Phase I clinical trial of 7-cyanoquinocarcinol (DX-52-1) in adult patients with refractory solid malignancies

PURPOSE

A phase I study of the antitumor antibiotic 7-cyanoquinocarcinol, DX-52-1, was conducted in patients with refractory solid malignancies. This study sought to determine the maximum tolerated dose and principal toxicities of this agent and to characterize its pharmacokinetic behavior.

METHODS

Patients were required to have adequate bone marrow, renal and hepatic function. DX-52-1 was administered by i.v. continuous infusion over a 6-h period each week for four consecutive weeks followed by a 2-week rest period, which constituted one cycle of treatment.

RESULTS

Initial dose levels were 3, 6, and 10 mg/m2. An intermediate dose level of 8 mg/m2 was added after acceptable toxicity was observed at the 6 mg/m2 dose level, but dose-limiting toxicities, including life-threatening ones, were seen at the 10 mg/m2 dose level in all three patients. The maximum tolerated dose (MTD) was subsequently determined to be 6 mg/m2. Because a clear pattern of toxicities was not initially evident, a larger than usual number of additional patients (16) were enrolled at the MTD to better distinguish toxicities due to the study drug from those secondary to the patients' underlying malignancies. Even at the MTD, the drug was poorly tolerated, with gastrointestinal toxicities (abdominal pain, nausea, vomiting and increased liver function tests) predominating and dose-limiting. Pharmacokinetic studies revealed that the mean maximum plasma concentration of DX-52-1 in patients evaluated at the MTD (138.8 +/- 59.3 ng/ml, n = 19) was considerably lower than the concentrations required for cytostatic or cytotoxic activity against sensitive human tumor cell lines in vitro. Further, the weekly dose intensity of the most efficacious treatment schedule identified during in vivo antitumor efficacy studies was 60 times greater than the 6 mg/m2 weekly dose tolerated by cancer patients. None of the 33 patients participating in this study, including the 22 patients evaluated at the MTD, had any response to treatment.

CONCLUSION

Given the poor tolerability, the inability to achieve drug levels necessary to inhibit in vitro or in vivo tumor growth, and the lack of any responses in our study, DX-52-1, as given by this schedule, does not appear to warrant further investigation in phase II studies.

A Phase I-II study of 96-hour infusional topotecan and paclitaxel for patients with recurrent Müllerian tumors

BACKGROUND

Topotecan and paclitaxel are schedule dependent chemotherapeutic agents with activity against ovarian carcinoma. A Phase I-II study in which both drugs were administered concurrently by 96-hour, continuous, intravenous infusion was performed to determine the maximum tolerated dose (MTD), toxicities, pharmacokinetics, and efficacy of the combination.

METHODS

Women with ovarian or primary peritoneal carcinoma and documented recurrent disease were eligible for the study. The dose of topotecan was escalated from 1.6 mg/m(2) while maintaining the paclitaxel dose constant at 100 mg/m(2). Plasma concentrations of both drugs were monitored daily during the first cycle of therapy.

RESULTS

Forty-five patients with a median age of 54 years (range, 42-70 years) received 181 cycles of therapy. Five patients were recruited to each of four dose levels (topotecan 1.6 mg/m(2), 2.0 mg/m(2), 2.8 mg/m(2), and 3.6 mg/m(2)), and an additional 25 patients were treated at the MTD (Phase II). Neutropenia and thrombocytopenia became dose limiting toxicities (DLT) at the fourth dose level. Emesis, mucositis, peripheral neuropathy, diarrhea, and alopecia were mild. Twenty patients (44%) had line-related occlusion, thrombosis, or infection. The mean values (+/- standard deviation) of the apparent steady-state plasma concentrations at the Phase II doses were 2.3 nM +/- 0.5 nM for topotecan lactone, 5.6 nM +/- 2.1 nM for total topotecan, and 40.1 nM +/- 16.8 nM for paclitaxel. There were seven partial responses (Phase II) contributing to an objective response rate of 28% and a median survival time of 11.7 months (range, 0.6-20.1 months).

CONCLUSIONS

Topotecan at a dose of 2.8 mg/m(2) and paclitaxel at a dose of 100 mg/m(2) administered by concurrent, 96-hour, continuous intravenous infusions shows activity against tumors of Müllerian origin.

Plasma pharmacokinetics and bioavailability of 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea after intravenous and oral administration to mice and dogs

PURPOSE

Chloroethylnitrosoureas are among the most widely used chemotherapeutic agents for the treatment of brain tumors. SarCNU (1-(2-chloroethyl)3-sarcosinamide-1-nitrosourea) is an investigational nitrosourea analogue that has shown greater antitumor activity and a more favorable toxicity profile than 1,3-bis(2-chloroethyl)-1-nitrosourea in preclinical studies. The purpose of the present study was to characterize the plasma pharmacokinetics and oral bioavailability of SarCNU in mice and dogs treated by intravenous infusion and gastric intubation.

METHODS

SarCNU was administered to mice by i.v. injection or orally at doses ranging from 10 to 100 mg/kg. Plasma samples were obtained from groups of five animals at each time-point at intervals ranging from 3 min to 2.5 h after dosing. A group of three male beagle dogs were treated with Sar CNU 10 mg/kg given both by i.v. infusion and orally in a crossover design. The concentration of SarCNU in plasma was measured by high-performance liquid chromatography.

RESULTS

During the initial 90 min after i.v. injection to mice, SarCNU was eliminated from plasma in a monoexponential manner with a mean half-life of 9.8 +/- 0.8 min. The total plasma clearance was 47.3 +/- 8.7 ml/min per kg and the apparent volume of distribution was 0.7 +/- 0.1 l/kg. SarCNU exhibited linear pharmacokinetic behavior following both i.v. and oral administration of doses ranging from approximately 10 to 100 mg/kg. Peak plasma levels provided by a dose of 100 mg/kg given by the i.v. and oral routes were 142.4 microg/ml (0.5 min) and 27.8 microg/ml (9.8 min), respectively. The mean oral bioavailability of the drug was 57.3 +/- 12.6% in mice. In comparison, the disposition of SarCNU in dogs after rapid i.v. injection was biexponential, with half-lives of 5.4 +/- 8.4 min and 40.8 +/- 9.0 min for the initial and terminal disposition phases, respectively. Mean values of the total plasma clearance and apparent volume of distribution were 17.8 +/- 1.8 ml/min per kg and 1.1 +/- 0.3 l/kg, respectively. The Cmax was 18.5 +/- 6.5 microg/ml after i.v. injection and 8.5 0.4 microg/ml after oral administration of a 10 mg/kg dose. Oral bioavailability of the drug in dogs (71.7 +/- 21.2%) was greater than that observed in mice.

