Abemaciclib does not increase the corrected QT interval in healthy participants.

Abemaciclib is an orally administered, potent, and selective small molecule inhibitor of cyclin-dependent kinases 4 and 6, approved for advanced or metastatic breast cancer. This study aimed to use an exposure-response approach to investigate the effect of abemaciclib and its active metabolites (M2 and M20) on QTc interval and delay in cardiac repolarization at clinically relevant exposures. This was a single-blind, randomized, and placebo-controlled study of ascending doses of abemaciclib. Thirty-five healthy participants were administered a single dose of 200-600 mg abemaciclib. Twelve-lead electrocardiogram tracings and pharmacokinetic samples were collected serially pre- and post-dose. The primary objective was to study the relationship between abemaciclib and its active metabolites (M2 and M20) and QTc interval following ascending oral doses of abemaciclib. The secondary objective included evaluating the safety and tolerability of single ascending doses of abemaciclib in healthy participants. Exposure-response analysis demonstrated that there was no significant relationship between placebo-corrected change from baseline QTcF (ΔΔQTcF), abemaciclib, and metabolite plasma concentrations. Additionally, the ΔΔQTcF slopes of abemaciclib, its metabolites, and total analyte concentrations were not statistically different from zero. Single doses of abemaciclib, up to 400 mg, were well-tolerated by healthy participants; however, at the 600 mg dose (three times the highest registered dose), the frequency and severity of treatment-related gastrointestinal events (primarily diarrhea, nausea, and vomiting) increased. In conclusion, single doses of abemaciclib, up to 400 mg, had no statistically or clinically relevant effects on QTc, and abemaciclib was well tolerated up to a dose of 400 mg in this study.

Abemaciclib Does Not Have a Clinically Meaningful Effect on Pharmacokinetics of CYP1A2, CYP2C9, CYP2D6, and CYP3A4 Substrates in Patients with Cancer.

Abemaciclib is an orally administered, potent inhibitor of cyclin-dependent kinases 4 and 6 and is metabolized extensively by CYP3A4. The effects of abemaciclib on several CYPs were qualified in vitro and subsequently evaluated in a clinical study. In vitro, human hepatocytes were treated with vehicle, abemaciclib, or abemaciclib metabolites [N-desethylabemaciclib (M2) or hydroxyabemaciclib (M20)]. mRNA levels for eight CYPs were measured using reverse-transcription quantitative polymerase chain reaction, and, additionally, catalytic activities for three CYPs were determined. In the clinical study, adult patients with cancer received a drug cocktail containing CYP substrates [midazolam (3A), warfarin (2C9), dextromethorphan (2D6), and caffeine (1A2)] either alone or in combination with abemaciclib. Plasma pharmacokinetics (PK) samples were analyzed for all substrates, caffeine metabolite paraxanthine, and abemaciclib; polymorphisms of CYP2C9, CYP2D6, CYP3A4, and CYP3A5 were evaluated. In vitro, downregulation of CYP mRNA, including 1A2, 2B6, 2C8, 2C9, 2D6, and 3A, by abemaciclib and/or M2 and M20 was observed at clinically relevant concentrations. In humans, abemaciclib did not affect the PK of CYP2D6 or CYP2C9 substrates. Minor statistically significant but clinically irrelevant changes were observed for midazolam [area under the concentration versus time curve from zero to infinity (AUC0-inf) (13% lower), Cmax (15% lower)], caffeine [AUC0-inf (56% higher)], and paraxanthine: caffeine [area under the concentration versus time curve from 0 to 24 hours ratio (was approximately 30% lower)]. However, given the magnitude of the effect, these changes are not considered clinically relevant. In conclusion, the downregulation of CYP mRNA mediated by abemaciclib in vitro did not translate into clinically meaningful drug-drug interactions in patients with cancer. SIGNIFICANCE STATEMENT: Despite observations that abemaciclib alters the mRNA of various CYP isoforms in vitro, a clinical study using a drug cocktail approach found no clinically meaningful drug-drug interactions between abemaciclib and a range of CYP substrates [midazolam (CYP3A4), S-warfarin (CYP2C9), dextromethorphan (CYP2D6), and caffeine (CYP1A2)]. This lack of translation suggests greater understanding of mechanisms of CYP downregulation is needed to accurately predict clinical drug-drug interaction risk from in vitro data.

