A phase I-II study of 9-cis retinoic acid and interferon-alpha2b in patients with advanced renal-cell carcinoma: an NCIC Clinical Trials Group study.

Although advanced renal-cell carcinoma (RCC) responds poorly to standard therapies, phase I-II trials have shown activity for combinations of interferon-alpha2b (IFN) with a retinoid. Alitretinoin (9-cis RA) is an endogenous retinoid with high binding affinity for both RAR and RXR receptor families. This phase I-II study enrolled 38 patients with RCC in a dose-escalation study of tolerability, pharmacokinetics (PK), and efficacy of twice daily oral 9-cis RA with subcutaneous IFN. In contrast to studies with similar doses of daily 9-cis RA, PK studies found a consistent reduction in 9-cis RA concentrations of about 50% after multiple b.i.d. doses of 30 or 50 mg/m2, independent of cotreatment with IFN. In the phase I portion, toxicities included systemic symptoms typical of IFN and biochemical abnormalities previously associated with retinoids. Two patients experienced dose-limiting toxicity at 50 mg/m2 b.i.d. of 9-cis RA, thus the recommended phase II dose was 30 mg/m2 b.i.d. One of twenty-six evaluable patients achieved a durable objective partial remission, and repeated dosing with this regimen was poorly tolerated. This combination of retinoid and interferon is not recommended for further study in RCC.

Phase I study of 9-cis-retinoic acid (ALRT1057 capsules) in adults with advanced cancer.

9-cis-Retinoic acid (9-cis-RA) and all-trans-RA (ATRA) are naturally occurring hormones. The nuclear receptors that mediate the effects of retinoids are the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). ATRA binds RAR with high affinity but does not bind to RXR, whereas 9-cis-RA, an isomer of ATRA, is a ligand that binds and transactivates both RARs and RXRs. The goals of this study were to determine the safety, tolerability, pharmacokinetics, and metabolic profile of 9-cis-RA in advanced cancer patients. Forty-one patients received oral 9-cis-RA (ALRT1057; Panretin capsules) at doses ranging from 5-140 mg/m2/day. Twenty-six patients were treated once daily with up to 140 mg/m2; a subsequent cohort of 15 patients were treated twice daily (b.i.d.) at 100-140 mg/m2/day (50, 60, and 70 mg/m2 b.i.d.) to evaluate a b.i.d. dosing regimen. Headache was the most frequent adverse event and was dose limiting in 3 of 41 patients. Skin toxicity was the next most common toxicity and was seen in 11 of 41 patients; it was typically mild and limited to skin dryness and erythema. Other toxicities included conjunctivitis, flushing, diarrhea, transaminitis, hypercalcemia, and asymptomatic hypertryglyceridemia. Toxicities were typically dose related, occurred primarily above 83 mg/m2/day, and were not ameliorated by b.i.d. dosing. No tumor responses were observed. The mean day 1 area under the plasma concentration-time curve and peak plasma concentration values were dose-proportional over all dose levels, whereas day 15 area under the plasma concentration-time curve and peak plasma concentration values were nonlinear above 83 mg/m2/day, suggesting that 9-cis-RA induced its own metabolism at doses equal to and above 140 mg/m2/day. 9-cis-RA is a retinoid receptor pan agonist with a more favorable pharmacokinetic and toxicity profile than that observed with previously studied retinoids and merits further investigation.

A HPLC method for the determination of 9-cis retinoic acid (ALRT1057) and its 4-oxo metabolite in human plasma.

A HPLC method was developed and validated for the quantitation of 9-cis-retinoic acid (ALRT1057) and its major metabolite, 4-oxo-9-cis-retinoic acid (LG100182) in human plasma. Samples were buffered and extracted with methyl-tert-butyl-ether. The analytes and an I.S. were separated on a C18 HPLC column using a shallow gradient of 70-89% organic solvent. The analytes were quantitated by UV detection at 348 nm. Selectivity against endogenous compounds and potential metabolites (retinol, all trans-, 13-cis-, and 4-hydroxy-9-cis-retinoic acid) was demonstrated. The run time was 29 min. The standard curve was linear from 2.5 to 450 ng ml-1. Interassay precision for both analytes in quality control samples was less than 5.0% RSD. Accuracy was within 11.0% RE for both compounds. Analyte stability during sample storage, extraction processing, and chromatography was established. Method ruggedness was tested by two analysts and on two HPLC systems. This method has been applied to the quantitation of clinical samples.

