Safety considerations for dietary supplement manufacturers in the United States.

Due to significant dietary supplement use in the US, product manufacturers must understand the importance of implementing a robust approach to establishing safety for all ingredients, including dietary ingredients, components, and finished dietary supplement products. Different regulatory pathways exist by which the safety of dietary ingredients can be established, and thus allowed to be marketed in a dietary supplement. For individual dietary ingredients, safety information may come from a variety of sources including history of safe use, presence of the ingredient in foods, and/or non-clinical and clinical data. On occasion safety data gaps are identified for a specific ingredient, particularly those of botanical origin. Modern toxicological methods and models can prove helpful in satisfying data gaps and are presented in this review. For finished dietary supplement products, issues potentially impacting safety to consider include claims, product labeling, overages, contaminants, residual solvents, heavy metals, packaging, and product stability. In addition, a safety assessment does not end once a product is marketed. It is important that manufacturers actively monitor and record the occurrence of adverse events reported in association with the use of their products, in accordance with the law. Herein, we provide a comprehensive overview of considerations for assessing dietary supplement safety.

The Antitussive Benzonatate Is Not Tumorigenic in Rodent Carcinogenicity Studies.

Benzonatate is a peripheral oral antitussive that dampens the activity of cough stretch receptors. Rodent carcinogenicity studies were performed in Tg.rasH2 mice and Wistar Han rats. Mice were orally gavaged benzonatate at 10, 30, 75, and 100 mg/kg/day for males and 5, 15, and 50 mg/kg/day for females. Rats were gavaged at 10, 30, and 90 mg/kg/day for males and 5, 15, and 50 mg/kg/day for females. Higher doses in males were due to differences in maximum tolerated doses in dose-ranging studies. In both species, benzonatate was not detected in plasma because of rapid ester hydrolysis producing 4-(butylamino) benzoic acid (BBA) and methylated polyethylene glycol polymer. This metabolism was similar in human plasma; therefore, plasma BBA was used to show systemic exposure. Both species had no evidence of a benzonatate-related increase in any neoplasm. A slight increase in nasal cavity exudative inflammation was present in benzonatate-dosed male mice. Retinal atrophy was observed in male rats at ≥30 mg/kg/day, but the incidence was within historical control data range and not related to benzonatate. In conclusion, benzonatate and its 2 major metabolites were not carcinogenic in rodent carcinogenicity studies at BBA exposures of ≥32 and 70 times a 200 mg human benzonatate dose, respectively.

Genotoxicity assessment of the novel antitussive agent Benzonatate and its major metabolite.

Benzonatate (TESSALON®) is a peripherally acting oral antitussive. It undergoes rapid ester hydrolysis producing 4-(butylamino) benzoic acid (BBA) and methylated polyethylene glycol (MPG) metabolites, which are eliminated in urine and feces. The nonclinical and clinical efficacy of Benzonatate has been demonstrated over the last 60 years, but its safety was not fully assessed. In this study, we tested the genotoxicity of Benzonatate and its major metabolite BBA in an in vitro bacterial reverse mutation and in vivo micronucleus assays. A chromosomal aberration assay was also performed on Benzonatate and BBA. In the reverse mutation assay, Benzonatate and BBA doses 1.5-5000 µg/plate ±â€¯S9 metabolic activation were used and the numbers of revertants/plate were compared to various controls. Chromosomal aberration assays with human peripheral blood lymphocytes used Benzonatate and BBA concentrations 25-2000 and 62.5-1930 µg/mL, respectively. A CByB6F1 mouse bone marrow micronucleus assay was performed as part of a 28-day oral toxicology study at up to 250 mg/kg/day. The frequencies of micronuclei in polychromatic erythrocytes in treated groups were compared with the control group. Neither Benzonatate nor BBA induced significant mutagenicity in any of the bacterial strains, with or without metabolic activation. They also did not produce any biologically relevant structural or numerical aberrations in human chromosomes. Benzonatate and its BBA and MPG metabolites rapidly produced from esterase activity did not produce any significant increase in the incidence of micronucleated polychromatic erythrocytes. In conclusion, Benzonatate and its major metabolite BBA were not mutagenic and did not cause numerical or structural chromosome alterations. While the MPG metabolite was not tested, studies on structural analogues indicated it was also unlikely to be genotoxic. This was supported by oral rodent carcinogenicity assays showing no increase in malignancies.

