A Phase I clinical and pharmacological evaluation of sodium phenylbutyrate on an 120-h infusion schedule.

PURPOSE: Sodium phenylbutyrate (PB) demonstrates potent differentiating capacity in multiple hematopoietic and solid tumor cell lines. We conducted a Phase I and pharmacokinetic study of PB by continuous infusion to characterize the maximum tolerated dose, toxicities, pharmacokinetics, and antitumor effects in patients with refractory solid tumors. PATIENTS AND METHODS: Patients were treated with a 120-h PB infusion every 21 days. The dose was escalated from 150 to 515 mg/kg/day. Pharmacokinetics were performed during and after the first infusion period using a validated high-performance liquid chromatographic assay and single compartmental pharmacokinetic model for PB and its principal metabolite, phenylacetate. RESULTS: A total of 24 patients were enrolled on study, with hormone refractory prostate cancer being the predominant tumor type. All patients were evaluable for toxicity and response. A total of 89 cycles were administered. The dose-limiting toxicity (DLT) was neuro-cortical, exemplified by excessive somnolence and confusion and accompanied by clinically significant hypokalemia, hyponatremia, and hyperuricemia. One patient at 515 mg/kg/day and another at 345 mg/kg/day experienced this DLT. Toxicity resolved < or =12 h of discontinuing the infusion. Other toxicities were mild, including fatigue and nausea. The maximum tolerated dose was 410 mg/kg/day for 5 days. Pharmacokinetics demonstrated that plasma clearance of PB increased in a continuous fashion beginning 24 h into the infusion. In individuals whose V(max) for drug elimination was less than their drug-dosing rate, the active metabolite phenylacetate accumulated progressively. Plasma PB concentrations (at 410 mg/kg/day) remained above the targeted therapeutic threshold of 500 micromol/liter required for in vitro activity. CONCLUSION: The DLT in this Phase I study for infusional PB given for 5 days every 21 days is neuro-cortical in nature. The recommended Phase II dose is 410 mg/kg/day for 120 h.

A phase I dose escalation and bioavailability study of oral sodium phenylbutyrate in patients with refractory solid tumor malignancies.

PURPOSE: Phenylbutyrate (PB) is an aromatic fatty acid with multiple mechanisms of action including histone deacetylase inhibition. Preclinically, PB demonstrates both cytotoxic and differentiating effects at a concentration of 0.5 mM. We conducted a Phase I trial of p.o. PB patients with refractory solid tumor malignancies to evaluate toxicity, pharmacokinetic parameters, and feasibility of p.o. administration. EXPERIMENTAL DESIGN: Twenty-eight patients with refractory solid tumor malignancies were enrolled on this dose-escalation to maximally tolerated dose trial. Five dose levels of PB were studied: 9 g/day (n = 4), 18 g/day (n = 4), 27 g/day (n = 4), 36 g/day (n = 12), and 45 g/day (n = 4). Pharmacokinetic studies were performed and included an p.o. bioavailability determination. Compliance data were also collected. RESULTS: The recommended Phase II dose is 27 g/day. Overall the drug was well tolerated with the most common toxicities being grade 1-2 dyspepsia and fatigue. Nonoverlapping dose-limiting toxicities of nausea/vomiting and hypocalcemia were seen at 36 g/day. The p.o. bioavailability of PB was 78% for all dose levels, and the biologically active concentration of 0.5 mM was achieved at all dose levels. Compliance was excellent with 93.5% of all possible doses taken. No partial remission or complete remission was seen, but 7 patients had stable disease for more than 6 months while on the drug. CONCLUSIONS: PB (p.o.) is well tolerated and achieves the concentration in vivo that has been shown to have biological activity in vitro. PB may have a role as a cytostatic agent and should be additionally explored in combination with cytotoxics and other novel drugs.

Phase I and pharmacological study of CI-980, a novel synthetic antimicrotubule agent.

