Phase I study of WR-2721 and carboplatin

Dose Individualization of Carboplatin After a 120-hour Infusion Schedule: Higher Dose Intensity but Fewer Toxicities

Carboplatin (CBDCA) is a widely used anticancer agent for which dose-effect and dose-toxicity relationships have been demonstrated, thus stressing the need for a controlled exposure to this drug. So far, carboplatin administration could only be individualized a priori following 2 classic methods, which are based on the evaluation of renal clearance: Calvert's and Chatelut's formulas. This study was designed to develop and evaluate the performance of an alternative CBDCA 120-hour schedule coupled to a Bayesian adaptive dosing with feedback strategy. Precision of the dosing method was assessed in 84 patients (256 courses performed during a 10-year period), by comparing CBDCA plasma concentrations observed at the end of the infusion with initial target values. A comprehensive monitoring of treatment-related toxicities also was performed. Finally, the authors compared doses actually delivered following the dose-tailoring method with the theoretical, standard, ones calculated retrospectively with Calvert's and Chatelut's formulas. No significant differences were found between experimental and theoretical concentrations. According to the target exposure chosen (3 levels), the mean doses administered to our patients were 517, 719, and 902 mg of CBDCA compared with 550, 509, and 538 or 657, 604, and 644 mg, which would have been given following Calvert or Chatelut formulas, respectively. These results showed that our Bayesian method led to the administration of up to 60% higher doses of carboplatin compared with those based only on the evaluation of renal clearance. Despite the markedly higher doses administered, no severe toxicities were reported in the patients treated following this new schedule. It is noteworthy that neither hematologic growth factors nor stem cells, usually associated with high-dose regimen, were used as support in this study. These data strongly suggest that it is possible to deliver higher dose- intensities of carboplatin, even in elderly, unselected patients, without increasing toxicities and with no growth factor support, provided that a therapeutic drug monitoring strategy with real-time tailored dosing is performed.

Paclitaxel and carboplatin with amifostine in advanced, recurrent, or refractory endometrial adenocarcinoma: a phase II study of the Southwest Oncology Group

OBJECTIVES

To evaluate the response rate and progression free and overall survival of patients with advanced endometrial cancer treated with paclitaxel, carboplatin and amifostine. To evaluate the toxicity of amifostine when used in combination with carboplatin and paclitaxel.

METHODS

Forty-seven eligible patients (median age: 66; range 45-82) with bidimensionally measurable advanced, recurrent, or refractory endometrial cancer were treated with carboplatin (AUC = 6), paclitaxel (175 mg/M2) and amifostine (740 mg/M2) every 4 weeks for 6 cycles or until disease progression or unacceptable toxicity.

RESULTS

There were 4 CRs (8%) (2 confirmed, 2 unconfirmed) and 15 PRs (32%) (9 confirmed, 6 unconfirmed) for a total response rate of 40% (95% confidence interval [CI], 26% to 56%). The median progression-free survival (PFS) was 7 months (95% CI, 6-9 months) and a 6-month PFS rate of 64% (95% CI, 50% to 78%). The median overall survival was 14 months (95% CI, 12 to 17 months). Toxicity was tolerable. While 79% of patients developed Grade 3/4 neutropenia (30% Grade 3, 49% Grade 4), there were no episodes of Grade 4 febrile neutropenia and one episode of infection with grades 3-4 neutropenia.

CONCLUSION

The combination of paclitaxel and carboplatin with amifostine was well reasonably tolerated in this cohort. The regimen demonstrated significant activity in endometrial cancer, comparable to other multi-agent chemotherapy programs in terms of response rate and survival, and with a favorable toxicity profile.

Amifostine pretreatment for protection against topotecan-induced hematologic toxicity: results of a multicenter phase III trial in patients with advanced gynecologic malignancies

OBJECTIVE

To determine if amifostine could reduce the hematologic toxicity associated with topotecan.

METHODS

Thirty patients with recurrent/refractory gynecologic malignancies were randomized to receive topotecan (TOPO) (1.5 mg/m(2)/day days 1-5) with or without amifostine (AMI/TOPO) (500 mg/m(2)/day days 1-5) every 3 weeks for six cycles. The primary study endpoints were the incidence of grade 3 and 4 neutropenia.