Thalidomide as a novel therapeutic agent: new uses for an old product.

Thalidomide and its immunomodulatory analogues have numerous effects on the body's immune system, including potential anti-cancer and anti-inflammatory activities. Thalidomide is currently used experimentally to treat various cancers, dermatological, neurological and inflammatory diseases. This drug is approved in the USA for cutaneous manifestations of lepromatous leprosy and is in Phase III trials for multiple myeloma. Thalidomide and its analogues modulate the immune system in various ways. Some of these immunomodulatory activities, together with the anti-angiogenic, anti-proliferative and pro-apoptotic properties, are believed to mediate anti-tumor responses as observed in multiple myeloma and some solid tumors. The analogue lenalidomide has shown potential in treating the bone marrow disorders multiple myeloma and myelodysplastic syndrome, and is presently in Phase II and III trials, respectively.

Thalidomide in the treatment of leprosy.

Leprosy is a chronic infection of the skin and nerves caused by Mycobacterium leprae. Erythema nodosum leprosum (ENL) is a reactive state in lepromatous leprosy. Thalidomide has been used to treat ENL since the 1960s. One of its mechanisms of action is anti-inflammatory through selective inhibition of the pro-inflammatory cytokine TNF-alpha produced by monocytes.

Clinical pharmacokinetics of thalidomide.

Thalidomide is a racemic glutamic acid derivative approved in the US for erythema nodosum leprosum, a complication of leprosy. In addition, its use in various inflammatory and oncologic conditions is being investigated. Thalidomide interconverts between the (R)- and (S)-enantiomers in plasma, with protein binding of 55% and 65%, respectively. More than 90% of the absorbed drug is excreted in the urine and faeces within 48 hours. Thalidomide is minimally metabolised by the liver, but is spontaneously hydrolysed into numerous renally excreted products. After a single oral dose of thalidomide 200 mg (as the US-approved capsule formulation) in healthy volunteers, absorption is slow and extensive, resulting in a peak concentration (C(max)) of 1-2 mg/L at 3-4 hours after administration, absorption lag time of 30 minutes, total exposure (AUC( infinity )) of 18 mg. h/L, apparent elimination half-life of 6 hours and apparent systemic clearance of 10 L/h. Thalidomide pharmacokinetics are best described by a one-compartment model with first-order absorption and elimination. Because of the low solubility of the drug in the gastrointestinal tract, thalidomide exhibits absorption rate-limited pharmacokinetics (the 'flip-flop' phenomenon), with its elimination rate being faster than its absorption rate. The apparent elimination half-life of 6 hours therefore represents absorption, not elimination. The 'true' apparent volume of distribution was estimated to be 16L by use of the faster elimination-rate half-life. Multiple doses of thalidomide 200 mg/day over 21 days cause no change in the pharmacokinetics, with a steady-state C(max) (C(ss)(max)) of 1.2 mg/L. Simulation of 400 and 800 mg/day also shows no accumulation, with C(ss)(max) of 3.5 and 6.0 mg/L, respectively. Multiple-dose studies in cancer patients show pharmacokinetics comparable with those in healthy populations at similar dosages. Thalidomide exhibits a dose-proportional increase in AUC at doses from 50 to 400 mg. Because of the low solubility of thalidomide, C(max) is less than proportional to dose, and t(max) is prolonged with increasing dose. Age, sex and smoking have no effect on the pharmacokinetics of thalidomide, and the effect of food is minimal. Thalidomide does not alter the pharmacokinetics of oral contraceptives, and is also unlikely to interact with warfarin and grapefruit juice. Since thalidomide is mainly hydrolysed and passively excreted, its pharmacokinetics are not expected to change in patients with impaired liver or kidney function.

A single-dose, two-way crossover, bioequivalence study of dexmethylphenidate HCl with and without food in healthy subjects.

