Nanoparticle albumin-bound paclitaxel (ABI-007): a newer taxane alternative in breast cancer

Breast cancer remains the most common malignancy in women of developed countries. Taxanes are cornerstones in the treatment of breast cancer. Nanoparticle albumin-bound paclitaxel (ABI-007, Abraxane) is a novel taxane that obviates the need of using a toxic solvent such as Cremophor EL leading to a safer administration without standard premedication. Several factors such as the presence of albumin receptors in cell surface, the increased need of nutrients such as albumin by tumor cells and the lack of sequestering Cremophor micelles lead to increased intratumoral concentration of this new taxane. Recent trials have shown that ABI-007 is not only well tolerated but, compared with conventional paclitaxel, is associated with superior response rate, longer time to tumor progression and prolonged survival as second-line therapy in patients with metastatic breast cancer.     

Comparative preclinical and clinical pharmacokinetics of a cremophor-free, nanoparticle albumin-bound paclitaxel (ABI-007) and paclitaxel formulated in Cremophor (Taxol).

PURPOSE: To compare the preclinical and clinical pharmacokinetic properties of paclitaxel formulated as a Cremophor-free, albumin-bound nanoparticle (ABI-007) and formulated in Cremophor-ethanol (Taxol). EXPERIMENTAL DESIGN: ABI-007 and Taxol were given i.v. to Harlan Sprague-Dawley male rats to determine pharmacokinetic and drug disposition. Paclitaxel pharmacokinetic properties also were assessed in 27 patients with advanced solid tumors who were randomly assigned to treatment with ABI-007 (260 mg/m(2), 30 minutes; n = 14) or Taxol (175 mg/m(2), 3 hours; n = 13), with cycles repeated every 3 weeks. RESULTS: The volume of distribution at steady state and clearance for paclitaxel formulated as Cremophor-free nanoparticle ABI-007 were significantly greater than those for paclitaxel formulated with Cremophor (Taxol) in rats. Fecal excretion was the main elimination pathway with both formulations. Consistent with the preclinical data, paclitaxel clearance and volume of distribution were significantly higher for ABI-007 than for Taxol in humans [21.13 versus 14.76 L/h/m(2) (P = 0.048) and 663.8 versus 433.4 L/m(2) (P = 0.040), respectively]. CONCLUSIONS: Paclitaxel formulated as ABI-007 differs from paclitaxel formulated as Taxol, with a higher plasma clearance and a larger volume of distribution. This finding is consistent with the absence of paclitaxel-sequestering Cremophor micelles after administration of ABI-007. This unique property of ABI-007 could be important for its therapeutic effectiveness.     

Phase I and pharmacokinetics trial of ABI-007, a novel nanoparticle formulation of paclitaxel in patients with advanced nonhematologic malignancies.

PURPOSE: ABI-007 is a novel solvent-free, albumin-bound, 130-nm particle formulation of paclitaxel designed to avoid solvent-related toxicities and to deliver paclitaxel to tumors via molecular pathways involving an endothelial cell-surface albumin receptor (gp60) and an albumin-binding protein expressed by tumor cells and secreted into the tumor interstitium (secreted protein acid rich in cysteine). This study determined the maximum-tolerated dose (MTD) of ABI-007 monotherapy administered weekly (three weekly doses, repeated every 4 weeks) and assessed the pharmacokinetics of paclitaxel administered as ABI-007. PATIENTS AND METHODS: Patients with advanced nonhematologic malignancies received ABI-007 without premedication at dose levels from 80 to 200 mg/m(2) as a 30-minute intravenous infusion once a week for 3 weeks, followed by 1 week of rest (one cycle). RESULTS: Thirty-nine patients were treated with an average of five cycles of ABI-007; 33% of patients received > or = six cycles of treatment. MTDs for heavily and lightly pretreated patients were 100 and 150 mg/m(2), respectively; and the dose-limiting toxicities were grade 4 neutropenia and grade 3 peripheral neuropathy, respectively. Maximum paclitaxel concentration and area under the curve increased linearly with dose. Dose-dependent changes in plasma clearance did not occur. Partial responses were observed in five patients with breast, lung, and ovarian cancers, all of whom had previously been treated with paclitaxel containing polyoxyethylated castor oil in the formulation. CONCLUSION: This study demonstrated that weekly ABI-007 can be administered at doses exceeding those typically used for paclitaxel containing polyoxyethylated castor oil. Pharmacokinetics were linear over the dose range studied. Antitumor responses occurred in patients previously treated with paclitaxel containing polyoxyethylated castor oil.     

