ABSTRACT The objective of this study was to support posaconazole dose regimens in pediatric patients aged ≥2 years, using a population pharmacokinetic (PK) approach with data from a phase 1b study (NCT02452034). A one-compartment model with first-order absorption was fit to pharmacokinetic data from 144 participants aged 2 to 17 years, who were administered posaconazole as intravenous (IV) and powder for oral suspension (PFS) formulations, or IV only, at dosing regimens of 3.5, 4.5, and 6 mg/kg. The influence of demographic and clinical factors on pharmacokinetic parameters was evaluated using a stepwise forward inclusion/backward exclusion procedure. The final model simulated posaconazole exposure in patients aged 2 to <7 and 7 to 17 years at dosing regimens of 4.5, 6, and 7.5 mg/kg. Plasma concentration data following IV and PFS administration were well-described by a one-compartment model with first-order absorption and estimated bioavailability, where clearance and volume were subject to allometric scaling by body weight. The 6-mg/kg dosing regimen achieved the pharmacokinetic target (90% of the pediatric population having an average steady-state plasma concentration of ≥500 and <2,000 ng/mL) for both age groups, regardless of whether patients received IV and PFS or IV only. In a virtual adolescent population (body weight >40 kg), the 300 mg/day posaconazole tablet was also predicted to achieve the pharmacokinetic target and remain within a safe range of exposure. These data informed a weight-based nomogram for PFS dosing to maximize the number of pediatric patients achieving the pharmacokinetic target across weight bands, while also maintaining a favorable benefit/risk profile.

Purpose/Background This study was designed as an early assessment of the safety of the orexin receptor antagonist suvorexant, but also included exploratory assessments of balance and psychomotor performance that are the focus of this report. Methods/Procedures This was a double-blind, randomized, 3-period, crossover, phase 1 study. Balance and psychomotor performance were evaluated during the night in 12 healthy elderly participants after bedtime administration of suvorexant 30 mg (a supratherapeutic dose), the GABAergic agonist zolpidem 5 mg (the recommended dose in the elderly), or placebo. Balance (body sway measured by platform stability) and psychomotor performance (measured by choice reaction time) were assessed predose and at 1.5, 4, and 8 hours postdose in each period. Memory (measured by word recall) was assessed predose and at 4 hours postdose. Findings/Results At 1.5 hours after nighttime administration of each drug (the approximate time of their anticipated maximal plasma concentrations), both zolpidem and suvorexant increased body sway versus placebo, with a greater increase for zolpidem than suvorexant. Suvorexant increased choice reaction time compared with placebo or zolpidem at 1.5 hours. There were no treatment differences on body sway or choice reaction time at 4 or 8 hours, or on word recall at 4 hours. Implications/Conclusions These exploratory data suggest that a 30-mg dose of suvorexant (supratherapeutic) and a 5-mg dose of zolpidem (recommended dose in the elderly) impaired balance at 1.5 hours in healthy elderly people, with potentially less impairment for suvorexant relative to zolpidem, but no treatment differences on body sway or psychomotor performance at 4 and 8 hours. Because of their exploratory nature, these findings and their clinical relevance, if any, require confirmation in a prospective study.

This study characterized the multidose pharmacokinetic (PK) characteristics of posaconazole tablets used as prophylactic antifungal therapy in Chinese patients with acute myelogenous leukemia (AML) at risk for invasive fungal infection (IFI). Participants in this open-label, single-arm, phase 1b study received posaconazole 300 mg twice daily on day 1 and then once daily for up to 28 days. In the intensive PK sampling subgroup, posaconazole was administered under fasting conditions on days 1 and 8, and blood samples were regularly collected over 24 h. Trough PK sampling was conducted in all participants on days 1, 2, 3, 8, 14, 21, and 28 without regard for food intake. Population PK characteristics were predicted using PK modeling. Primary endpoints were steady-state average concentration (Cavg) and percentage of participants with steady-state Cavg (predicted and observed) > 500 ng/ml. Treatment safety and efficacy were secondary endpoints. Sixty-five adult Chinese participants were enrolled. On day 8, steady-state arithmetic mean Cavg was 1610 ng/ml (% coefficient of variation [%CV] 42.8%) in the intensive PK subgroup (n = 20). All participants achieved a steady-state Cavg > 500 ng/ml. Predicted Cavg (pCavg) was 1770 ng/ml (%CV 33.7%) in the total population (n = 64); 92.2% of participants had pCavg values ≥ 500 ng/ml (n = 59). The posaconazole tablet safety profile was consistent with that of the oral formulation, and the IFI rate was 3%. In Chinese AML patients, the posaconazole 300-mg tablet provided PK data comparable with those of previous studies and was generally well tolerated and efficacious. ClinicalTrials.gov, NCT02387983.