Initial clinical trial of a selective retinoid X receptor ligand, LGD1069.

PURPOSE: The retinoid response is mediated by nuclear receptors, including retinoic acid receptors (RARs) and retinoid "X" receptors (RXRs). All-trans retinoic acid (RA) binds only RARs, while 9-cis RA is an agonist for both RARs and RXRs. Recently, LGD1069 was identified as a highly selective RXR agonist with low affinity for RARs. We undertook a dose-ranging study to examine the safety, clinical tolerance, and pharmacokinetics of LGD1069 in patients with advanced cancer. PATIENTS AND METHODS: Fifty-two patients received. LGD1069 administered orally once daily at doses that ranged from 5 to 500 mg/m2 for 1 to 41 weeks. Treatment proceeded from a starting dose of 5 mg/m2. Pharmacokinetic sampling was performed on selected patients on days 1, 15, and 29. RESULTS: Reversible, asymptomatic increases in liver biochemical tests were the most common dose-limiting adverse effect. Less prominent reactions included leukopenia, hypertriglyceridemia, and hypercalcemia. Characteristic retinoid toxicities, such as cheilitis, headache, and myalgias/arthralgias, were mild or absent. Two patients with cutaneous T-cell lymphoma experienced major antitumor responses. Pharmacokinetic studies obtained in 27 patients at eight dose levels showed that the day 1 area under the plasma concentration-times-time curves (AUCs) were proportional to dose. At all doses studied, the day 1 AUCs were similar to those on days 15 and 29, indicating a lack of induced metabolism. CONCLUSION: LGD1069 is a unique compound that exploits a newly identified pathway of retinoid receptor biology that may be relevant to tumor-cell proliferation and apoptosis. Further investigation of this drug is warranted. Based on the results of this study, a dose of 300 mg/m2 is recommended for single-agent trials.

Initial clinical trial of the retinoid receptor pan agonist 9-cis retinoic acid.

The retinoid response is mediated by families of nuclear receptors, the retinoic acid receptors (RARs), and the retinoid X receptors. All-trans retinoic acid (RA) binds only RARs and induces its own metabolism. In contrast, 9-cis RA is a newly identified agonist for both RARs and retinoid X receptors. We undertook a dose-ranging study to examine the safety, clinical tolerance, and pharmacokinetics of 9-cis RA in patients with advanced cancer. Thirty-four patients received once daily p.o. doses of 9-cis RA (administered as LGD1057) ranging from 5 to 230 mg/m2 for 4 weeks. Pharmacokinetic studies were performed on 28 patients at seven dose levels. 9-cis RA was generally well tolerated. Headache was the most common dose-limiting adverse effect. Other prominent reactions included facial flushing, myalgia, dyspnea, hypertriglyceridemia, and hypercalcemia. Relative to other retinoids, mucocutaneous reactions were mild. No major antitumor responses were observed. Pharmacokinetic analysis revealed that the day 1 area under the plasma concentration x time curves (AUCs) were proportional to the dose. Up through doses of 140 mg/m2, the day 1 AUCs were similar to those on days 15 and 29. At higher doses, however, AUCs tended to decline with repeat dosing. 9-cis RA is a novel compound that exploits a newly identified pathway of retinoid receptor biology that may be relevant to tumor cell proliferation and differentiation. We recommend a dose of 140 mg/m2 for single-agent trials utilizing a once-daily schedule of administration.

Analysis of polymorphic variation in drug metabolism: III. Glucuronidation and sulfation of diflunisal in man.

The urinary excretion of diflunisal (D) and its metabolites diflunisal sulfate (DS), diflunisal phenolic glucuronide (DPG), and diflunisal acyl glucuronide (DAG) were measured in 110 healthy, drug-free Caucasian volunteers given 50 mg of diflunisal by mouth. When expressed as fractional recoveries, DS, DPG, and DAG were strongly negatively correlated with one another. Metabolic ratios, on the other hand, correlated positively and tended to localize variability within a single enzyme pathway. Thus, females using estrogen-containing oral contraceptives were shown to excrete 50% less DS and 20% more DAG than non-users, and recoveries of DS were reduced by about 30% in cigarette smokers. Kernel density analyses of the log metabolic ratios of DS and DPG were broad-based and unimodal. However, kernel density estimates of the distribution of log metabolic ratios of DAG showed 3 peaks, 1 of which (an extensive metabolizer polymorph) could be removed by excluding contraceptive-using females. Similarly, there were 2 poor metabolizer peaks in the distribution of log metabolic ratios of DS attributable to cigarette smoking and, in females, use of an oral contraceptive. Thus, we conclude that the metabolism of diflunisal is altered by cigarette smoking and oral contraceptives, and that kernel density estimation, as applied to log metabolic ratios, is a sensitive and specific method for detection of polymorphic variation in drug metabolism.

