Survey of Pharmaceutical Industry's Best Practices around In Vitro Transporter Assessment and Implications for Drug Development: Considerations from the International Consortium for Innovation and Quality for Pharmaceutical Development Transporter Working Group.

The International Consortium for Innovation and Quality in Pharmaceutical Development Transporter Working Group had a rare opportunity to analyze a crosspharma collation of in vitro data and assay methods for the evaluation of drug transporter substrate and inhibitor potential. Experiments were generally performed in accordance with regulatory guidelines. Discrepancies, such as not considering the impact of preincubation for inhibition and free or measured in vitro drug concentrations, may be due to the retrospective nature of the dataset and analysis. Lipophilicity was a frequent indicator of crosstransport inhibition (P-gp, BCRP, OATP1B, and OCT1), with high molecular weight (MW ≥500 Da) also common for OATP1B and BCRP inhibitors. A high level of overlap in in vitro inhibition across transporters was identified for BCRP, OATP1B1, and MATE1, suggesting that prediction of DDIs for these transporters will be common. In contrast, inhibition of OAT1 did not coincide with inhibition of any other transporter. Neutrals, bases, and compounds with intermediate-high lipophilicity tended to be P-gp and/or BCRP substrates, whereas compounds with MW <500 Da tended to be OAT3 substrates. Interestingly, the majority of in vitro inhibitors were not reported to be followed up with a clinical study by the submitting company, whereas those compounds identified as substrates generally were. Approaches to metabolite testing were generally found to be similar to parent testing, with metabolites generally being equally or less potent than parent compounds. However, examples where metabolites inhibited transporters in vitro were identified, supporting the regulatory requirement for in vitro testing of metabolites to enable integrated clinical DDI risk assessment. SIGNIFICANCE STATEMENT: A diverse dataset showed that transporter inhibition often correlated with lipophilicity and molecular weight (>500 Da). Overlapping transporter inhibition was identified, particularly that inhibition of BCRP, OATP1B1, and MATE1 was frequent if the compound inhibited other transporters. In contrast, inhibition of OAT1 did not correlate with the other drug transporters tested.

Comparison of Two Manufacturing Processes of Daprodustat for Bioequivalence and Dissolution in Healthy Volunteers: A Randomized Crossover Study.

Daprodustat, an orally bioavailable hypoxia-inducible factor-prolyl hydroxylase enzyme inhibitor, has recently completed phase 3 clinical development for treating anemia of chronic kidney disease. Part A of this 2-part, randomized, double-blind, single-dose, cross-over study (NCT04640311) compared pharmacokinetic properties of a single oral dose of daprodustat 4 mg tablets manufactured via twin-screw wet granulation (process 1) to 2 sets of 4 mg tablets manufactured via high-shear wet granulation (process 2), to assess the impact of different dissolution profiles on pharmacokinetics. Part B assessed the bioequivalence of daprodustat tablets manufactured via process 1 with tablets manufactured via process 2 at 5 different dose strengths (1, 2, 4, 6, and 8 mg). In part A, mean plasma concentrations of daprodustat were comparable over a 24-hour period despite differences in manufacturing processes and dissolution profiles. In part B, the 90% confidence intervals of the ratios of the least squared means for area under the concentration-time curve and maximum observed plasma concentration fell within the 0.8-1.25 bioequivalence range for all doses, except for maximum observed plasma concentration at 8 mg. A prespecified sensitivity analysis jointly assessing all doses showed bioequivalence for all doses tested. No new safety concerns for daprodustat were identified.

Pharmacokinetics of Daprodustat and Metabolites in Individuals with Normal and Impaired Hepatic Function.

Daprodustat is a hypoxia-inducible factor-prolyl hydroxylase inhibitor in development for treatment of anemia of chronic kidney disease. We evaluated the role of hepatic impairment on daprodustat pharmacokinetics, pharmacodynamics, and tolerability. Participants with mild (Child-Pugh Class A, score 5-6) and moderate (Child-Pugh Class B, score 7-9) hepatic impairment and matched healthy controls were administered single 6-mg doses of daprodustat. Exposure parameters were determined for daprodustat and its six metabolites. Comparisons resulted in 1.5- and 2.0-fold higher daprodustat Cmax and area under the curve (AUC) exposures in participants with mild and moderate hepatic impairment, respectively, versus controls; Cmax in mild hepatic impairment was comparable to controls. Similarly, aligned with parent drug, unbound daprodustat Cmax and AUC exposures increased 1.6- to 2.3-fold in hepatic-impaired participants versus controls, and metabolite exposures were 1.2- to 2.0-fold higher in participants with hepatic impairment. Erythropoeitin (EPO) baseline-corrected AUC exposures were between 0.3-fold lower and 2.2-fold higher in matched controls versus hepatic-impaired participants. No serious or study drug-related adverse events were reported. Daprodustat exposure was increased in participants with moderate and mild hepatic impairment compared with matched controls; however, no meaningful differences in EPO were observed and no new safety concerns were identified (ClinicalTrials.gov: NCT03223337).

