A total of 48 Subjects are planned to be enrolled in a 6-cohort SAD study (36 in the treatment groups and 12 in the control groups). All SAD cohorts will have 6 Subjects in the treatment group and 2 Subjects in placebo group. All cohorts in the SAD study will incorporate sentinel dosing which will include 1 active and 1 placebo Subject. All remaining Subjects will be dosed at least 24 hours after the sentinel cohort participants. A total of 16 Subjects are planned to be enrolled in a 2 cohort MAD study (12 in the treatment groups and 4 in the control groups). All MAD cohorts will have 6 Subjects in the treatment group and 2 Subjects in placebo group. A total of 6 subjects are planned to be enrolled in a single cohort CSF capture study. The CSF cohort will have 4 in the treatment group and 2 in the placebo group.

(2R,6R)-Hydroxynorketamine hydrochloride will be administered intravenously over a 40-minute period as a solution in a 25 mM sodium phosphate 0.9% w/v saline solution. The SAD doses will range from 0.1 mg/kg to 4.0 mg/kg and the investigational drug product will be diluted into a 53 mL total volume of formulant. Placebo will be made up of a 0.9% w/v saline solution (53 mL total volume) also administered via slow IV infusion over a 40-minute period. The MAD doses will range from 1.0 mg/kg to 2.0 mg/kg administered as a 40 minute infusion period in a solution of 25 mM sodium phosphate 0.9% w/v saline solution on days 1, 4, 8 and 11. The CSF capture doses will be 0.25 mg/mk and 2.0 mg/kg administered via slow infusion over a 40 minute period in 0.9% w/v saline solution.

Serial PK blood samples will be collected during the SAD portion for each Subject receiving drug and placebo at 9 timepoints (preinfusion, end-of-infusion \[approximately 40 minutes\], 1, 2, 4, 8, 12, 24, and approximately 48 hr after the start of the infusion). Pharmacokinetic urine samples will be collected during the SAD study for each Subject receiving drug and placebo at set intervals following the initiation-of-infusion (0-4, \>4-8, \>8-12, \>12-24 hr). Serial PK blood samples will be collected for for each Subject receiving drug and placebo. Blood PK samples will be obtained at 8 timepoints for teh first and forth (last) dosing in the MAD study (preinfusion, end-of-infusion \[approximately 40 minutes\], 1, 2, 4, 8, 12, and approximately 24 hrs after the start of the infusion). Two PK blood samples will be collected for the second and third dosing in the MAD study for each subject receiving drug and placebo at approximately 10 minutes predose and at the end of the infusion. Serial PK blood samples will be collected for the single dose CSF capture study for each Subject receiving drug and placebo. Blood PK samples will be obtained at 8 timepoints (preinfusion, end-of-infusion \[approximately 40 minutes\], 1, 2, 4, 8, 12, and approximately 24hr after the start of the infusion). CSF samples will be obtained preinfusion, and at 2 timepoints (1h and 8 hours) post infusion.

Safety will be assessed throughout the study. Baseline and follow-up safety assessments will include height, body mass index (BMI), weight, temperature, medical, visual and ocular history, physical examinations, ocular examinations, visual acuity, color vision tests, electrocardiograms (ECGs), vital signs (VS), clinical laboratory tests (hematology, serum chemistry, and urinalysis), the Profile of Mood States (POMS), the Columbia-Suicide Severity Rating Scale (C-SSRS), the Clinician Administered Dissociative States Scale (CADSS), and adverse events (AEs). Safety assessments will include AEs, ECGs, VS, clinical laboratory results, and physical observations. Assessment of each Subject's level of alertness/sedation will be accomplished using the Modified Observer's Assessment of Alertness/Sedation (MOAA/S). Evaluation of safety in the MAD study will utilize the same safety assessments used in the SAD study. Evaluation of safety in the CSF capture study will utilize the same safety assessments used in the SAD and MAD study with the exception of the POMS and CADSS assessments. Monitoring of AEs will be governed by change from baselines established during prescreening and Day -1 examinations and clinical laboratory tests. Dose escalation in the SAD study or continued dosing in the MAD study may be stopped according to the predefined halting rules or if a Subject's scores demonstrate acute suicidality on the C-SSRS assessment or at the discretion of the study Principal Investigator and/or sponsor. Determination of whether to escalate to the next dose level in the SAD study or continue dosing in the MAD will be made by the Principal Investigator in consultation with the Medical Monitor and Study Sponsor.