CONCLUSIONS

SarCNU exhibited linear and consistent pharmacokinetics in mice and dogs with very good oral bioavailability in both species. These findings support the rationale for evaluating SarCNU given by the oral route of administration in phase I clinical trials.

A phase II trial of the cyclin-dependent kinase inhibitor flavopiridol in patients with previously untreated stage IV non-small cell lung cancer

PURPOSE

Flavopiridol is a potent cyclin-dependent kinase inhibitor with preclinical activity against non-small cell lung cancer (NSCLC), inhibiting tumor growth in vitro and in vivo by cytostatic and cytotoxic mechanisms. A Phase II trial was conducted to determine the activity and toxicity of flavopiridol in untreated patients with metastatic NSCLC.

EXPERIMENTAL DESIGN

A total of 20 patients were treated with a 72-h continuous infusion of flavopiridol every 14 days at a dose of 50 mg/m(2)/day and a concentration of 0.1-0.2 mg/ml. Dose escalation to 60 mg/m(2)/day was permitted if no significant toxicity occurred. Response was initially assessed after every two infusions; patients treated longer than 8 weeks were then assessed after every four infusions. Plasma levels of flavopiridol were measured daily during the first two infusions to determine steady-state concentrations.

RESULTS

This study was designed to evaluate a total of 45 patients in two stages. However, because no objective responses were seen in the first 20 patients, the early-stopping rule was invoked, and patient accrual was halted. In four patients who received eight infusions, progression was documented at 15, 20, 40, and 65 weeks, respectively. The most common toxicities included grade 1 or 2 diarrhea in 11 patients, asthenia in 10 patients, and venous thromboses in 7 patients. The mean +/- SD steady-state concentration of drug during the first infusion was 200 +/- 89.9 nM, sufficient for cytostatic effects in in vitro models.

CONCLUSIONS

At the current doses and schedule, flavopiridol does not have cytotoxic activity in NSCLC, although protracted periods of disease stability were observed with an acceptable degree of toxicity.

A phase I clinical and pharmacokinetic study of the dolastatin analogue cemadotin administered as a 5-day continuous intravenous infusion

PURPOSE

The dolastatins are a class of naturally occurring cytotoxic peptides which function by inhibiting microtubule assembly and tubulin polymerization. Cemadotin is a synthetic analogue of dolastatin 15 with potent antiproliferative and preclinical antitumor activity. This report describes a phase I study to evaluate the administration of cemadotin to adult cancer patients by a 5-day continuous intravenous (CIV) infusion.

METHODS

All patients had histologically confirmed refractory solid tumors. The dose was escalated from an initial level of 2.5 mg/m2 (0.5 mg/m2 daily) according to a modified Fibonacci algorithm. A minimum of three patients was evaluated at each dose level until the maximum tolerated dose (MTD) was established. Treatment was repeated every 21 days until patients were removed from the study due to toxicity or disease progression. Drug-related toxicities were evaluated and graded by the U.S. National Cancer Institute's Common Toxicity Criteria. A radioimmunoassay (RIA) that detected both the parent drug and its metabolites with an intact N-terminal region of the molecule was used for pharmacokinetic studies.

RESULTS

Twenty heavily pretreated patients received a total of 40 courses of cemadotin over five dose levels ranging from 2.5 to 17.5 mg/m2. Reversible dose-related neutropenia was the principal dose-limiting toxicity and 12.5 mg/m2 was established as the MTD. Nonhematologic toxicities attributed to the drug were moderate, and there was no evidence of the cardiovascular toxicity noted in the prior phase I studies of cemadotin given IV as a 5-min injection or 24-h infusion. There were no objective antitumor responses. Time courses of the cemadotin RIA equivalent concentration in whole blood were defined in 14 patients during the first cycle of therapy. The RIA-detectable species exhibited apparent first-order pharmacokinetics across the entire range of doses. The mean +/- SD of the observed steady-state blood concentration at the 12.5 mg/m2 MTD was 282 +/- 7 nM (n = 3). Blood levels decayed monoexponentially following the end of the infusion, with a mean half-life of 13.2 +/- 4.3 h (n = 14) in all patients. Mean values (n = 14) of the total blood clearance and apparent volume of distribution at steady state were 0.52 +/- 0.09 lh/m2 and 9.9 +/- 3.3 l/m2, respectively.

CONCLUSIONS

The cardiotoxic effects of cemadotin were completely avoided by administering it as a 120-h CIV infusion. Thus. cardiovascular toxicity appears to be associated with the magnitude of the peak blood levels of the parent drug or its metabolites, whereas myelotoxicity is related to the duration of time that blood levels exceed a threshold concentration. Nevertheless, the data acquired during the extensive clinical experience with cemadotin requires careful examination to assess whether advancing this compound into disease-oriented efficacy studies is merited.

Phase I and pharmacokinetic study of ecteinascidin 743 administered as a 72-hour continuous intravenous infusion in patients with solid malignancies