RESULTS

Fifteen patients were randomized to each arm for a total of 49 TOPO and 53 AMI/TOPO cycles. Patient characteristics and pretreatment ANC were similar between groups. Topotecan 1.5 mg/m(2)/day days 1-5 was initially administered to seven patients. Five developed neutropenic fevers, one an uncomplicated grade 4 neutropenia, and the other an uncomplicated grade 3 neutropenia. There were two treatment-related deaths due to sepsis (one in each treatment arm). The starting dose was thereafter reduced to 1.25 mg/m(2)/day days 1-5 every 21 days. No treatment related deaths occurred after this dose reduction. The incidence of combined grade 3/4 neutropenia was reduced from 67% (33/49 cycles) to 38% (20/53 cycles) with the addition of amifostine (P = 0.003; OR 0.29; 95% CI 0.12-0.71).

CONCLUSIONS

Topotecan at 1.5 mg/m(2)/day days 1-5 in heavily pretreated patients resulted in excessive toxicity not manageable with amifostine. At the reduced topotecan dose (1.25 mg/m(2) x 5 days), pretreatment with amifostine reduced the hematologic toxicity associated with topotecan chemotherapy in women with recurrent/refractory gynecologic malignancies.

Amifostine in clinical oncology: current use and future applications

Amifostine (Ethyol), an inorganic thiophosphate, is a selective broad-spectrum cytoprotector of normal tissues that provides cytoprotection against ionizing radiation and chemotherapeutic agents, thus preserving the efficacy of radiotherapy and chemotherapy. This review summarizes the preclinical data and clinical experience with amifostine, and provides insight into future clinical directions. Amifostine, an inactive pro-drug, is transformed to an active thiol after dephosphorylation by alkaline phosphatase found in the normal endothelium. The absence of alkaline phosphatase in the tumoral endothelium and stromal components, and the hypovascularity and acidity of the tumor environment, may explain its cytoprotective selectivity. The cytoprotective mechanism of amifostine is complicated, involving free radical scavenging, DNA protection and repair acceleration, and induction of cellular hypoxia. Intravenous administration of amifostine 740-900 mg/m(2) before chemotherapy and 250-350 mg/m(2) before each radiotherapy fraction are widely used regimens. The US Food and Drug Administration has approved the use of amifostine as a cytoprotector for cisplatin chemotherapy and for radiation-induced xerostomia. Ongoing trials are being conducted to determine the efficacy of amifostine in reducing radiation-induced mucositis and other toxicities. Novel schedules and routes of administration are under investigation, and may further simplify the use of amifostine and considerably broaden its applications.

Phase I trial of a twice-daily regimen of amifostine with ifosfamide, carboplatin, and etoposide chemotherapy in children with refractory carcinoma

BACKGROUND

Amifostine protects normal tissues against chemotherapy and radiation-induced toxicity without loss of antitumor effects. Evidence suggests that multiple daily doses of amifostine may improve its cytoprotective effects. The purpose of this study was to assess the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of twice-daily doses of amifostine with ifosfamide, carboplatin, and etoposide (ICE) chemotherapy for children with refractory malignancies and to determine the pharmacokinetic properties of amifostine, WR-1065, and the disulfide metabolites of amifostine.

METHODS

Patients with refractory malignancies were treated with amifostine 15 minutes before and 2 hours after chemotherapy with ifosfamide (3 g/m(2) per dose on Days 1 and 2) and carboplatin (635 mg/m(2) on Day 3). Etoposide was administered on Days 1 and 2 (150 mg/m(2)). The starting dose of amifostine was 740 mg/m(2). Pharmacokinetic studies were performed after the first dose of amifostine.

RESULTS

Twelve patients received 23 courses of ICE and amifostine. Dose-limiting toxicities for amifostine at 740 mg/m(2) were somnolence and anxiety. The other Grade 3 and 4 toxicities included asymptomatic, reversible hypocalcemia, vomiting, and reversible hypotension. At a dose of 600 mg/m(2), amifostine was well tolerated. Hypocalcemia, due to rapid, transient suppression of parathyroid hormone production, required close monitoring and aggressive intravenous calcium supplementation. Pharmacokinetic studies revealed high interpatient variability with rapid plasma clearance of amifostine and WR-1065. The median elimination half-life of amifostine (9.3 minutes) and WR-1065 (15 minutes) was much shorter than the disulfide metabolites (74.4 minutes).

CONCLUSIONS

The recommended pediatric dose of amifostine for a twice-daily regimen is 600 mg/m(2) per dose (1200 mg/m(2)/day) with DLTs of anxiety and somnolence, lower than the previously recommended single dose of 1650 mg/m(2).

