, dorsal root ganglion, and peripheral nerve were then removed and snap-frozen. These tissues were sectioned at 10 microns in a cryostat and exposed to autoradiography film for 2 weeks. The distribution and concentrations of [3H]-paclitaxel in plasma, urine and cerebrospinal fluid were also determined using liquid scintillation spectrometry. [3H]-paclitaxel concentrations (and organ/plasma concentration ratios) in plasma, urine and cerebrospinal fluid were 2.6 nM (1), 38 nM (15) and 0.7 nM (0.3), respectively. A relatively homogeneous distribution of [3H]-paclitaxel was observed in liver [412 nM (151)], spleen [351 nM (133)], heart [319 nM (117)], lung [268 nM (93)] and muscle [69 nM (26)]. Higher concentrations of [3H]-paclitaxel were noted in the portal triads [869 nM (361)], glomeruli [797 nM (304)], and renal medulla [961 nM (363)], which may reflect biliary excretion and glomerular filtration. A high concentration of [3H]-paclitaxel was also noted in the choroid plexus [432 nM (167)], but [3H]-paclitaxel was not detected in the brain parenchyma, spinal cord, dorsal root ganglion, peripheral nerve, or the testicles. The pathogenesis of paclitaxel-induced neurotoxicity remains obscure given its limited distribution in the nervous system. In addition, these results suggest that systemically administered paclitaxel is not likely to be effective for the treatment of malignancies in the testes or the nervous system.

Animals↗

PubMed1995

Taxol inhibits neointimal smooth muscle cell accumulation after angioplasty in the rat.

Despite significant improvements in the primary success rate of the medical and surgical treatments for atherosclerotic disease, including angioplasty, bypass grafting, and endarterectomy, secondary failure due to late restenosis continues to occur in 30-50% of individuals. Restenosis and the later stages in atherosclerotic lesions are due to a complex series of fibroproliferative responses to vascular injury involving potent growth-regulatory molecules (such as platelet-derived growth factor and basic fibroblast growth factor) and resulting in vascular smooth muscle cell (VSMC) proliferation, migration, and neointimal accumulation. We show here, based on experiments with both taxol and deuterium oxide, that microtubules are necessary for VSMCs to undergo the multiple transformations contributing to the development of the neointimal fibroproliferative lesion. Taxol was found to interfere both with platelet-derived growth factor-stimulated VSMC migration and with VSMC migration and with VSMC proliferation, at nanomolar levels in vitro. In vivo, taxol prevented medial VSMC proliferation and the neointimal VSMC accumulation in the rat carotid artery after balloon dilatation and endothelial denudation injury. This effect occurred at plasma levels approximately two orders of magnitude lower than that used clinically to treat human malignancy (peak levels achieved in this model were approximately 50-60 nM). Taxol may therefore be of therapeutic value in preventing human restenosis with minimal toxicity.

Angioplasty, Balloon↗

PubMed1995

Phase I and pharmacologic studies of pyrazoloacridine, a novel DNA intercalating agent, on single-dosing and multiple-dosing schedules.

PURPOSE: To determine the maximum-tolerated doses (MTDs), principal toxicities, and pharmacologic behavior of pyrazoloacridine (PZA), a novel DNA intercalator with a unique mechanism of action, on single- and multiple-dosing schedules. PATIENTS AND METHODS: PZA was administered on a single-dosing schedule as a 1- to 3-hour infusion and on a multiple-dosing schedule as a 1-hour infusion daily for 5 days to cancer patients at doses ranging from 400 to 935 mg/m2 and 40 to 180 mg/m2/d every 3 weeks, respectively. RESULTS: On the single-dosing 1-hour schedule, CNS toxicity, characterized by neuropsychiatric and neuromotor effects, prompted prolongation of the infusion duration to 3 hours and led to a study of PZA on a multiple-dosing schedule. Both measures resulted in lower incidence of CNS toxicity. Neutropenia was the principal toxicity and precluded dose escalation to levels greater than 750 mg/m2 on the single-dosing (3-hour) schedule and 150 mg/m2/d x 5 (total dose, 750 mg/m2) on the multiple-dosing schedule. Thrombocytopenia, anemia, and nonhematologic effects occurred less frequently. Responses were observed in several patients with platinum- and taxane-refractory ovarian carcinoma; antitumor activity was also noted in patients with cervical and colorectal carcinomas. Significant intraindividual variability characterized by the presence of multiple drug peaks and troughs was observed in the pharmacologic studies. The maximal PZA concentrations achieved in both studies exceeded drug concentrations associated with significant cytotoxicity in preclinical studies and correlated with the occurrence of CNS toxicity. CONCLUSION: Neutropenia is the dose-limiting toxicity on both schedules and 750 mg/m2 and 150 mg/m2/d are the recommended starting doses of PZA on single- and multiple-dosing schedules, respectively, for minimally pretreated patients in phase II studies; slightly lower doses are recommended for more heavily pretreated subjects. The favorable toxicity profile of PZA and its antitumor activity in several refractory tumors warrant broad phase II evaluations of this agent.