Abemaciclib Inhibits Renal Tubular Secretion Without Changing Glomerular Filtration Rate.

Abemaciclib, an inhibitor of cyclin dependent kinases 4 and 6, is indicated for metastatic breast cancer treatment. Reversible increases in serum creatinine levels of ~15-40% over baseline have been observed following abemaciclib dosing. This study assessed the in vitro and clinical inhibition of renal transporters by abemaciclib and its metabolites using metformin (a clinically relevant transporter substrate), in a clinical study that quantified glomerular filtration and iohexol clearance. In vitro, abemaciclib inhibited metformin uptake by organic cation transporter 2, multidrug and toxin extrusion (MATE)1, and MATE2-K transporters with a half-maximal inhibitory concentration of 0.4-3.8 µM. Clinically, abemaciclib significantly increased metformin exposure but did not significantly affect measured glomerular filtration rate, serum neutrophil gelatinase-associated lipocalin (NGAL), serum cystatin-C, or the urinary markers of kidney tubular injury, NGAL and kidney injury molecule-1.

Impact of Increased Gastric pH on the Pharmacokinetics of Evacetrapib in Healthy Subjects.

STUDY OBJECTIVE: To examine the effect of increased gastric pH on exposure to evacetrapib, a cholesteryl ester transfer protein inhibitor evaluated for the treatment of atherosclerotic heart disease. DESIGN: Open-label, two-treatment, two-period, fixed-sequence crossover study. SETTING: Clinical research unit. SUBJECTS: Thirty-four healthy subjects. INTERVENTION: In period 1, subjects received a single oral dose of evacetrapib 130 mg on day 1, followed by 7 days of analysis for evacetrapib plasma concentrations. In period 2, subjects received a once/day oral dose of omeprazole 40 mg on days 8-20, with a single oral dose of evacetrapib 130 mg administered 2 hours after the omeprazole dose on day 14, followed by 7 days of pharmacokinetic sampling. Subjects were discharged on day 21 and returned for a follow-up visit at least 14 days after the last dose of evacetrapib in period 2. Gastric pH was measured before subjects received each evacetrapib dose. MEASUREMENTS AND MAIN RESULTS: Noncompartmental pharmacokinetic parameters were estimated from plasma concentration-time data and compared between periods 1 and 2. Geometric mean ratios with 90% confidence intervals (CIs) were reported. Safety and tolerability were also assessed. The mean age of the 34 subjects was 40.9 years; mean body mass index was 27.2 kg/m(2) . Omeprazole treatment increased mean gastric pH across all subjects by 2.80 and increased evacetrapib area under the concentration versus time curve from time zero extrapolated to infinity (AUC0-∞ ) and maximum observed drug concentration (Cmax ) by 15% (90% CI -2 to 35) and 30% (90% CI 3-63), respectively. For both parameters, the upper bound of the 90% CI of the ratio of geometric least-squares means exceeded 1.25 but was less than 2, indicating a weak interaction. To assess the effect of gastric pH on subjects who responded best to omeprazole treatment, the analyses were repeated to include only the 22 subjects whose predose gastric pH was 3.0 or lower in period 1 and 4.0 or higher in period 2. In this subpopulation, mean gastric pH increased by 4.15 during omeprazole treatment, and evacetrapib AUC0-∞ and Cmax increased by 22% (90% CI 4-42) and 35% (90% CI 1-80), respectively. Despite the small mathematical differences between the analyses, the overall effect in both was a minimal increase in evacetrapib exposure. Of 35 adverse events reported during the study, 4 (11.4%) were considered to be treatment-related, and most were mild in severity. CONCLUSION: The impact of increased gastric pH on evacetrapib pharmacokinetics would not be expected to be clinically relevant. The magnitude of change in pH did not affect the degree of the interaction.

Effect of hepatic or renal impairment on the pharmacokinetics of evacetrapib.