[Chemoprotectors. Mechanisms of action and clinical applications]

Toxicity of chemotherapy remains an important point in the care of patients with malignancies. Since a few years, new compounds without any intrinsic anti tumoral activity have been developed to decrease the toxicity or to enhance the activity of anti-cancer drugs. From those used against the toxic activity of anti-cancer drugs, two classes could be isolated: the chemoprotectors that interact through a specific of chemotherapy in normal cells, and the chemocorrectors that enhance the spontaneous recovery after exposition to cytotoxic drugs. The most widely used chemoprotector remains the 2-mercaptoethanesulfonate (mesna) which protects against the bladder toxicity of ifosfamide and cyclophosphamide. However, two new drugs, amifostine and dextrazoxane have been recently or will be approved in France against the toxicity of cisplatin and anthracyclines, respectively. Mechanism of action and clinical applications of these new drugs in cancer chemotherapy are reviewed.

The need for cytoprotection

The toxicity associated with chemotherapy is significant and dose limiting. Multiple organ systems can be affected, with both acute and chronic side effects producing adverse effects. The concept of cytoprotection, or the selective protection of normal tissues is a strategy now being investigated in preclinical and clinical models. Systemic approaches have included the use of compounds such as sodium thiosulphate, diethyldithiocarbamate and amifostine. The most promising results have been obtained with the organic thiophosphate compound amifostine (Ethyol, WR-2721).

Cardioprotection of rat heart myocytes with amifostine (Ethyol) and its free thiol, WR-1065, in vitro

Cultured neonatal rat heart myocytes form a synchronously-contracting cell syncytium from one to two days after isolation, plating on plastic and incubation at 37 degrees C. On day 3 after plating, myocytes were exposed to the anthracycline doxorubicin, 0.1-10 micrograms/ml, for 1 h with or without a 15-min pretreatment with the thiophosphate compound amifostine (WR-2721, Ethyol) or its dephosphorylated metabolite, WR-1065. The concentration of each WR-compound was limited to 2 micrograms/ml or 10% of the maximal achievable plasma concentration of amifostine after an intravenous dose of 740 mg/m2. Both amifostine and the free thiol significantly reduced doxorubicin-induced heart-cell toxicity, measured by adenosine triphosphate content normalised to total cellular protein. A concurrent 1-h exposure to these compounds and doxorubicin was also cardioprotective, but neither compound was effective when administered after doxorubicin. Although both amifostine and WR-1065 were approximately equipotent in preventing doxorubicin-induced cardiotoxicity, only amifostine significantly increased glutathione levels in the myocytes. These results complement prior in vitro and in vivo studies in rodents showing cardioprotectant activity for amifostine and its free thiol, WR-1065, when administered prior to doxurubicin.

Amifostine (Ethyol): pharmacokinetic and pharmacodynamic effects in vivo

Amifostine (Ethyol) administered to cancer patients is rapidly cleared from plasma by a biphasic decay with an alpha half-life (T1/2 alpha) of 0.88 min and a T1/2 beta of 8.8 min. The result is that more than 90% of the drug has disappeared from the plasma compartment 6 min after intravenous (i.v.) administration. Only approximately 1% of the dose appears in the ascites. Animal studies indicate that amifostine is primarily excreted in urine-approximately 6% of the dose is excreted in the urine as amifostine and its metabolites WR-1065 and disulphides-which means that a large percentage of the dose is taken up by the tissues. Maximal tissue concentrations of WR-1065 and the disulphides were obtained between 10 and 30 min after an intraperitoneal injection of amifostine in mice, with the lowest concentrations in tumour tissues. Because WR-1065 gives protection to normal tissues rather than rescue, the pharmacokinetic data indicate that amifostine must be given shortly before administration of the cytostatic drug or radiation from which protection is required. For these reasons, amifostine is given to patients as a 15-min i.v. infusion before cisplatin and carboplatin to protect against their dose-limiting toxicities. In some regimens carboplatin is combined with three doses of amifostine because of the high concentration of the active carboplatin species during the first 4 h after administration. When carboplatin was administered as a 15-min i.v. infusion of 400 mg/m2 and amifostine as a 15-min i.v. infusion of 740 mg/m2 just before and 2 and 4 h after carboplatin, the area under the plasma concentration-time curve for ultrafilterable platinum increased from 253 +/- 45 microM.h (n = 6) for carboplatin alone to 305 +/- 63 microM.h (n = 11) for carboplatin+three doses of amifostine. Experiments in nude mice bearing OVCAR-3 xenografts showed that amifostine, given once before cisplatin or three times in combination with carboplatin, did not affect the antitumour effect of these drugs. When amifostine was only given just before carboplatin, it even stimulated the antitumour effect of carboplatin significantly.

