Reduction in Multiple Cardiometabolic Risk Factors With Combined Olanzapine/Samidorphan Compared With Olanzapine: Post Hoc Analyses From a 24-Week Phase 3 Study.

BACKGROUND AND HYPOTHESES: Weight gain and adverse cardiometabolic effects often limit the clinical utility of olanzapine. In ENLIGHTEN-2, combining olanzapine with the opioid receptor antagonist samidorphan (OLZ/SAM) mitigated olanzapine-associated weight gain. These analyses tested the hypothesis that OLZ/SAM would be associated with reduced adverse cardiometabolic effects compared with olanzapine. STUDY DESIGN: This phase 3 double-blind study randomized adults with schizophrenia to OLZ/SAM or olanzapine for 24 weeks. Post hoc analyses assessed changes from baseline to week 24 in cardiometabolic risk parameters, including body mass index (BMI), risk of developing obesity (BMI ≥30 kg/m2) or metabolic syndrome, waist circumference, along with mean and potentially clinically significant changes in blood pressure, glucose, and lipids. RESULTS: After 24 weeks' treatment, compared with olanzapine, OLZ/SAM was associated with smaller least-squares mean (LSM) changes from baseline in systolic blood pressure (LSM difference, -2.63 mm Hg; 95% CI: -4.78, -0.47), diastolic blood pressure (LSM difference, -0.75 mm Hg; 95% CI: -2.31, 0.80), and BMI (LSM difference, -0.65 kg/m2; 95% CI: -1.01, -0.28). OLZ/SAM treatment was also associated with reduced risk of shifting from normal blood pressure to stage 1/2 hypertension (odds ratio [OR], 0.48; 95% CI: 0.24, 0.96), becoming obese (OR, 0.52; 95% CI: 0.32, 0.82), and developing metabolic syndrome (OR, 0.55; 95% CI: 0.31, 0.99) compared with olanzapine. No treatment group differences were noted for risk of hyperglycemia or hyperlipidemia. CONCLUSIONS: OLZ/SAM treatment was associated with lower risk of worsening cardiometabolic risk factors related to obesity, hypertension, and metabolic syndrome relative to olanzapine. NCT02694328, https://clinicaltrials.gov/ct2/show/NCT02694328.

An Evidence-Based Review of OLZ/SAM for Treatment of Adults with Schizophrenia or Bipolar I Disorder.

Olanzapine effectively treats schizophrenia and bipolar I disorder (BD-I); however, its use is limited by the risk of significant weight gain and metabolic effects. OLZ/SAM, a combination of olanzapine and samidorphan, was recently approved in the United States for the treatment of adults with schizophrenia or BD-I. OLZ/SAM provides the efficacy of olanzapine while mitigating olanzapine-associated weight gain through opioid-receptor blockade. Here, we summarize OLZ/SAM clinical data characterizing pharmacokinetics, antipsychotic efficacy, weight mitigation efficacy, safety, and long-term treatment effects. In an acute exacerbation of schizophrenia, OLZ/SAM and olanzapine provided similar symptom improvements versus placebo at week 4. In stable outpatients with schizophrenia, OLZ/SAM treatment resulted in significantly less weight gain, reducing the risk for clinically significant weight gain and waist circumference increases of ≥5 cm by half, compared with olanzapine at week 24. Based on open-label extension studies, OLZ/SAM is safe and well tolerated for up to 3.5 years of treatment, while maintaining schizophrenia symptom control and stabilizing weight. The olanzapine component of OLZ/SAM was bioequivalent to branded olanzapine (Zyprexa); adjunctive OLZ/SAM had no clinically significant effects on lithium or valproate pharmacokinetics. Additionally, OLZ/SAM had no clinically relevant effect on electrocardiogram parameters in a dedicated thorough QT study. Overall, safety and tolerability findings from clinical studies with OLZ/SAM indicate a similar safety profile to that of olanzapine, with the exception of less weight gain. As OLZ/SAM contains the opioid antagonist samidorphan, it is contraindicated in patients using opioids and in those undergoing acute opioid withdrawal. Clinical trial results from more than 1600 subjects support the use of OLZ/SAM as a new treatment option for patients with schizophrenia or BD-I.

A phase 3, multicenter study to assess the 1-year safety and tolerability of a combination of olanzapine and samidorphan in patients with schizophrenia: Results from the ENLIGHTEN-2 long-term extension.