PURPOSE: The aim of this study is to investigate the effect of hepatic or renal impairment on the pharmacokinetics of a single 130-mg evacetrapib dose. METHODS: Two open-label, parallel-design studies in males and females with normal hepatic function or Child-Pugh mild, moderate, or severe hepatic impairment, or with normal renal function or severe renal impairment. Non-compartmental pharmacokinetic parameters were estimated from plasma concentration-time data. Evacetrapib safety and tolerability were assessed. RESULTS: Pharmacokinetic parameter estimates were comparable between controls and mildly hepatically impaired subjects. Geometric mean area under the concentration-time curve (AUC) was greater, half-life (t1/2) was longer, and maximum concentration (Cmax) was lower in subjects with moderate and severe hepatic impairment than in controls. Apparent clearance (CL/F) did not differ between controls and those with mild hepatic impairment, but CL/F decreased for moderate and severe impairment. Spearman correlation coefficient showed no relationship between CL/F and Child-Pugh score. In the renal study, AUC and t1/2 were similar between groups, while Cmax was 15 % lower in subjects with severe impairment. CL/F in severely renally impaired subjects differed by <6 % from that in controls. Spearman correlation coefficient showed no apparent relationship between CL/F and estimated creatinine clearance or glomerular filtration rate. Neither study noted changes in clinical laboratory parameters or clinically significant findings. Adverse event incidence was low, and all were mild or moderate in severity. CONCLUSION: Evacetrapib exposure did not differ between mild hepatic impairment and normal hepatic function, but increased along the progression from mild to moderate to severe hepatic impairment. Severe renal impairment did not affect evacetrapib exposure.

Absolute bioavailability of evacetrapib in healthy subjects determined by simultaneous administration of oral evacetrapib and intravenous [(13) C8 ]-evacetrapib as a tracer.

This open-label, single-period study in healthy subjects estimated evacetrapib absolute bioavailability following simultaneous administration of a 130-mg evacetrapib oral dose and 4-h intravenous (IV) infusion of 175 µg [(13) C8 ]-evacetrapib as a tracer. Plasma samples collected through 168 h were analyzed for evacetrapib and [(13) C8 ]-evacetrapib using high-performance liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameter estimates following oral and IV doses, including area under the concentration-time curve (AUC) from zero to infinity (AUC[0-∞]) and to the last measureable concentration (AUC[0-tlast ]), were calculated. Bioavailability was calculated as the ratio of least-squares geometric mean of dose-normalized AUC (oral : IV) and corresponding 90% confidence interval (CI). Bioavailability of evacetrapib was 44.8% (90% CI: 42.2-47.6%) for AUC(0-∞) and 44.3% (90% CI: 41.8-46.9%) for AUC(0-tlast ). Evacetrapib was well tolerated with no reports of clinically significant safety assessment findings. This is among the first studies to estimate absolute bioavailability using simultaneous administration of an unlabeled oral dose with a (13) C-labeled IV microdose tracer at about 1/1000(th) the oral dose, with measurement in the pg/mL range. This approach is beneficial for poorly soluble drugs, does not require additional toxicology studies, does not change oral dose pharmacokinetics, and ultimately gives researchers another tool to evaluate absolute bioavailability.

A Multidose Study to Examine the Effect of Food on Evacetrapib Exposure at Steady State.

PURPOSE: To determine the effect of a high-fat meal on evacetrapib exposure at steady state in healthy participants. METHODS: This was a randomized, 2-period, 2-sequence, open-label, crossover study. Patients were randomly assigned to 1 of the 2 treatment sequences in which they received evacetrapib 130 mg/d for 10 days following a 10-hour fast each day or following a high-fat breakfast each day. Plasma samples collected through 24 hours were analyzed for evacetrapib concentrations and pharmacokinetic parameter estimates including area under the concentration-time curve during a dosing interval (AUCτ), maximum observed concentration (Cmax), and time of Cmax (tmax) were calculated. Pharmacodynamic parameters, including cholesteryl ester transfer protein (CETP) activity, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol, and triglycerides, were also assessed. RESULTS: A total of 34 males and 6 females, mean age 41.5 years and mean body mass index 26.6 kg/m(2), were enrolled. Statistical analysis showed AUCτ was 44% higher (90% confidence interval [CI]: 29%-62%) and Cmax was 51% higher (90% CI: 28%-79%) in the fed state than in the fasted state, indicating an effect of food. Consistent with higher evacetrapib exposure, changes in HDL-C, LDL-C, and CETP activity appeared to be greater in the fed state than in the fasted state. There were no notable changes in total cholesterol or triglycerides following administration in the fed and fasted states. The 130-mg doses of evacetrapib were well tolerated with and without food. CONCLUSION: A high-fat meal increased evacetrapib mean exposure at steady state by 44% in healthy participants.

Safety, tolerability, and pharmacokinetic evaluation of single- and multiple-ascending doses of a novel kappa opioid receptor antagonist LY2456302 and drug interaction with ethanol in healthy subjects.