Ecteinascidin 743 (ET-743) is a cytotoxic tetrahydroisoquinoline alkaloid that covalently binds to DNA in the minor groove. The in vitro chemosensitivity of cancer cells to ET-743 is markedly enhanced by prolonging the duration of exposure to the drug. A Phase I study of ET-743 given as a 72-h continuous i.v. infusion every 21 days was performed. Characteristics of the 21 adult patients with refractory solid tumors enrolled in the study were as follows: (a) 12 men; (b) 9 women; (c) median age, 59 years; (d) Eastern Cooperative Oncology Group performance status < or = 1, 20 patients; and (e) two prior regimens of chemotherapy, 7 patients. Dose limiting toxicity (DLT) was defined by typical criteria, except that grade 3 transaminitis did not constitute a DLT. There were no DLTs in the six patients evaluated at the first two dose levels of 600 and 900 microg/m2. Reversible grade 4 transaminitis occurred in two of nine patients after treatment with the first cycle of therapy at the third dose level of 1200 microg/m2. Another patient experienced grade 4 rhabdomyolysis, renal failure requiring hemodialysis, grade 4 neutropenia, and grade 3 thrombocytopenia during the second cycle of therapy with this dose. The maximum tolerated dose was 1200 microg/m2, and an additional six patients were enrolled at an intermediate dose level of 1050 microg/m2. This well-tolerated dose was established as the recommended Phase II dose. The disposition of ET-743 was distinctly biexponential, and a departure from linear pharmacokinetic behavior was evident at the 1200-microg/m2 dose level. Pharmacokinetic parameters determined at 1050 microg/m2 were (mean +/- SD): maximum plasma concentration, 318 +/- 147 pg/ml; initial disposition phase half-life, 9.0 +/- 10.3 min; terminal phase half-life, 69.0 +/- 56.7 h; and total plasma clearance, 28.4 +/- 22.5 liters/h/m2. Prolonged systemic exposure to concentrations of the agent that are cytotoxic in vitro were achieved. Toxicity of the drug is clearly schedule-dependent, because increasing the duration of infusion from 3 or 24 h to 72 h results in decreased myelosuppression and comparable hepatotoxicity. Although there were no objective responses to therapy, clear evidence of antitumor activity was observed in a patient with epithelioid mesothelioma, as confirmed by positron emission tomography studies. A Phase II trial to assess the efficacy of ET-743 against this highly refractory neoplasm has been initiated on the basis of this observation. The therapeutically optimal administration schedule remains to be established, inasmuch as there have been indications of activity against a variety of tumors during Phase I studies when the drug was infused over times ranging from 1 to 72 h. Characterizing the pharmacokinetics of ET-743 during the course of Phase II trials and Phase I combination studies is recommended to assure that this promising new anticancer drug can be used with an acceptable margin of safety.

Characterization of a novel degradation product of 2,2'-dithiobis[N-isoleucylbenzamide], an inhibitor of HIV nucleocapsid protein zinc fingers

Zinc finger motifs have been found to be important in a variety of protein structures including transcription factors and viral nucleocapsid proteins. Recently, it was demonstrated that various aromatic disulfides effectively remove the metal ion from the zinc finger, resulting in an alteration of tertiary structure in this region of the protein, thereby inhibiting transcription. Among these compounds, 2,2'-dithiobis[N-isoleucylbenzamide] exhibits activity against human immunodeficiency virus (HIV)-type 1 in vitro and has been selected for preclinical development as an anti-HIV agent. Analysis of this agent by reversed-phase high-performance liquid chromatography (HPLC) indicated a significant quantity of two additional compounds. Identifying the parent disulfide was accomplished by scanning eluting peaks with positive ion thermospray ionization (TSP) mass spectrometry (MS). Solution-induced disproportionation of the disulfide into its sulfhydryl monomer was demonstrated by treating the drug with dithiothreitol (DTT) prior to HPLC analysis. TSP-MS analysis of the remaining chromatographic peak suggested a molecular weight of 265, which, with 1H-nuclear magnetic resonance (NMR) data of the isolated material, allowed us to elucidate the chemical structure as N-isoleucyl-benzisothiazolone. Contact with stainless steel, such as that employed in an HPLC system, was found to accelerate degradation of the parent disulfide to the benzisothiazolone.

Adaptation of solid phase extraction to an automated column switching method for online sample cleanup as the basis of a facile and sensitive high-performance liquid chromatographic assay for paclitaxel in human plasma

An improved method for assaying paclitaxel in human plasma by high-performance liquid chromatography (HPLC) with UV detection at 227 nm has been developed by adapting previously reported sample preparation methods and chromatographic conditions to facilitate semi-automated sample cleanup using a column switching technique. Manual sample manipulations were limited to isolating the drug and internal standard from plasma (1.0 ml) by liquid-liquid extraction using tert-butyl methyl ether. The sample extract was initially loaded onto a short cartridge column containing a cyanopropyl stationary phase. During the predetermined time interval that the drug and internal standard eluted from the cartridge, 1.50-2.20 min, a fully automated 6-position switching valve was used to direct the effluent onto an octylsilica analytical column. The same mobile phase, composed of acetonitrile-methanol-ammonium acetate buffer (pH 5.0; 20 mM) (76:19:105, v/v/v) and delivered at flow rate of 1.0 ml/min, was used for both separations. The overall retention times of paclitaxel and the internal standard were 10.9 and 18.1 min, respectively. The analytical method was thoroughly validated for quantitating paclitaxel in plasma at concentrations ranging from 6 to 586 nM (5-500 ng/ml). The lowest concentration of paclitaxel measured with acceptable day-to-day accuracy (100.2%) and precision (RSD 11.7%, n = 21, 5 months) was 6 nM (5 ng/ml). The sensitivity and selectivity of the assay proved to be more than adequate for monitoring steady-state plasma concentrations of the drug when administered to cancer patients as a 96 h continuous intravenous infusion in combination with other anticancer agents, such as doxorubicin and topotecan. Moreover, the heart-cutting procedure prevented the problematic introduction of interfering nonpolar plasma components onto the analytical column, thereby enhancing sample throughput while decreasing the technical demands of the assay. The method was found to be extremely reproducible and robust during extended use for the routine analysis of plasma specimens acquired from several clinical trials.

A Phase I study of continuous infusion doxorubicin and paclitaxel chemotherapy with granulocyte colony-stimulating factor for relapsed epithelial ovarian cancer

A Phase I study of paclitaxel and doxorubicin administered as concurrent 96-h continuous i.v. infusion was performed to determine the maximum tolerated dose (MTD), principal toxicities, and pharmacokinetics of this combination in women with relapsed epithelial ovarian cancer. The paclitaxel dose was fixed at 100 mg/m2 (25 mg/m2/day for 4 days). The dose of doxorubicin was escalated from 30 mg/m2 (7.5 mg/m2/day for 4 days) in increments of 10 mg/m2 until dose-limiting toxicity was observed. All patients received granulocyte colony-stimulating factor 5 microg/kg/day prophylactically. Apparent steady-state plasma levels of both drugs were determined in the final cohort of patients treated at the MTD. A total of 17 patients received 52 cycles of therapy. The median age was 58 years, and all patients had previously received one to five different regimens (median, 2) of chemotherapy, including both platinum and paclitaxel. The treatment was tolerated well, with grade 1-2 nausea being the most frequent side effect (73% of cycles). Anemia, neutropenia, thrombocytopenia, and mucositis became dose limiting at the fourth dose level, defining the MTD of doxorubicin in this regimen as 50 mg/m2. There were four partial responses and one complete response in 15 evaluable patients. Apparent steady-state plasma concentrations (mean +/- SD) of paclitaxel and doxorubicin in the three patients treated at the MTD were 33.9 +/- 12.5 nM and 15.7 +/- 1.3 nM, respectively. Paclitaxel and doxorubicin by continuous infusion is a well-tolerated and active chemotherapy regimen for recurrent ovarian cancer.