Amifostine (Ethyol): dosing, administration and patient management guidelines

Cytoprotection utilising amifostine (Ethyol, WR-2721) is an evolving strategy to protect normal cells from the toxicity of chemotherapy. The dosing and administration guidelines are reviewed. The recommended dose of amifostine is 910 mg/m2 as a 15-min infusion prior to chemotherapy. Toxicity of this agent is moderate with hypotension and nausea/vomiting being observed in variable numbers of patients. Administration of amifostine with chemotherapy is simple and is associated with acceptable toxicity.

Clinical effects of amifostine (Ethyol) in patients treated with carboplatin

Amifostine is a compound that has been developed as a radio- and chemoprotectant. It is a prodrug, giving rise to the active thiol, WR-1065. Amifostine has been demonstrated to reduce the toxicity of ionising radiation, alkylating agents and platinum compounds. Preclinical studies have shown that amifostine can reduce the myelosuppression of carboplatin in a murine model tumour system without reducing the efficacy of therapy. In fact, in this model system, the antitumour effects of carboplatin against the OVCAR-3 cell line were actually greater with than without amifostine. Based on these preclinical studies, clinical trials of the combination of carboplatin and amifostine have been undertaken. A phase I trial of carboplatin and amifostine in pretreated patients demonstrated that two doses of amifostine 740 mg/m2/dose may be safely administered with carboplatin. The maximum tolerated dose (MTD) of carboplatin that could be administered with amifostine was 500 mg/m2, suggesting the hypothesis that amifostine increases the MTD of carboplatin from 400 to 500 mg/m2. To test this hypothesis, a randomised trial of carboplatin 500 mg/m2 versus carboplatin 500 mg/m2 plus two doses of amifostine 910 mg/m2/dose has been performed. Analysis of this trial is not complete, but initial results suggest a reduction of first-cycle thrombocytopenia, from a median platelet nadir value of 85 x 10(9) cells/l for carboplatin alone to 144 x 10(9) cells/l for the combination of carboplatin plus amifostine. Similarly, the median first-cycle granulocyte nadir was 1.6 x 10(9) cells/l without amifostine but 2.4 x 10(9) cells/l with the cytoprotectant. Neither of these first-cycle differences was statistically significant, but these effects are being maintained with repeated dosing, so that an increase in delivered cumulative carboplatin dose seems possible with the use of amifostine. These promising data indicate that continued studies of amifostine with carboplatin are justified and that the effects of amifostine on the thrombocytopenia produced by carboplatin-containing combination chemotherapy regimens should be investigated.

Amifostine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential as a radioprotector and cytotoxic chemoprotector

Amifostine (WR-2721) was originally developed as a radioprotective agent. In animals, it protects normal tissues from the damaging effects of irradiation and, as shown in more recent studies, of several cytotoxic agents. Protection of tumours is generally reduced compared with that of normal tissues in animals, suggesting that amifostine may increase the therapeutic window of cytotoxic therapies. Clinical data concerning amifostine suggest that cytotoxic chemotherapy-induced haematological toxicity and cisplatin-induced neurotoxicity, nephrotoxicity and ototoxicity are decreased upon administration of amifostine prior to cytotoxic drugs. Similarly, amifostine reduces damage to normal tissues caused by radiotherapy. Available data show that this protection is achieved without adversely affecting tumour response or patient survival. In 1 large trial, the reduction in cyclophosphamide- and cisplatin-related toxicities manifested as a decrease in the incidence and severity of neutropenia-related fever and sepsis and in the number of patients with ovarian cancer who discontinue therapy before completion of treatment, thus improving the tolerability of this antineoplastic regimen. In addition, the incidences of cisplatin-induced nephro- and neurotoxicity were reduced. Increased doses of cytotoxic therapy have also been administered when amifostine was given prior to therapy, which may increase tumour response. The predominant adverse effect associated with amifostine are hypotension, nausea and vomiting, somnolence and sneezing. Thus, amifostine is likely to be a useful adjuvant to the treatment of patients with malignancy, particularly those receiving cyclophosphamide plus cisplatin. discontinued therapy before completion of treatment, thus improving the tolerability of this antineoplastic regimen. In addition, the incidences of cisplatin-induced.