Clinical Pharmacokinetics of Daprodustat: Results of an Absorption, Distribution, and Excretion Study With Intravenous Microtracer and Concomitant Oral Doses for Bioavailability Determination.

Daprodustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, is being investigated for treatment of anemia in chronic kidney disease. This phase 1, nonrandomized, 2-period, crossover study in 6 healthy men characterized the absorption, distribution, and excretion of daprodustat when administered as oral and intravenous (IV) doses of unlabeled and radiolabeled daprodustat ([14 C]-GSK1278863). Tolerability and pharmacokinetic properties of daprodustat, and its 6 metabolites in the systemic circulation, were also evaluated. The mean recovery of radiolabeled daprodustat was ≈95% by day 5, with the majority in feces and minor renal elimination, indicating that daprodustat and metabolites are primarily eliminated via hepatobiliary and fecal routes. Approximately 40% of total circulating radioactivity in plasma following both IV and oral administration was daprodustat; thus, 60% was attributed to metabolites. It was estimated that ≈80% of daprodustat was absorbed across the gastrointestinal tract, and ≈18% cleared by hepatic extraction. Pharmacokinetics were essentially dose proportional, with moderate (≈66%) oral tablet bioavailability. Following IV administration, daprodustat plasma clearance (19.3 L/h) and volume of distribution (14.6 L) were low, suggesting low tissue distribution outside systemic circulation with likely low penetration into tissues. Daprodustat was generally well tolerated, with no deaths or serious or significant adverse events reported.

A Single-Dose, Open-Label, Randomized, Two-Way Crossover Study in Healthy Japanese Participants to Evaluate the Bioequivalence and the Food Effect on the Pharmacokinetics of Daprodustat.

Daprodustat is a prolyl hydroxylase inhibitor that stimulates erythropoiesis in a manner similar to the natural response to hypoxia, whereby inhibition of hypoxia inducible factor (HIF) prolyl-4-hydroxylases by daprodustat ultimately results in increased levels of HIF-responsive genes. Daprodustat is under development as an emerging new class of agents for the treatment of anemia associated with chronic kidney disease (CKD). This was a single-center, single-dose, open-label, randomized, 2-way crossover study in healthy Japanese male participants consisting of 2 parts. The primary objective was to evaluate the bioequivalence (BE) between daprodustat tablet strengths (part 1) and to evaluate the food effect on the pharmacokinetics (PK) of daprodustat (part 2). A total of 64 healthy Japanese male participants were enrolled; 52 participants were included in part 1 and 12 in part 2. BE was demonstrated between the daprodustat 2-mg tablet and the daprodustat 4-mg tablet. A standard CKD meal did not have a large effect on the PK parameters of daprodustat after a single oral dose of daprodustat 4 mg. Administration of single oral doses of daprodustat 4 mg was generally well tolerated in the healthy Japanese participants, and no new safety signals were identified without regard to food.

Effect of renal function and dialysis modality on daprodustat and predominant metabolite exposure.