Posaconazole is approved for use in adults as an intravenous (IV) solution and two different oral formulations (a suspension and an improved bioavailability tablet). Data on the pharmacokinetics (PK), dosing and safety of posaconazole in children are limited. A novel powder for oral suspension (PFS) offers the bioavailability of the tablet formulated for weight-based dosing in children. A non-randomised, openlabel, sequential dose-escalation, phase 1b trial evaluated the PK and safety of posaconazole IV and PFS in children aged 2 to 17 years with documented or expected neutropenia (ClinicalTrials.gov, NCT02452034; MSD protocol number, MK-5592-P097). Participants received posaconazole IV 3.5, 4.5 or 6.0 mg/kg/d for >= 10 days, with an option to switch to posaconazole PFS at the identical dose for <= 18 days. The target exposure was a mean within-dose cohort average steady-state plasma concentration (C-avg) of similar to 1200 ng/mL, with similar to 90% of participants achieving C avg between 500 and 2500 ng/mL. Doses of 4.5 and 6.0 mg/kg/d achieved the PK target of similar to 90% of participants with a C-avg >= 500 ng/mL. PFS resulted in lower posaconazole exposures than IV across age groups at all doses. Posaconazole IV and PFS were well tolerated and had safety profiles similar to those reported for adults. Posaconazole PK following IV and PFS administration was well characterised by the data and enable selection of appropriate paediatric doses. Both formulations were well tolerated without dose-, exposure- or age-related differences in the safety profiles. (c) 2020 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.

Fine‐needle aspiration (FNA) for serial hepatic sampling may be an efficient and less invasive alternative to core needle biopsy (CNB), the current standard for liver tissue sampling. In this randomized, open‐label trial in 31 participants with hepatitis C virus genotype 1 infection (NCT01678131/Merck protocol PN048), we evaluated the feasibility of using FNA to obtain human liver tissue samples appropriate for measuring hepatic pharmacokinetics (PK), using vaniprevir as a tool compound. The primary end point was successful retrieval of liver tissue specimens with measurable vaniprevir concentrations at two of three specified FNA time points. Twenty‐nine patients met the primary end point and, therefore, were included in the PK analyses. Hepatic vaniprevir concentrations obtained with FNA were consistent with known vaniprevir PK properties. The shape of liver FNA and CNB concentration‐time profiles were comparable. In conclusion, FNA may be effective for serial tissue sampling to assess hepatic drug exposure in patients with liver disease.