Phase I and pharmacokinetic study of ABI-007, a Cremophor-free, protein-stabilized, nanoparticle formulation of paclitaxel.

PURPOSE: ABI-007 is a novel Cremophor-free, protein-stabilized, nanoparticle formulation of paclitaxel. The absence of Cremophor EL may permit ABI-007 to be administered without the premedications used routinely for the prevention of hypersensitivity reactions. Furthermore, this novel formulation permits a higher paclitaxel concentration in solution and, thus, a decreased infusion volume and time. This Phase I study examines the toxicity profile, maximum tolerated dose (MTD), and pharmacokinetics of ABI-007. EXPERIMENTAL DESIGN: ABI-007 was administered in the outpatient setting, as a 30-min infusion without premedications. Doses of ABI-007 ranged from 135 (level 0) to 375 mg/m2 (level 3). Sixteen patients participated in pharmacokinetic studies. RESULTS: Nineteen patients were treated. No acute hypersensitivity reactions were observed during the infusion period. Hematological toxicity was mild and not cumulative. Dose-limiting toxicity, which occurred in 3 of 6 patients treated at level 3 (375 mg/m2), consisted of sensory neuropathy (3 patients), stomatitis (2 patients), and superficial keratopathy (2 patients). The MTD was thus determined to be 300 mg/m2 (level 2). Pharmacokinetic analyses revealed paclitaxel C(max) and area under the curve(inf) values to increase linearly over the ABI-007 dose range of 135-300 mg/m2. C(max) and area under the curve(inf) values for individual patients correlated well with toxicity. CONCLUSIONS: ABI-007 offers several features of clinical interest, including rapid infusion rate, absence of requirement for premedication, and a high paclitaxel MTD. Our results provide support for Phase II trials to determine the antitumor activity of this drug.     

Phase III trial of nanoparticle albumin-bound paclitaxel compared with polyethylated castor oil-based paclitaxel in women with breast cancer.

PURPOSE: ABI-007, the first biologically interactive albumin-bound paclitaxel in a nanameter particle, free of solvents, was compared with polyethylated castor oil-based standard paclitaxel in patients with metastatic breast cancer (MBC). This phase III study was performed to confirm preclinical studies demonstrating superior efficacy and reduced toxicity of ABI-007 compared with standard paclitaxel. PATIENTS AND METHODS: Patients were randomly assigned to 3-week cycles of either ABI-007 260 mg/m(2) intravenously without premedication (n = 229) or standard paclitaxel 175 mg/m(2) intravenously with premedication (n = 225). RESULTS: ABI-007 demonstrated significantly higher response rates compared with standard paclitaxel (33% v 19%, respectively; P = .001) and significantly longer time to tumor progression (23.0 v 16.9 weeks, respectively; hazard ratio = 0.75; P = .006). The incidence of grade 4 neutropenia was significantly lower for ABI-007 compared with standard paclitaxel (9% v 22%, respectively; P < .001) despite a 49% higher paclitaxel dose. Febrile neutropenia was uncommon (< 2%), and the incidence did not differ between the two study arms. Grade 3 sensory neuropathy was more common in the ABI-007 arm than in the standard paclitaxel arm (10% v 2%, respectively; P < .001) but was easily managed and improved rapidly (median, 22 days). No hypersensitivity reactions occurred with ABI-007 despite the absence of premedication and shorter administration time. CONCLUSION: ABI-007 demonstrated greater efficacy and a favorable safety profile compared with standard paclitaxel in this patient population. The improved therapeutic index and elimination of corticosteroid premedication required for solvent-based taxanes make the novel albumin-bound paclitaxel ABI-007 an important advance in the treatment of MBC.     

Multicenter phase II trial of ABI-007, an albumin-bound paclitaxel, in women with metastatic breast cancer.