Accumulating evidence indicates that selective antagonism of kappa opioid receptors may provide therapeutic benefit in the treatment of major depressive disorder, anxiety disorders, and substance use disorders. LY2456302 is a high-affinity, selective kappa opioid antagonist that demonstrates >30-fold functional selectivity over mu and delta opioid receptors. The safety, tolerability, and pharmacokinetics (PK) of LY2456302 were investigated following single oral doses (2-60 mg), multiple oral doses (2, 10, and 35 mg), and when co-administered with ethanol. Plasma concentrations of LY2456302 were measured by liquid chromatography-tandem mass spectrometry method. Safety analyses were conducted on all enrolled subjects. LY2456302 doses were well-tolerated with no clinically significant findings. No safety concerns were seen on co-administration with ethanol. No evidence for an interaction between LY2456302 and ethanol on cognitive-motor performance was detected. LY2456302 displayed rapid oral absorption and a terminal half-life of approximately 30-40 hours. Plasma exposure of LY2456302 increased proportionally with increasing doses and reached steady state after 6-8 days of once-daily dosing. Steady-state PK of LY2456302 were not affected by coadministration of a single dose of ethanol. No clinically important changes in maximum concentration (Cmax ) or AUC of ethanol (in the presence of LY2456302) were observed.

The effects of laropiprant on the antiplatelet activity of co-administered clopidogrel and aspirin.

Laropiprant is an antagonist of the prostaglandin PGD2 receptor DP1. Laropiprant has a weak affinity for the thromboxane A2 receptor TP. Two double-blinded, randomized, placebo-controlled, crossover studies evaluated the effects of multiple-dose laropiprant at steady state on the antiplatelet effects of multiple-dose aspirin and clopidogrel. Study 1 had two treatment periods, in which each healthy subject received laropiprant 40 mg, clopidogrel 75 mg, and aspirin 80 mg (Treatment A), or placebo, clopidogrel 75 mg, and aspirin 80 mg (Treatment B) once daily for 7 days. Study 2 consisted of three treatment periods. In the first two, each patient with hypercholesterolemia or mixed dyslipidemia received laropiprant 40 mg, clopidogrel 75 mg, and aspirin 81 mg (Treatment A), or placebo, clopidogrel 75 mg, and aspirin 81 mg (Treatment B) once daily for 7 days. In period 3, patients received a single dose of two tablets of extended release nicotinic acid 1 g/laropiprant 20 mg (Treatment C). In both studies, pharmacodynamic endpoints included bleeding time at 24 (primary) and 4 hours (secondary) post-dose following 7 days of once-daily laropiprant in combination with clopidogrel and aspirin, and platelet aggregation in platelet-rich plasma at 4 and 24 hours post-dose on day 7 (secondary). After 7 days, increased bleeding time of 27% (Study 1) and 23% (Study 2) at 24 hours post-dose was observed with laropiprant compared to placebo (both combined with clopidogrel and aspirin), with corresponding upper bounds of the 90% CI marginally exceeding the prespecified upper comparability bound of 1.50 in both studies. The GMR and 90% CI for bleeding time of laropiprant compared to placebo (both combined with clopidogrel and aspirin) at 4 hours post-dose on day 7 was 0.92 (0.70, 1.21) in Study 1, and 1.46 (1.20, 1.78) in Study 2. Compared with placebo, laropiprant (both combined with clopidogrel and aspirin) increased the inhibition of collagen- and ADP-induced platelet aggregation, respectively, by ∼2.4% and ∼8.1% in Study 1 and by ∼4% and ∼5.4% in Study 2, at 24 hours post-dose on day 7. The inhibition of collagen- and ADP-induced platelet aggregation, respectively, was increased by ∼0.1% and ∼5.0% in Study 1, and by ∼5% and ∼12% in Study 2, at 4 hours post-dose on day 7. In conclusion, co-administration of multiple doses of laropiprant with aspirin and clopidogrel induced a prolongation of bleeding time and an inhibitory effect on platelet aggregation ex vivo in healthy subjects and patients with dyslipidemia.

Investigation of safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of a long-acting α-MSH analog in healthy overweight and obese subjects.