BACKGROUND: Current therapies for anemia of chronic kidney disease (CKD) include administration of supplemental iron (intravenous and/or oral), blood transfusions and replacement of erythropoietin through the administration of recombinant human erythropoietin (rhEPO) and rhEPO analogs, each with limitations. Daprodustat is an orally active, small molecule hypoxia-inducible factor-prolyl hydroxylase inhibitor that is currently in Phase 3 clinical studies. As it is well appreciated that the kidney represents a major route of elimination of many drugs, and daprodustat will be administered to patients with advanced CKD as well as patients with end-stage kidney disease, it is important to characterize the pharmacokinetic profile in these patient populations to safely dose this potential new medicine. METHODS: The primary objective of these studies, conducted under two separate protocols and with identical assessments and procedures, was to characterize the steady-state pharmacokinetics of daprodustat and the six predominant metabolites (i.e. metabolites present in the highest concentration in circulation) in subjects with normal renal function, anemic non-dialysis (ND)-dependent CKD subjects (CKD Stage 3/4) and anemic subjects on either hemodialysis (HD) or peritoneal dialysis (PD). All enrolled subjects were administered daprodustat 5 mg once daily for 14 days (all except HD subjects) or 15 days (for HD subjects). Blood, urine and peritoneal dialysate were collected at various times for measurement of daprodustat, predominant metabolite, erythropoietin and hepcidin levels. RESULTS: The pharmacokinetic properties of steady-state daprodustat peak plasma concentration (Cmax), area under the plasma daprodustat concentration-time curve (AUC) and the time of Cmax (tmax) were comparable between all cohorts in this study. In addition, there was no clinically relevant difference in these properties in the HD subjects between a dialysis and ND day. For CKD Stage 3/4, HD (dialysis day) and PD subjects, the AUC of all daprodustat metabolites assessed was higher, while the C max was slightly higher than that in subjects with normal renal function. Over the course of the 14 or 15 days of daprodustat administration, hemoglobin levels were seen to be relatively stable in the subjects with normal renal function, CKD Stage 3/4 and PD subjects, while HD subjects had a decrease of 1.9 gm/dL. All renally impaired subjects appeared to have similar erythropoietin responses to daprodustat, with approximately a 3-fold increase in these levels. In subjects with minimal to no change in hemoglobin levels, hepcidin levels remained relatively stable. Daprodustat, administered 5 mg once daily for 14-15 days, was generally well tolerated with a safety profile consistent with this patient population. CONCLUSION: These studies demonstrated no clinically meaningful change in the pharmacokinetic properties of daprodustat when administered to subjects with various degrees of renal impairment, while for CKD Stage 3/4, HD (dialysis day) and PD subjects, the C max and AUC of all daprodustat metabolites assessed were higher than in subjects with normal renal function. Administration of daprodustat in this study appeared to be generally safe and well tolerated.

A randomized, 29-day, dose-ranging, efficacy and safety study of daprodustat, administered three times weekly in patients with anemia on hemodialysis.

BACKGROUND: Daprodustat is a hypoxia-inducible factor-prolyl hydroxylase inhibitor currently being investigated as a treatment for anemia of chronic kidney disease (CKD) in both dialysis and nondialysis patients. In clinical studies to date, daprodustat has been administered orally as a once-daily regimen. This randomized, double-blind, placebo-controlled study characterized the initial dose-hemoglobin response as well as the efficacy and safety of three times weekly (TIW) daprodustat in hemodialysis patients switched from stable recombinant human erythropoietin (rhEPO), in accordance with a TIW hemodialysis schedule. METHODS: 103 patients on hemodialysis with baseline hemoglobin of 9.0 to 11.5 g/dL and previously receiving a stable dose of rhEPO or its analogs were randomized 1:1:1:1:1 to receive daprodustat 10, 15, 25, or 30 mg or placebo TIW over 29 days. RESULTS: Mean baseline hemoglobin was 10.6 g/dL for the placebo group and each daprodustat cohort. Daprodustat produced dose-dependent changes in mean hemoglobin from baseline to day 29. Using a Bayesian approach, the estimated dose conversion ratio between once-daily and TIW daprodustat was ~ 2.0 across the evaluated dose range using an Emax model. Daprodustat was generally well tolerated, with an adverse event (AE) profile consistent with the hemodialysis population. CONCLUSIONS: These data help inform the appropriate dose conversion ratio to be applied to daily doses to obtain equivalent daprodustat TIW doses and suggest TIW treatment with daprodustat can treat anemia of CKD safely, supporting future long-term studies for this indication using a TIW dosing regimen. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02689206 ; date registered: 02/11/2016.

A Randomized, Placebo-Controlled Trial to Assess the Effects of 8 Weeks of Administration of GSK256073, a Selective GPR109A Agonist, on High-Density Lipoprotein Cholesterol in Subjects With Dyslipidemia.

