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S J Clarke

Publications and source records attributed to S J Clarke.

At least 19 recordsLinked to original sources
PubMed2000

Clinical pharmacokinetics of the irinotecan metabolite 4-piperidinopiperidine and its possible clinical importance.

PURPOSE: To investigate the clinical relevance of 4-piperidinopiperidine (4PP) in the activity of irinotecan (CPT-11), a high-performance liquid chromatography-turboionspray-tandem mass spectrometry assay for plasma 4PP was developed. METHODS: Plasma samples were prepared for analysis following C18 solid-phase extraction. Chromatography was performed on a Waters Nova-Pak Phenyl column. Selected reaction monitoring with the mass transitions m/z 169.2 --> 84.2 and 139.2 --> 98.1 was used for the detection of 4PP and the internal standard (IS), 1-piperidineproprionitrile, respectively. RESULTS: The assay was linear from 14.8 to 591.0 nM with absolute recoveries of 4PP (59.1 nM) and IS (143.7 nM) of 85.7% (n = 10) and 86.7% (n = 10), respectively. The accuracy and imprecision of the method (total) was > or = 96.8% and < or = 8.5% over the concentration range studied, respectively. 4PP was detectable in plasma following the administration of 125, 350, 500 mg/m2 and 600 mg/m2 CPT-11 to patients, with AUC(4PP) correlated with the dose (r2 = 0.66). Plasma concentrations of 4PP declined slowly with a long terminal half-life (33.4 +/- 17.1 h). CONCLUSIONS: Overall, the concentrations of 4PP in plasma were in the sub-micromolar range (< 206.9 nM) and substantially lower than those capable of inducing apoptosis of cancer cells.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Balb/c mice as a preclinical model for raltitrexed-induced gastrointestinal toxicity.

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor used for the treatment of advanced colorectal cancer. RTX induces proliferating tissue toxicities that are largely confined to the intestine, with diarrhea being a severe side effect in a small but significant minority of patients. Similarly, weight loss and diarrhea were observed in BALB/c mice, and a maximum tolerated dose (MTD) was determined as approximately 5-10 mg/kg/day x 5 days. At an equivalent dose of 10 mg/kg/day x 5 days (dl-5), DBA2 mice lost considerably less weight, leading to a higher MTD (>500 mg/kg/day x 5 days), and there was no evidence of diarrhea. Histopathological consequences of damage, such as changes in small intestinal crypt architecture and villus atrophy induced by the 10-mg/kg/day dose, were greater and of longer duration in BALB/c mice. A higher dose of RTX (100 mg/kg/day x 5) induced weight loss and histopathological damage similar to that seen in BALB/c mice (10 mg/kg/ day x 5) but was of later onset, nadir, and recovery. Small changes to the colon were only observed in BALB/c mice. Pretreatment levels of plasma thymidine, deoxyuridine (approximately 1 microM), and folate (approximately40 ng/ml) were similar in both mouse strains. A single injection of radiolabeled RTX (5 mg/kg/ day) did not lead to any marked difference 24 h later in the total drug concentration and distribution of polyglutamates (comprising 70-80% of drug extracted) in the liver, kidney, and intestinal epithelium (large and small intestine) between the two mouse strains. Further studies used a RIA to measure RTX polyglutamate formation in tissues at various times and drug doses. This led to the conclusion that, although there was a higher accumulation of RTX in BALB/c small intestinal epithelium (days 4-6), it may be an effect secondary to another undetermined cause of increased drug sensitivity. This model represents a vehicle by which the etiology and treatment of severe clinical toxicity induced by RTX may be evaluated.

Animals↗
PubMed1999

Clinical pharmacokinetics of docetaxel.