AIM: A combination of olanzapine and samidorphan (OLZ/SAM) is in development for the treatment of patients with schizophrenia or bipolar I disorder and is intended to provide the efficacy of olanzapine while mitigating olanzapine-associated weight gain. This 52-week open-label extension (NCT02873208; ENLIGHTEN-2-EXT) assessed the long-term safety and tolerability of OLZ/SAM in patients with schizophrenia. METHODS: Patients completing the 24-week randomized, double-blind, phase 3 ENLIGHTEN-2 study (NCT02694328) comparing weight change from baseline to week 24 with OLZ/SAM versus olanzapine were eligible to enroll in the 52-week ENLIGHTEN-2-EXT study. Assessments included adverse events (AEs; each visit), weight/waist circumference (every other week for the first 8 weeks, then every 4 weeks thereafter), metabolic laboratory parameters (weeks 4, 12, 24, 36, and 52), Positive and Negative Syndrome Scale (PANSS) scores (weeks 2, 4, 8, 12, 24, 36, and 52), and Clinical Global Impression-Severity (CGI-S) scores (weeks 2 and 4, then every 4 weeks thereafter through week 48, and at week 52). Analyses were based on observed results using descriptive statistics. Baseline was relative to the first OLZ/SAM dose in the extension study. RESULTS: In total, 265 patients were enrolled and received at least 1 dose of OLZ/SAM; 167 (63.0%) completed the 52-week extension study. Common AEs (≥5%) were weight decreased (n = 23; 8.7%), extra dose administered (n = 21; 7.9%), headache (n = 18; 6.8%), and weight increased (n = 16; 6.0%). At week 52, the mean (SD) change from baseline for weight and waist circumference was -0.03 (6.17) kg and - 0.35 (6.12) cm, respectively. Changes in fasting lipid and glycemic parameters were generally small and remained stable over 52 weeks. During the extension, PANSS total scores remained stable, and at week 52, 81.3% of patients had CGI-S scores of 3 or less, reflecting mild illness severity. CONCLUSIONS: OLZ/SAM was generally well tolerated over 52 weeks. Weight, waist circumference, metabolic laboratory parameters, and schizophrenia symptoms remained stable throughout the study.

Effects of Olanzapine Combined With Samidorphan on Weight Gain in Schizophrenia: A 24-Week Phase 3 Study.

OBJECTIVE: A combination of olanzapine and the opioid receptor antagonist samidorphan is under development for the treatment of schizophrenia and bipolar I disorder. The single-tablet combination treatment is intended to provide the efficacy of olanzapine while mitigating olanzapine-associated weight gain. In this phase 3 double-blind trial, the authors evaluated the weight profile of combined olanzapine/samidorphan compared with olanzapine in patients with schizophrenia. METHODS: Adults (ages 18‒55 years) with schizophrenia were randomly assigned to receive either combination treatment with olanzapine and samidorphan or olanzapine treatment for 24 weeks. Primary endpoints were percent change from baseline in body weight and proportion of patients with ≥10% weight gain at week 24. The key secondary endpoint was the proportion of patients with ≥7% weight gain. Waist circumference and fasting metabolic laboratory parameters were also measured. RESULTS: Of 561 patients who underwent randomization (olanzapine/samidorphan combination, N=280; olanzapine, N=281), 538 had at least one postbaseline weight assessment. At week 24, the least squares mean percent weight change from baseline was 4.21% (SE=0.68) in the olanzapine/samidorphan group and 6.59% (SE=0.67) in the olanzapine group (the difference of -2.38% [SE=0.76] was significant). Significantly fewer patients in the olanzapine/samidorphan combination group compared with the olanzapine group had weight gain ≥10% (17.8% and 29.8%, respectively; number needed to treat [NNT]=7.29; odds ratio=0.50) and weight gain ≥7% (27.5% and 42.7%, respectively; NNT=6.29; odds ratio=0.50). Increases in waist circumference were smaller in the olanzapine/samidorphan combination group compared with the olanzapine group. Schizophrenia symptom improvement was similar between treatment groups. Adverse events (in ≥10% of the groups) in the olanzapine/samidorphan and olanzapine groups included weight gain (24.8% and 36.2%), somnolence (21.2% and 18.1%), dry mouth (12.8% and 8.0%), and increased appetite (10.9% and 12.3%). Metabolic changes were small and similar between treatments. CONCLUSIONS: Olanzapine/samidorphan combination treatment was associated with significantly less weight gain and smaller increases in waist circumference than olanzapine and was well tolerated. The antipsychotic efficacy of the combination treatment was similar to that of olanzapine monotherapy.