Attention deficit hyperactivity disorder (ADHD) in children is effectively treated by racemic oral methylphenidate (dl-MPH). The d-isomer (d-MPH) has been developed as an improved treatment for ADHD since only half the racemic dose is used. This study, performed in healthy subjects, assessed the effect of food on the pharmacokinetics of dexmethylphenidate hydrochloride (d-MPH HCl) in a single dose (2 x 10-mg tablets), two-way crossover with d-MPH administered to subjects in both a fasting state or after a high-fat breakfast. There were no serious or unexpected adverse events during the course of this study, with most events reported in comparable numbers of fed and fasted subjects. The bioequivalence of d-MPH was similar with or without food, with 90% confidence intervals of 88.2% to 104.6% and 105.9% to 118.2% for ln(C(max)) and ln[(AUC(0-infinity))], respectively. There was a marginal but statistically significant 1-hour increase in t(max) in the fed versus fasted state, reflecting an absorption delay. The rate of formation of the major metabolite, d-ritalinic acid (d-RA), was marginally decreased ( approximately 14%) after food. The extent of exposure to d-RA was similar (within 1.2%) between both treatments. There was a marginal but statistically significant difference in mean t(max) for d-RA between fed and fasted conditions, with peak concentration occurring 1.5 hours later after d-MPH administration with food. There was no measurable in vivo chiral inversion of d-MPH to l-MPH in plasma. In addition, the metabolism of d-MPH was stereospecific as d-MPH only produced d-RA. In summary, food had no substantial effect on the bioavailability of d-MPH, with an equivalent rate and extent of exposure obtained. Therefore, d-MPH can be administered without regard to food intake.

Effects of thalidomide on developmental, peri- and postnatal function in female New Zealand white rabbits and offspring.

The present study determined effects of thalidomide on three successive generations of New Zealand White rabbits after oral dosing to F0 maternal rabbits during the later third of gestation (post major organogenesis) and lactation. One hundred and twenty four time-mated F0 rabbits (31/dose) were gavaged with 0, 30, 150, or 500 mg/kg thalidomide from gestation day 18 (DG 18) to lactation day 28 (DP or day postpartum 28) for approximately 42 days. At 6 months, 12 F1 males and 12 F1 females were randomly paired within each dose group and mated. Reproductive evaluation and/or gross necropsy of the thoracic, abdominal, and pelvic viscera was performed on day 29 postpartum (DP 29) for F0 rabbits, on DP 49 for F1 pups not selected for continued evaluation, after completion of mating for F1 rabbits, and on DG 29 for F1 rabbits on continued evaluation of F2 litter. There was no thalidomide-related mortality in F0 and F1 rabbits. One F0 doe at 30 and 150 mg/kg and 2 at 500 mg/kg aborted. Maternal F0 rabbits had reductions in feed consumption but not body weight gain during the gestation and lactation periods for 150 and 500 mg/kg. The numbers of does with stillborn and all pups dying from DP 1-4 was increased at 150 and 500 mg/kg. Mean number of liveborn (litter size) and percentage of live pups were decreased at 500 mg/kg. A significantly increased number of pups died at 150 and 500 mg/kg, resulting in a reduced viability index and decreased litter size. There were some F1 male and female body weight reductions at 150 and 500 mg/kg postweaning with no change in feed consumption. F1 Caesarean-sectioning and litter observations were normal. Fertility of F1 offspring was not affected by maternal doses of thalidomide, but the pregnancy index may have been reduced by the 500 mg/kg maternal thalidomide dose. There was an apparent dose-related increase in splayed limbs in F1 pups. Splaying has been reported in New Zealand White rabbits and may be a recessive trait. The splay could be caused by the nerve and muscle fiber degeneration and skeletal muscle atrophy observed in some pups. It could also be due to the decrease in litter size, resulting in fewer pups per litter for nursing, leading to rapid weight gain and a failure of the pups to support this weight. No F2 fetal gross external alterations were observed. In summary, pregnant rabbits orally dosed with up to 500 mg/kg thalidomide from gestation day 18 to lactation day 28 had increased abortion, changes in some natural delivery and litter parameters, and limb splay in some F1 pups. No gross external changes were observed in F1 and F2 pups.

A 90-day oral gavage toxicity study of D-methylphenidate and D,L-methylphenidate in Sprague-Dawley rats.