PURPOSE: ABI-007 is a novel nanoparticle, albumin-bound paclitaxel that is free of solvents. This multicenter phase II study was designed to evaluate the efficacy and safety of ABI-007 for the treatment of metastatic breast cancer (MBC). PATIENTS AND METHODS: Sixty-three women with histologically confirmed and measurable MBC received 300 mg/m2 ABI-007 by intravenous infusion over 30 minutes every 3 weeks without premedication. Forty-eight patients received prior chemotherapy; 39 patients received no prior treatment for metastatic disease. RESULTS: Overall response rates (complete or partial responses) were 48% (95% CI, 35.3% to 60.0%) for all patients. For patients who received ABI-007 as first-line and greater than first-line therapy for their metastatic disease, the respective response rates were 64% (95% CI, 49.0% to 79.2%) and 21% (95% CI, 7.1% to 42.1%). Median time to disease progression was 26.6 weeks, and median survival was 63.6 weeks. No severe hypersensitivity reactions were reported despite the lack of premedication. Toxicities observed were typical of paclitaxel and included grade 4 neutropenia (24%), grade 3 sensory neuropathy (11%), and grade 4 febrile neutropenia (5%). Patients received a median of six treatment cycles; 16 patients had 25% dose reductions because of toxicities, and two of these patients had subsequent dose reductions. CONCLUSION: ABI-007, the first biologically interactive albumin-bound form of paclitaxel in the nanoparticle state, uses the natural carrier albumin rather than synthetic solvents to deliver paclitaxel and allows for safe administration of high paclitaxel doses without premedication, resulting in significant antitumor activity in patients with MBC, including those receiving the drug as first-line therapy.     

紫杉醇新剂型的开发及临床研究进展

紫杉醇广泛用于卵巢癌、乳腺癌、肺癌等多种肿瘤的治疗.但由于其难溶于水,需溶于聚氧乙烯蓖麻油(cremophor EL)与无水乙醇混合溶媒中增加水溶性,而cremophor EL在体内降解时释放组胺,导致不同程度的过敏反应,亦可引起神经细胞内颗粒释放及脱髓鞘改变而加重紫杉醇的外周神经毒性.为降低毒性,提高其疗效,近年来临床上陆续开发了紫杉醇的新剂型,其中不含聚氧乙烯蓖麻油注射紫杉醇白蛋白纳米混悬液(ABI-007)已在欧美上市,具有不用抗过敏预处理、疗效较好、毒性较低等特点;现正在国内进行临床研究我国研发的紫杉醇脂质体已开始在临床应用而紫杉醇的前体药物(DHA-PTX)和聚合物剂型genexol-PM及xyotax也正在临床前和临床Ⅰ～Ⅲ期研究中,显示了良好的前景.本文就紫杉醇的作用机制,不良反应及新制剂的开发和应用进行回顾和综述.     

Phase I and pharmacokinetic trial of carboplatin and albumin-bound paclitaxel, ABI-007 (Abraxane®) on three treatment schedules in patients with solid tumors

Purpose

Albumin-bound paclitaxel, ABI-007 (Abraxane^®), has a different toxicity profile than solvent-based paclitaxel, including a lower rate of severe neutropenia. The combination of ABI-007 and carboplatin may have significant activity in a variety of tumor types including non-small and small cell lung cancer, ovarian cancer, and breast cancer. The purpose of this study was to determine the maximum tolerated dose (MTD) of ABI-007, on three different schedules in combination with carboplatin.

Methods

Forty-one patients with solid tumors were enrolled, and received ABI-007 in combination with carboplatin AUC of 6 on day 1. Group A received ABI-007 at doses ranging from 220 to 340 mg/m² on day 1 every 21 days; group B received ABI-007 at 100 or 125 mg/m² on days 1, 8, and 15 every 28 days; and group C received ABI-007 125 or 150 mg/m² on days 1 and 8 every 21 days. Dose-limiting toxicities were assessed after the first cycle. Doses were escalated in cohorts of three to six patients. Fifteen patients participated in a pharmacokinetic study investigating the effects of the sequence of infusion. ABI-007 was infused first followed by carboplatin in cycle 1, and vice versa in cycle 2.

Results

The MTD of ABI-007 in combination with carboplatin was 300, 100, and 125 mg/m² in groups A, B, and C, respectively. Myelosuppression was the primary dose limiting toxicity. No unexpected or new toxicities were reported. Sequence of infusion did not affect either the pharmacokinetics of ABI-007 or the degree of neutropenia. Responses were seen in melanoma, lung, bladder, esophageal, pancreatic, breast cancer, and cancer of unknown primary.