Olanzapine Plus Samidorphan (ALKS 3831) in Schizophrenia and Comorbid Alcohol Use Disorder: A Phase 2, Randomized Clinical Trial.

OBJECTIVE: Alcohol use disorder (AUD) is a common comorbidity of schizophrenia. No effective pharmacologic treatment is available for both disorders to date. METHODS: In a phase 2, double-blind study, patients with schizophrenia and AUD experiencing ≥ 10 drinking and ≥ 2 heavy-drinking days in the previous month and recent (≤ 6 mo) disease symptom exacerbation were recruited between June 2014 and March 2017. DSM-IV-TR and DSM-5 criteria were used to assign the diagnoses of schizophrenia and AUD, respectively. After a 6-week lead-in period, 234 eligible patients were randomized (1:1) to olanzapine + 10 mg samidorphan tablets (OLZ/SAM) or olanzapine + placebo tablets (olanzapine) for 36-60 weeks of treatment. The primary outcome of time to the first event of exacerbation of disease symptoms (EEDS) was evaluated using the log rank test for treatment comparison, and the Cox proportional-hazards model was used to estimate hazard ratio. Safety was assessed as adverse events and laboratory measures. RESULTS: No significant difference was observed between groups in the time to first EEDS (hazard ratio = 0.91; 95% CI, 0.53-1.56; P = .746). Patients treated with OLZ/SAM vs olanzapine had numerically lower rates in 6 of 8 criteria to evaluate EEDS. Change from baseline in percentage of heavy-drinking days during the double-blind treatment period was similar in OLZ/SAM- vs olanzapine-treated patients. OLZ/SAM was generally well tolerated with a safety profile similar to olanzapine. CONCLUSIONS: OLZ/SAM was not superior to olanzapine in the time to EEDS and was well tolerated in patients with schizophrenia and AUD. Further research is needed to identify effective treatments for this difficult-to-treat population. TRIAL REGISTRATIONS: ClinicalTrials.gov identifier: NCT02161718; EudraCT number: 2014-001211-39 ​.

Course of Psychosis in Schizophrenia With Alcohol Use Disorder: A Post Hoc Analysis of the Clinical Antipsychotic Trials of Intervention Effectiveness in Schizophrenia Phase 1 Study.

OBJECTIVE: Patients with schizophrenia and comorbid alcohol use disorder remain understudied. This post hoc analysis evaluated data from Phase 1 of the Clinical Antipsychotic Trials of Intervention Effectiveness in Schizophrenia study (January 2001-December 2004). METHODS: Patients without substance abuse (except marijuana use) in the month before study entry were categorized into those with a history of alcohol use disorder (SZ + AUD) within 5 years before study entry and those without alcohol use disorder (SZ-only) per DSM-IV criteria. Time to first and recurrent exacerbations and hospitalizations were compared between disease states and between olanzapine and perphenazine, quetiapine, risperidone, and ziprasidone. RESULTS: A total of 1,338 patients (SZ + AUD = 22.6%; SZ-only = 77.4%) were included. Time to first exacerbation of SZ was significantly shorter in the SZ + AUD versus SZ-only population (median = 5.4 vs 6.4 months; hazard ratio [HR] = 1.20 [95% CI, 1.01-1.42]; P = .039). Similar findings were observed for first hospitalization (HR = 1.63 [95% CI, 1.20-2.22]; P = .002) and recurrent hospitalizations (HR = 1.60 [95% CI, 1.18-2.15]; P = .002). The most common reasons leading to exacerbation in both groups were an increase in symptom severity and lack of efficacy. In patients with SZ + AUD related or unrelated to marijuana, perphenazine, quetiapine, risperidone, and ziprasidone were associated with significantly shorter time to first exacerbation versus olanzapine. CONCLUSIONS: This post hoc analysis confirmed that patients with SZ + AUD had a worse illness course than patients with SZ-only and suggests that olanzapine may be associated with a longer time to first and recurrent exacerbations versus other antipsychotics in this difficult-to-treat population. Further research is needed to identify effective treatments for this important yet understudied patient population. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00014001.

Efficacy and Safety of a Combination of Olanzapine and Samidorphan in Adult Patients With an Acute Exacerbation of Schizophrenia: Outcomes From the Randomized, Phase 3 ENLIGHTEN-1 Study.