Docetaxel (Taxotere), a semi-synthetic analog of paclitaxel (Taxol), is a promoter of microtubule polymerization leading to cell cycle arrest at G2/M, apoptosis and cytotoxicity. Docetaxel has significant activity in breast, non-small-cell lung, ovarian and head and neck cancers. Docetaxel has undergone phase I study in a number of schedules, including different infusion durations and various treatment cycles. Doses studied in adults have ranged from 5 to 145 mg/m2 and those in children from 55 to 235 mg/m2. The most frequently used regimen in adults is 100 mg/m2 every 3 weeks. A 1-hour infusion every 3 weeks has been favoured in phase II and III studies, and the disposition of docetaxel after such treatment is best described by a 3 compartment model with alpha, beta and gamma half-lives of 4.5 minutes, 38.3 minutes and 12.2 hours, respectively. The disposition of docetaxel appears to be linear, the area under the plasma concentration-time curve (AUC) increasing proportionately with dose. Docetaxel is widely distributed in tissues with a mean volume of distribution of 74 L/m2 after 100 mg/m2, every 3 weeks. The mean total body clearance after this schedule is approximately 22 L/h/m2, principally because of hepatic metabolism by the cytochrome P450 (CYP)3A4 system and biliary excretion into the faeces. Renal excretion is minimal (< 5%). Docetaxel is > 90% bound in plasma. Population pharmacokinetic studies of docetaxel have demonstrated that clearance is significantly decreased with age, decreased body surface area, increased concentrations of alpha 1-acid glycoproteinand albumin. Importantly, patients with elevated plasma levels of bilirubin and/or transaminases have a 12 to 27% decrease in docetaxel clearance and should receive reduced doses. Although docetaxel is metabolised by CYP3A4, phase I combination studies have not shown major evidence of significant interaction between docetaxel and other drugs metabolised by the same pathway. Nevertheless, care should be taken with the use of known CYP3A4 inhibitors such as erythromycin, ketoconazole and cyclosporin. Conversely, increased doses may be required for patients receiving therapy known to induce this cytochrome (e.g. anticonvulsants). Perliminary data suggest the erythromycin breath test, an indicator of CYP3A4 function, is a predictor of toxicity after treatment with docetaxel. Such methodologies may eventually enable clinicians to individualise doses of docetaxel for patients with cancer.

Animals↗
PubMed1998

Comparison of plasma and tissue levels of ZD1694 (Tomudex), a highly polyglutamatable quinazoline thymidylate synthase inhibitor, in preclinical models.

ZD1694 (Tomudex, raltitrexed) is a specific quinazoline antifolate thymidylate synthase inhibitor that relies on polyglutamation for high potency. Antibodies to ZD1694 have been used to establish a sensitive radioimmunoassay as an alternative to high-performance liquid chromatography (HPLC). The radioimmunoassay is reproducible, accurate and provides a means of determining low levels of ZD1694 in plasma (< 1 nM). By virtue of the high cross-reactivity of the antibodies with polyglutamated forms of ZD1694, it is also possible to measure the total concentration of drug in tissues. Results obtained in L1210 mouse leukaemia cells and in mouse tissues were similar to those previously determined using radiolabelled drug. Pharmacokinetic studies in mice have confirmed that the compound is rapidly eliminated from the plasma and that there is a prolonged terminal elimination phase. ZD1694 was measured in plasma (0.56 ng ml(-1); 1.2 pmol ml(-1)) up to 7 days after a single i.p. dose of 100 mg kg(-1) ZD1694. Liver, kidney and gut epithelium had a substantially higher level of ZD1694 immunoreactivity than plasma. For example, 24 h after a single i.p. dose at 1, 10 and 100 mg kg(-1), total drug levels in the liver were 480, 325 and 152 times higher than plasma levels respectively. In kidney and gut epithelium, total drug levels at these doses were approximately 55 and 34 times those of plasma. The high tissue to plasma ratios were maintained for at least 7 days after administration. Similarly, high tissue to plasma ratios (> 100) were found in dogs treated with a clinically relevant dose of ZD1694. These were maintained for 4 weeks in liver and kidney tissue (> 100). Total gastrointestinal concentrations of ZD1694 were approximately 10 times higher than plasma 3 days after administration, but levels were near to the limit of detection at 4 weeks. These results are consistent with extensive polyglutamation of ZD1694 within tissues in both mice and dog and provide further support for the infrequent schedule that has been used clinically. Although it has not been possible to measure individual polyglutamated forms of ZD1694, the radioimmunoassay provides a convenient means of assessing total drug levels in tissues and is currently the only method suitable for measuring the extent of drug retention in normal tissue and tumour biopsies obtained from patients treated with ZD1694.

Animals↗
PubMed1998

An exploration of screening practices for prostate cancer and the associated community expenditure.