GPR109A (HM74A), a G-protein-coupled receptor, is hypothesized to mediate lipid and lipoprotein changes and dermal flushing associated with niacin administration. GSK256073 (8-chloro-3-pentyl-1H-purine-2,6[3H,7H]-dione) is a selective GPR109A agonist shown to suppress fatty acid levels and produce mild flushing in short-term clinical studies. This study evaluated the effects of GSK256073 on lipids in subjects with low high-density lipoprotein cholesterol (HDLc). Subjects (n = 80) were randomized (1:1:1:1) to receive GSK256073 5, 50, or 150 mg/day or matching placebo for 8 weeks. The primary end point was determining the GSK256073 exposure-response relationship for change from baseline in HDLc. No significant exposure response was observed between GSK256073 and HDLc levels. GSK256073 did not significantly alter HDLc levels versus placebo, but rather revealed a trend at the 150-mg dose for a nonsignificant decrease in HDLc (-6.31%; P = .12) and an increase in triglycerides (median, 24.4%; 95% confidence interval, 7.3%-41.6%). Flushing was reported in 21%, 25%, and 60% of subjects (5, 50, and 150 mg, respectively) versus 24% for placebo. Results indicated that selective activation of the GPR109A receptor with GSK256073 did not produce niacin-like lipid effects. These findings add to the increasing evidence that niacin-mediated lipoprotein changes occur predominantly via GPR109A-independent pathways.

Randomized Phase I Trial to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Topical Daprodustat in Healthy Volunteers and in Patients With Diabetic Foot Ulcers.

Daprodustat, a small-molecule inhibitor of prolyl hydroxylases, prevents breakdown of hypoxia-inducible factor (HIF), leading to increased transcription of HIF-responsive genes. This randomized, placebo-controlled study evaluated the safety, tolerability, and pharmacokinetics of a topical formulation of daprodustat in healthy volunteers (intact skin) and in patients with diabetic foot ulcers (DFUs) following single and/or 14-day repeat-dose administration. In the diabetic patients, exploratory assessments of wound area, volume, and depth were made to qualitatively assess effectiveness. Systemic absorption via topical application was limited across doses up to 1.0% at 100 mg/cm2 for 14 days. Systemic pharmacokinetics were quantifiable in a few samples from a few patients. Because only sporadic concentrations were observed versus pharmacokinetic profiles, pharmacokinetic parameters were not determined. Wound area, depth, and volume showed consistent but weak improvements in the treatment arm; however, the variability in response and small sample size of the standard-of-care and placebo arms limited the ability to assess trends in wound healing compared with the daprodustat arm. Overall, topically applied daprodustat was well tolerated, raised no safety concerns, and provided limited to nonquantifiable systemic exposures. The healing of DFUs will need to be evaluated in studies designed to test this hypothesis over a longer treatment duration.

The drug interaction potential of daprodustat when coadministered with pioglitazone, rosuvastatin, or trimethoprim in healthy subjects.

This study was conducted to evaluate the likelihood of daprodustat to act as a perpetrator in drug-drug interactions (DDI) with the CYP2C8 enzyme and OATP1B1 transporter using the probe substrates pioglitazone and rosuvastatin as potential victims, respectively. Additionally, this study assessed the effect of a weak CYP2C8 inhibitor, trimethoprim, as a perpetrator of a DDI with daprodustat. This was a two-part study: Part A assessed the effect of coadministration of daprodustat on the pharmacokinetics of pioglitazone and rosuvastatin in 20 subjects; Part B assessed the coadministration of trimethoprim on the pharmacokinetics of daprodustat in 20 subjects. Coadministration of 100 mg of daprodustat with pioglitazone or rosuvastatin had no effect on the plasma exposures of either probe substrate. When trimethoprim was coadministered with 25-mg daprodustat plasma daprodustat AUC and Cmax increased by 48% and 28%, respectively. Additionally, AUC and Cmax for the metabolite GSK2531401 were decreased by 32% and 40%, respectively. Cmax for the other metabolites was slightly decreased (~8-15%) but no changes in AUC were observed. As 100-mg daprodustat exceeds the planned top therapeutic dose, interaction potential of daprodustat as a perpetrator with substrates of the CYP2C8 enzyme and OATP1B1 transporters is very low. Conversely, daprodustat exposure (AUC and Cmax) is likely to increase moderately with coadministration of weak CYP2C8 inhibitors.

Single- and Multiple-Day Dosing Studies to Investigate High-Dose Pharmacokinetics of Epelsiban and Its Metabolite, GSK2395448, in Healthy Female Volunteers.