OBJECTIVE: To assess the antipsychotic efficacy and safety of a combination of olanzapine and samidorphan (OLZ/SAM). METHODS: This 4-week, phase 3, randomized, double-blind, placebo- and olanzapine-controlled study was conducted from December 2015 to June 2017 in adults with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria who were experiencing an acute exacerbation. Patients were randomized 1:1:1 to OLZ/SAM, olanzapine monotherapy, or placebo. The primary and key secondary efficacy endpoint assessed was the change in Positive and Negative Syndrome Scale (PANSS) total score and Clinical Global Impressions-Severity of Illness Scale (CGI-S) score between baseline and week 4, respectively, for OLZ/SAM versus placebo. Safety monitoring occurred throughout. RESULTS: 401 patients received ≥ 1 dose of study drug; 352 completed treatment. Treatment with OLZ/SAM resulted in significant improvements versus placebo in PANSS total and CGI-S scores from baseline to week 4 (least squares [LS] mean ± SE: -6.4 ± 1.8 [P < .001] and -0.38 ± 0.12 [P = .002], respectively). Olanzapine treatment resulted in similar improvements (PANSS and CGI-S LS mean ± SE of -5.3 ± 1.84 [P = .004] and -0.44 ± 0.12 [P < .001], respectively). Adverse events (AEs) occurred in 54.5%, 54.9%, and 44.8% of patients on OLZ/SAM, olanzapine, and placebo, respectively. Weight gain, somnolence, dry mouth, anxiety, and headache were the most common AEs (ie, ≥ 5%) with active treatment. CONCLUSIONS: OLZ/SAM treatment resulted in statistically and clinically significant efficacy improvements over 4 weeks versus placebo in adults with acutely exacerbated schizophrenia. Improvements were similar to those observed with olanzapine. OLZ/SAM was well tolerated, with a safety profile similar to that of olanzapine. TRIAL REGISTRATIONS: ClinicalTrials.gov identifier: NCT02634346; EudraCT number: 2015-003373-15​​.

Olanzapine Plus Samidorphan in Subjects with Schizophrenia and Comorbid Alcohol Use Disorder: Rationale and Design for a Phase II, Double-blind, Randomized Study.

Background: Alcohol use disorder (AUD) is a common comorbidity in patients with schizophrenia. Although pharmacological options for the management of each disease exist separately, there is no agent approved for both. Moreover, studies conducted in this patient population, who face practical and social challenges as a consequence of being diagnosed with schizophrenia and comorbid AUD, are limited. Methods: We describe the design of a Phase II, double-blind, randomized trial to evaluate adult outpatients with schizophrenia and comorbid AUD receiving a combination of olanzapine plus samidorphan (OLZ+SAM; ALKS 3831), a novel entity currently under development for the treatment of schizophrenia. The combination drug formulation of OLZ+SAM is intended to provide the antipsychotic efficacy of OLZ while mitigating the weight gain and concomitant metabolic abnormalities commonly associated with OLZ alone. In considering this patient population, the novel primary efficacy endpoint is the time from randomization to the first event of exacerbation of disease symptoms (EEDS) based on the occurrence of any of eight prespecified events related to worsening of disease symptoms and/or AUD, as confirmed by a blinded independent adjudication committee. The rate and number of EEDS, improvement in drinking level, and the safety and tolerability of OLZ in combination with SAM will also be assessed. Discussion: A limited number of studies have been conducted in patients with schizophrenia and AUD, and the need for further research in this difficult-to-study population is well documented. This study is, to our knowledge, the largest and longest trial with a randomized, double-blind, active-controlled design. In addition to providing evidence for the development of OLZ+SAM (ALKS 3831) as a therapeutic option, the study aims to provide insights into the clinical management of subjects with schizophrenia and comorbid AUD. Trial registration: Clinical trials NCT02161718, registered May 2014; EudraCT Number: 2014-001211-39.

Mitigation of Olanzapine-Induced Weight Gain With Samidorphan, an Opioid Antagonist: A Randomized Double-Blind Phase 2 Study in Patients With Schizophrenia.