MC4-NN2-0453 is a novel, long-acting, selective, melanocortin-4-receptor agonist developed for treatment of obesity. This first-human-dose, randomized, double-blind, placebo-controlled trial investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of MC4-NN2-0453 in overweight to obese but otherwise healthy subjects. The trial included a single-dose part of ascending subcutaneous 0.03-1.50 mg/kg doses in overweight to obese but otherwise healthy men, and a multiple-dose part of ascending subcutaneous 0.75-3.0 mg/day doses in obese but otherwise healthy men/women. The single-dose part included 7 cohorts of 8 subjects, randomized 6:2 to active drug/placebo; the multiple-dose part included 4 cohorts of 20 subjects, randomized 16:4 to active drug/placebo. MC4-NN2-0453 was well tolerated and raised no safety concerns except for nonserious skin-related adverse events, this along with lack of weight loss effect led to premature termination of the trial. Headache, sexual-arousal disturbance, and penile erection were also reported. Single-dose pharmacokinetics showed dose-linearity and dose-proportionality. Maximum plasma concentration was observed after 50-100 hours, which then declined with a of approximately 250 hours. Plasma concentration reached steady state after 4 weeks for 0.75 and 1.5 mg/day multiple-dose cohorts, and the was similar to single dose. There were no significant pharmacodynamic effects, including effect on body weight.

Effects of extended release niacin/laropiprant, laropiprant, extended release niacin and placebo on platelet aggregation and bleeding time in healthy subjects.

Laropiprant (LRPT) has been shown to reduce flushing symptoms induced by niacin and has been combined with niacin for treatment of dyslipidemia. LRPT, a potent PGD(2) receptor (DP1) antagonist that also has modest activity at the thromboxane receptor (TP), may have the potential to alter platelet function either by enhancing platelet reactivity through DP1 antagonism or by inhibiting platelet aggregation through TP antagonism. Studies of platelet aggregation ex vivo and bleeding time have shown that LRPT, at therapeutic doses, does not produce clinically meaningful alterations in platelet function. The present study was conducted to assess platelet reactivity to LRPT using methods that increase the sensitivity to detect changes in platelet responsiveness to collagen and ADP. The responsiveness of platelets was quantified by determining the EC(50) of collagen to induce platelet aggregation ex vivo. At 24 hours post-dose on Day 7, the responsiveness of platelets to collagen-induced aggregation was similar following daily treatment with extended-release niacin (ERN) 2 g/LRPT 40 mg or ERN 2 g. At 2 hours post-dose on Day 7, the EC(50) for collagen-induced platelet aggregation was approximately two-fold higher in the presence of LRPT, consistent with a small, transient inhibition of platelet responsiveness to collagen. There was no clinical difference between treatments for bleeding time, suggesting that this small effect on collagen EC(50) does not result in a clinically meaningful alteration of platelet function in vivo. The results of this highly sensitive method demonstrate that LRPT does not enhance platelet reactivity when given alone or with ERN.

Single therapeutic and supratherapeutic doses of laropiprant, a selective prostaglandin D2 receptor 1 antagonist, do not prolong the QTcF interval in healthy volunteers.

Laropiprant (LRPT), a prostaglandin D(2) receptor-1 antagonist shown to reduce niacin-induced flushing symptoms, has been combined with niacin for treatment of dyslipidemia. This study evaluated the effects of LRPT (50 mg and 600 mg, respectively) on the QT interval with Fridericia's correction (QTcF). QTcF measurements were made over a 24-hour period following administration of single-dose moxifloxacin 400 mg, LRPT 50 mg, LRPT 600 mg, or placebo. The primary hypothesis was supported if the 90% confidence intervals (CIs) for the least squares (LS) mean differences between placebo and LRPT in change from baseline in QTcF interval were <10 milliseconds at every time point. The upper limits of the 90% CIs for LS mean differences from placebo in changes from baseline in QTcF intervals for LRPT 50 mg and 600 mg were <5 milliseconds at every time point. The lower limits of the 90% CIs for placebo-adjusted LS mean changes from baseline in QTcF intervals for moxifloxacin exceeded 0 milliseconds at every time point, demonstrating the sensitivity of this assay to detect increases in the QTcF interval. In conclusion, single doses of LRPT 50 mg and 600 mg do not prolong the QTcF interval relative to placebo and are generally well tolerated.

Effects of aspirin when added to the prostaglandin D2 receptor antagonist laropiprant on niacin-induced flushing symptoms.