Abstract Background Posaconazole is approved in adults for prophylaxis and treatment of invasive fungal disease. Two formulations that offer weight-based dosing—intravenous (IV) and oral powder for suspension (PFS)—are being evaluated in children. A population pharmacokinetic (popPK) approach was used to characterize and predict the PK exposure of posaconazole PFS and IV formulations in children to identify dosages associated with achieving a target PK of 1200 ng/mL as the mean Cavg and individual Cavg ≥500 ng/mL and <2500 ng/mL in ~90% of patients. Methods A popPK model was developed through nonlinear mixed-effects modeling using data obtained from a trial in children with neutropenia (ClinicalTrials.gov, NCT02452034; Merck protocol, MK-5592-097). Three dose cohorts (3.5, 4.5, and 6 mg/kg/day [≤300 mg/day]) were studied in two age groups (2–<7 years and 7–17 years). Posaconazole IV was administered twice on day 1 then once daily through at least day 10, followed by PFS once daily through day 28 at clinician discretion. A compartmental model, including both formulations, was fit to the data. Model selection was based on the Log-Likelihood Criterion, goodness-of-fit plots, and scientific plausibility. Significance of the covariates was assessed in a stepwise forward inclusion/backward procedure. An additional assessment characterized the impact of different food covariates on bioavailability. Results An open one-compartmental PK model with first-order absorption and estimated bioavailability, as well as allometrically scaled effects of body weight on clearance and volume, adequately described the PK of posaconazole IV and PFS formulations. Model predictions are shown in the Table. Effects of the different food covariates were not statistically significant. Simulations indicated that for the 6-mg/kg/d dose, model-predicted Cavg generally met PK targets. Model-predicted Cavg was ≥500 ng/mL in >90% of subjects in all cohorts. The 1200-ng/mL target geometric mean Cavg was achieved for all but the 2–<7 years cohort receiving the PFS formulation. Conclusion This popPK-based analysis demonstrated that the 6-mg/kg/d dose of IV or PFS posaconazole formulation (≤300 mg/days) is appropriate for children (2–17 years) and that PFS can be administered without regard to food. Disclosures All authors: No reported disclosures.

New intravenous and solid oral formulations of the antifungal agent posaconazole have been developed. This randomized, open-label, crossover study in 18 healthy adult Chinese male and female subjects evaluated the pharmacokinetics of single-dose posaconazole (oral 300-mg posaconazole tablet fasted, intravenous 300-mg posaconazole solution fasted, and oral 300-mg posaconazole tablet with standard high-fat breakfast). Primary objectives were to determine the single-dose pharmacokinetics of posaconazole in healthy Chinese subjects when administered as an intravenous solution and as an oral tablet under fasted conditions and the effect of food on the absorption of posaconazole. The three treatments consisted of the following: a single oral dose of posaconazole 300 mg (fasted), a single oral dose of posaconazole 300 mg (high-fat breakfast), and a single intravenous dose of posaconazole 300 mg (fasted). Blood samples for pharmacokinetic analysis were collected before dosing and at regular intervals after dosing. Adverse events were monitored throughout. The pharmacokinetic population included the per-protocol population. The safety population included all subjects who received one or more doses of the study drug. Time to maximum plasma concentration of intravenous posaconazole coincided with the end of infusion; the half-life (t½) was 25.76 h. Geometric mean (% coefficient of variation) values of area under the plasma concentration–time curve from time 0 extrapolated to infinity (AUC0–∞) and maximum plasma concentration (Cmax) were 59,925 (36.2%) h·ng/mL and 3999 (28.5%) ng/mL, respectively. The posaconazole tablet had a time to maximum plasma concentration of 4 h and a t½ of 25.21 h after fasting. Geometric mean (coefficient of variation) values of AUC0–∞ and Cmax were 25,263 (39.9%) h·ng/mL and 674.5 (29.6%) ng/mL, respectively. Standard high-fat breakfast increased the exposure of posaconazole approximately twofold with geometric mean ratios (high-fat breakfast/fasted) for AUC0–∞ and Cmax of 2.06 (90% confidence interval 1.86–2.30) and 1.95 (90% confidence interval 1.65–2.31), respectively. The geometric mean absolute bioavailability of the tablet formulation was 42.2% in the fasted state and 87.1% under high-fat breakfast conditions. The most commonly reported adverse events were nausea, vomiting, dizziness, and first-degree atrioventricular block for intravenous posaconazole 300 mg and nausea for oral posaconazole 300 mg (high-fat breakfast). All adverse events were mild and resolved without sequelae. Posaconazole was generally well tolerated in healthy Chinese male and female subjects. The safety and the high-fat breakfast and fasted pharmacokinetics of posaconazole in healthy Chinese subjects are within exposures demonstrated to be generally well tolerated and efficacious and compare reasonably well with the overall posaconazole data across Western countries.