D-methylphenidate is an enantiomer of D,L-methylphenidate and was developed as an improved treatment for attention deficit hyperactivity disorder in children. The current study was performed to determine and compare the toxicity of 2-50 mg/kg per day D-MPH and 100 mg/kg per day D,L-MPH for 90 days in rats with the top D-MPH dose being equimolar to 100 mg/kg D,L-MPH. The top D-MPH and D,L-MPH doses were at least 67 times that of the human dose and produced systemic exposures that were over 10 times higher than those typically achieved in children. During the course of the study, one male each from the 50 mg/kg per day and D,L-MPH groups and one female from the 50 mg/kg group died. Incidences of material around nose/eyes, scabbing, foot swelling, alopecia and abrasions were evident at 50 mg/kg per day D-MPH and 100 mg/kg per day D,L-MPH doses. Body weight and its changes decreased in a dose-dependent manner for D-MPH males. There were significant changes in some clinical chemistry measurements at the terminal bleed in the high dose groups of both sexes although most of these changes were resolved by the recovery bleed. Differences in absolute and relative body and certain organ weights for high dose D-MPH and D,L-MPH groups were seen at terminal necropsy with the differences no longer present after the recovery period. No abnormal or gross histopathological changes were associated with any of these organ weight changes reported for the terminal and recovery periods. Based on body weight changes, the no observed adverse effect level for D-MPH in rats was 20 mg/kg. Overall, the toxicity profile observed in rats with 50 mg/kg per day D-MPH was comparable to that of an equimolar dose of D,L-MPH (100 mg/kg per day) when given repeatedly for 90 days using a twice a day dosing regimen.

Sensitive and rapid method for the determination of thalidomide in human plasma and semen using solid-phase extraction and liquid chromatography-tandem mass spectrometry.

Liquid chromatography-tandem mass spectrometric assays were developed for the sensitive, rapid and high throughput bioanalyses of thalidomide in human plasma and semen. The matrices were first stabilized with 0.025 M Sorensen's citrate buffer at pH 1.5 to prevent spontaneous hydrolysis. Buffered thalidomide was stable when stored at room temperature for 24 h and for up to three freeze-thaw cycles. Samples were extracted using SPE cartridges. Extracts were then injected into the LC-MS-MS equipped with a reversed-phase column and an APCI interface in the negative ion mode. Calibration curves for both matrices were linear with r>0.99 from 2 to 250 ng/ml and ng/g. Inter-assay precision (RSD) of plasma and semen calibration standards were 2.6-11.6 and 1.9-12.4%, respectively. Recoveries from plasma and semen were greater than 69 and 78%, respectively. Batch sizes of 100 samples per matrix were analyzed with a total run time of 5 h. The methods successfully determined concentrations of thalidomide from a clinical study to levels as low as 7 ng/ml plasma and 8 ng/g semen, respectively.

The perinatal and postnatal toxicity of D-methylphenidate and D,L-methylphenidate in rats.

D-methylphenidate is an enantiomer of D,L-methylphenidate and was developed as an improved treatment for attention deficit hyperactivity disorder (ADHD) in children. The current study was performed to assess the potential perinatal and postnatal toxicity of both compounds in rats. About 125 presumed pregnant rats were assigned to five dose groups of 25 each. They were dosed with 2, 6, and 20 mg/kg/day D-methylphenidate and 40 mg/kg/day D,L-methylphenidate from gestation Day 7 to lactation Day 20. F1 generation rats were rebred to produce F2 fetuses. Various perinatal and postnatal measurements were made for the F0 and F1 rats. Among the significant findings were a reduction in maternal body weight gain for 20 mg/kg/day D-methylphenidate and D,L-methylphenidate and increased incidences of dilated pupil and vocalization for D,L-methylphenidate during the gestation period. Neither compound produced any other significant adverse findings in F0 and F1 generation rats at doses that were at least 25 times the maximum daily human therapeutic dose.

D-Methylphenidate is non-genotoxic in in vitro and in vivo assays.

D-Methylphenidate (dexmethylphenidate; D-MPH) and its racemate D,L-methylphenidate (D,L-MPH) are currently prescribed for the chronic treatment of attention deficit hyperactivity disorder (ADHD) in children. Studies have shown that D-MPH is the pharmacologically active enantiomer for ADHD and is therefore the preferred drug for the treatment of ADHD symptoms. Although studies on the mutagenicity of D,L-MPH have been conducted, similar data for D-MPH are lacking. Therefore, D-MPH was evaluated in the bacterial reverse mutation and mouse lymphoma assays with and without S9 and in a bone marrow micronucleus test in male and female CD-1 mice. As a comparison, the L-enantiomer and racemate were also included in the assessments. While MPH-associated toxicity was observed in the mammalian tests, none of the three compounds tested induced mutagenic or clastogenic effects. Our present results along with published epidemiological data from patient populations are consistent with the conclusion that D-MPH and D,L-MPH do not present a carcinogenic risk to humans.

Neurobehavioral effects of racemic threo-methylphenidate and its D and L enantiomers in rats.