Niacin is an effective lipid-modifying therapy whose use has been limited by suboptimal tolerability. The adverse effect of flushing is due to prostaglandin D2 (PGD2)-mediated cutaneous vasodilation. Adjunctive treatment with the PGD2 receptor antagonist laropiprant significantly reduces the incidence and severity of niacin-induced flushing. The objective of this study was to assess the effect of aspirin pretreatment on flushing symptoms with extended-release (ER) niacin/laropiprant in healthy volunteers. A randomized, double-blind, placebo-controlled crossover study compared patient-rated flushing following pretreatment with aspirin 325 mg versus placebo administered 30 minutes before ER niacin 2 g/laropiprant 40 mg. Flushing responses were assessed using participant-reported overall symptom severity score (OSSS), including individual characteristics of redness, warmth, tingling, or itching. The overall incidence and severity of flushing were comparable for participants receiving aspirin or placebo before ER niacin 2 g/laropiprant 40 mg. The difference in 3-day average OSSS between treatments was 0.2 (P=.180). Profiles of flushing severity, frequency, and bothersomeness were comparable for the aspirin/ER niacin/laropiprant and ER niacin/laropiprant regimens. All treatments were safe and well tolerated. Coadministration of aspirin 325 mg daily with ER niacin 2 g/laropiprant 40 mg does not further reduce residual flushing symptoms associated with ER niacin 2 g/laropiprant 40 mg alone.

Comparative inhibitory activity of etoricoxib, celecoxib, and diclofenac on COX-2 versus COX-1 in healthy subjects.

We determined cyclo-oxygenase-1 and cyclo-oxygenase-2 inhibition in healthy middle-aged subjects (41-65 years) randomly assigned to four 7-day treatment sequences of etoricoxib 90 mg every day, celecoxib 200 mg twice a day, diclofenac 75 mg twice a day, or placebo in a double-blind, randomized, 4-period crossover study. Maximum inhibition of thromboxane B(2) (cyclo-oxygenase-1 activity) in clotting whole blood on day 7 (0-24 hours postdose) was the primary endpoint. Inhibition of lipopolysaccharide-induced prostaglandin E(2) in whole blood (cyclo-oxygenase-2 activity) was assessed on day 7 (0-24 hours postdose) as a secondary endpoint. Diclofenac had significantly greater maximum inhibition of thromboxane B(2) versus each comparator (P < .001); placebo 2.4% (95% confidence interval: -8.7% to 12.3%), diclofenac 92.2% (91.4% to 92.9%), etoricoxib 15.5% (6.6% to 23.5%), and celecoxib 20.2% (11.5% to 28.1%). Prostaglandin E(2) synthesis was inhibited with a rank order of potency of diclofenac > etoricoxib > celecoxib. In summary, at doses commonly used in rheumatoid arthritis, diclofenac significantly inhibits both cyclo-oxygenase-1 and cyclo-oxygenase-2, whereas etoricoxib and celecoxib significantly inhibit cyclo-oxygenase-2 and do not substantially inhibit cyclo-oxygenase-1.

Lack of effect of aprepitant on hydrodolasetron pharmacokinetics in CYP2D6 extensive and poor metabolizers.

To prevent chemotherapy-induced nausea and vomiting, aprepitant is given with a corticosteroid and a 5-hydroxytryptamine type 3 antagonist, such as dolasetron. Dolasetron is converted to the active metabolite hydrodolasetron, which is cleared largely via CYP2D6. The authors determined whether aprepitant, a moderate CYP3A4 inhibitor, alters hydrodolasetron pharmacokinetics in CYP2D6 poor and extensive metabolizers. Six CYP2D6 poor and 6 extensive metabolizers were randomized in an open-label, crossover fashion to treatment A (dolasetron 100 mg on day 1) and treatment B (dolasetron 100 mg plus aprepitant 125 mg on day 1, aprepitant 80 mg on days 2-3). For hydrodolasetron area under the concentration-versus-time curve (AUC0-infinity) and peak plasma concentration (Cmax), geometric mean ratios (B/A) and 90% confidence intervals (CIs) fell below the predefined limit (2.0) for clinical significance (AUC0-infinity, 1.09 [90% CI, 1.01-1.18], Cmax, 1.08 [90% CI, 0.94-1.24]). Aprepitant did not affect the pharmacokinetics of hydrodolasetron, regardless of CYP2D6 metabolizer type, and was generally well tolerated when coadministered with dolasetron in volunteers.