Acridines↗

PubMed1995

Treatment of metastatic breast cancer with combination paclitaxel/cyclophosphamide.

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has demonstrated substantial single-agent activity against both minimally pretreated and resistant metastatic breast cancer. Evaluation of paclitaxel-based combinations has demonstrated appreciable activity, but also toxicity, for the paclitaxel/doxorubicin combination. The paclitaxel/cyclophosphamide combination is potentially attractive because of the significant single-agent activity of both drugs against metastatic breast cancer and the paucity of shared nonhematologic toxicities. This combination is being evaluated in women with doxorubicin-refractory metastatic breast cancer. Dose escalation to paclitaxel 200 mg/m2 over 24 hours and cyclophosphamide 2,000 mg/m2 administered every 21 days with granulocyte colony-stimulating factor support has been performed. The final dose level was complicated by dose-limiting toxicity. The maximum tolerated dose for this combination is currently being defined. There is preliminary evidence of sequence-dependent toxicity. Grade 4 neutropenia and neutropenic fevers are more frequent in cycles in which paclitaxel is administered first.

Adult↗

PubMed1995

Phase I study of paclitaxel as a 3-hour infusion followed by carboplatin in untreated patients with stage IV non-small cell lung cancer.

Preliminary results of a phase I study of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), given by 3-hour infusion, followed by carboplatin in chemotherapy-naive patients with stage IV non-small cell lung cancer indicate that both agents can be combined at clinically relevant single-agent doses. The paclitaxel (mg/m2)/carboplatin area under the concentration-time curve (mg.min/mL) dose level of 225/7 is projected to be the maximally tolerated and recommended phase II dose level for future evaluations. Dose-limiting neutropenia, thrombocytopenia, and nausea and vomiting preclude treatment with carboplatin doses estimated to target an area under the concentration-time curve of 9 mg.min/mL when given with paclitaxel 225 mg/m2. The heterogeneous nature of the principal toxicities, as well as the ability to administer clinically relevant single-agent doses of both agents in combination, also indicate that further dose escalation of paclitaxel and carboplatin using hematopoietic growth factors would not be feasible. The preliminary antitumor activity noted to data, as well as the safety associated with the clinically relevant single-agent doses that can be given in combination, indicate that phase II/III evaluations of this regimen are warranted in patients with both advanced and early stage non-small cell lung cancer.

Adult↗

PubMed1995

Pretreatment H2 receptor antagonists that differ in P450 modulation activity: comparative effects on paclitaxel clearance rates and neutropenia.

Histamine-2 receptor antagonists (H2RAs) are principal components of the premedication regimen used to prevent major hypersensitivity reactions in patients receiving paclitaxel. Several different H2RAs, including cimetidine, ranitidine and famotidine, have been used in clinical trials of paclitaxel, as well as by clinicians in different geographic regions and hospitals primarily because of differences in the availability of the various H2RAs. However, H2RAs have highly variable cytochrome P450-modulating capabilities, and the P450 system appears to play a major role in paclitaxel metabolism and disposition. Therefore, the use of different H2RAs may result in different pharmacologic, toxicologic and antitumor profiles due to differential effects on paclitaxel metabolism. This study evaluated whether cimetidine and famotidine, which possess disparate P450-modulating capabilities, differentially affect paclitaxel clearance rates and the agent's principal toxicity, neutropenia. Women with advanced, platinum-refractory ovarian carcinoma received two courses of treatment with 135 mg/m2 paclitaxel over 24 h while participating in the National Cancer Institute's Treatment Referral Center Protocol. A crossover design was employed in which consecutive patients received either 300 mg cimetidine i.v. or 20 mg famotidine i.v. before their first course of paclitaxel and the alternate H2RA before their second course. In order to evaluate the differential effects of cimetidine and famotidine on pertinent pharmacologic and toxicologic parameters in the same individual, paclitaxel concentrations at steady-state (Css), paclitaxel clearance rates, and absolute neutrophil counts (ANCs) were obtained during both courses. Paclitaxel Css values were not significantly different in individual patients when either cimetidine or famotidine preceded paclitaxel (p = 0.16). Mean paclitaxel clearance rates were 271 and 243 ml/min per m2 following cimetidine and famotidine, respectively. These clearance rates were not significantly different in paired analysis (p = 0.30). The likelihood of subsequently requiring granulocyte-colony stimulating factor (G-CSF) for severe neutropenia during course 1 did not differ significantly between the two H2RAs (p = 0.9). Among patients who did not require G-CSF, mean percentage decreases in ANC were 87.7% and 84.2% after paclitaxel cycles preceded by cimetidine and famotidine, respectively. These measures of neutropenia did not differ significantly in paired analysis (p = 0.13). These results show that the H2RAs cimetidine and famotidine do not differentially affect the pharmacologic and toxicity profiles of paclitaxel when used in the premediation regimen to prevent major hypersensitivity reactions, and may be interchanged.