Disappearance of endogenous luteinizing hormone is prolonged in postmenopausal women

Pituitary secretion of LH is increased after menopause, but it is not known whether changes in LH clearance also contribute to elevated serum levels. To determine whether the disappearance of endogenous LH is decreased in postmenopausal women (PMW), compared with normal cycling women, GnRH receptor blockade was used to inhibit endogenous secretion of LH and the glycoprotein free alpha-subunit (FAS), and the decline of serum levels was monitored. The NAL-GLU GnRH antagonist ([Ac-D-2Nal1,D-4ClPhe2, D-3Pal3,Arg5,D-4-p-methoxybenzoyl-2-aminobutyric acid6,D-Ala10]GnRH) was administered s.c., at doses of 5, 15, 50, and 150 microg/kg, to 15 euthyroid PMW in 21 studies. Blood was sampled every 10 min, for 4 h before and 8 h after a single sc injection of the GnRH antagonist, followed by hourly samples, ending at 20 h after injection. Results of the maximally suppressive doses (50 and 150 microg/kg) were compared with those of 24 normal cycling women in the early follicular phase and late follicular phase or early luteal phase, and 8 women at the midcycle surge (MCS), who also received these doses of the GnRH antagonist. The best fit curve describing the decay of hormone serum levels after maximal GnRH receptor blockade was determined by nonlinear regression analysis. The elimination of both LH and FAS, after GnRH receptor blockade, exhibited apparent first-order kinetics characterized by a single exponential phase. No differences were seen in percent suppression or half-lives (t1/2) of LH or FAS, between the 50- and 150-microg/kg antagonist doses, in any of the subject populations; and percent suppression of LH was similar across all groups. The t1/2 of LH was prolonged in PMW (139 +/- 35 min, mean +/- est. SD), in comparison with both the MCS (78 +/- 20 min; P < 0.0005) and other cycle stages (57 +/- 28 min; P < 0.0001). However, the disappearance of FAS was not different in PMW, compared with MCS or other cycle stages (t1/2 = 51 +/- 26, 41 +/- 12, and 41 +/- 19 min, respectively). Our conclusions were: 1) Disappearance of endogenous LH after GnRH receptor blockade is significantly prolonged in PMW, compared with the MCS or other cycle stages; 2) The disappearance of FAS is not altered in PMW, suggesting that differences in the disappearance of LH relate to LH microheterogeneity rather than systemic factors.

Assay for the quinocarmycin analog DX-52-1 in human plasma using high-performance liquid chromatography with automated column switching and low wavelength ultraviolet detection

The hydrocyanated derivative of the antitumor antibiotic quinocarmycin, DX-52-1 (I), exhibits impressive activity against human melanoma xenograft models in vivo. Phase I clinical trials to evaluate this compound as an antineoplastic agent have been initiated by the US National Cancer Institute. We have developed an HPLC assay for the determination of I in human plasma involving automated column switching and UV detection at 210 nm. The preparation of samples for chromatographic analysis entails the preliminary removal of plasma proteins by precipitation with acetonitrile, acidifying the clear supernatant to pH 4.5, then extracting twice with tert.-butyl methyl ether to recover the drug. A heart-cutting procedure employing two HPLC columns with contrasting retention characteristics under isocratic reversed-phase conditions was used to achieve the selectivity required for low wavelength UV detection of the analyte. The sample extract was initially loaded onto a column packed with a cyanopropyl stationary phase. During the predetermined time interval that I eluted from this column, a fully automated six-position switching valve was used to direct the effluent onto an octadecylsilane analytical column. The assay has been thoroughly validated with regard to linearity, inter- and intra-day accuracy and precision, recovery, selectivity and specificity. Using a sample volume of 1.0 ml, the lowest concentration of I quantified with acceptable day-to-day reproducibility was found to be 2.56 ng/ml (R.S.D. 18.9%, n=21, 4 months). This proved to be sufficiently sensitive for pharmacokinetic drug level monitoring in cancer patients treated with a 6-h continuous intravenous infusion of I, even at the starting dose of 3 mg/m2. The successful performance and reliability of the assay has been demonstrated through extensive application to the routine analysis of plasma specimens acquired during a phase I clinical trial of the drug.

Analysis of brefeldin A and the prodrug breflate in plasma by gas chromatography with mass selective detection

Breflate is a water soluble prodrug developed to facilitate parenteral administration of the investigational antineoplastic agent brefeldin A (BFA). Previously, using analytical methods based upon reversed-phase high performance liquid chromatography (HPLC) with low wavelength UV detection or gas chromatography (GC) with electron capture detection following derivatization with heptafluorobutyrylimidazole, it was demonstrated that breflate undergoes rapid and efficient conversion to BFA following bolus i.v. injection in mice and dogs. However, plasma concentrations of the drug and prodrug achieved during the administration of nontoxic doses of breflate to beagle dogs as a 72 h continuous i.v. infusion were undetectable (< 0.1 microgram ml-1) by these methods. The sensitivity and specificity required for therapeutic drug level monitoring were achieved by GC with selected-ion mass spectrometry (MS) detection. Breflate, BFA and 1-eicosanol, the latter added to the sample as an internal standard (IS), were extracted from plasma into tert-butyl methyl ether (TBME) and esterified with trifluoroacetic anhydride. Methanol was added to the reaction mixture to effect the convenient removal of excess reagent as the volatile methyl ester during evaporation of the solvent. The residual material was analyzed directly upon reconstitution by capillary GC with automated splitless injection. Electron-ionization (70 eV) MS detection was performed by sequentially scanning ions at m/z 58, 202 and 325. The lowest concentration of either analyte quantified with acceptable reproducibility, as defined by an inter-day R.S.D. of about 20%, was near 10 ng ml-1 in plasma using a sample volume of 100 microliters. The assay has proven to be sufficiently sensitive, specific and reproducible for the routine analysis of pharmacokinetic specimens acquired during IND (investigational new drug)-directed toxicology studies in dogs.