The effect of multiple dosage on the kinetics of glucuronidation and sulphation of diflunisal in man.

1. The single (250 and 500 mg) and multiple dose (250 and 500 mg twice daily for 15 days) pharmacokinetics of diflunisal were compared in young volunteers. 2. The plasma clearance of diflunisal was lowered significantly after multiple dose administration (5.2 +/- 1.2 and 4.2 +/- 0.7 ml min-1 for the 250 and 500 mg twice daily regimens, respectively) as compared with single dose administration 11.4 +/- 3.1 and 9.9 +/- 2.0 ml min-1 for the 250 and 500 mg single doses, respectively). 3. The partial metabolic clearances of diflunisal by acyl and phenolic glucuronide formation were lowered significantly (greater than 50%) after multiple dose administration. 4. The urinary recovery of diflunisal sulphate increased as a function of dose: 6.1 +/- 2.8 and 9.1 +/- 3.5% following the 250 and 500 mg single dose, respectively, and 10.9 +/- 3.1 and 15.9 +/- 3.6% following the 250 and 500 mg twice daily regimens. The partial metabolic clearance of diflunisal by sulphate conjugation was unchanged following multiple dose administration. 5. The plasma protein binding of diflunisal was concentration-dependent. Analysis of unbound plasma clearances of diflunisal showed that its total plasma clearance following 500 mg twice daily was affected by both saturable glucuronidation and concentration-dependent plasma binding.

High-performance liquid chromatographic method for the simultaneous quantitation of diflunisal and its glucuronide and sulfate conjugates in human urine.

A direct high-performance liquid chromatographic (HPLC) assay was developed to simultaneously quantitate diflunisal and its three known metabolites (i.e., the phenolic and acyl glucuronides and the sulfate conjugate) in human urine. Chromatographically pure standards of the diflunisal conjugates were isolated from urine of volunteers following ingestion of multiple doses of diflunisal (500 mg twice daily). Diflunisal, its three conjugates, and an internal standard (naproxen) were separated on a reversed-phase column using gradient elution. The column eluate was monitored fluorometrically (excitation: 258 nm; emission: 428 nm). Urine samples were diluted with phosphate buffer (pH 5.75) and injected onto the column. The limit of detection was approximately 1 microgram/mL for each conjugate and 0.1 microgram/mL for diflunisal. Due to the presence in most urine samples of significant concentrations of rearrangement products of the biosynthetic 1-O-acyl glucuronide of diflunisal, the acyl glucuronide could not be reliably quantitated by direct injection of diluted urine samples. Instead, diflunisal acyl glucuronide was quantitated indirectly following alkaline hydrolysis of the urine samples. The method has been successfully used to investigate the dose-dependent glucuronidation and sulfation of diflunisal in humans.

Effect of dose on the glucuronidation and sulphation kinetics of diflunisal in man: single dose studies.

1. The effect of dose (100 mg, 250 mg, 500 mg, 750 mg and 1000 mg) on the glucuronidation and sulphation of diflunisal was studied in six healthy volunteers. 2. Total urinary recovery ranged from 78.9 +/- 11.9% to 91.5 +/- 18.7% of the administered dose. Urinary recovery (normalized for total urinary recovery) of diflunisal sulphate (DS) significantly increased with dose from 9.3 +/- 3.7% to 18.1 +/- 4.8%. 3. Normalized urinary recovery for diflunisal phenolic glucuronide (DPG) was unaffected by dose (range: 30.6 +/- 3.8% to 40.6 +/- 6.6%). Normalized urinary recovery for the acyl glucuronide (DAG) significantly decreased from 52.3 +/- 4.6% to 40.2 +/- 3.4% as the dose increased. 4. Total plasma clearance of diflunisal significantly decreased from 14.4 +/- 1.4 ml min-1 to 8.7 +/- 1.4 ml min-1 as the dose increased from 100 mg to 750 mg. A further increase in dose to 1000 mg resulted in an unexplained increase in total plasma clearance to 10.3 +/- 1.8 ml min-1. 5. Dose-dependent plasma clearance of diflunisal was caused mainly by saturation of the formation of DAG, whereas the formation of DS and DPG were relatively unaffected by dose.