CI-980 (NSC 613862) is one of a novel class of 1,2-dihydropyrido[3, 4-b]pyrazines that inhibits tubulin polymerization, presumably by binding to the colchicine binding site of tubulin. In a Phase I and pharmacological study, 16 patients with advanced solid neoplasms were treated with CI-980 on a continuous 72-h infusion schedule at doses ranging from 3.0-5.4 mg/m2/day every 3 weeks. High rates of central nervous system (CNS) toxicity and neutropenia occurred in both minimally and heavily pretreated patients who were treated with CI-980 doses above 3.75 mg/m2/day, which is the maximum tolerated dose and the recommended dose for additional evaluations. CNS effects, characterized by neurocortical, mood, and cerebellar manifestations, were generally observed toward the end of the infusion and immediately posttreatment and usually resolved within 48 h after the completion of treatment. Toxicity was mild to modest at the 3.75 mg/m2/day dose level. Neither clinical nor pharmacological risk factors that may predispose patients to the development of CNS effects were evident. Although no objective antineoplastic activity was observed in this Phase I study, CI-980 steady-state plasma concentrations achieved at the recommended dose of 3.75 mg/m2/day (mean +/- SE, 5.74 +/- 0.54 nM) approached and exceeded concentrations that have been associated with significant activity in preclinical studies, indicating that additional disease-directed evaluations of CI-980 may be warranted.

A phase I and pharmacological study of topotecan infused over 30 minutes for five days in patients with refractory acute leukemia.

The principal objectives of this study were to determine the feasibility of escalating doses of the hydrophilic topoisomerase I (topo I) inhibitor topotecan (TPT) as a 30-min infusion daily for 5 days in adults with refractory or relapsed acute leukemia and to study the pharmacokinetic behavior of high doses of TPT and pharmacodynamic determinants of TPT activity. Fourteen patients received 27 courses of TPT at doses ranging from 3.5 to 5.75 mg/m2/day every 3 weeks. A constellation of unusual adverse effects, consisting of high fever, rigors, precipitous anemia, and hyperbilirubinemia, was the principal dose-limiting toxicity of high doses of TPT on this schedule. These toxicities were consistently intolerable at the 5.75 mg/m2/day dose level; however, they were neither severe nor common at lower doses. Although the precise etiology of these effects is not known, high doses of TPT may induce acute hemolytic reactions in this patient population. Severe, albeit transient, mucositis was experienced by two of eight patients in 2 of 17 courses at the next lower dose level, 4.5 mg/m2/day, which was determined to be the maximum tolerated dose and the dose recommended for further trials. The pharmacokinetic behavior of TPT at high doses was not dose dependent and resembled that at lower doses. In view of preclinical data suggesting that TPT sensitivity might correlate with topo I levels, topo I content in leukemia blasts was assessed by Western blotting. Variations in topo I content were observed. Moreover, strong correlations were evident between topo I content and two markers of proliferation, proliferating cell nuclear antigen and nuclear protein B23, raising the possibility that differences in topo I content observed among various leukemia specimens might reflect differences in the proliferating fractions of cells in various leukemia samples. Although complete clearance of circulating leukemia blasts occurred in most courses, neither sustained responses nor hematopoietic recovery were observed in the heavily pretreated, poor-risk patients enrolled in this study, and it was not possible to correlate these differences in topo I content with clinical response. These results indicate that substantial dose escalation of TPT as a 30-minute infusion for a 5-day schedule above myelosuppressive doses is feasible in adults with refractory or relapsed leukemias; however, further development of alternate high-dose schedules in leukemia may be warranted in view of the nature of the dose-limiting toxicity and the lack of sustained clinical responses in this preliminary investigation.

Sequences of topotecan and cisplatin: phase I, pharmacologic, and in vitro studies to examine sequence dependence.