Phase I trial of the colloidal dispersion formulation of 9-amino-20(S)-camptothecin administered as a 72-hour continuous intravenous infusion

The camptothecins are a class of potent cytotoxic anticancer agents that interact with the nuclear enzyme topoisomerase I to produce lethal DNA strand cleavages. 9-Amino-20(S)-camptothecin (9AC) was introduced into Phase I clinical trials in dimethylacetamide and polyethylene glycol 400 in a 10 mM phosphoric acid vehicle for i.v. solubility. A lyophilized colloidal dispersion (CD) of 9AC for reconstitution with 20% dextrose in normal saline was developed as an alternative formulation. Patients (ages 25-75 years) with normal liver and kidney function, Eastern Cooperative Oncology Group performance status < or = 2, and up to two prior chemotherapy regimens were treated. The initial infusion rate was 37.5 micrograms/m2/h as a 72-h continuous infusion (2.7 mg/m2 total dose). Patient cohorts were treated with escalating infusion rates until grade 4 hematological or other grade 3 toxicity developed. Pharmacokinetic sampling was performed on all patients, and 9AC lactone concentrations in plasma were determined by a high-performance liquid chromatographic assay. Twenty-five patients received a total of 65 courses of 9AC CD at doses from 2.70 to 4.65 mg/m2. The dose-limiting toxicity was neutropenia, with little nonhematological toxicity. Nonlinear regression analysis of pooled patient data yielded a total plasma clearance of 30.3 +/- 4.5 liters/h/m2, a half-life of 22.5 +/- 8.5 h, a mean residence time of 9.7 +/- 3.5 h, and a steady-state volume of distribution of 325 +/- 145 liters/m2. Although no objective responses were seen, 9 of 25 patients exhibited stable disease for 2-6 months. The plasma pharmacokinetics of 9AC lactone in cancer patients were comparable between the 9AC CD and soluble formulations. The dosing regimen recommended for Phase II trials of the 9AC CD formulation is 54.2 micrograms/m2/h, given as a 72-h continuous i.v. infusion every 3 weeks.

Specific high-performance liquid chromatographic assay with ultraviolet detection for the determination of 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea in plasma

A facile, sensitive and highly specific HPLC method for assaying 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) in plasma has been developed. The drug was efficiently isolated from plasma by extraction with tert.-butyl methyl ether. A structurally related compound with similar physicochemical properties served as the internal standard (I.S.). Following evaporation of the organic solvent, the extract was reconstituted with 0.05 M ammonium acetate buffer, pH 5.0, and loaded onto a 4 micron Nova-Pak C18 column (15 cm x 3.9 mm), which was preceded by a 7 micron Brownlee RP-18 precolumn (1.5 cm x 3.2 mm). Chromatography was performed at ambient temperature using a mobile phase of methanol-0.1 M ammonium formate buffer, pH 3.7 (25:75, v/v). UV absorbance of the effluent was monitored at 240 nm. A flow-rate of 1.0 ml/ min was used for analyzing mouse and dog plasma extracts. Under these conditions, the drug eluted at 4.0 min and was followed by the I.S. at 6.1 min. An automatic switching valve was employed to allow the precolumn to be flushed 1.5 min into the run, without interrupting the flow of the mobile phase to the analytical column, thereby preventing the apparent build-up of extractable, strongly retained, UV-absorbing components present in mouse and dog plasma. Operating in this manner, more than 100 samples could be analyzed during a day using a refrigerated autosampler for overnight injection. The method was readily adapted to the determination of SarCNU in human plasma by simply decreasing the eluent flow-rate to 0.6 ml/min, whereby SarCNU and the I.S. eluted at approximately 5.8 and 9.1 min, respectively. Furthermore, the switching valve was not necessary for the analysis of human plasma samples. With a 50-microliter sample volume, the lowest concentration of SarCNU included in the plasma standard curves, 0.10 micrograms/ml, was quantified with a 7.8% R.S.D. (n = 27) over a 2 month period. Plasma standards, with concentrations of 0.26 to 5.1 micrograms/ml, exhibited R.S.D. values ranging from 1.3 to 4.7%. Thermospray-ionization MS detection was used to definitively establish the specificity of the method. The sensitivity of the assay was shown by application to be more than adequate for characterizing the plasma pharmacokinetics of SarCNU in mice.

Inhibitors of HIV nucleocapsid protein zinc fingers as candidates for the treatment of AIDS

Strategies for the treatment of human immunodeficiency virus-type 1 (HIV-1) infection must contend with the obstacle of drug resistance. HIV-1 nucleocapsid protein zinc fingers are prime antiviral targets because they are mutationally intolerant and are required both for acute infection and virion assembly. Nontoxic disulfide-substituted benzamides were identified that attack the zinc fingers, inactivate cell-free virions, inhibit acute and chronic infections, and exhibit broad antiretroviral activity. The compounds were highly synergistic with other antiviral agents, and resistant mutants have not been detected. Zinc finger-reactive compounds may offer an anti-HIV strategy that restricts drug-resistance development.

Tyrphostin AG17, [(3,5-Di-tert-butyl-4-hydroxybenzylidene)- malononitrile], inhibits cell growth by disrupting mitochondria

[(3,5-Di-tert-butyl-4-hydroxybenzylidene)-malononitrile] (AG17), a "tyrphostin" tyrosine kinase antagonist, was found to inhibit tumor cell growth with 50% growth inhibition ranging from 0.7 to 4.0 microM in a panel of 13 human tumor cell lines, as evaluated by tetrazolium dye reduction and inhibition of precursor incorporation into macromolecules. The promyelocytic leukemia cell line HL-60(TB), was the most sensitive with irreversible total growth inhibition after 12 h of exposure to 1.5 microM drug. Antiproliferative effects of AG17 in HL-60(TB) cells were temporally related to disruption of mitochondrial function, which occurred within 1 h after drug exposure as demonstrated by a significantly decreased mass of ATP in drug-treated cells, loss of the fluorescent mitochondrial membrane potential probe rhodamine 123, and ultrastructural examination of mitochondria using fluorescence and electron microscopy. Specific decreases of total or tyrosine-phosphorylated substrate at concentrations of the drug not affecting ATP levels were not detected. These data raise the possibility that AG17 may act in part by altering mitochondrial function and/or structure, and that impairment of mitochondrial function may be exploitable as a potentially useful mechanism to modulate tumor cell proliferation. This study also emphasizes the importance of evaluating carefully the effects of potential protein kinase antagonists, since these structures have effects in intact cells in addition to what might be expected from in vitro enzyme assays.