Carboplatin combined with amifostine, a bone marrow protectant, in the treatment of non-small-cell lung cancer: a randomised phase II study

Amifostine (WR-2721), a thiol compound, has been shown to protect normal tissue from alkylating agents and cisplatin-induced toxicity without loss of anti-tumour effects. To confirm this result, we conducted a phase II randomised trial to determine if the addition of amifostine reduces the toxicity of carboplatin without loss of anti-tumour activity in patients with inoperable non-small-cell lung cancer (NSCLC). After the first course of carboplatin (600 mg m-2 i.v. infusion), 21 patients were randomised to receive three cycles of carboplatin alone (C arm) or three infusions of amifostine at 910 mg m-2 (CA arm) at 28 day intervals. The amifostine was given 20 min before and at 2 and 4 h after carboplatin. Since the 910 mg m-2 amifostine infusion led to hypotension in six patients, the dosage was reduced by 25%, to 683 mg m-2 t.i.d., in the other four patients. Amifostine was well tolerated at this dose level. Five patients in the CA arm and three in the C arm had their planned treatment discontinued owing to progressive disease (n = 3), amifostine side-effects (hypotension, sneezing and sickness, n = 4), and carboplatin-induced thrombocytopenia (n = 1). Bone marrow and renal function at study entry and after the first course of carboplatin before randomisation were similar in both treatment arms. Twenty courses of carboplatin+amifostine have been compared with 25 courses of carboplatin alone. Although there was no statistically significant difference with respect to haematological values comparing both arms, the median time to platelet recovery (> 100 x 10(9) l-1) (13.5 days vs 21 days; P = 0.04) and the need for hospitalisation for i.v. antibiotic and other supportive treatment tended to be reduced in the CA arm (0/20 vs 6/25 patient courses; P = 0.06). Response rates and median survival (14 vs 9 months) were no different, excluding tumour protection activity by amifostine. These results with a small number of patients suggest that amifostine given with carboplatin may reduce the duration of thrombocytopenia and hospitalisation.

Protection of normal tissues from the cytotoxic effects of chemotherapy and radiation by amifostine (WR-2721): preclinical aspects

Amifostine is a radioprotective agent that prevents radiation- and chemotherapy-induced cellular injury through free-radical scavenging, hydrogen donation, and inhibition of DNA damage. Amifostine is metabolised and accumulated to a much greater extent in normal cells than in tumour cells. As a result, it exerts a protective effect from toxicity on normal tissues induced by chemo- or radiotherapy without reducing the antitumour effects of cancer therapy. Extensive preclinical studies have shown that amifostine protects against radiation damage and against the myelotoxic, nephrotoxic and neurotoxic effects of chemotherapeutic agents such as alkylating agents and platinum compounds. In some cases, the antitumour effects of these agents have been potentiated by amifostine. Amifostine has also been shown to protect against radiation- and chemotherapy-induced mutagenesis and, as a result, carcinogenesis. Use of amifostine allows for safer and more effective administration of radio- and anticancer therapy.

Amifostine: potential for clinically useful cytoprotection

The ability to target malignant cells for cytotoxicity while sparing normal host tissues has proven to be limited. These limitations have resulted in unacceptable toxicity or insufficiently effective therapy. Continuing investigation of new, potentially useful cytotoxic agents must continue. An alternative approach, also worthy of study, is the selective protection of normal tissues. This approach, used in conjunction with available therapeutic agents, may open the therapeutic window and incrementally enhance the effectiveness of cytotoxic therapy. A variety of methods have been used to protect normal tissues selectively. Regional protection can be used for certain organ systems, such as the oral mucosa. Selective protection on a systemic level is more difficult but agents that seem to protect normal but not malignant tissues selectively are being developed. Among these is amifostine, which was originally selected by the U.S. defense department for study as a radioprotectant. Pre-clinical studies have suggested that amifostine is differentially concentrated in normal tissues but not in malignant tissues. Tissue-specific differences in the activity of alkaline phosphatase, which dephosphorylates amifostine to its active metabolite WR-1065, and in pH are thought to be involved in this relative specificity. Clinical studies indicate that amifostine can reduce the myelosuppression produced by cyclosphosphamide, the combination of cyclophosphamide and cisplatin, and, perhaps, carboplatin. The protective effects of amifostine on nonhematopoietic toxicities are being investigated. Future trials will investigate the integration of amifostine with cytokine-based supportive care in order to define the role of this potentially clinically useful cytoprotectant agent.