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Biomedical subjects

R P Warrell

Publications and source records attributed to R P Warrell.

At least 91 records · Page 5Linked to original sources
PubMed1990

Phase I clinical and pharmacological study of merbarone.

Merbarone, a nonsedating derivative of thiobarbituric acid, has demonstrated excellent activity against certain murine tumors, including L1210 and P388 leukemias, B16 melanoma, and M5076 sarcoma. Preclinical studies suggested that the antitumor effects of this drug were schedule dependent, since repeated dosing increased killing of tumor cells when compared to intermittent injections. We have completed a Phase I clinical and pharmacological study of merbarone in which the drug was administered both as a 2-h infusion and as a continuous i.v. infusion over 24 h. In view of the increased toxicity observed in animals following bolus injections and the possibility of schedule-dependent anticancer activity, a schedule of drug administration daily for 5 days was selected. Fifty patients with advanced cancer were treated at dose levels that ranged from 100 to 1500 mg/m2/day. When the drug was administered by peripheral vein, phlebitis was observed at the infusion site at daily doses greater than or equal to 150 mg/m2. Therefore, all patients who received drug doses greater than or equal to 200 mg/m2 were treated by continuous i.v. infusion using central venous catheters. Renal insufficiency, initially observed at a dose of 1000 mg/m2/day, was the dose-limiting toxic reaction at 1500 mg/m2/day. Three of five patients treated at the highest dose level were unable to complete the infusion due to this effect. Marked hypouricemia was observed in all patients. Other toxic effects were mild and included nausea, fatigue, leukopenia, thrombocytopenia, and anorexia. Alopecia was noted in several patients who received doses greater than or equal to 1000 mg/m2/day. No major antitumor effects were observed. Dose-dependent, steady-state plasma concentrations of merbarone were reached within 24-48 h after beginning the continuous i.v. infusion. Elimination of drug from plasma followed a two-compartment model, with a t1/2 alpha of 4.2 h and a t1/2 beta of 15.3 h. Renal excretion of merbarone and its major metabolites accounted for less than 30% of the administered dose. We conclude that merbarone is relatively well tolerated with few constitutional symptoms. The current formulation of the drug causes phlebitis when administered by peripheral vein, and renal insufficiency is commonly observed at daily doses which exceed 1250 mg/m2. The recommended dose for extended Phase II evaluation is 1000 mg/m2/day daily for 5 days administered by central venous catheter.

Adult↗
PubMed1990

Trace elemental analysis in bone using x-ray microscopy.

Following in vivo administration of gallium nitrate, the greatest concentrations of the therapeutic element gallium localized in the metaphysis and at the endosteal and periosteal surfaces of the diaphysis. These are the regions of greatest metabolic activity, where new bone formation and remodeling are occurring. The lowest levels of gallium were noted in the mid-cortical region of the diaphyseal shaft where bone turnover is least. The accumulation of gallium in the metaphysis was associated with a concomitant fall in iron and zinc. The gallium-induced change in the metaphysis may reflect a subtle modulation of metal dependent enzymes that are necessary for the active bone modeling that occurs in this bone region. X-ray microscopy has provided the first insights into the localization and possible mechanisms of action of gallium in bone.

Animals↗
PubMed1990

Distribution of trace levels of therapeutic gallium in bone as mapped by synchrotron x-ray microscopy.

Gallium nitrate, a drug that inhibits calcium release from bone, has been proven a safe and effective treatment for the accelerated bone resorption associated with cancer. Though bone is a target organ for gallium, the kinetics, sites, and effects of gallium accumulation in bone are not known. We have used synchrotron x-ray microscopy to map the distribution of trace levels of gallium in bone. After short-term in vivo administration of gallium nitrate to rats, trace (nanogram) amounts of gallium preferentially localized to the metabolically active regions in the metaphysis as well as the endosteal and periosteal surfaces of diaphyseal bone, regions where new bone formation and modeling were occurring. The amounts measured were well below the levels known to be cytotoxic. Iron and zinc, trace elements normally found in bone, were decreased in amount after in vivo administration of gallium. These studies represent a first step toward understanding the mechanism(s) of action of gallium in bone by suggesting the possible cellular, structural, and elemental "targets" of gallium.