D,L-methylphenidate (Ritalin) is used to treat attention deficit hyperactivity disorder (ADHD) in children. The therapeutic effect is predominantly due to the d enantiomer. Dexmethylphenidate (D-MPH; Focalin) was therefore developed for its better therapeutic index. The present study determined and compared the acute behavioral toxicity of D,L-MPH, D-MPH and L-MPH in rats after oral dosing. Comprehensive functional observational battery (FOB) evaluations and rota-rod tests were performed 30, 60 and 120 min after dosing. Ten rats/sex/dose were administered a single dose of vehicle, 2, 20, 100 mg/kg D,L-MPH and 1, 10, 50 mg/kg D-MPH or 1, 100, 500 mg/kg L-MPH. There was no mortality. Certain FOB evaluations were statistically significant from vehicle control at any of the time points with most occurring at 60 and 120 min in the high D,L-MPH dose. These included increases in rearing, difficulty in removal from box, arousal, click, tail-pinch and decreases in hind-limb splay distance, hind-limb grip strength and handling reactivity. Behavioral responses were also present at the mid-dose D,L-MPH and high dose D- and L-MPH. Responses in female were significantly different from males in D,L- and L-MPH groups suggesting a sex difference in sensitivity. In the rota-rod test, mean latency to remain on the rod was significantly less for males compared to control given high dose D-MPH and D,L-MPH. In females, latency times were significantly less for high doses of all three compounds. In summary, fewer significant FOBs were seen with D- and L-MPH compared to equimolar doses of D,L-MPH. L-MPH was the least potent in producing FOBs. These results were supported by rota-rod studies.

Effects of thalidomide on reproductive function and early embryonic development in male and female New Zealand white rabbits.

BACKGROUND: The present work was performed to determine the effect of thalidomide exposure on reproductive function and early embryonic development. METHODS: Twenty-five female New Zealand White rabbits were orally gavaged with 0, 10, 50, or 100 mg/kg/day thalidomide 14 days prior to mating through to gestation day 7 for a total of 22 days. Treated females were Caesarean-sectioned approximately 29 days after the date of attempted mating. Following mating with treated females, male rabbits (25/dose) were gavaged with 0, 30, 150, or 500 mg/kg/day beginning 14 days prior to mating with a group of untreated females (25/dose). Doses were administered through mating until the day before sacrifice for a minimum of 56 days. Untreated females were Caesarean-sectioned 29 days after the last attempted mating. Comprehensive necropsy and histopathology of the reproductive system were performed. RESULTS: Treated females had reduction in body weight gain during gestation. Mating and pregnancy parameters were unaffected by thalidomide. At 100 m/kg, litter averages for corpora lutea, implantations, litter sizes, does with viable fetuses and live fetuses decreased and the number of early resorptions, does with any resorptions, does with all conceptuses resorbed, and the percent resorbed conceptuses per litter increased. The number of early resorptions, the average number of early resorptions per litter, and the percent resorbed conceptuses per litter increased at 10 and 50 mg/kg. There were no thalidomide-related external fetal malformations. Mating and fertility in male rabbits were unaffected by thalidomide. There was an increased incidence of flaccid testes at 150 and 500 mg/kg and of bilateral small testes in all treated groups. At 500 mg/kg, there was degeneration of the germinal epithelium of the testicles with an increase in multinucleated giant cells in seminiferous tubule and a loss of round and elongating spermatids. CONCLUSIONS: Thalidomide had no adverse effects on mating and fertility in male and female rabbits dosed up to 500 and 100 mg/kg/day, respectively, for 14 days prior to mating. After 56 day of dosing, histopathologic changes with no associated sperm abnormalities were observed in the testicles. Embryonic development NOAEL for treated females mated to untreated males was <10 mg/kg. Corresponding fertility NOAEL for treated males mated to untreated females was 500 mg/kg.