Conclusions

The recommended dose for phase II studies of ABI-007 in combination with carboplatin (AUC of 6) is 300, 100, 125 mg/m² for the schedules A, B, and C, respectively. The combination of ABI-007 and carboplatin is well tolerated and active in this heavily pretreated patient population.     

Abraxane, a novel Cremophor-free, albumin-bound particle form of paclitaxel for the treatment of advanced non-small-cell lung cancer.

BACKGROUND: Abraxane (ABI-007) is a novel 130-nm, albumin-bound (nab) particle form of paclitaxel designed to utilize endogenous albumin pathways to increase intratumor concentrations of the active drug. This multicenter phase II study was designed to evaluate the efficacy and safety of Abraxane 260 mg/m2 every 3 weeks in patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with histologically confirmed, measurable NSCLC received Abraxane as first-line therapy. RESULTS: Forty-three patients were enrolled. The overall response rate was 16%; the disease control rate was 49%. Median time to progression was 6 months, and median survival was 11 months. The probability of not having progressed by 1 year was 13%; the probability of surviving 1 year was 45%. No severe hypersensitivity reactions were reported despite the lack of premedication; 95% of patients were treated without dose reduction. Two patients (5%) discontinued therapy because of treatment-related toxicities (neuropathy, fatigue [1 each]). No grade 4 treatment-related toxicity occurred. CONCLUSIONS: Abraxane 260 mg/m2 administered IV over 30 min without premedication was well tolerated. Significant tumor responses and prolonged disease control were documented in this group of patients with NSCLC. Exploration of higher doses of ABI-007 alone and in combination with other drugs active in NSCLC is warranted.     

Neovascular targeting chemotherapy: encapsulation of paclitaxel in cationic liposomes impairs functional tumor microvasculature

Cationic liposomes have been shown to be internalized selectively by angiogenic tumor endothelial cells after intravenous injection. Therefore, encapsulation of cytotoxic substances in cationic liposomes is a new approach to target tumor vasculature. It was the aim of our study to quantify the effects of paclitaxel encapsulated in cationic liposomes (MBT-0206) on tumor microvasculature and growth in vivo. Experiments were performed in the dorsal skinfold chamber preparation of Syrian Golden hamsters bearing syngeneic A-Mel-3 melanomas. Tumors were treated with intravenous infusion of MBT-0206 (20 mM) resulting in an effective paclitaxel dose of 5 mg/kg body weight (b.w.). Control animals received conventional paclitaxel in Cremophor EL (Taxol(R); 5 mg/kg b.w.), unloaded cationic liposomes (20 mM) or the solvent 5% glucose, respectively. Using intravital microscopy, tumor growth and effects on intratumoral microvasculature were analyzed. Tumor growth was significantly retarded after treatment with MBT-0206 compared to the treatment with paclitaxel. Analysis of intratumoral microcirculation revealed a reduced functional vessel density in tumors after application of liposomal paclitaxel. At the end of the observation time, vessel diameters were significantly smaller in animals treated with paclitaxel encapsulated in cationic liposomes while red blood cell velocity was less affected. This resulted in a significantly reduced blood flow in vessel segments and a reduced microcirculatory perfusion index in these animals. Histochemical TUNEL stain was vessel-associated after treatment with liposomal paclitaxel in contrast to few apoptotic tumor cells in the control groups. Our data demonstrate that encapsulation of paclitaxel in cationic liposomes significantly increased the antitumoral efficacy of the drug. Remarkable microcirculatory changes indicate that encapsulation of paclitaxel in cationic liposomes resulted in a mechanistic switch from tumor cell toxicity to an antivascular therapy.     

白蛋白结合型紫杉醇的研究进展

纳米颗粒白蛋白结合型紫杉醇是一种全新剂型紫杉醇类药物,它不需要合成的溶剂作为载体,不需要皮质类固醇或抗组胺药物等预处理,静脉滴注时间短(30min)。白蛋白结合型紫杉醇利用了白蛋白的自然生物特性,通过gp-60介导的内皮细胞跨膜转运和一种与白蛋白结合的蛋白SPARC(一种酸性的富含半胱氨酸的分泌蛋白)的相互作用而增加肿瘤组织对紫杉醇的摄取和蓄积,临床前模型研究证实白蛋白结合型紫杉醇与溶剂型紫杉醇相比,抗肿瘤活性明显增强。以此为基础,近年国内外进行了一系列白蛋白结合型紫杉醇应用于各种恶性肿瘤化疗的临床研究,并且取得了令人鼓舞的结果。     