Pharmacokinetics of active drug metabolites after oral administration of perillyl alcohol, an investigational antineoplastic agent, to the dog

The monocyclic terpene d-limonene, a major component in many citrus essential oils (1-3), has been used for many years as a flavoring agent, food additive, and fragrance (1, 2). It was recently demonstrated that limonene exhibits both chemopreventive and therapeutic effects against chemically induced mammary tumors in rats (4-10). Mechanistic studies revealed that limonene inhibits the posttranslational isoprenylation of 21-26 kDa cellular proteins implicated in cell growth and proliferation (11-13). Limonene is extensively metabolized by a variety of mammalian species (14-17). Its principal circulating metabolites identified in the rat, perillic acid and dihydroperillic acid, are also effective inhibitors of isoprenylation and cellular proliferation in vitro (17, 18). Furthermore, one of the metabolic precursors of these compounds, perillyl alcohol (16), is considerably more potent than limonene against the in vivo rat mammary tumor models (19). A preliminary report of an ongoing phase I clinical trial with limonene indicated that a single oral dose of 100 mg/kg is well tolerated (20). However, an extrapolation based upon the rat mammary tumor regression studies suggests that the minimum human dose requirement would be 1000 mg/kg/ day (6). The administration of such a large dose, which amounts to more than 80 ml of an oily volatile liquid, on a continuing basis may cause problems. Thus, perillyl alcohol is currently being developed as a clinical candidate at the National Cancer Institute because of its greater potency than limonene, which may enable potentially effective systemic concentrations of the active principals to be achieved at considerably lower doses.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic assay for genistein in biological fluids

A specific, sensitive and technically convenient HPLC method for assaying genistein in biological fluids has been developed. The compound and 4-hydroxybenzophenone, added as an internal standard, were efficiently isolated from both plasma and urine by extraction with tert-butyl methyl ether. Following evaporation of the organic solvent, the extract was reconstituted with methanol-0.05 M ammonium acetate buffer, pH 4.7 (30:70, v/v), and loaded onto a 4 microns Nova-Pak C8 column (15 cm x 3.9 mm I.D.). Chromatography was performed at ambient temperature using a mobile phase of acetonitrile-0.05 M ammonium formate buffer, pH 4.0 (27:73, v/v), at a flow-rate of 1.0 ml/min, with UV detection at 260 nm. Mean values of the tR for the drug and internal standard, determined from chromatograms of the 1 microgram/ml plasma standard during a 6 month period, were 8.27 +/- 0.55 and 11.92 +/- 0.71 min, respectively (S.D., n = 29). With a sample volume of 50 microliters, the lowest concentration of genistein included in the plasma standard curve, 0.020 microgram/ml, was quantified with a 10.7% R.S.D. over a 5 month period. Plasma standards having concentrations of 0.050 to 1.02 micrograms/ml exhibited R.S.D. values ranging from 2.3 to 6.1%. The drug was quantified in urine with similar reproducibility. The sensitivity of the assay was adequate for characterizing the plasma pharmacokinetics of genistein in the mouse and dog. However, a 10-fold improvement in sensitivity was afforded by increasing the sample size to 250 microliters, without otherwise modifying the method. Thus, this procedure may prove suitable for determining plasma and urine levels of genistein in humans consuming dietary isoflavonoids in a much more convenient manner than permitted by existing methodology.

Pharmacokinetics of michellamine B, a naphthylisoquinoline alkaloid with in vitro activity against human immunodeficiency virus types 1 and 2, in the mouse and dog

Michellamine B (MB) is a naturally occurring naphthylisoquinoline alkaloid of novel chemical structure with activity against human immunodeficiency virus (HIV) types 1 and 2 in vitro. In conjunction with its preclinical evaluation, the plasma pharmacokinetics of MB was characterized in mice and dogs treated by intravenous infusions of 1- and 15-min durations, respectively. At doses ranging from 1 to 9 mg/kg of body weight, the drug exhibited apparent first-order kinetics in both species, affording triexponential plasma concentration-time profiles. Treatment with doses of 5 to 9 mg/kg provided peak plasma levels within the range that completely inhibits the cytopathic effects of HIV upon cultured human lymphoblastoid cells (50 to 100 micrograms/ml) without evidence of toxicity. MB had a biological half-life of 2.8 +/- 0.8 h in mice, with a mean residence time of 2.1 +/- 0.3 h, and a total plasma clearance of 2.4 +/- 0.5 ml/min/kg (mean +/- standard deviation; n = 3); however, the terminal-phase contribution to the area under the plasma profile from time zero to infinity was 44.6% +/- 12.9%. In contrast, the terminal phase was the primary determinant of drug disposition in dogs, accounting for 74.1% +/- 2.8% (n = 3) of the area under the curve. Furthermore, the systemic duration of MB was significantly longer in the dogs than in mice, as indicated by mean values of the apparent half-life (11.6 +/- 1.2 h), mean residence time (12.3 +/- 1.8 h), and clearance (0.50 +/- 0.08 ml/min/kg). However, there were no statistical difference between its apparent volume of distribution in the mice (0.60 +/- 0.08 liters/kg) and dogs (0.50 +/- 0.07 liters/kg). A single dog was also treated with a total dose of 97 mg/kg given as a 72-h constant-rate intravenous infusion, since prolonged systemic exposure to potentially therapeutic drug concentrations will very likely be required for clinical anti-HIV effects. Within 4 h after starting the infusion, the plasma MB concentration exceeded 18 micrograms/ml, it reported 50% effective concentration against HIV in vitro, and subsequently increased to 41 micrograms/ml at the end of the infusion. There were no clinical or pathological indications of toxicity. Whereas the total plasma clearance (0.48 ml/min/kg) was within the range observed for dogs treated by 15-min infusion, extension of the postinfusion sampling period from 24 h to 4 days facilitated better definition of the terminal exponential phase, yielding a value of 25.6 h for the biological half-life of MB. The amount of drug excreted by dogs unchanged in the urine ranged from 3.7 to 11.1% of the administered dose. Thus, the major pathways by which the drug is eliminated from the body remain to be identified. On the basis of these findings, continued development of MB as a novel lead compound for the treatment of HIV infection is warranted.