Animals↗
PubMed1989

Induction of profound hypouricemia by a non-sedating thiobarbiturate.

5-[N-phenylcarboxamido]-2-thiobarbituric acid (merbarone) is a non-sedating derivative of thiobarbituric acid originally developed for anticancer use. In the initial clinical study, a profound reduction in serum uric acid was observed. In 20 patients who received five daily doses of merbarone ranging from 100 to 750 mg/m2, serum uric acid concentration was reduced from a mean pretreatment value of 5.7 +/- 1.6 mg/dL to a mean lowest value of 1.3 +/- 0.5 mg/dL. In most patients, the onset of the effect occurred with 24 hours and was maximal by 48 to 72 hours. Metabolic studies in two patients showed an increase in urinary uric acid excretion within 24 hours after initiation of drug treatment. A marked increase in fractional excretion of uric acid was sustained throughout the period of drug treatment. Urinary excretion of total oxypurines (xanthine and hypoxanthine) was increased twofold to threefold relative to baseline levels. Ultrafiltration studies showed that merbarone did not significantly displace binding of urate from albumin. When merbarone was incubated with xanthine oxidase in vitro, several reaction products were observed, including 2-oxo-2-desthio-merbarone and a compound with retention time similar to 4'-OH-merbarone. Both of these compounds have been described previously as metabolites of merbarone in human subjects. The parent drug and both metabolites were found to inhibit xanthine oxidase (Ki = 41, 36, and 240 mumols/L, respectively). However, this inhibitory effect was substantially less potent than allopurinol (Ki = 0.025 mumols/L). This study indicates that merbarone induces profound hypouricemia primarily by increasing uric acid excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1988

Effect of gallium on bone mineral properties.

Gallium nitrate is biologically active in blocking bone resorption in vitro as well as in vivo. Administration of gallium nitrate to growing rats results in a dose-dependent accumulation of low levels of gallium in bone that is associated with specific changes in the mineral properties of bone. To elucidate in greater detail the changes induced by gallium, the properties of whole and density-fractionated bone samples from control and gallium-treated rats were examined. These studies showed that short-term treatment with gallium nitrate caused an increase in bone calcium and phosphate content. Devitalized bone powder from the gallium-treated rats was less soluble in acetate buffer and less readily resorbed by monocytes. Density fractionation analyses demonstrated that the largest proportion (76% by weight) of powdered metaphyseal bone particles from rats had a density of less than 2.15 g/cc. Following short-term treatment (14 days) with gallium nitrate (45 mg/kg body weight), a significant increase in the relative proportion of more dense bone (greater than or equal to 2.15 g/cc) was observed (24% for the control vs. 39% for the gallium-treated rats, P less than 0.01). In the diaphyseal samples, the largest proportion (88% by weight) of the bone powder had a density of greater than or equal to 2.15 g/cc. After short-term treatment with gallium, a slight decrease in mean diaphyseal particle density was observed. Measurement of calcium accretion with 45Ca in the gallium-treated rats demonstrated increased specific activity in the metaphyseal bone samples, densities = 2.0, 2.1, 2.15, and 2.25 g/cc; the difference was significant only for the 2.25 g/cc fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Gallium nitrate for acute treatment of cancer-related hypercalcemia. A randomized, double-blind comparison to calcitonin.