白蛋白结合型紫杉醇的研究进展

纳米颗粒白蛋白结合型紫杉醇是一种全新剂型紫杉醇类药物,它不需要合成的溶剂作为载体,不需要皮质类固醇或抗组胺药物等预处理,静脉滴注时间短（30min）。白蛋白结合型紫杉醇利用了白蛋白的自然生物特性,通过gp-60介导的内皮细胞跨膜转运和一种与白蛋白结合的蛋白SPARC（一种酸性的富含半胱氨酸的分泌蛋白）的相互作用而增加肿瘤组织对紫杉醇的摄取和蓄积,临床前模型研究证实白蛋白结合型紫杉醇与溶剂型紫杉醇相比,抗肿瘤活性明显增强。以此为基础,近年国内外进行了一系列白蛋白结合型紫杉醇应用于各种恶性肿瘤化疗的临床研究,并且取得了令人鼓舞的结果。     

P450 induction alters paclitaxel pharmacokinetics and tissue distribution with multiple dosing

Purpose Paclitaxel (Taxol) is an effective agent against a broad range of human cancers. Studies on the metabolism and disposition of paclitaxel have shown that it is primarily eliminated via hepatic metabolism by P450 enzymes (2C8 and 3A4) to essentially inactive metabolites, and that biliary and gut transport by P-glycoprotein (PGP) as well as urinary elimination of the parent compound play relatively minor roles. Recent studies in vitro have shown that paclitaxel treatment increases the level of CYP2C8 and CYP3A4 in human hepatocytes as well as PGP in colon tumor cells. The data suggest that previous paclitaxel exposure may influence metabolism and elimination of subsequent doses. Further, since weekly paclitaxel dose schedules are becoming more common as opposed to the original every 21-day dosing, the likelihood of enzyme induction from previous doses impacting that from subsequent doses is increased.Methods To study the potential for such sequence-dependent alterations in paclitaxel pharmacokinetics, we carried out pharmacokinetic studies in mouse plasma and tissues following day 1 and days 1 and 5 dosing at 20 mg/kg. Paclitaxel concentrations were determined by a sensitive LC/MS/MS assay out to 16 h post-dosing in plasma, liver, kidney, gut and heart. The effect of paclitaxel treatment on hepatic expression of PGP and P450 isoforms (CYP2C and CYP3A) was determined to elucidate the mechanism by which paclitaxel disposition is altered by previous drug exposure.Results Pharmacokinetic analysis of the data showed that plasma and tissue AUC values after treatment on day 5 following a dose on day 1 were between 50% and 74% of those determined following a single dose on day 1. The terminal elimination half-life was not different. Activity and protein levels for CYP2C in liver were elevated at 24 and 96 h after paclitaxel dosing. Cremophor EL, a carrier solvent for paclitaxel, also caused elevated CYP2C activity. Neither CYP3A nor PGP levels in liver were altered by paclitaxel or Cremophor EL treatment at the 24-h and 96-h time points. The levels of 6-OH-paclitaxel in feces were increased on day 5 as opposed to day 1 while paclitaxel levels in feces were unchanged.Conclusions The results of our studies showed that paclitaxel pharmacokinetics are altered by previous paclitaxel exposure up to 96 h earlier.     

Randomized crossover pharmacokinetic study of solvent-based paclitaxel and nab-paclitaxel

PURPOSE: Abraxane (ABI-007) is a 130-nm albumin-bound (nab) particle formulation of paclitaxel, devoid of any additional excipients. We hypothesized that this change in formulation alters the systemic disposition of paclitaxel compared with conventional solvent-based formulations (sb-paclitaxel; Taxol), and leads to improved tolerability of the drug. Patients and Methods: Patients with malignant solid tumors were randomized to receive the recommended single-agent dose of nab-paclitaxel (260 mg/m(2) as a 30-minute infusion) or sb-paclitaxel (175 mg/m(2) as a 3-hour infusion). After cycle 1, patients crossed over to the alternate treatment. Pharmacokinetic studies were carried out for the first cycle of sb-paclitaxel and the first two cycles of nab-paclitaxel. RESULTS: Seventeen patients were treated, with 14 receiving at least one cycle each of nab-paclitaxel and sb-paclitaxel. No change in nab-paclitaxel pharmacokinetics was found between the first and second cycles (P = 0.95), suggesting limited intrasubject variability. Total drug exposure was comparable between the two formulations (P = 0.55) despite the dose difference. However, exposure to unbound paclitaxel was significantly higher after nab-paclitaxel administration, due to the increased free fraction (0.063 +/- 0.021 versus 0.024 +/- 0.009; P < 0.001). CONCLUSION: This study shows that paclitaxel disposition is subject to considerable variability depending on the formulation used. Because systemic exposure to unbound paclitaxel is likely a driving force behind tumoral uptake, these findings explain, at least in part, previous observations that the administration of nab-paclitaxel is associated with augmented antitumor efficacy compared with solvent-based paclitaxel.     