Adult↗

PubMed1995

The suitability of selected new anticancer agents for infusional therapy and the effects of others on infusional therapy practices.

The comprehensive development of new antineoplastic agents mandates a thorough evaluation of schedule-dependent cytotoxicity and toxicity. This report focuses on the topoisomerase I inhibitors as an example of a novel class of anticancer agents in exposure duration may be a critical factor in the achievement of an optimal therapeutic index. The mechanistic and pharmacologic determinants and rationale for using protracted exposure schedules in administering several topoisomerase I inhibitors are discussed. The review also discusses dihydropyrimidine dehydrogenase as a pharmacologic target, enabling administration of oral fluoropyrimidines.

Administration, Oral↗

PubMed1994

Phase I and pharmacological study of the novel topoisomerase I inhibitor 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) administered as a ninety-minute infusion every 3 weeks.

7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11; Irinotecan), a semisynthetic analogue of camptothecin (CPT) with broad preclinical antitumor activity, has demonstrated impressive activity in phase II trials in Japan in advanced small and non-small cell lung, colorectal, cervical, and ovarian carcinomas, as well as in refractory lymphomas and leukemias. In this phase I and pharmacological study, 90-min infusions of CPT-11 were administered every 3 weeks at doses ranging from 100 to 345 mg/m2 to patients with solid malignancies. Acute, severe, and refractory vomiting, diarrhea, and/or abdominal cramps associated with flushing, warmth, and diaphoresis occurred in the immediate posttreatment period at the 240-mg/m2 dose level in several patients who were not treated with premedications. The characteristics and temporal nature of these toxicities, the prompt resolution of symptoms following treatment with diphenhydramine, and the successful use of a premedication regimen consisting of ondansetron and diphenhydramine in preventing these acute effects suggest that vasoactive substances are involved in the mediation of these acute toxicities. With the routine use of these premedications, there was no single toxicity type that limited the escalation of CPT-11 doses. Instead, a constellation of severe hematological and gastrointestinal effects precluded the repetitive administration of CPT-11 at doses above 240 mg/m2, the maximum tolerated dose and recommended phase II dose on this schedule. Major responses were observed in patients with advanced colorectal, cervical, and renal cancers. The disposition of total CPT-11 in plasma was fit by a biexponential kinetic model with renal elimination accounting for 37 +/- 4% (SE) of total drug disposition. The Cmax for the active metabolite of CPT-11, 7-ethyl-10-hydroxycamptothecin (SN-38), was achieved at 2.2 +/- 0.1 h after treatment, and mean residence times for both CPT-11 and SN-38 were long, 9.1 and 10.0 h, respectively. Compared with topotecan, another CPT analogue under development, a larger proportion of total drug exposure was accounted for by the active lactone (closed-ring) forms of CPT-11 and SN-38; areas under the time-versus concentration curve for their respective lactone were 44 and 50% of areas under the time-versus-concentration curve for total CPT-11 and SN-38. Although intermittent dosing schedules appear to be superior to single dosing schedules for CPT and some CPT analogues in preclinical tumor models, the maintenance of biologically relevant concentrations of SN-38 for relatively long durations may negate the potential pharmacological benefits of intermittent and continuous administration schedules for CPT-11.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1994

Peripheral neuropathy from taxol and cisplatin combination chemotherapy: clinical and electrophysiological studies.