Preclinical pharmacologic evaluation of geldanamycin as an antitumor agent

The plasma pharmacokinetics of the anti-tumor antibiotic geldanamycin (GM: NSC 122750), a naturally occurring benzoquinoid ansamycin, was characterized in mice and a beagle dog. Concentrations of GM well above 0.1 microgram/ml, which was typically effective against neoplastic cell lines responsive to the drug in vitro, were achieved in the plasma of the mice and the dog treated by i.v. injection. However, the systemic duration of the drug was relatively short. Plasma levels decayed below 0.1 microgram/ml within 3-4 h after administration of the apparent maximum tolerated doses, which were approximately 20 mg/kg for the mice and 4 mg/kg for the dog. The drug exhibited linear pharmacokinetic behavior within the dose ranges studied. However, there were significant interspecies differences in its disposition. Whereas the mean biological half-life of GM was slightly longer in the mice (77.7 min) than in the dog (57.9 min), its mean residence time in the dog (46.6 min) was more than twofold greater than that observed in the mice (20.7 min). Nevertheless, the drug was cleared from plasma much faster by the dog (49.4 ml/min per kg) than by the mice (30.5 ml/min per kg). These apparent anomalies were principally associated with differences in the relative significance of the terminal phase upon overall drug disposition. The liver appeared to be the principal target organ of acute drug toxicity in the dog. Doses of 2.0 and 4.2 mg/kg both produced elevations in serum levels of the transaminases and other indicators of liver function characteristic of acute hepatic necrosis. Additional effects included symptoms of minor gastrointestinal toxicity and alterations in serum chemistry parameters consistent with less severe nephrotoxicity. Drug-related toxicity appeared to be reversible. In consideration of the potential for acute hepatotoxic reactions to GM, as well as to the other benzoquinoid ansamycins based upon structural analogy, additional pharmacological and therapeutic information is required to ascertain whether these compounds are viable candidates for clinical development.

Dose-dependent pharmacokinetics of rapamycin-28-N,N-dimethylglycinate in the mouse

Rapamycin-28-N,N-dimethylglycinate methanesulfonate salt (RG), synthesized as a potential water-soluble prodrug to facilitate parenteral administration of the antineoplastic macrolide rapamycin (RA), is active against intracranially implanted human glioma in mice. Preclinical pharmacokinetic studies to evaluate the prodrug were conducted in male CD2F1 mice treated with 10, 25, 50 and 100 mg/kg doses of RG by rapid i.v. injection. The plasma concentration of RG decayed in a distinctly triphasic manner following treatment with the 100 mg/kg dose; however, prodrug disposition was apparent biexponential at each of the lower doses. RG exhibited dose-dependent pharmacokinetics, characterized by an increase in the total plasma clearance from 12.5 to 39.3 ml.min-1.kg-1 for dosage escalations in the range 10-50 mg/kg, while clearance values at doses of 50 and 100 mg/kg were similar. The terminal rate constants decreased linearly as the dose was increased from 10 to 100 mg/kg, eliciting an apparent prolongation of the biological half-life from 2.1 to 4.8 h. There was also a sequential increase in the steady state apparent volume of distribution from 1.73 to 8.75 l/kg. These observations are consistent with saturable binding of RG to plasma proteins while binding to tissue remains linear. Nevertheless, conversion to RA appeared to represent a prominent route of RG elimination. The molar plasma concentration of RA exceeded that of the prodrug within 30-90 min after i.v. treatment and declined very slowly thereafter, with plasma levels sustained between 0.1 and 10 microM for 48 h at each of the doses evaluated. Thus, RG effectively served as a slow release delivery system for RA, implying the possibility of maintaining therapeutic plasma levels of the drug from a more convenient dosing regimen than a continuous infusion schedule. The present findings, coupled with the demonstrated in vivo activity of RG against human brain tumor models, warrant its continued development as a much needed chemotherapeutic agent for the treatment of brain neoplasms.

Determination of michellamine B in biological fluids by high-performance liquid chromatography with fluorescence detection

The National Cancer Institute is pursuing preclinical development of michellamine B (MB), a novel dimeric polyhydroxylated naphthalene-tetrahydroisoquinoline alkaloid isolated from Ancistrocladus abbreviatus, as an anti-human immunodeficiency virus (HIV) agent. MB protects human lymphoid cells from the cytopathic effects of both HIV-1 and HIV-2 in vitro. A specific, sensitive, and convenient method for assaying the compound in biological fluids has been developed. Samples were prepared for analysis by initial treatment with dilute trichloroacetic acid followed by thorough mixing with a solution of the internal standard (alpha-naphthoflavone) in acetonitrile to denature macromolecules. The supernatant afforded by centrifugation, upon dilution with the aqueous component of the liquid chromatographic eluent, was loaded onto a 4-microns Nova-Pak phenyl column (3.9 mm x 15 cm). Chromatography was performed at ambient temperature using an isocratic mobile phase composed of 10 mM octyl sodium sulfate and 15 microM tetrabutylammonium hydrogen sulfate in acetonitrile/0.05 M ammonium formate buffer, pH 4.0 (46/54, v/v), at a flow rate of 0.6 ml/min. The intense native fluorescence of MB, which exhibited excitation and emission maxima in the mobile phase at 232 and 393 nm, respectively, provided a highly sensitive and selective means of detection. Mean values of the retention times for the drug and internal standard determined over 11 months were 10.71 +/- 0.53 and 13.14 +/- 0.52 min, respectively (SD, n = 52). Employing a sample volume of 50 microliters, the lowest concentration of MB included in the standard curves of mouse, dog, and human plasma, 10 ng/ml (11.4 nM), was quantified with coefficients of variation less than 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase I evaluation and pharmacokinetic study of pyrazine-2-diazohydroxide administered as a single bolus intravenous injection in patients with advanced solid tumors