An investigation of the antitumour activity and biodistribution of polymeric micellar paclitaxel

 Purpose: To evaluate in vitro cytotoxicity, in vivo antitumour activity and biodistribution of a novel polymeric (poly(DL-lactide)-block-methoxy polyethylene glycol) micellar paclitaxel. Methods: Hs578T breast, SKMES non-small-cell lung, and HT-29 colon human tumour cells were exposed, either for 1 h or continuously, to conventionally formulated paclitaxel (Cremophor paclitaxel) or polymeric micellar paclitaxel. After a period of incubation, cytotoxicity was measured using a radiometric system. In the in vivo antitumour study, B6D2F1 mice, bearing P388 leukaemia tumour intraperitoneally (i.p.), were treated with polymeric micellar paclitaxel or Cremophor paclitaxel by i.p. injection. The number of deaths and body weights were recorded. In the biodistribution study, CD-1 mice were given micellar paclitaxel i.p. at a dose of 100 mg/kg. The mice were sacrificed after a given time and the organs were harvested. Paclitaxel in the organs was extracted by acetonitrile and analysed using HPLC. Results: The polymeric micellar paclitaxel showed similar in vitro cytotoxicity to Cremophor paclitaxel against the tumour cell lines. The polymeric micellar formulation of paclitaxel produced a fivefold increase in the maximum tolerated dose (MTD) as compared with Cremophor paclitaxel when administered i.p. In addition, micellar paclitaxel was more efficacious in vivo when tested in the murine P388 leukaemia model of malignancy than Cremophor paclitaxel when both were administered i.p. at their MTDs. Micellar paclitaxel-treated animals had an increased survival time and, importantly, long-term survivors (20% of those tested) were obtained only in the polymeric paclitaxel formulation group. Biodistribution studies indicated that a significant amount of paclitaxel could be detected in blood, liver, kidney, spleen, lung and heart of mice after i.p. dosing of the polymeric micellar paclitaxel formulation. Conclusion: These preliminary results indicate that polymeric micellar paclitaxel could be a clinically useful chemotherapeutic formulation. Received: 18 April 1996 / Accepted: 12 September 1996     

Intraarterial chemotherapy with polyoxyethylated castor oil free paclitaxel, incorporated in albumin nanoparticles (ABI-007): Phase II study of patients with squamous cell carcinoma of the head and neck and anal canal: preliminary evidence of clinical activity.

BACKGROUND: This study was designed to determine the feasibility, maximum tolerated dose, and toxicities of intraarterial administration of paclitaxel-albumin nanoparticles in patients with advanced head and neck and recurrent anal canal squamous cell carcinoma. Antitumor activity also was assessed. METHODS: Forty-three patients (31 with advanced head and neck and 12 with recurrent anal canal squamous cell carcinoma) were treated intraarterially with ABI-007 every 4 weeks for 3 cycles. In total, 120 treatment cycles were completed, 86 in patients with head and neck carcinoma (median, 3 cycles; range, 1-4) and 34 in patients with anal canal carcinoma (median, 3 cycles; range, 1-4). ABI-007 was compared preliminarily with Taxol for in vitro cytostatic activity. Increasing dose levels from 120 to 300 mg/m2 were studied in 18 patients. Pharmacokinetic profiles after intraarterial administration were obtained in a restricted number of patients. RESULTS: The dose-limiting toxicity of ABI-007 was myelosuppression consisting of Grade 4 neutropenia in 3 patients. Nonhematologic toxicities included total alopecia (30 patients), gastrointestinal toxicity (3 patients, Grade 2), skin toxicity (5 patients, Grade 2), neurologic toxicity (4 patients, Grade 2) ocular toxicity (1 patient, Grade 2), flu-like syndrome (7 patients, Grade 2; 1 patient, Grade 3). In total, 120 transfemoral, percutaneous catheterization procedure-related complications occurred only during catheterization of the neck vessels in 3 patients (2 TIA, 1 hemiparesis) and resolved spontaneously. CONCLUSIONS: Intraarterial administration of ABI-007 by percutaneous catheterization does not require premedication, is easy and reproducible, and has acceptable toxicity. The maximum tolerated dose in a single administration was 270 mg/m2. Most dose levels showed considerable antitumor activity (42 assessable patients with 80.9% complete response and partial response). The recommended Phase II dose is 230 mg/m2 every 3 weeks.     