OBJECTIVES: To determine: (i) the prevalence, reasons for, and demographic and psychosocial predictors of prostate cancer screening among a randomly selected sample of men; and (ii) to estimate the community expenditure involved in the screening of asymptomatic men. SUBJECTS AND METHODS: A random sample of men aged 40-79 years was selected from the State Electoral Register of New South Wales, Australia, and asked to complete a computer-assisted telephone interview. The questions determined their demographic characteristics, their subjective health rating compared with others of the same age (5-point scale), the prevalence and reasons for any screening for prostate cancer ('ever screened' and 'screened within the last 12 months'), whether they had undergone a digital rectal examination (DRE), a blood test for prostate-specific antigen (PSA) or transrectal ultrasonography (TRUS), and the prevalence of urinary symptoms. Those who had been screened were then asked to nominate the single most important factor in the decision to undergo prostate cancer screening. To estimate community expenditure, the costs for prostate cancer screening were estimated by applying Medicare schedule charges to the screening and subsequent diagnostic tests performed. Two scenarios were developed to estimate costs: the first used guidelines which do not recommend the use of routine screening for all asymptomatic men, and the second was based on guidelines where the routine use of PSA or TRUS as part of a periodic health examination is not recommended, but the use of DRE in asymptomatic men aged 50-70 years is. RESULTS: Of the 551 eligible participants, 86% completed the interview; 44% of participants reported that they had 'ever' been screened, whilst 23% had been screened in the year before the study. Among those who had been screened, the reason reported most often for screening, apart from symptoms and family history, was the doctor's recommendation after a medical assessment of their prostate cancer risk status. Screening status was predicted both by the age of the man and his symptom score. As a result, the community expenditure in New South Wales for screening among asymptomatic men was estimated to be A$6.4 million and A$5.2 million for the first and second scenarios, respectively. CONCLUSIONS: The results of this study suggest that, despite the recommendations of primary bodies that asymptomatic men not be screened for prostate cancer, screening is occurring at a high level and with significant costs to the healthcare system.

Adult↗
PubMed1998

Non-surgical therapy for patients with advanced non-small cell lung cancer.

Non-small cell lung cancer is the major cancer problem in the Western World. Treatment and prognosis are highly stage dependent, although overall only 5-10% of patients will be alive 5 years after diagnosis. Patients with early stage disease are treated with surgery alone. However, for patients with locally advanced disease there is increasing evidence that combined modality approaches, incorporating chemotherapy, radiotherapy and/or surgery result in modest improvements in survival. For patients with metastatic non-small cell lung cancer there is evidence from metaanalyses and randomised studies that chemotherapy results in improvements in both duration and quality of life. Despite these advances, there is substantial room for further improvement and therefore, wherever possible, patients should be enrolled in well designed clinical studies.

Antineoplastic Agents↗
PubMed1998

Clinical management and treatment outcomes of Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC), first described in 1972, is an uncommon, highly malignant tumour of skin. Its aetiology is unknown although the tumour occurs most frequently in sun-exposed sites. This skin cancer is characterized by a high incidence of metastases, local and regional recurrence and has a high mortality. Few survival data beyond 3 years are available. Treatment strategies include wide local excision of the primary and lymph node dissection, as indicated together with adjuvant radiotherapy. The tumour has also been shown to be chemosensitive. Definitive treatment is inconclusive due to the relative rarity of this malignancy. METHODS: A retrospective study was undertaken between the years 1985 and 1996 of 33 patients with MCC at Concord Repatriation General Hospital (CRGH). Demographic details were noted, together with the site and appearance of the primary lesion and the sites and date of metastases. The response and outcome to various modalities of treatment were documented. RESULTS: There were 27 men and six women with an average age of 80 years (range: 60-86 years). The primary lesion in the present series most often resembled a basal cell carcinoma (BCC), with 53% occurring in the head and neck region. Twenty-seven patients (82%) developed metastatic disease, with an average interval of 13.4 months between diagnosis of the primary lesion and the development of metastases. The incidence of locoregional recurrence in the present series was 42%. Radiation combined with surgery achieved locoregional control in 15 of 19 patients with primary, regional or recurrent locoregional disease. Fourteen patients died of MCC and five others from unrelated causes. The 14 survivors have a mean survival of 54 months with six patients surviving more than 5 years. CONCLUSIONS: Local excision together with regional lymph node clearance as indicated, combined with adjuvant radiation treatment was associated with an improved survival. The role of chemotherapy remains unclear.

Aged↗
PubMed1997

Recent advances in managing non-small-cell lung cancer: 4. Chemotherapy of metastatic cancer.

Chemotherapy has been shown to prolong survival and to be cost effective in the palliative treatment of non-small-cell lung cancer. A meta-analysis of 11 randomised trials has found a small benefit from combination chemotherapy in advanced NSCLC, increasing one-year survival rates from 5% to 15%. New combination regimens, especially carboplatin-paclitaxel, show higher response rates in selected patients, and promise improved survival rates, but this has yet to be confirmed in randomised trials.

Antimetabolites, Antineoplastic↗
PubMed1996

Long-term follow-up of a randomised trial of combined chemoradiotherapy induction treatment, with and without maintenance chemotherapy in patients with small cell carcinoma of the lung.