Taxol is a novel antineoplastic agent that has demonstrated impressive clinical activity in breast, ovarian, lung, and head and neck cancers. This broad antitumor activity of taxol in cisplatin-sensitive tumors suggests that the combination of taxol and cisplatin may become one of the most commonly used taxol-based chemotherapeutic regimen in the treatment of solid tumors. Both taxol and cisplatin, however, are neurotoxic. To study the neurotoxic effects of these two agents when used in combination, we prospectively evaluated neurological function at baseline, during, and following treatment, in 21 cancer patients treated with taxol (135-350 mg/m2), cisplatin (75-100 mg/m2), and granulocyte-colony stimulating factor (5 micrograms/kg). Twenty of the 21 patients (95%) developed a sensory-motor neuropathy 1 to 21 weeks after the initiation of therapy, that was progressive with each additional course of chemotherapy. The neuropathy was symmetrical, length dependent, axonal in nature by physiological studies, and more pronounced in those patients who received higher doses of taxol. The neuropathy appeared earlier and at lower taxol doses in those patients with preexisting neuropathies. We conclude that sensory-motor neuropathy is a frequent dose-dependent toxicity of combined cisplatin and taxol use. Peripheral neuropathy is likely to become the major dose-limiting toxicity of taxol-cisplatin combination chemotherapy when higher doses of these agents are administered with granulocyte-colony stimulating factor.

Adult↗

PubMed1994

Camptothecin analogues: studies from the Johns Hopkins Oncology Center.

The camptothecin analogues topotecan and irinotecan (CPT-11) are active anticancer drugs. This article reviews the accumulated results of clinical and laboratory studies performed with these agents at The Johns Hopkins Oncology Center. In a phase I clinical and pharmacology trial of topotecan given as a 30-min infusion daily for 5 days every 3 weeks, profound neutropenia precluded dose escalation above 1.5-2.0 mg/m2 per day, the maximum tolerated dose (MTD). The daily x5 schedule has been developed further with dose escalation using granulocyte-colony-stimulating factor support in patients who have kidney or liver dysfunction and given in combination with cisplatin. In addition, a phase I trial of topotecan given as a 5-day continuous intravenous infusion to patients with refractory leukemia has had promising antileukemic responses. A separate series of in vitro studies indicates that a modest degree of resistance to the cytotoxicity of topotecan can be mediated by P-glycoprotein. A phase I and pharmacology study of irinotecan given as a 90-min infusion every 3 weeks has defined an MTD of 240 mg/m2, with dose escalation being limited by several toxicities. These included an acute treatment-related syndrome of flushing, warmth, nausea, vomiting, and diarrhea; a subacute combination of nausea, diarrhea, anorexia, and weight loss; and/or neutropenia. Antitumor activity has been observed with topotecan and irinotecan in patients with a variety of solid tumors and refractory leukemia in our studies, which supports the widespread enthusiasm for this group of compounds.

Antineoplastic Agents↗

PubMed1994

Relation between age and clearance rate of nine investigational anticancer drugs from phase I pharmacokinetic data.

Aging influences the disposition and effects of several classes of drugs. Although drug clearance rate is correlated with toxicity for many anticancer drugs, few data have been published concerning the relationship of aging and clearance of chemotherapy. This study was performed to identify any relationship between age and clearance rate for anticancer drugs in phase I trials at the Johns Hopkins Oncology Center. In a retrospective study, we examined the clinical and pharmacokinetic data for 344 adults (aged 21-77 years) who received 9 phase I drugs with linear clearance in 13 clinical trials. We sought correlations between age and clearance for each drug and for the whole group. Data available for 9 of the 13 trials were used to compare age (< 65 or > 65 years) versus dose delivered [< the maximum tolerated dose (MTD) vs > or = the MTD] or toxicity (< grade 3 vs > or = grade 3). Of 344 patients, 81 (23.5%) were > 65 years old, 34 (9.9%) were > or = 70 years old, and 5 (1.5%) were > or = 75 years old. There was no significant correlation between drug clearance and age for individual drugs or the group as a whole. There was no significant difference between patients of the older and younger age groups with regard to dose or toxicity. Although only a small number of patients aged > or = 75 years were treated, our results suggest that the elderly do not experience greater toxicity even when treated at doses comparable with those given younger patients and should not be excluded from phase I trials on the basis of age. As the population of the United States ages, more elderly patients will be candidates for chemotherapy. A more thorough examination of the relationships between age, clearance rate, and toxicity can be accomplished as active drugs enter phase II/III studies.