Open-label single- and double-blind repeat-dose studies in healthy female volunteers were conducted to investigate the pharmacokinetics (PK) and safety/tolerability of epelsiban total daily doses ranging from 600 to 900 mg. In 1 study (n = 12), epelsiban was dosed at 300 or 450 mg twice daily (every 12 hours) for a single day. In the repeat-dose double-blind study, epelsiban and placebo were administered to 31 subjects as 200 mg 3 times daily, 300 mg 3 times daily (TID), or 450 mg twice daily (BID) for 14 days. After both single and 14 daily repeat doses, the PK profiles for epelsiban and its metabolite, GSK2395448, remained linear at all administered doses. The exposures at a given total daily dose were also similar between BID and TID dosing regimens. Exposure (AUC0-τ ), based on dosing intervals, for both epelsiban and GSK2395448 was similar. However, compared with morning dosing, Cmax was lower after evening dosing, possibly because of a food effect. The highest accumulation of epelsiban and GSK2395448 exposures (AUC0-τ ) was approximately 34% for each after repeat dosing, consistent with the short half-life. At total daily doses of 600 and 900 mg, epelsiban was generally well tolerated, and there were no significant safety concerns identified.

A single- and multiple-dose study to investigate the pharmacokinetics of epelsiban and its metabolite, GSK2395448, in healthy female volunteers.

An open-label single- and repeat-dose study was conducted to investigate the pharmacokinetics, safety, and tolerability of ascending doses of epelsiban in healthy female volunteers (n = 48). The pharmacokinetics of the epelsiban metabolite, GSK2395448, were also assessed. Epelsiban was readily absorbed and parent and metabolite readily appeared in plasma. The parent drug's median tmax was approximately 0.5 hours, and the metabolite's median tmax ranged from 0.5 to 1.0 hours post-parent dosing. Both epelsiban and GSK2395448 had rapid elimination half-lives, ranging between 2.66 and 4.85 hours. The metabolite:parent ratios for exposure (AUC and Cmax ) ranged from approximately 70% to greater than 100%, and therefore, GSK2395448 is considered a major metabolite of epelsiban. Mean epelsiban and GSK2395448 AUC values increased in a dose-proportional manner following both single-dose administration from 10 to 200 mg and repeat administration from 10 to 150 mg following twice daily or 4-times-daily dosing. Single-dose epelsiban pharmacokinetics in women was similar to single-dose pharmacokinetics previously observed in men. Epelsiban was generally well tolerated, and no events of clinical concern were observed in volunteers dosed in this study. The safety findings were consistent with the previous study in men, with headache the most commonly reported adverse effect.

Short-term treatment with a novel HIF-prolyl hydroxylase inhibitor (GSK1278863) failed to improve measures of performance in subjects with claudication-limited peripheral artery disease.

Hypoxia inducible factor (HIF) stabilization by HIF-prolyl hydroxylase (PHD) inhibitors may improve ischemic conditions such as peripheral artery disease (PAD). This multicenter, randomized, placebo-controlled study evaluated the safety and efficacy of GSK1278863 (an oral PHD inhibitor) in subjects with PAD. The study assessed two active treatment paradigms: single dosing and subchronic daily dosing (300 mg single dose and 15 mg daily for 14 days, respectively). Neither regimen improved exercise performance compared with placebo (change from baseline in the 6-minute walk test (6MWT; feet), (GSK1278863, placebo): single dose (-46, -44), p=0.96; repeat dose (9, 8), p=0.99; change in number of contractions to onset of claudication (goniometry): single dose (4, -1), p=0.053; repeat dose (-2, 1), p=0.08). A calf-muscle biopsy substudy showed no increases in mRNA or protein levels of HIF target genes. More subjects receiving GSK1278863 than placebo experienced adverse events, particularly following the 300 mg single dose. Thus, assessing the safety of GSK1278863 in this setting would require a larger population exposed to the agent for a longer duration. These data do not support a benefit of GSK1278863 in PAD using the regimens tested. CLINICALTRIALSGOV IDENTIFIER NCT01673555:

Safety and efficacy of epelsiban in the treatment of men with premature ejaculation: a randomized, double-blind, placebo-controlled, fixed-dose study.