Inhibition of paclitaxel elimination in the isolated perfused rat liver by Cremophor EL

Purpose: Cremophor can alter the pharmacokinetics of cytotoxic drugs, including doxorubicin and etoposide. In view of its presence in the formulation of paclitaxel, the aim of this study was to investigate the influence of Cremophor on the hepatobiliary elimination of paclitaxel. Methods: In a recirculating isolated perfused rat-liver system the elimination of 1.7 mg paclitaxel given as a bolus into the perfusate reservoir was monitored in perfusate and bile in controls and after the administration of either 80 or 800 μl Cremophor. The higher dose of Cremophor yields clinically relevant perfusate concentrations. Paclitaxel was measured in perfusate, bile, and liver tissue by high-performance liquid chromatography. Results: Cremophor caused a dose-dependent inhibition of the elimination of paclitaxel, with a statistically significant mean value ± SD, n = 3; (P < 0.05 versus controls Bonferroni t-test) 9-fold increase in AUC (2227±106 versus 245 ± 40 g ml⁻¹min), 9-fold decrease in total clearance (0.8±0.1 versus 7.0±1.1 ml/min), and 5-fold increase in elimination half-life (92±14 versus 18±4 min) being observed after a dose of 800 μl Cremophor. With the addition of Cremophor the amount of paclitaxel remaining after 3 h increased in perfusate from none to 20, increased in liver tissue from 4 to 18, and remained constant in bile at 11–13%. In the control group, 86 of the paclitaxel dose was recovered in bile as five putative metabolites, which were measured in paclitaxel equivalents, with the major metabolite. M3 co-eluting with 3′-p-hydroxypaclitaxel. This decreased to 45 of the dose on the addition of Cremophor, and the ratio of M3 to paclitaxel in bile decreased. Conclusions: Cremophor inhibits the hepatic elimination of paclitaxel in the isolated perfused rat liver, primarily by preventing the drug from reaching sites of metabolism and excretion. The presence of Cremophor in the paclitaxel formulation may therefore contribute to the nonlinear pharmacokinetics and pharmacodynamics of paclitaxel. Received: 24 February 1998 / Accepted: 22 June 1998     

The co-solvent Cremophor EL limits absorption of orally administered paclitaxel in cancer patients.

The purpose of this study was to investigate the effect of the co-solvents Cremophor EL and polysorbate 80 on the absorption of orally administered paclitaxel. 6 patients received in a randomized setting, one week apart oral paclitaxel 60 mg m(-2) dissolved in polysorbate 80 or Cremophor EL. For 3 patients the amount of Cremophor EL was 5 ml m(-2), for the other three 15 ml m(-2). Prior to paclitaxel administration patients received 15 mg kg(-1) oral cyclosporin A to enhance the oral absorption of the drug. Paclitaxel formulated in polysorbate 80 resulted in a significant increase in the maximal concentration (C(max)) and area under the concentration-time curve (AUC) of paclitaxel in comparison with the Cremophor EL formulations (P = 0.046 for both parameters). When formulated in Cremophor EL 15 ml m(-2), paclitaxel C(max) and AUC values were 0.10 +/- 0.06 microM and 1.29 +/- 0.99 microM h(-1), respectively, whereas these values were 0.31 +/- 0.06 microM and 2.61 +/- 1.54 microM h(-1), respectively, when formulated in polysorbate 80. Faecal data revealed a decrease in excretion of unchanged paclitaxel for the polysorbate 80 formulation compared to the Cremophor EL formulations. The amount of paclitaxel excreted in faeces was significantly correlated with the amount of Cremophor EL excreted in faeces (P = 0.019). When formulated in Cremophor EL 15 ml m(-2), paclitaxel excretion in faeces was 38.8 +/- 13.0% of the administered dose, whereas this value was 18.3 +/-15.5% for the polysorbate 80 formulation. The results show that the co-solvent Cremophor EL is an important factor limiting the absorption of orally administered paclitaxel from the intestinal lumen. They highlight the need for designing a better drug formulation in order to increase the usefulness of the oral route of paclitaxel     

Effect of dimethyl sulfoxide on bladder tissue penetration of intravesical paclitaxel.