Adult↗

PubMed1994

Update on the antitumor activity of paclitaxel in clinical trials.

Paclitaxel is one of the most active new agents introduced in cancer therapy in the last decade. Results from both completed and ongoing Phase II studies provide evidence that paclitaxel is active as salvage therapy in patients with several advanced or metastatic tumor types, including NSCLC, ovarian, breast, and head and neck cancers. The response rates achieved in these tumors are particularly impressive because heavily pretreated patients, and those who are refractory to prior standard chemotherapy, have had a high rate of objective responses to paclitaxel. Ongoing studies should define clearly the role of paclitaxel in ovarian cancer. The role of this agent in breast cancer will be defined when the optimal use of paclitaxel in combination with other drugs is determined. In other cancers, including NSCLC and head and neck cancer, future studies will use combinations of cisplatin and paclitaxel. Use of paclitaxel also is being investigated in bladder, esophageal, and stomach cancers, as well as pediatric malignancies, including leukemias and solid tumors. It will be important to determine if there is a dose-response relationship in the range of dosages currently used clinically. Important unresolved issues in the development of paclitaxel include its role in primary therapy of solid tumors, the optimal length of its infusion, a clearer understanding of the toxicities associated with paclitaxel and the development of methods to prevent or minimize these toxicities, and the efficacy and safety of paclitaxel in combination with other agents.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1994

Patient care issues: the management of paclitaxel-related toxicities.

At the low-to-moderate doses that are recommended, paclitaxel is a well-tolerated drug. Although adverse reactions do occur, most of these are manageable and do not have a long-lasting effect on the patients' quality of life. The starting dose of paclitaxel, as approved by the Food and Drug Administration for refractory ovarian cancer, is 135 mg/m2. A slightly higher dose (175 mg/m2) is being investigated for heavily pretreated patients with metastatic breast cancer. In the investigational setting, the highest dose that may safely be administered when paclitaxel is used as a single agent is 250 mg/m2 for minimally pretreated patients. If G-CSF is also given, the same dose may safely be administered to heavily pretreated patients. When paclitaxel is administered in combination with cisplatin, a dose of 135 mg/m2 may safely be given prior to cisplatin, which is administered at a dose of 75 mg/m2. These dose levels may be increased when G-CSF is also used. Dose modifications should be considered only in patients who experience severe neutropenia or neurotoxicity. Patients who received high doses of paclitaxel in Phase II trials frequently required dose reductions. However, when the drug is administered at the recommended dose of 135 mg/m2, neutropenia does not often necessitate further dose reduction. Hematopoietic growth factors, such as G-CSF, seem to be helpful in preventing prolonged grade IV and febrile neutropenia, and in avoiding treatment delays for longer than one week.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials, Phase I as Topic↗

PubMed1994

Phase I and pharmacodynamic study of the topoisomerase I-inhibitor topotecan in patients with refractory acute leukemia.