BACKGROUND:Posaconazole (POS) is a potent triazole antifungal agent approved in adults for treatment and prophylaxis of invasive fungal infections (IFIs). The objectives of this study were to evaluate the pharmacokinetics (PK), safety, and tolerability of POS oral suspension in pediatric subjects with neutropenia.METHODS:This was a prospective, multicenter, sequential dose-escalation study. Enrolled subjects were divided into 3 age groups: AG1, 7 to <18 years; AG2, 2 to <7 years; and AG3, 3 months to <2 years. AG1 and AG2 were divided into 3 dosage cohorts: DC1, 12 mg/kg/day divided twice daily (BID); DC2, 18 mg/kg/day BID; and DC3, 18 mg/kg/day divided thrice daily (TID). AG3 was also divided into DC1 and DC2; however, no subjects were enrolled in DC2. Subjects received 7-28 days of POS oral suspension. PK samples were collected at predefined time points. The POS PK target was predefined as ~90% of subjects with Cavg (AUC /dosing interval) between 500 and 2500 ng/mL, with an anticipated mean steady state Cavg exposure of ~1200 ng/mL.RESULTS:The percentage of subjects meeting the PK target was <90% across all age groups and dosage cohorts (range: 31% to 80%). The percentage of subjects that achieved the Cavg target of 500 to 2500 ng/mL on Day 7 ranged from 31% to 80%, with the lowest proportion in subjects 2 to <7 years receiving 12 mg/kg/day BID (AG2/DC1) and the highest proportion in subjects 7 to <18 years receiving 18 mg/kg/day TID (AG1/DC3). At all three dose levels (12 mg/kg/day BID, 18 mg/kg/day BID and 18 mg/kg/day TID), subjects in AG1 (7 to <18 years old) had higher mean PK exposures at steady state than those in AG2. High variability in exposures was observed in all groups. POS oral suspension was generally well tolerated and most of the reported adverse events were related to the subjects' underlying diseases.CONCLUSION:The POS PK target of 90% of subjects with Cavg between 500 and 2500 ng/mL was not achieved in any of the age groups across the different dosage cohorts. New formulations of the molecule with a greater potential to achieve the established PK target are currently under investigation.TRIAL REGISTRATION:ClinicalTrials.gov identifier: NCT01716234.

Treatment of individuals coinfected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) requires careful consideration of potential drug‐drug interactions. We evaluated the pharmacokinetic interaction of the direct‐acting antiviral agents elbasvir and grazoprevir coadministered with the nucleotide reverse transcriptase inhibitor tenofovir disoproxil fumarate (TDF). Three open‐label, multidose studies in healthy adults were conducted. In the first study (N = 10), participants received TDF 300 mg once daily, elbasvir 50 mg once daily, and elbasvir coadministered with TDF. In the second study (N = 12), participants received TDF 300 mg once daily, grazoprevir 200 mg once daily, and grazoprevir coadministered with TDF. In the third study (N = 14), participants received TDF 300 mg once daily and TDF 300 mg coadministered with coformulated elbasvir/grazoprevir 50 mg/100 mg once daily. Pharmacokinetics and safety were evaluated. Following coadministration, the tenofovir area under the plasma concentration‐time curve to 24 hours and maximum plasma concentration geometric mean ratios (90% confidence intervals) for tenofovir and coadministered drug(s) versus tenofovir were 1.3 (1.2, 1.5) and 1.5 (1.3, 1.6), respectively, when coadministered with elbasvir; 1.2 (1.1, 1.3) and 1.1 (1.0, 1.2), respectively, when coadministered with grazoprevir; and 1.3 (1.2, 1.4) and 1.1 (1.0, 1.4), respectively, when coadministered with the elbasvir/grazoprevir coformulation. TDF had minimal effect on elbasvir and grazoprevir pharmacokinetics. Elbasvir and/or grazoprevir coadministered with TDF resulted in no clinically meaningful tenofovir exposure increases and was generally well tolerated, with no deaths, serious adverse events (AEs), discontinuations due to AEs, or laboratory AEs reported. No dose adjustments for elbasvir/grazoprevir or TDF are needed for coadministration in HCV/HIV‐coinfected people.

The original version of this article unfortunately contained a mistake.