OBJECTIVE: Preclinical evidence and data from a proof-of-concept study in healthy volunteers suggest that samidorphan, an opioid antagonist, mitigates weight gain associated with olanzapine. This study prospectively compared combination therapy of olanzapine plus either samidorphan or placebo for the treatment of schizophrenia. METHODS: This was an international, multicenter, randomized phase 2 study of olanzapine plus samidorphan in patients with schizophrenia. The study had a 1-week open-label olanzapine lead-in period followed by a 12-week double-blind treatment phase in which patients were randomly assigned in a 1:1:1:1 ratio to receive olanzapine plus placebo (N=75) or olanzapine plus 5 mg (N=80), 10 mg (N=86), or 20 mg (N=68) of samidorphan. The primary aims were to confirm that the antipsychotic efficacy of olanzapine plus samidorphan was comparable to olanzapine plus placebo, to assess the effect of combining olanzapine with samidorphan on olanzapine-induced weight gain, and to assess the overall safety and tolerability of olanzapine plus samidorphan. RESULTS: Antipsychotic efficacy, as assessed by total score on the Positive and Negative Syndrome Scale (PANSS), was equivalent across all treatment groups. Treatment with olanzapine plus samidorphan resulted in a statistically significant lower weight gain (37% lower weight gain compared with olanzapine plus placebo). The least square mean percent change from baseline in body weight was 4.1% (2.9 kg) for the olanzapine plus placebo group and 2.6% (1.9 kg) for the olanzapine plus samidorphan group (2.8% [2.1 kg] for the 5 mg group, 2.1% [1.5 kg] for the 10 mg group, and 2.9% [2.2 kg] for the 20 mg group). Adverse events reported at a frequency ≥5% in any of the olanzapine plus samidorphan groups and occurring at a rate ≥2 times greater than in the olanzapine plus placebo group were somnolence, sedation, dizziness, and constipation. Other safety measures were comparable between the olanzapine plus samidorphan groups and the olanzapine plus placebo group. CONCLUSIONS: The antipsychotic efficacy of olanzapine plus samidorphan was equivalent to that of olanzapine plus placebo, and olanzapine plus samidorphan was associated with clinically meaningful and statistically significant mitigation of weight gain compared with olanzapine plus placebo. Olanzapine plus samidorphan was generally well tolerated, with a safety profile similar to olanzapine plus placebo.

Abuse Potential of Samidorphan: A Phase I, Oxycodone-, Pentazocine-, Naltrexone-, and Placebo-Controlled Study.

Samidorphan is a µ-opioid receptor antagonist in development for the treatment of schizophrenia, in combination with olanzapine, and major depressive disorder, in combination with buprenorphine, at proposed therapeutic doses of samidorphan 10 mg and 2 mg, respectively. A double-blind, double-dummy, active- and placebo-controlled, crossover study evaluated the abuse potential of samidorphan in healthy, nondependent, recreational opioid users. Following a qualification phase, participants were randomized to 1 of 6 treatment sequences of study drugs: placebo, samidorphan (10 or 30 mg), oxycodone (40 mg), pentazocine (30 mg), and naltrexone (100 mg) in a 6 × 6 Williams design. The primary end point was maximum effect (Emax ) for "at-the-moment" Drug Liking visual analog scale scores. Secondary end points included Emax visual analog scale scores for Take Drug Again and Overall Drug Liking and safety assessments. Among 47 participants, at-the-moment Emax Drug Liking scores for positive study controls oxycodone and pentazocine were significantly higher than placebo (P < .001) and samidorphan (both doses; P < .001). Both samidorphan doses had Emax Drug Liking scores similar to placebo and naltrexone (median within-subject differences of 0.0). Emax Take Drug Again scores for samidorphan (both doses) were higher than placebo, but similar to naltrexone, an unscheduled µ-opioid receptor antagonist. Adverse events to evaluate abuse potential occurred less frequently with samidorphan, naltrexone, and placebo than with oxycodone and pentazocine. Findings from this study support a lack of abuse potential with samidorphan at doses up to 30 mg and a safety profile consistent with previous samidorphan clinical studies.

A randomized, double-blind, placebo-controlled proof of concept study to evaluate samidorphan in the prevention of olanzapine-induced weight gain in healthy volunteers.