PURPOSE: To determine the feasibility of escalating the hydrophilic topoisomerase I (topo I)-inhibitor topotecan (TPT) above myelosuppressive doses in adults with refractory or relapsed acute leukemias and to assess pharmacodynamic determinants of TPT action. PATIENTS AND METHODS: Seventeen patients received 33 courses of TPT as a 5-day infusion at doses ranging from 0.70 to 2.7 mg/m2/d. Pharmacologic studies were performed to determine the TPT concentrations at steady-state (Css) and to examine parameters in the patients' leukemic blasts ex vivo that may be related to TPT sensitivity, eg, topo I content, p-glycoprotein (Pgp) expression, and the inhibitory effects of relevant TPT concentrations on the growth of blast colonies in clonogenic assays relative to the range of TPT Css values achieved. RESULTS: Severe mucositis of the oropharynx and perianal tissues was intolerable at TPT doses greater than 2.1 mg/m2/d, the recommended dose for phase II studies in leukemia. One complete response (CR) in a patient with chronic myelogenous leukemia in blast crisis (CML-B) and one partial response (PR) in a patient with acute myelogenous leukemia (AML) were noted. Significant reductions in circulating blast-cell numbers occurred in all courses, and complete leukemia clearance from the peripheral blood, albeit transient, was noted in 11 courses. TPT Css values ranged from 4.8 to 72.5 nmol/L. Colony-forming assays showed that the TPT LD90 (dose that inhibits the growth of leukemia blast colonies by 90%) values for blasts varied from 6 to 22 nmol/L, a range that overlapped with TPT Css values. In view of these variations in TPT sensitivity, several aspects of topo I-mediated drug action were also studied. In 10 of 11 samples, the multi-drug resistance (Mdr) modulator quinidine altered nuclear daunorubicin (DNR) accumulation and whole-cell TPT accumulation by less than 15%, which suggests that Pgp-mediated effects on drug efflux are insufficient to explain the fourfold range of TPT sensitivities in the colony-forming assays. Immunohistochemistry showed that topo I was expressed in all of the blasts from individual patients without detectable cell-to-cell heterogeneity in each marrow. Western blots indicated that topo I content varied over a 10-fold range. Although the sample size was small, topo I content appeared to be higher in acute lymphoblastic leukemia (ALL), intermediate in AML, and lower in CML-B. Topo I content did not appear to be related to the proliferative status of the blasts. CONCLUSION: These results indicate that substantial dose escalation of TPT above myelosuppressive doses reached in solid-tumor patients is feasible in patients with refractory leukemia, that biologically relevant TPT Css values are achievable, and that further developmental trials are warranted.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Pharmacokinetic, bioavailability, and feasibility study of oral vinorelbine in patients with solid tumors.

PURPOSE: The feasibility of administering vinorelbine (Navelbine, Burroughs Wellcome Co, Research Triangle Park, NC), a semisynthetic vinca alkaloid with broad activity, as a liquid-filled gelatin capsule was evaluated in a bioavailability (F) and pharmacokinetic study. PATIENTS AND METHODS: Each of 17 cancer patients had pharmacokinetic studies performed after receiving vinorelbine 30 mg/m2 intravenously (IV), which is the maximum-tolerated dose (MTD) for weekly IV administration, and twice after receiving the oral formulation at a nominal dose of 100 mg/m2. Subsequently, these patients and 10 other subjects received the oral formulation at a dose of 100 mg/m2/wk to evaluate the feasibility of chronic oral administration. RESULTS: Plasma drug disposition was well described by a triphasic model. Mean central volume of distribution and steady-state volume of distribution (Vss) were large (0.66 +/- 0.46 L/kg and 20.02 +/- 8.55 L/kg, respectively); the mean harmonic terminal half-life (t1/2) was long (18 hours); and the high mean clearance (CI) rate (0.80 +/- 0.68 L/h/kg) approached hepatic blood flow. F was low (0.27 +/- 12), and absorption was rapid (mean time of maximum plasma concentration [Tmax], 0.91 +/- 0.22 hours). Absorption parameters after the first and second oral doses were similar, with mean F values of 0.27 +/- 0.14 and 0.25 +/- 0.11, respectively. Coefficients of variability (CVs) for F, maximum plasma concentration (Cmax), and Tmax were 32%, 42%, and 78%, respectively, indicating moderate intraindividual variability. The pharmacologic profile of this oral formulation indicates that there is a large first-pass effect. Neutropenia was the principal toxicity of oral vinorelbine. Grade 3 or 4 neutropenia occurred in 63% of patients, but only 11% developed neutropenia and infection. Nausea, vomiting, and diarrhea were also common with oral administration, but these effects were rarely severe and could be ameliorated by using a divided-dose schedule and/or prophylactic antiemetic and antidiarrheal agents. The mean nominal oral dose was 82 mg/m2, and the mean percentage of intended dose that was received was 92%. Although dose escalations were permitted for negligible toxicity, doses were not escalated to greater than 100 mg/m2/wk in any patient. Vinorelbine given as a liquid-filled gelatin capsule at 100 mg/m2 provided equivalent pharmacologic exposure as 30 mg/m2 IV. CONCLUSION: The oral administration of vinorelbine, specifically as a liquid-filled, soft gelatin capsule, is a feasible route of administration. Weekly oral dosing at 100 mg/m2 induces a consistent degree of myelosuppression, but the high frequency of grade 3 or 4 neutropenia, albeit brief and uncomplicated, warrants the recommendation of a slightly lower starting dose, ie, 80 mg/m2/d, for subsequent phase II evaluations, especially in heavily pretreated patients.

Absorption↗