BACKGROUND Elbasvir/grazoprevir is a once-daily fixed-dose combination therapy for the treatment of chronic HCV infection, including HCV/HIV coinfection. OBJECTIVES To evaluate the pharmacokinetic interaction of elbasvir and grazoprevir with raltegravir or dolutegravir. METHODS Three open-label trials in healthy adult participants were conducted. In the raltegravir trials, participants received a single dose of raltegravir 400 mg, a single dose of elbasvir 50 mg or grazoprevir 200 mg, and raltegravir with either elbasvir or grazoprevir. In the dolutegravir trial, participants received a single dose of dolutegravir 50 mg alone or co-administered with once-daily elbasvir 50 mg and grazoprevir 200 mg. RESULTS The raltegravir AUC0-∞ geometric mean ratio (GMR) (90% CI) was 1.02 (0.81-1.27) with elbasvir and 1.43 (0.89-2.30) with grazoprevir. Dolutegravir AUC0-∞ GMR (90% CI) was 1.16 (1.00-1.34) with elbasvir and grazoprevir. The elbasvir AUC0-∞ GMR (90% CI) was 0.81 (0.57-1.17) with raltegravir and 0.98 (0.93-1.04) with dolutegravir. The grazoprevir AUC0-24 GMR (90% CI) was 0.89 (0.72-1.09) with raltegravir and 0.81 (0.67-0.97) with dolutegravir. CONCLUSIONS Elbasvir or grazoprevir co-administered with raltegravir or dolutegravir resulted in no clinically meaningful drug-drug interactions and was generally well tolerated. These results support the assertion that no dose adjustments for elbasvir, grazoprevir, raltegravir or dolutegravir are needed for co-administration in HCV/HIV-coinfected people.

Odanacatib (ODN), an oral selective inhibitor of cathepsin K, was an investigational agent previously in development for the treatment of osteoporosis. In this phase 1 open‐label study, 12 healthy Chinese postmenopausal women received single‐dose ODN 50 mg on day 1 and multiple‐dose ODN 50 mg once weekly on days 15, 22, 29, and 36 under fasted conditions. Pharmacokinetic (PK) parameters were evaluated on days 1 and 36. Multiple‐dose area under the concentration–time profile (AUC0–168h) and maximum plasma concentration (Cmax) were compared with historical data from 9 non‐Chinese postmenopausal women who also received ODN 50 mg once weekly for 4 weeks. Median time to Cmax (tmax) was 3 and 4 hours following single‐ and multiple‐dose administration, respectively. The arithmetic mean ± SD terminal half‐life was 81.0 ± 14.0 and 106.7 ± 14.4 hours following single‐ and multiple‐dose administration, respectively. Comparison of multiple‐dose PK parameters showed that the geometric mean ratios (Chinese/non‐Chinese) and 95%CIs for AUC0–168h and Cmax were 0.81 (0.55‒1.19) and 0.87 (0.69‒1.11), respectively. All adverse events were mild, none were serious, and none led to discontinuation. Single‐ and multiple‐dose PKs of ODN 50 mg in Chinese postmenopausal women were generally similar to those previously reported in non‐Chinese postmenopausal women.

ABSTRACT This phase I study assessed the intrapulmonary pharmacokinetic profiles of relebactam (MK-7655), a novel β-lactamase inhibitor, and imipenem. Sixteen healthy subjects received 250 mg relebactam with 500 mg imipenem-cilastatin, given intravenously every 6 h for 5 doses, and were randomized to bronchoscopy/bronchoalveolar lavage at 0.5, 1, 1.5, or 3 h after the last dose (4 subjects per time point). Both drugs penetrated the epithelial lining fluid (ELF) to a similar degree, with the profiles being similar in shape to the corresponding plasma profiles and with the apparent terminal half-lives in plasma and ELF being 1.2 and 1.3 h, respectively, for relebactam and 1.0 h in both compartments for imipenem. The exposure (area under the concentration-time curve from time zero to infinity) in ELF relative to that in plasma was 54% for relebactam and 55% for imipenem, after adjusting for protein binding. ELF penetration for relebactam was further analyzed by fitting the data to a two-compartment pharmacokinetic model to capture its behavior in plasma, with a partitioning coefficient capturing its behavior in the lung compartment. In this model, the time-invariant partition coefficient for relebactam was found to be 55%, based on free drug levels. These results support the clinical evaluation of relebactam with imipenem-cilastatin for the treatment of bacterial pneumonia.