Our laboratory has shown that the efficacy of bladder cancer intravesical therapy is in part limited by the poor penetration of drugs into the urothelium. We further found that paclitaxel, because of its lipophilicity, shows a higher penetration than other commonly used drugs such as mitomycin C and doxorubicin. However, the commercial formulation of paclitaxel (i.e., Taxol) contains Cremophor, which forms micelles that entrap the drug and reduce its free fraction. The present study evaluated the effect of DMSO on paclitaxel release from Cremophor micelles and paclitaxel penetration in bladders of dogs given an intravesical dose of paclitaxel (500 microg/20 ml in 0.22% Cremophor, 0.21% ethanol, and 50% DMSO). Cremophor produced a concentration-dependent reduction of the free fraction of paclitaxel (reduced to 23% at 0.25% Cremophor). This Cremophor effect was reversed by DMSO in a concentration-dependent manner, resulting in a 92% free fraction at 50% DMSO. DMSO also increased the average size of Cremophor micelles from 13 nm to 230 nm at 50% DMSO. A comparison of the tissue penetration data in the presence of Cremophor and/or DMSO indicates the following effects of DMSO: (a). increase in urine production rate and, consequently, a 36% reduction of the final urine concentration; (b). 2-fold increase in paclitaxel penetration across bladder urothelium; (c). increase in drug removal from bladder tissues (30% more rapidly); and (d). a 60% increase of the amount of drug in bladder tissue. These results indicate that DMSO caused rearrangement of Cremophor micelles, reversed the entrapment of paclitaxel in Cremophor micelles and thereby increased the free fraction of paclitaxel in solution, enhanced the urine production rate and enhanced drug removal by the perfusing capillaries, with an overall effect of increasing the bladder tissue delivery of paclitaxel formulated in Cremophor.     

Phase I and pharmacokinetic study of Genexol-PM, a cremophor-free, polymeric micelle-formulated paclitaxel, in patients with advanced malignancies.

PURPOSE: The rationale for developing an alternative paclitaxel formulation concerns Cremophor EL-related side effects, and a novel paclitaxel delivery system might augment its therapeutic efficacy. Genexol-PM is a polymeric micelle formulated paclitaxel free of Cremophor EL. A phase I study was performed to determine the maximum tolerated dosage, dose-limiting toxicities, and the pharmacokinetic profile of Genexol-PM in patients with advanced, refractory malignancies. EXPERIMENTAL DESIGN: Twenty-one patients were entered into the study. Genexol-PM was i.v. administered over 3 h every 3 weeks without premedication. The Genexol-PM dose was escalated from 135 mg/m(2) to 390 mg/m(2). RESULTS: All of the patients were evaluable for toxicity and response. Acute hypersensitivity reactions were not observed. Neuropathy and myalgia were the most common toxicities. During cycle 1, grade 3 myalgia occurred in 1 patient at 230 and 300 mg/m(2), respectively. At 390 mg/m(2), 2 of 3 patients developed grade 4 neutropenia or grade 3 polyneuropathy. Therefore, the maximum tolerated dosage was determined to be 390 mg/m(2). There were 3 partial responses (14%) among the 21 patients. Of the 3 responders, 2 were refractory to prior taxane therapy. The paclitaxel area under the curve from time 0 to infinity and peak or maximum paclitaxel concentration seemed to increase with escalating dose, except at 230 mg/m(2), which suggests that Genexol-PM has linear pharmacokinetics. CONCLUSION: The main dose-limiting toxicities were neuropathy, myalgia, and neutropenia, and the recommended dosage for a phase II study is 300 mg/m(2). Genexol-PM is believed to be superior to conventional paclitaxel in terms of the obviation of premedication and the delivery of higher paclitaxel doses without additional toxicity.