Isolation and identification of a new major metabolite of diflunisal in man. The sulfate conjugate.

A new metabolite of diflunisal has been identified in volunteers and patients after multiple dose administration. The metabolite was isolated from human urine by silica gel chromatography and was further purified by reversed phase HPLC. Arylsulfatase from Helix pomatia and from Aerobacter aerogenes completely hydrolyzed the isolated metabolite to diflunisal, although hydrolysis by bacterial arylsulfatase was extremely slow. Electron impact mass spectra for diflunisal and its sulfate conjugate were virtually identical. Negative ion fast atom bombardment mass spectra clearly showed the quasimolecular ion [M-H]- at m/z 329 (base peak) as well as a large fragment ion (90% relative intensity) at m/z 249 corresponding to the loss of the sulfate moiety. Urinary excretion patterns in volunteers and rheumatoid arthritis patients revealed that sulfate conjugation of diflunisal is a minor metabolic pathway after single 500-mg dose administration (less than 10% of the dose), whereas it becomes a major pathway (21.3-44.3% of the dose) following multiple doses (500 mg b.i.d.). In one volunteer, who ingested 500 mg diflunisal b.i.d. for 5 weeks, it was shown that the percentage of the dose excreted as diflunisal sulfate gradually increased during the first week to approximately 30% and stayed virtually unchanged for the remaining 4 weeks of diflunisal intake. These preliminary observations are not compatible with the idea that sulfate conjugation is capacity-limited at lower substrate concentrations than glucuronide conjugation, nor do they suggest that sulfation of diflunisal is rate-limited by depletion of inorganic sulfate body stores.

Clinical pharmacokinetics of non-steroidal anti-inflammatory drugs.

The number of non-steroidal anti-inflammatory drugs (NSAIDs) available for clinical use has dramatically increased during the last decade. As a general rule, NSAIDs are well absorbed from the gastrointestinal tract, with the exception of aspirin (and possibly diclofenac, tolfenamic acid and fenbufen) which undergoes presystemic hydrolysis to form salicylic acid. Concomitant administration of NSAIDs with food or antacids may in some cases lead to delayed or even reduced absorption. The NSAIDs are highly bound to plasma proteins (mainly albumin), which limits their body distribution to the extracellular spaces. Apparent volumes of distribution of NSAIDs are, therefore, very low and usually less than 0.2 L/kg. The elimination of these drugs depends largely on hepatic biotransformation; renal excretion of unchanged drugs is usually small (less than 5% of the dose). Total body clearance is low and for most NSAIDs is less than 200 ml/min. The effect of age and disease on the disposition of NSAIDs has not been extensively studied. Due to the central role of the liver in the overall elimination of the majority of these compounds, hepatic disease will most likely lead to a significant alteration in their pharmacokinetic behaviour. NSAIDs have been reported to be involved in numerous pharmacokinetic drug interactions. Aspirin decreases the plasma concentrations of many other NSAIDs, although the clinical significance of this is uncertain. Due to the extremely high plasma protein binding of NSAIDs (around 99% in many cases), competition for the same binding sites on plasma proteins may be at least partly responsible for some interactions of NSAIDs with other highly bound drugs; however, another mechanism such as decreased metabolism or decreased urinary elimination is usually involved as well. The most important interactions with NSAIDs are those involving the oral anticoagulants and oral hypoglycaemic agents, though not all NSAIDs have been found to interact with these drugs. In clinical practice, there appear to be no clear-cut guidelines to assist the clinician in the selection of the most appropriate drug for an individual patient. The selection of an anti-inflammatory drug should be based on clinical experience, patient convenience (e.g. once or twice daily dosage schedule), side effects and cost. Since a marked interindividual variability exists in the clinical response to a given NSAID, clinicians prescribing these agents may try several of them sequentially until an adequate response is obtained.