A 90-day oral gavage toxicity study of d-methylphenidate and d,l-methylphenidate in beagle dogs.

d-Methylphenidate (d-MPH) was approved as a treatment for attention deficit hyperactivity disorder (ADHD) in children. The repeated-dose toxicity of the d enantiomer of d,l-methylphenidate (d,l-MPH) was assessed in male and female Beagle dogs. Dogs were orally dosed twice a day in equally divided doses 6 hours apart for total daily doses of 1, 3, and 10 mg/kg/day d-MPH or 20 mg/kg/day d,l-MPH for 90 days, followed by a 30-day recovery period. The top d-MPH dose of 10 mg/kg was equimolar to 20 mg/kg d,l-MPH in d-MPH content. The 10-mg/kg d-MPH and d,l-MPH doses were at least 13 times the maximum therapeutic dose giving rise to systemic exposures that were equivalent to or at least 2 times greater than those at the maximum therapeutic doses in children. The 10-mg/kg d-MPH and 20-mg/kg d,l-MPH doses had systemic exposures that were equivalent to or two to five times greater than the maximum therapeutic plasma levels in children respectively. There was no treatment-related mortality in all doses tested. Reversible salivation, hyperactivity, and diarrhea were seen in the high-dose d-MPH and d,l-MPH groups. Significant body weight loss and reduction in food consumption were observed in males for both high-dose groups with weights comparable to control values by the end of the recovery period. There were no abnormal clinical pathology or macroscopic or microscopic findings. Based on body weight changes, the no-observed-adverse-effect level (NOAEL) of d-MPH in beagle dogs was 3 mg/kg/day.

D-methylphenidate and D,L-methylphenidate are not developmental toxicants in rats and rabbits.

BACKGROUND: D,L-threo-Methylphenidate (D,L-MPH) is marketed currently for attention deficit hyperactivity disorder in children. D-threo-methylphenidate (dexmethylphenidate; D-MPH) is a refined formulation of D,L-methylphenidate containing only the active enantiomer and was recently approved in the U.S. for the same condition. D-Methylphenidate has been shown to be efficacious in patients at half the dose of D,L-MPH with a potentially improved therapeutic profile. The developmental toxicity of both compounds was determined and compared in rats and rabbits according to current International Conference on Harmonization (ICH) guidelines. METHODS: Groups of pregnant rats were orally dosed twice daily 6 hr apart from Days 7 to 17 of presumed gestation (DG 7-17) for total daily doses of 2, 6 and 20 mg/kg D-MPH and 40 mg/kg D,L-MPH. Groups of presumed pregnant rabbits were similarly dosed from DG 6 to 18 for total daily doses of 4, 20 and 100 mg/kg D-MPH and 200 mg/kg D,L-MPH. Control groups for both studies were given water vehicle. Comprehensive clinical and developmental measurements were made. Satellite groups of animals were included in the main rat and rabbit studies for toxicokinetic assessment. RESULTS: No drug-related mortality was seen in the F0 rats and rabbits. The number of rats with repetitive pawing, dilated pupil and aggression was significantly greater for the 40 mg/kg D,L-MPH compared to the 20 mg/kg D-MPH dosed rats. Maternal body weight and body weight gain were significantly reduced for both D-MPH and D,L-MPH groups compared to control. Maternal reproductive and litter parameters were unaffected by both drugs. No gross external, soft tissue, or skeletal alterations related to both compounds were seen in the fetuses. In rabbits, head-bobbing and hyperpnea were significantly greater for the 200 mg/kg D,L-MPH compared to 100 mg/kg D-MPH. No other maternal or fetal effects related to both compounds were seen. Exposure to D-MPH (as assessed by AUC) showed no teratogenic effects at exposures of up to 5.6 and 1.7 times for the rat and rabbit respectively compared to children taking the maximum therapeutic dose of 20 mg/day (10 mg twice a day). No teratogenic effects were seen for D,L-MPH in rat and rabbit at exposures of up to 3.7 to 11.7 times that of the maximum therapeutic pediatric dose of 60 mg/ day. CONCLUSIONS: Rats and rabbits dosed with D,L-MPH exhibited significantly greater incidence of maternal clinical observations at twice the dose of D-MPH. Both D-MPH and D,L-MPH were not teratogenic in rats and rabbits at higher exposure levels compared to humans.

Chiral inversion of the second generation IMiD CC-4047 (ACTIMID ) in human plasma and phosphate-buffered saline.

CC-4047 is a racemic second-generation immunomodulatory drug currently in clinical development for various oncologic indications. It has potent effects on key cytokines including tumor necrosis factor-alpha, interleukin (IL-10), and interferon (IFN-gamma). The S-isomer of CC-4047 has been reported to be the more potent enantiomer of the racemate. In this article we report on the rapid racemization of the S-isomer of CC-4047 in human plasma and phosphate-buffered saline. These results support the further development of the racemate instead of the S-isomer.