Volume 62, no. 9, e00280-18, 2018, https://doi.org/10.1128/AAC.00280-18. The Acknowledgments section was incomplete and should appear as shown below. At the time the study was conducted, E.G.R., M.L.R., N.C., M.N., M.S.S., E.M., K.B., P.B., F.C.-G., P.J., Y.L., and J.R.B. were employees of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA (MSD), and they may own stock and/or stock options in the company. S.J.W. is an employee of Hammersmith Medicines Research Ltd., London, UK. Funding for this research was provided by MSD. All authors are responsible for the work described in this paper. All authors were involved in at least one of the following: study conception and design of work or acquisition, analysis, or interpretation of data; and drafting the manuscript and/or revising/reviewing the manuscript for important intellectual content. All authors provided final approval of the version to be published. All authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Medical writing and/or editorial assistance was provided by Stephanie Doerner and Alanna Kennedy of The Lockwood Group, Stamford, CT, USA. This assistance was funded by MSD.

Relebactam is a novel class A and C β-lactamase inhibitor that is being developed in combination with imipenem-cilastatin for the treatment of serious infections with Gram-negative bacteria. Here we report on two phase 1 randomized, double-blind, placebo-controlled pharmacokinetics, safety, and tolerability studies of relebactam administered with or without imipenem-cilastatin to healthy participants: (i) a single-dose (25 to 1,150 mg) and multiple-dose (50 to 625 mg every 6 h [q6h] for 7 to 14 days) escalation study with men and (ii) a single-dose (125 mg) study with women and elderly individuals. Following single- or multiple-dose intravenous administration over 30 min, plasma relebactam concentrations declined biexponentially, with a terminal half-life (t1/2) ranging from 1.35 to 1.85 h independently of the dose. Exposures increased in a dose-proportional manner across the dose range. No clinically significant differences in pharmacokinetics between men and women, or between adult and elderly participants, were observed. Urine pharmacokinetics demonstrated that urinary excretion is the major route of relebactam elimination. No drug-drug interaction between relebactam and imipenem-cilastatin was observed, and the observed t1/2 values for relebactam, imipenem, and cilastatin were comparable, thus supporting coadministration. Relebactam administered alone or in combination with imipenem-cilastatin was well tolerated across the dose ranges studied. No serious adverse events or deaths were reported. The pharmacokinetic profile and favorable safety results supported q6h dosing of relebactam with imipenem-cilastatin in clinical treatment trials.

Oral contraceptive pills (OCPs) are an important element of hepatitis C virus (HCV) treatment in women of childbearing potential. These studies evaluated the safety and pharmacokinetic interactions between elbasvir (EBR) and grazoprevir (GZR) and ethinyl estradiol/levonorgestrel (EE/LNG).