STUDY OBJECTIVE: To determine whether gallium nitrate therapy is superior to maximally approved doses of calcitonin for acute control of cancer-related hypercalcemia. DESIGN: Randomized, double-blind comparison of active treatments. SETTING: Comprehensive cancer center. PATIENTS: One hundred ninety-eight consecutive hypercalcemic events in 164 patients screened for entry. ELIGIBILITY CRITERIA: hospitalization and intravenous hydration for at least 2 days; persistent elevated serum calcium levels of 2.99 mmol/L or greater (adjusted for serum albumin); serum creatinine levels of 221 mumol/L or less; no cytotoxic chemotherapy, radiation, or mithramycin within the preceding 7 days or during study; no concurrent use of aminoglycoside antibiotics; life expectancy greater than 4 weeks; lymphoma and parathyroid carcinoma excluded. Patients were stratified by histologic type of tumor (epidermoid or nonepidermoid). Fifty patients were randomized and treated. INTERVENTIONS: Gallium nitrate 200 mg/m2 body surface area for 5 days by continuous intravenous infusion, or salmon calcitonin 8 IU/kg body weight every 6 hours for 5 days by intramuscular injection. Patients randomized to receive gallium nitrate received sham injections of saline to simulate calcitonin; patients randomized to receive calcitonin received 1000 mL 5%-dextrose solution to simulate gallium nitrate. MEASUREMENTS AND MAIN RESULTS: All patients were evaluable. Eighteen of twenty-four patients who received gallium nitrate achieved normocalcemia compared with 8 of 26 patients who received calcitonin for an observed difference of 44% (95% confidence interval, 19% to 69%; P = 0.002). Median duration of normocalcemia before other cytotoxic or hypocalcemic therapy was 6 days for patients treated with gallium nitrate compared with 1 day for patients treated with calcitonin (P less than 0.001). Median duration of normocalcemia regardless of intercurrent treatment and without adjustment for serum albumin was 11+ days for patients treated with gallium nitrate and 2 days for patients treated with calcitonin (P less than 0.01). Mean daily fluid intake and mean daily dose of furosemide were similar in both treatment groups. No additional benefit was seen in 9 patients randomized to receive calcitonin who incidentally received corticosteroids. CONCLUSIONS: Gallium nitrate therapy is highly effective and superior to maximally approved doses of calcitonin for acute control of cancer-related hypercalcemia.

Adult↗
PubMed1987

Gallium nitrate inhibits accelerated bone turnover in patients with bone metastases.

Bone metastases are a major source of morbidity in patients with cancer. Previously, we found that gallium nitrate was a highly effective treatment for cancer-related hypercalcemia. Laboratory studies have shown that this drug inhibits bone resorption in vitro and that short-term treatment in vivo increases the calcium content of bone. We evaluated the clinical effects of gallium nitrate on biochemical parameters of increased bone turnover in 22 patients with bone metastases. Treatment with gallium nitrate for five to seven days caused a median reduction in 24-hour urinary calcium excretion of 66% relative to baseline measurements (P less than .01). Hydroxyproline (OHP) excretion was also significantly reduced (P less than .01). The greatest reduction in hydroxyprolinuria occurred in patients with high baseline excretion. Ionized serum calcium and serum phosphorous declined significantly after treatment (P less than .01 for each). Serum immunoreactive parathyroid hormone (PTH) increased significantly (P less than .01), as did serum levels of 1,25 (OH)2-vitamin D3 (P less than .05). Urinary phosphorous excretion and serum levels of 25-OH-vitamin D3 were not significantly changed. No major toxic reactions occurred as a result of this treatment. These results indicate that gallium nitrate significantly reduces biochemical parameters associated with accelerated bone turnover and that this agent may be useful for preventing pathologic conditions associated with bone metastases.

Adult↗
PubMed1987

Gallium nitrate for treatment of refractory hypercalcemia from parathyroid carcinoma.

Intractable hypercalcemia is the major cause of morbidity and mortality in patients with parathyroid carcinoma. Because gallium nitrate previously was shown to inhibit the bone resorptive activity of parathyroid hormone (PTH) in vitro, we used it to treat two patients with parathyroid carcinoma and resistant hypercalcemia. In both patients, total serum calcium levels were reduced from initial values of 3.62 and 3.77 mmol/L to posttreatment values of 2.32 and 1.45 mmol/L, respectively. Urinary excretion of calcium and hydroxyproline also declined significantly. Serum PTH levels were lower in both patients after therapy, although all levels remained markedly elevated. Nephrogenous cyclic adenosine monophosphate and tubular reabsorption of phosphate remained unchanged. These data indicate that treatment with gallium nitrate can control hypercalcemia in patients with high circulating levels of PTH. Gallium nitrate antagonizes the bone resorptive activity of PTH without altering renal effects of the hormone.