The toxicity and efficacy of concomitant chemotherapy and radiotherapy as induction therapy was evaluated in patients with previously untreated small cell carcinoma of the lung (SCLC), and in responding patients the value of maintenance chemotherapy was examined. 202 patients received induction chemotherapy with cisplatin and etoposide (EP), in combination with cranial and local radiotherapy. 85 patients (42%) developed grades III and IV myelosuppression, the main toxicity of induction treatment. Of the 154 responding patients, 129 were randomised to maintenance chemotherapy with vincristine, doxorubicin and cyclophosphamide (VAC) or no further treatment. The response rate for the limited disease patients (LD) was 87%, 62% achieving a complete response (CR) and the response rate for extensive disease patients (ED) was 68%, with 26% achieving a CR. 17 patients (11%) completed 10 courses of maintenance chemotherapy. 32 patients (57%) developed grade III and IV neutropenia. Median survival for all patients was 53 weeks (LD, 70 weeks; ED, 42.5 weeks). There was no significant difference in overall survival (OS) or disease-free survival (DFS) in the two randomisation arms. This study shows that EP combined with radiotherapy is an effective induction regimen in SCLC. Maintenance chemotherapy with VAC is not associated with increased survival but has significant toxicity after such induction treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Phase I trial of ZD1694, a new folate-based thymidylate synthase inhibitor, in patients with solid tumors.

PURPOSE: To perform a phase I clinical and pharmacologic study of ZD1694 (Tomudex, Alderley Park, United Kingdom), a new folate-based thymidylate synthase (TS) inhibitor, in patients with advanced malignancy. PATIENTS AND METHODS: From February 1991 to January 1993, 61 patients with a range of solid tumor received 161 courses of ZD1694 given as a single 15-minute intravenous infusion every 3 weeks, at escalating doses from 0.1 to 3.5 mg/m2. Pharmacokinetic (PK) analysis was performed with the first two courses of treatment. There were 33 men and 28 women with a median age of 53 years (range, 21 to 73). Fifty-five patients (90%) had previously received chemotherapy. RESULTS: Reversible liver toxicity and dose-related gastrointestinal (GI) and bone marrow toxicity occurred at > or = 1.6 mg/m2. Liver function usually returned to normal with repeated treatment, but GI and bone marrow toxicities generally became more severe. No renal toxicity was observed. The maximum-tolerated dose (MTD) was 3.5 mg/m2, at which, in addition to antiproliferative toxicities, four of six patients (67%) developed severe malaise that consisted of anorexia, nausea, and asthenia, with rapidly decreasing performance status that limited re-treatment. Abnormal liver function was also seen in four patients (67%). At 3.0 mg/m2, grades III and IV diarrhea were seen in six of 23 patients (26%) and grade IV myelosuppression in two others. Liver toxicity was self-limiting and not associated with severe malaise. Two patients had a partial response to treatment. PK analysis showed that plasma elimination was triexponential, with pronounced variability in the mean terminal half-life (t1/2gamma) for a given dose ranging from 8.2 to 105 hours. There was a linear relationship between dose and both the area under the concentration-time curve (AUC) and maximum concentration (Cmax), but no clear association between these parameters and response or toxicity. CONCLUSION: The dose of ZD1694 recommended for phase II trials is 3.0 mg/m2.

Adult↗
PubMed1993

The history of the development and clinical use of CB 3717 and ICI D1694.

The antifolate thymidylate synthase inhibitors represent an exciting area in new drug development and show that with an understanding of the structural basis for toxicity, new drugs can be synthesised which have a more manageable spectrum of side effects whilst retaining activity. ICI D1694 does not show the nephrotoxicity which affected the development of CB 3717. Myelosuppression and gut toxicity are seen and are more typical of the toxicities one associates with this class of agent. Changes in hepatic enzymes have been seen with both drugs, and are also seen with other anti-folates including MTX, but these changes settle with repeat dosing and with cessation of treatment. We await the results of the planned phase II trials of ICI D1694 with great interest.

Animals↗
PubMed1992

Social intervention and the elderly: a randomized controlled trial.