Abstract Background POS, a triazole antifungal approved for prophylaxis and treatment of adults with invasive fungal infections, is available as an IV solution and 2 oral formulations: an oral suspension and a tablet with improved bioavailability. A novel powder for oral suspension (PFS) has been developed to offer the bioavailability of the tablet in a formulation optimized for weight-based dosing in children. The objective of this study is to evaluate the safety, tolerability, and PK of POS IV and POS PFS in pediatric patients (patients) aged 2 to 17 y with documented or expected neutropenia. Methods This is an ongoing, nonrandomized, multicenter, open-label, sequential dose-escalation study evaluating POS IV and POS PFS. Pts are divided into 2 age groups: 2 to <7 and 7 to 17 y. Each age group includes 2 dose cohorts: 3.5 mg/kg/d and 4.5 mg/kg/d. Patients received 10–28 d of POS initially as IV solution with the option to switch to PFS after 10 d for the remainder of the treatment period. PK sampling was conducted after 7–10 days on each formulation. Target PK exposure was ~90% of patients with Cavg 500–2,500 ng/mL. Cavg is defined as AUC over a dosing interval. Results 57 of 66 patients (86%) who received POS IV were PK evaluable; 35 patients (53%) received POS PFS, of whom 30 (86%) were PK evaluable. Table 1 shows Cavg and proportion in target range of PK-evaluable patients by dose cohort and age group. The safety profiles of POS IV and PFS were similar to those previously reported for adults treated with oral/IV POS. Conclusion POS PFS resulted in lower POS exposure than IV across age groups at both dose levels. POS exposure was substantially lower in the younger age group for both IV and PFS. At 4.5 mg/kg, the patients in this study achieved the predefined target but did not achieve systemic exposures (mean Cavg) comparable to those seen in adults with POS IV or tablet. These results suggest that study of POS IV and PFS dosing >4.5 mg/kg/d is warranted. Disclosures A. H. Groll, Merck Sharp & Dohme: Consultant, Investigator, Scientific Advisor and Speaker’s Bureau, Consulting fee and Speaker honorarium. T. Lehrnbecher, Merck/MSD: Scientific Advisor and Speaker’s Bureau, Speaker honorarium. Astellas: Scientific Advisor and Speaker’s Bureau, Speaker honorarium. Basilea: Scientific Advisor, Consulting fee. Gilead: Investigator, Scientific Advisor and Speaker’s Bureau, Research grant and Speaker honorarium.Pfizer: Speaker’s Bureau, Speaker honorarium. W. Steinbach, Merck: Consultant, Consulting fee. Astellas: Consultant, Consulting fee. Gilead: Consultant, Consulting fee. R. Murray, Merck: Employee, Salary. A. Paschke, Merck: Employee, Salary. E. Mangin, Merck: Employee, Salary. G. A. Winchell, Merck: Research Contractor, Consulting fee. C. J. Bruno, Merck: Employee and Shareholder, Salary and Stock.

3063 Background: Monoclonal antibodies (mAb) can evoke immunogenicity, leading to production of antidrug antibodies (ADA). Pembro, a humanized mAb against PD-1, has demonstrated efficacy in NSCLC and MEL. Results from NSCLC cohorts of KEYNOTE-001 (NCT01295827) and KEYNOTE-010 (NCT01905657) and from MEL cohorts of KEYNOTE-001, KEYNOTE-002 (NCT01704287), and KEYNOTE-006 (NCT01866319) are presented. Methods: Samples were analyzed for antipembro antibodies using electrochemiluminescence immunoassay methodology following a standard 3-tiered assay approach consisting of screening, confirmatory, and antibody titer assessment. Screening positives were tested in a confirmatory assay checking specificity of signal for pembro. In confirmed positive samples Ab titer, neutralizing capacity, drug exposure, efficacy, and AEs were assessed. The immunogenicity approach classified ADA samples as positive, negative, or inconclusive. Overall immunogenicity incidence was defined as proportion of treatment-emergent (TE) positive pts to the number of evaluable pts with a confirmed TE, non–TE-positive or negative immunogenicity status. Negative immunogenicity status was confirmed if ADA results of the pretreatment and postdose samples were negative in the confirmatory assay, and the pembro concentration was below the drug tolerance level in the last postdose sample. Results: Across cohorts, 2910 pts provided 11,886 pretreatment and posttreatment serum samples. Overall, 2632 pts (n = 1535 MEL, n = 1097 NSCLC) were included in the immunogenicity analysis. False-positive rates were 2.7% and 2.8% with Intertek and PPD assays, respectively. Of the 1087 (41%) evaluable pts, 19 (1.7%) had a TE-positive ADA, 10 (0.9%) were non–TE-positive, and 1058 (97.3%) had negative immunogenicity status. Initial results indicate a higher incidence rate in NSCLC vs MEL (2.5% vs 0.7%). In pts with a TE-positive ADA, no impact of antipembro antibodies on drug exposure, safety, or efficacy was observed. Conclusions: Pembro has a low potential to elicit the formation of ADA, and if ADA formation occurs, it has been shown to have no clinically relevant impact. Clinical trial information: NCT01295827, NCT01905657, NCT01704287, NCT01866319.