Adult↗
PubMed1987

Salvage chemotherapy of advanced lymphoma with investigational drugs: mitoguazone, gallium nitrate, and etoposide.

Patients with advanced lymphoma who relapse from intensive first-line combination chemotherapy generally have a very poor prognosis. The use of investigational drugs which lack cross-resistance to agents commonly used for initial therapy represents an important approach to the management of such patients. Based upon our prior experience, we developed a protocol which employed a combination of three new agents. Mitoguazone (600 mg/m2) was administered on Days 1 and 10; etoposide (100-125 mg/m2) was administered on Days 2, 3, and 4; and gallium nitrate (300 mg/m2/day) was administered as a continuous iv infusion over 24 hours on Days 1-7. Treatment cycles were repeated every 3-4 weeks pending tolerance to toxic reactions. Forty-two patients are evaluable for response (35 with non-Hodgkin's lymphoma and seven with Hodgkin's disease). All patients had received extensive prior treatment (median of two previous chemotherapy regimens). Less than one-half of patients had achieved complete remission (CR) with previous therapy. Twenty-two patients (52%) showed major antitumor responses (five CR, 17 partial). All patients who achieved CR had diffuse large cell lymphoma. Two patients in CR relapsed in the CNS. The median duration of response for patients who achieved partial response was 4 months (range, 1-11+). Major toxic reactions included myelosuppression, optic neuritis, mucositis, and corneal keratitis or conjunctivitis. This combination of experimental agents has major therapeutic activity in patients with advanced, resistant lymphoma. Optimal application of these drugs may be obtained by use as one arm of an intensive program of alternating non-cross-resistant regimens.

Adult↗
PubMed1986

Clinical study of a new antimetastatic compound, Nafazatrom (Bay g 6575). Effects on platelet consumption and monocyte prostaglandin production in patients with advanced cancer.

Nafazatrom (Miles Laboratories, West Haven, CT) is a potent inhibitor of metastasis in several animal model systems. The compound is active whether cancer cells are injected intravenously or are allowed to spontaneously metastasize from established tumors. Before studying the antimetastatic effects of Nafazatrom in a long-term randomized clinical trial, the authors conducted a preliminary study to evaluate its toxicity as well as its effects on certain parameters hat have been associated with the biology of metastasis. Since the interaction of platelets, monocytes, and tumor cells may be important for metastasis formation, the authors serially evaluated plasma levels of factors secreted from activated platelets (beta-thrombo-globulin and platelet factor 4) that are inversely correlated with platelet survival. Products of arachidonate metabolism from monocytes were also measured since Nafazatrom is known to modulate prostaglandin production. Thirty-one patients received doses of Nafazatrom ranging from 75 to 1500 mg/m2 orally three times a day. The dose was escalated every 2 weeks. There was no toxicity at any dose level. No major antitumor responses were observed. There was no consistent change in levels of platelet factors either within individual patients or for the population as a whole. Although Nafazatrom (20 microM) decreased tritiated arachidonate incorporation into peripheral blood monocytes from normal subjects in vitro, this effect was not seen in patients treated with the drug. Release of 3PGE2 and 3HETE from cultured monocytes was also not altered by treatment with Nafazatrom. It was concluded that Nafazatrom is safe and well-tolerated up to total doses of 4500 mg/day. The data suggest that the antimetastatic activity of Nafazatrom in vivo is mediated by mechanisms other than by a decrease in platelet consumption or by modulation of arachidonate metabolism by monocytes.

Adult↗
PubMed1986

Gallium increases bone calcium and crystallite perfection of hydroxyapatite.