The sodium salt of pyrazine-2-diazohydroxide (PZDH; NSC 361456) was identified as an active congener of the antitumor lead pyridine-2-diazotate with enhanced chemical stability under physiological conditions. In a phase I trial of PZDH administered as a single i.v. bolus injection, 19 patients with refractory solid tumors received 44 courses of therapy at dose levels ranging from 50 to 350 mg/m2. No objective responses to PZDH were noted. Myelosuppression characterized by prolonged, delayed onset leukopenia and thrombocytopenia was the dose limiting toxicity. A maximum tolerated dose of 350 mg/m2 was identified for this treatment schedule. Nonhematological toxicity was limited to severe nausea and vomiting, experienced by all patients treated at the lower doses, although reasonably well controlled when antiemetics were given prior to chemotherapy. The plasma pharmacokinetics of PZDH was evaluated following a single course of therapy in 16 patients. Drug levels were monitored using a specific capillary gas chromatographic assay with a 1-ng/ml lower limit of quantitation. In patients treated with doses greater than 50 mg/m2, the concentration of PZDH in plasma declined in a distinctly triexponential manner and remained above 1.5 ng/ml for at least 8 h. However, the initial decay phase, characterized by a harmonic mean half-life of 3.9 +/- 3.5 (SD) min (range, 2.2-6.3 min), was the primary determinant of drug disposition, as indicated by its 85.5-93.1% contribution to the area under the plasma concentration-time profiles from time zero to infinity. The harmonic mean terminal half-life increased with escalations in dose from 2.7 +/- 0.8 h (n = 2) at 100 mg/m2 to 8.5 +/- 3.0 h at 350 mg/m2 (n = 6). Total plasma drug clearance was very similar in patients treated with doses of 50-250 mg/m2, exhibiting a mean value of 42.5 +/- 7.8 liters/h/m2 (n = 10); however, it was significantly lower at the 350 mg/m2 dose level, 27.2 +/- 6.6 liters/h/m2 (n = 6; P < 0.002), denoting a departure from linear pharmacokinetic behavior. The rather low steady state apparent volume of distribution, which ranged from 6.0 +/- 1.5 (50 mg/m2, n = 2) to 12.7 +/- 8.0 (350 mg/m2, n = 6) liters/m2, was indicative of limited distribution of the drug into body tissue. The absence of objective antitumor effects should not discourage continued evaluation of PZDH against solid tumors selected for probable sensitivity as indicated by preclinical testing. A dose of 250 mg/m2 on a single i.v. bolus schedule is recommended for these phase II trials.

Pharmacokinetics of the 9-amino and 10,11-methylenedioxy derivatives of camptothecin in mice

Although 20(S)-camptothecin (CA) exhibited potent cytotoxicity against a broad spectrum of tumor models, clinical trials with the sodium salt of its opened lactone ring form were discontinued due to highly variable and severe toxicity. Recently, the 9-amino (AC) and 10,11-methylenedioxy (MC) derivatives of CA were selected for preclinical evaluation by the National Cancer Institute. In the present investigation, the pharmacokinetic behavior of CA, its sodium salt CA, AC, and MC in mice was characterized using specific liquid chromatographic assays which permitted determination of the intact lactone and opened ring carboxylate forms of these compounds. CA disposition was triexponential with a prolonged terminal phase that had a 24.6-h half-life (t1/2,z) that comprised only 14.6% of the area under the concentration-time profile. The relative magnitudes of the total body apparent volume of distribution (Vz) and terminal phase rate constant suggest that the high observed total plasma clearance (CL, 104 ml/min/kg) may be associated with extensive accumulation in peripheral tissue regions from which the drug is slowly released. In comparison, the terminal disposition phase of MC accounted for 49.7% of the area under the curve profile. It also had a shorter t1/2,z (15.2 h) and appreciably greater CL (526 ml/min/kg) and Vz (694 liters/kg). This suggested that the degree of binding to tissues relative to plasma proteins was enhanced by the methylenedioxy moiety. In contrast, the 9-amino substituent profoundly diminished the apparent extent of tissue distribution, as indicated by the magnitude of Vz (7.7 liters/kg), effecting an enhanced rate of elimination (t1/2,z, 1.4 h). Comparison of the CL of CA and its two derivatives provided an inaccurate indication of drug elimination due to the influence of their unusually large Vz values. For these compounds, the relative ease of elimination from the body was best represented by mean residence times, which were 0.55, 7.24, and 11.2 h for AC, CA, and MC, respectively. Intact lactone plasma levels achieved after dosing with the lactone form of CA and its 9-amino and 10,11-methylenedioxy derivatives exceeded the far less active carboxylate at all times. In summary, these studies indicate that considerable alterations in pharmacokinetic behavior result from structural modification of the A ring of CA.

Analysis of brefeldin A in plasma by gas chromatography with electron capture detection

The National Cancer Institute (NCI) is pursuing preclinical development of Brefeldin A (BFA), a macrolide isolated from Penicillium brefeldianum, as an antitumor agent. BFA exhibits a unique spectrum of activity against the human tumor cell line panel that composes the NCI's recently established in vitro antitumor screen. A specific method to assay the compound in biological fluids has been developed in which BFA and 1-eicosanol, added as the internal standard, are extracted from plasma specimens with diethyl ether. The residue afforded by evaporation of the organic solvent is dried in vacuo and derivatized with heptafluorobutyrylimidazole prior to analysis by capillary gas chromatography with electron capture detection. Derivatization of both secondary hydroxyl groups of BFA is rapid and quantitative, as confirmed by mass spectrometry. The lowest concentration of BFA quantified with acceptable reproducibility in 50 microliters of plasma is 0.1 microgram/ml, for which a 5.6% coefficient of variation has been determined from six standard curves assayed on separate days. Detector response exhibits a positive deviation from linearity for samples with BFA concentrations greater than 2.5 micrograms/ml. The assay is shown by application to be suitable for preliminary investigations of BFA plasma pharmacokinetics in mice. These studies reveal that BFA is subject to rapid elimination from the mouse, with plasma levels declining in an apparent biphasic manner from an initial concentration of 33 to 0.2 micrograms/ml at 60 min after intravenous treatment with a 26.3 mg/kg dose.