PURPOSE: A phase I and pharmacologic study was performed to evaluate the feasibility of administering the topoisomerase I (topo I) inhibitor topotecan (TPT) in combination with cisplatin (CDDP) in minimally pretreated adults with solid tumors. The study was designed to evaluate the magnitude of the toxicologic and pharmacologic differences between the two sequences of drug administration. MATERIALS AND METHODS: TPT was administered as a 30-minute infusion daily for 5 days and CDDP was given either before TPT on day 1 or after TPT on day 5. Each patient was treated with both schedules on an alternating basis every 3 weeks. Sequential dose escalation of TPT or CDDP resulted in three dosage permutation of TPT/CDDP (mg/m2): 0.75/50, 1/50, and 0.75/75. After the maximum-tolerated dose (MTD) level was achieved, the feasibility of using granulocyte colony-stimulating factor (G-CSF) to permit further dose escalation was studied. To examine the interaction of TPT and CDDP in vitro, human A549 lung cancer cells were exposed to these agents concurrently and sequentially. RESULTS: Dose-limiting neutropenia and thrombocytopenia resulted after the doses of TPT or CDDP were increased to greater than 0.75 and 50 mg/m2, respectively, without and with G-CSF. The sequence of CDDP before TPT induced significantly worse neutropenia and thrombocytopenia than the alternate sequence. In vitro studies failed to provide any evidence for the differences in the cytotoxicity of these two sequences. Instead, pharmacokinetic studies suggested that the differences in toxicity were due, in part, to lower TPT clearance and exposure when CDDP preceeds TPT, possibly due to subclinical renal tubular toxicity induced by CDDP. CONCLUSION: The sequence of CDDP before TPT at doses of 50 and 0.75 mg/m2, respectively, is recommended for subsequent clinical trials in tumor types in which both agents have significant single-agent activity. The potential for sequence-dependent cytotoxic, toxicologic, and pharmacologic effects should be evaluated in concurrent clinical and laboratory studies in the course of developing combination chemotherapy regimens that consist of topo I-targeting agents and other antineoplastic agents, particularly DNA-damaging agents.

Phase I and pharmacologic study of high doses of the topoisomerase I inhibitor topotecan with granulocyte colony-stimulating factor in patients with solid tumors.

PURPOSE: To evaluate the feasibility of escalating doses of the topoisomerase I (topo I) inhibitor topotecan (TPT) with granulocyte colony-stimulating factor (G-CSF) in minimally pretreated adults with solid tumors and to study whether G-CSF scheduling variably affects the ability to escalate TPT doses. MATERIALS AND METHODS: Thirty-six patients received 121 courses of TPT as a 30-minute infusion daily for 5 days every 3 weeks at doses that ranged from 2.0 to 4.2 mg/m2/d. G-CSF 5 microg/kg/d subcutaneously (SC) was initiated concurrently with TPT (starting on day 1). Because the concurrent administration of TPT and G-CSF resulted in severe myelosuppression at the lowest TPT dose level, an alternate posttreatment G-CSF schedule in which G-CSF dosing began after TPT (starting on day 6) was subsequently evaluated. Plasma sampling was performed to characterize the pharmacologic behavior of high-dose TPT and to determine whether G-CSF altered the pharmacokinetic profile of TPT. RESULTS: Severe myelosuppression precluded the administration of TPT at the first dose, 2.0 mg/m2/d, with G-CSF on the concurrent schedule. However, dose escalation of TPT with G-CSF on a posttreatment schedule proceeded to 4.2 mg/m2/d. The dose-limiting toxicities (DLTs) were thrombocytopenia and neutropenia. One partial response was noted in a patient with colorectal carcinoma refractory to fluoropyrimidines. Pharmacokinetics were linear within the dosing range of 2.0 to 3.5 mg/m2/d, but TPT clearance was lower at the 4.2-mg/m2/d dose level. At 3.5 mg/m2/d, which is the maximum-tolerated dose (MTD) and recommended dose for subsequent-phase studies of TPT with G-CSF, the area under the concentration-versus-time curves (AUCs) for total TPT and lactone averaged 2.2- and 2.3-fold higher, respectively, than the AUCs achieved at the lowest TPT dose, 2.0 mg/m2/d. The pharmacologic behavior of high-dose TPT was not significantly altered by the scheduling of G-CSF. CONCLUSION: G-CSF administered after 5 daily 30-minute infusions of TPT permits a 2.3-fold dose escalation of TPT above the MTD in solid-tumor patients, whereas concurrent therapy with G-CSF and TPT results in severe myelosuppression.

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.

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.

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.