AIM: To assess the efficacy and safety of the selective oxytocin receptor antagonist epelsiban in the treatment of premature ejaculation (PE). METHODS: Double-blind, randomized, parallel-group, placebo-controlled, stopwatch-monitored, phase 2, multicenter study (GSK557296; NCT01021553) conducted in men (N=77) 18-55 years of age, with PE defined as per International Society for Sexual Medicine consensus definition. Patients provided informed consent prior to a 4-week un-medicated run-in to determine baseline intravaginal ejaculatory latency times (IELT) recorded in an electronic diary. Patients needed to make a minimum of four intercourse attempts and have a mean IELT<65 seconds to be considered for randomization. Men with moderate-to-severe erectile dysfunction were excluded from the study. Eligible patients were randomized to placebo, epelsiban 50 mg, or 150 mg, taken 1 hour before sexual activity. Active treatment IELT times were recorded in an electronic diary, along with subjective measures of intercourse satisfaction, over an 8-week treatment period. The Modified Index of Premature Ejaculation and International Index of Erectile Function were completed at study visits. MAIN OUTCOME MEASURES: Stopwatch timed IELT recordings and a modified version of the patient-reported outcome questionnaire the IPE were used in this study to determine the effect of epelsiban when taken orally prior to intercourse in subjects diagnosed with PE. RESULTS: The baseline (mean) IELT for patients pretreatment was (0.52, 0.63, and 0.59 minutes) for placebo, epelsiban 50 mg and 150 mg, respectively. On-treatment, average geometric least squares means of the median IELT values (mean) were slightly higher in the 50 mg and 150 mg groups (0.72 and 0.69 minutes), respectively, vs. the placebo group (0.62 minutes). Headache was the most common adverse event, and rates were similar across all groups. CONCLUSIONS: Epelsiban 50 mg and 150 mg were well tolerated, but did not result in a clinically or statistically significant change in IELT in men with PE, compared with placebo.

Effects of Urotensin II Receptor Antagonist, GSK1440115, in Asthma.

BACKGROUND: Urotensin II (U-II) is highly expressed in the human lung and has been implicated in regulating respiratory physiology in preclinical studies. Our objective was to test antagonism of the urotensin (UT) receptor by GSK1440115, a novel, competitive, and selective inhibitor of the UT receptor, as a therapeutic strategy for the treatment of asthma. METHODS: Safety, tolerability, and pharmacokinetics (PK) of single doses of GSK1440115 (1-750 mg) were assessed in a Phase I, placebo controlled study in 70 healthy subjects. In a Phase Ib study, 12 asthmatic patients were randomized into a two-period, single-blind crossover study and treated with single doses of 750 mg GSK1440115 or placebo and given a methacholine challenge. RESULTS: Administration of GSK1440115 was safe and well-tolerated in healthy subjects and asthmatic patients. In both studies, there was a high degree of variability in the observed PK following oral dosing with GSK1440115 at all doses. There was a marked food effect in healthy subjects at the 50 mg dose. In the presence of food at the 750 mg dose, the time to maximal concentration was between 2 and 6 h and the terminal half-life was short at approximately 2 h. All asthmatic patients maintained greater than the predicted concentration levels necessary to achieve predicted 96% receptor occupancy for ≥3 h (between 4 and 7 h post-dose). There were no apparent trends or relationships between the systemic plasma exposure of GSK1440115 and pharmacodynamic endpoints, PC20 after methacholine challenge and FEV1, in asthmatics. CONCLUSION: While GSK1440115 was safe and well-tolerated, it did not induce bronchodilation in asthmatics, or protect against methacholine-induced bronchospasm, suggesting that acute UT antagonism is not likely to provide benefit as an acute bronchodilator in this patient population.

Gastric pH and gastric residence time in fasted and fed conscious beagle dogs using the Bravo pH system.

To further characterize the time course of gastric pH with respect to meals and gastric residence times (GRTs) in dogs, continuous pH measurements were recorded with Bravo capsules, which were attached to the dogs' stomach mucosa or administered as free capsules, respectively. Experiments took place in home or study cages, and meals were administered at designated times. Up until 2 h prior to mealtime, the fasted gastric pH remained constantly acidic (∼2.0) regardless whether the dogs were in the study or home cages. However, as feeding time became imminent, the pH was typically elevated for dogs in home cages, whereas the pH remained acidic for dogs in study cages. For both monitoring locations, the gastric pH remained acidic during meal consumption and for at least 10 h after meals. The GRT between fasted (25 ± 32 min) and fed (686 ± 352 min) conditions was significantly different with considerable inter- and intrasubject variability. Fasted gastric pH was similar to that of literature monkey and human values but differed after meals as the dog gastric pH remained acidic unlike monkey and human. In dogs, the fasted GRT was remarkably rapid and under fed conditions, longer than that observed in humans.