Antipsychotic medications are associated with weight gain and adverse metabolic effects that complicate the treatment and management of schizophrenia. Olanzapine (OLZ) in particular is associated with significant weight gain and adverse metabolic effects. The present Phase 1, proof of concept, multicenter, randomized, double-blind, placebo-controlled study investigated the safety and effect on weight of a combination of OLZ (10mg) and the opioid modulator samidorphan (SAM; 5mg) in comparison to OLZ alone in healthy, male normal weight volunteers. Altogether, 106 male subjects with stable body weight and BMI 18-25kg/m2 were randomized to OLZ alone, OLZ+SAM, SAM alone, or placebo in a 2:2:1:1 ratio. The primary efficacy endpoint, mean (SD) body weight change from baseline to last assessment in the 3-week treatment period, was significantly less for OLZ+SAM vs. OLZ alone subjects [+2.2 (1.4) kg vs. +3.1 (1.9) kg; respectively; p=0.02]. In contrast, there was no significant difference in weight from baseline for either SAM or placebo [+0.1 (1.0) kg and +0.8 (1.4) kg, respectively]; p=0.09. Overall, OLZ+SAM compared to OLZ alone had similar safety and tolerability. In addition, less nausea was observed in subjects given OLZ+SAM compared to SAM alone. Thus, OLZ+SAM may offer effective treatment of schizophrenia with less weight gain and metabolic risk. Additional research exploring additional doses over longer durations in psychiatric populations is warranted.

Opioid Modulation With Buprenorphine/Samidorphan as Adjunctive Treatment for Inadequate Response to Antidepressants: A Randomized Double-Blind Placebo-Controlled Trial.

OBJECTIVE: Major depressive disorder has been associated with dysregulation of the endogenous opioid system. The authors sought to determine whether opioid modulation achieved through administration of ALKS 5461, a combination of a µ- and κ-opioid partial agonist, buprenorphine, and a µ-opioid antagonist, samidorphan, would exhibit antidepressant activity in patients with major depression. METHOD: A multicenter, randomized, double-blind, placebo-controlled, two-stage sequential parallel comparison design study was conducted in adults with major depression who had an inadequate response to one or two courses of antidepressant treatment. Participants were randomly assigned to receive adjunctive treatment with 2 mg/2 mg of buprenorphine/samidorphan (the 2/2 dosage group), 8 mg/8 mg of buprenorphine/samidorphan (the 8/8 dosage group), or placebo. Antidepressant effect was measured based on change from baseline to the end of 4 weeks of treatment on the 17-item Hamilton Depression Rating Scale (HAM-D), the Montgomery-Åsberg Depression Rating Scale (MADRS), and the Clinical Global Impressions severity scale (CGI-S). RESULTS: Compared with the placebo group, there were significantly greater improvements in the 2/2 dosage group across the three depression outcome measures (HAM-D: -2.8, 95% CI=-5.1, -0.6; MADRS: -4.9, 95% CI=-8.2, -1.6; CGI-S: -0.5, 95% CI=-0.9, -0.1). There was also evidence of improvement in the 8/8 dosage group, although it did not achieve statistical significance. Overall, the buprenorphine/samidorphan combinations were well tolerated, and there was no evidence of opioid withdrawal on treatment discontinuation. CONCLUSIONS: The buprenorphine/samidorphan combination is a novel and promising candidate for treatment of major depressive disorder in patients who have an inadequate response to standard antidepressants.

Single- and multiple-dose pharmacokinetics of samidorphan, a novel opioid antagonist, in healthy volunteers.

PURPOSE: Samidorphan (3-carboxamido-4-hydroxy naltrexone) is a novel opioid receptor antagonist that is currently in clinical development. The oral dose pharmacokinetics, safety, and tolerability of samidorphan were evaluated in 2 double-blind, placebo-controlled, randomized studies in healthy adults. METHODS: The first study investigated single, ascending doses of 3.7 to 55.7 mg of samidorphan in 16 healthy adults; the second study evaluated multiple ascending doses of 10 or 20 mg of samidorphan administered for 7 days in 30 healthy adults. FINDINGS: Across the two studies, 39 of 46 subjects were male; 32 were white, 11 were black, and 3 were hispanic. Mean age was 34.9 years and mean weight was 84.2 kg. In both studies, samidorphan was rapidly absorbed, with a Tmax of 1 hour, and AUC increased with increasing dose. Samidorphan plasma levels declined in a monoexponential manner, with a half-life of ~7 to 9 hours. After multiple doses, steady state was approached by day 6 and achieved by day 7 after the 10-mg dose, but steady state was not reached for the 20-mg dose. Accumulation was low, with accumulation ratios <1.65. In both studies, samidorphan was generally well tolerated, with somnolence reported as the most common adverse event. IMPLICATIONS: In these single- and multiple-dose studies in healthy volunteers, samidorphan exhibited a pharmacokinetic profile consistent with once-daily dosing. ClinicalTrials.gov identifier: NCT00800319.