A randomized controlled trial was set up in 1985 to test the effect of social intervention over 3 years among elderly people, aged 75 and above, living alone. The sampling frame was the age/sex register of a large group practice of 12 general practitioners serving the town of Melton Mowbray, Leicestershire, England, with a list size of approximately 32,000 patients. A total of 523 elderly people living alone in 1985 were identified, interviewed, and randomized into experimental and control groups. A lay worker offered the experimental group (n = 261) individual packages of support that aimed at enhanced social contacts. The outcome measures, approximately 3 years later in 1988, were mortality; changes in physical status; demand for medical, paramedical, social, and voluntary services; and changes in a number of subjective variables (morale, loneliness, and self-perceived health). No significant differences were found for any of the variables with the exception of self-perceived health status, where the experimental group showed significantly greater improvements than did the control group. More importantly, half the elderly in this sample declined several offers of help.

Activities of Daily Living↗
PubMed1992

Transferrin: a potential source of iron for oxygen free radical-mediated endothelial cell injury.

The ability of transferrin to potentiate oxygen free radical-mediated endothelial cell injury was assessed. 51Cr-labeled endothelial cells derived from rat pulmonary arteries (RPAECs) were incubated with hydrogen peroxide (H2O2) in the presence and absence of holosaturated human transferrin, and the effect of transferrin on H2O2-mediated endothelial cell toxicity was determined. Addition of holosaturated transferrin potentiated H2O2-mediated RPAEC cytotoxicity at concentrations of H2O2 greater than 10 microM, suggesting that transferrin may provide a source of iron for free radical-mediated endothelial cell injury. Free radical-mediated injury is dependent on non-protein-bound iron. The ability of RPAECs to facilitate the release of iron from transferrin was assessed. We determined that RPAECs facilitate the release of transferrin-derived iron by reduction of transferrin-bound ferric iron (Fe3+) to ferrous iron (Fe2+). The reduction and release of transferrin-derived Fe2+ were inhibited by apotransferrin and chloroquine, indicating a dependence on receptor-specific binding of transferrin to the RPAEC cell surface, with subsequent endocytosis, acidification, and reduction of transferrin-bound Fe3+ to Fe2+. The release of transferrin-derived Fe2+ was potentiated by diethyldithiocarbamate, an inhibitor of intracellular superoxide dismutase (SOD). In contrast, exogenous SOD did not alter iron release, suggesting that intracellular superoxide anion (O2-) may play an important role in mediating the reduction and release of transferrin-derived iron. Results of this study suggest that transferrin may provide a source of iron for oxygen free radical-mediated endothelial cell injury and identify a novel mechanism by which endothelial cells may mediate the reduction and release of transferrin-derived iron.

Animals↗
PubMed1992

Cardiovascular and vasoactive hormone responses to bladder distension in spinal and normal man.

Many patients with high spinal cord injury experience exaggerated blood pressure rises in response to bladder distension. To examine the humoral mechanisms associated with these responses, ECG heart rate, blood pressure and vasoactive hormone levels were measured at baseline and during bladder distension following slow bladder filling in 23 subjects: 9 high spinal lesion patients, 7 low spinal lesion patients and 7 normal control subjects. Systolic blood pressure rose significantly during bladder distension in the high spinal lesion group by an average of 56 mm Hg (48%) and diastolic blood pressure rose by 22 mm Hg (47%), while heart rate fell by a mean of 7.4 beats per minute (15%). By contrast, neither systolic or diastolic blood pressure nor heart rate changed significantly during bladder distension in the low spinal lesion or normal control group. There were no significant changes in plasma levels of noradrenaline, renin, aldosterone, vasopressin, arginine, or atrial natriuretic peptide during bladder distension to account for the blood pressure rise in the high spinal lesion group. These findings suggest that humoral mechanisms are unlikely to play a major role in the mediation of pressor responses to bladder distension in high spinal lesion patients.

Blood Pressure↗
PubMed1992

Effect of acute inflammatory lung injury on the expression of monocyte chemoattractant protein-1 (MCP-1) in rat pulmonary alveolar macrophages.

Using a well-characterized rat model of immune complex-mediated acute inflammatory lung injury, we determined that there is a time-dependent elaboration of monocyte chemotactic activity in bronchoalveolar lavage fluid. Monocyte chemotactic activity is also significantly enhanced in culture supernatants from pulmonary alveolar macrophages (PAMs) from injured rat lungs. Northern hybridization analysis revealed markedly increased expression of rat monocyte chemoattractant protein 1 (MCP-1) mRNA in PAMs obtained from rats with immune complex-induced lung injury. The increased expression of MCP-1 mRNA and associated increase in monocyte chemotactic activity present in culture supernatants of PAMs from injured rat lungs suggest that PAMs may participate in the pathogenesis of acute inflammatory lung injury by the secretion of monocyte chemoattractants including MCP-1.

Animals↗