Gallium, a group IIIa metal, is known to interact with hydroxyapatite as well as the cellular components of bone. In recent studies we have found gallium to be a potent inhibitor of bone resorption that is clinically effective in controlling cancer-related hypercalcemia as well as the accelerated bone resorption associated with bone metastases. To begin to elucidate gallium's mechanism of action we have examined its effects on bone mineral properties. After short-term (14 days) administration to rats, gallium nitrate produced measurable changes in bone mineral properties. Using atomic absorption spectroscopy, low levels of gallium were noted to preferentially accumulate in regions of active bone formation, 0.54 +/- .07 microgram/mg bone in the metaphyses versus 0.21 +/- .03 microgram/mg bone in the diaphyses, P less than 0.001. The bones of treated animals had increased calcium content measured spectrophotometrically. Rats injected with radiolabeled calcium during gallium treatment had greater 45-calcium content compared to control animals. By wide-angle X-ray analyses, larger and/or more perfect hydroxyapatite was observed. The combined effects of gallium on bone cell function and bone mineral may explain its clinical efficacy in blocking accelerated bone resorption.

Animals↗
PubMed1986

Phase I and II study of fludarabine phosphate in leukemia: therapeutic efficacy with delayed central nervous system toxicity.

Fludarabine phosphate (9-beta-D-arabinofuranosyl-2-fluoroadenine), a novel purine nucleoside, has demonstrated excellent preclinical antitumor activity and little toxicity in phase I clinical trials. We evaluated the clinical use of fludarabine given as a continuous intravenous (IV) infusion for remission induction in patients with relapsed or refractory leukemia. Thirty infusions were administered to 25 patients. At doses less than or equal to 125 mg/m2/d for five days, only three of 17 patients cleared their bone marrow of leukemic cells, and none achieved complete remission (CR). Nine patients received doses of 150 mg/m2/d for five days or 125 mg/m2/d for seven days. Four of these patients achieved CR (three patients with acute nonlymphoblastic leukemia (ANLL), one patient with acute lymphoblastic leukemia (ALL]. However, severe CNS toxicity was encountered in five patients at the two highest dose levels. Initial symptoms of neurotoxicity were delayed from 21 to 43 days after starting treatment and consisted of optic neuritis, cortical blindness, altered mental status, and generalized seizure. Only one patient regained visual and neurologic function; four other patients experienced progressive neurologic deterioration and died. Clinicopathologic evaluation suggested widespread, severe demyelination as the etiology of these reactions. We conclude that fludarabine is an effective drug for remission induction in acute leukemia. However, doses required to achieve CR are associated with unacceptable CNS toxicity. In view of its potent antileukemic activity, further evaluation of fludarabine at lower doses (less than or equal to 75 mg/m2/d for five days) may be warranted in combination with other chemotherapeutic agents for the treatment of patients with acute leukemia.

Acute Disease↗
PubMed1986

Aclacinomycin A: clinical development of a novel anthracycline antibiotic in the haematological cancers.

Aclacinomycin A (aclarubicin; ACM) is a new class II anthracycline antibiotic. Preclinical studies suggested that ACM had approximately equivalent antitumour activity but produced substantially less cardiotoxicity compared to other anthracyclines. Because of the recognized importance of these compounds in the treatment of haematological tumours, clinical trials of ACM were initiated in the late 1970s. ACM has been extensively evaluated in patients with relapsed leukaemia and advanced malignant lymphoma. Analysis of results compiled from Europe, Japan, and the United States shows that ACM is probably equivalent to doxorubicin for remission induction of patients with relapsed acute non-lymphoblastic leukaemia. Initial studies using ACM alone and in combination with standard cytotoxic drugs in previously untreated patients compare favourably with the best standard treatment for this disease. The antitumour activity of ACM in patients with acute lymphoblastic leukaemia or malignant lymphoma who have previously received doxorubicin or daunorubicin is low, and the issue of whether ACM lacks clinical cross-resistance to other anthracyclines is unresolved. Acute cardiac arrhythmias have been observed following administration of ACM, but congestive cardiomyopathy has been uncommon. Results to date all indicate that ACM has fulfilled its early expectations of antileukaemic activity and reduced toxicity. These hypotheses should now be evaluated in prospective, randomized trials with conventional anthracyclines.

Aclarubicin↗