This is a randomized, open-label, single-dose, 2-cohort, 2-period crossover study to assess the effect of food on the pharmacokinetics, safety, and tolerability of zelquistinel tablet in healthy adult participants. Two dose levels, 3 and 10 mg, will each be evaluated for food effect, 1 dose level per cohort, with approximately 32 participants (16 per cohort).
* Cohort 1: zelquistinel, 3 mg single oral tablet administered under fasted and fed conditions
* Cohort 2: zelquistinel, 10 mg single oral tablet administered under fasted and fed conditions
Study Design: This is a randomized, open-label, single-dose, 2-cohort, 2-period crossover study to assess the effect of food on the pharmacokinetics, safety, and tolerability of GATE-251 tablet in healthy adult participants. Two dose levels, 3 and 10 mg, will each be evaluated for food effect, 1 dose level per cohort, with approximately 32 participants (16 per cohort).
* Cohort 1: zelquistinel, 3 mg single oral tablet administered under fasted and fed conditions
* Cohort 2: zelquistinel, 10 mg single oral tablet administered under fasted and fed conditions After meeting eligibility requirements, participants will be admitted to the clinical research unit on Day -1. Participants within each cohort will be randomly assigned in a 1:1 ratio to a treatment sequence. Cohorts will be enrolled sequentially. Participants will only participate in 1 cohort.
On Day 1 of each period, participants will receive one of the following treatments:
* Treatment A (reference): zelquistinel, 3 mg tablet, fasted conditions
* Treatment B (test): GATE-251, 3 mg tablet, fed conditions (high-fat, high-calorie meal)
* Treatment C (reference): zelquistinel, 10 mg tablet, fasted conditions
* Treatment D (test): zelquistinel, 10 mg tablet, fed conditions (high-fat, high-calorie meal) Fasted and fed conditions and test meal composition are defined by FDA guidance. For the fasted condition, zelquistinel will be administered after an overnight fast of at least 10 hours.
For the fed condition, after an overnight fast of at least 10 hours, participants will start the test meal approximately 30 minutes before administration of zelquistinel. The test meal will be entirely consumed within 30 minutes.
For both fasted and fed conditions, zelquistinel will be administered with approximately 240 mL of water. Up to 200 mL of additional water will be allowed in increments of 50 mL, as needed. No water will be allowed for at least 1 hour before or after zelquistinel administration, except for the water consumed during administration. No food will be allowed for at least 4 hours after zelquistinel administration. In addition, participants will be semi-recumbent during the test meal and for at least 4 hours after study drug administration, except for when procedures or adverse events require the supine position.
The test meal will be a standard high-fat, high-calorie meal consisting of approximately 1000 calories with approximately 50% of the total calories from fat.
There will be a 7-day washout interval between doses then participants will cross over to Period 2 and receive zelquistinel at the same dose as in Period 1 under the alternate fasted or fed condition. Participants will be confined to the clinical study unit from Study Day -1 through Study Day 10 and will return on approximately Study Day 15 (7±2 days from the last dose) for the Follow-Up Visit (end of study).
Samples will be collected for pharmacokinetic analysis at the following timepoints for plasma, urine, and CSF.
* Plasma: On Day 1 of each period, blood samples will be collected at: 0 (pre-dose) and 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 16, and 24 hours after dosing.
* Urine: On Day 1 of each period, urine samples will be collected at: 0 (pre-dose) and 0-4-, 4-8-, 8-12-, and 12-24-hour intervals after dosing.
* Cerebrospinal fluid (CSF) collection: On Day 1 of each period, CSF samples will be collected at: 0 (pre-dose) and 1, 2, 4, 8, 12, 16, and 24 hours after dosing.
Safety assessments will include reporting of adverse events; clinical laboratory test results; vital sign measurements; electrocardiogram (ECG) results; and Columbia Suidical Severity Rating Scale (C-SSRS), Brief Psychiatric Rating Scale Positive Symptoms (BPRS+), and Clinician Administered Dissociative States Scale (CADSS) results. Adverse events, including serious adverse events (SAEs) and adverse events of special interest (AESIs), will be recorded from the time of informed consent until study completion.
