Intervention: Isoleucyl-Tryptophan
Trial phase: Phase 2
SMILES: CCC(C)C(N)C(=O)NC(Cc1c[nH]c2ccccc12)C(=O)O
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 47
Group description: Suspension administered orally for 12 weeks.
Eligibility criteria:
Key Inclusion Criteria:

Signed and dated informed consent.
Male or female between 18 and 70 years of age, inclusive.
Diagnosed with current PTSD as defined by the CAPS-5 for DSM-5.

Currently not using any psychiatric medications except for:

No more than one selective serotonin reuptake inhibitor (SSRI) (fluvoxamine is excluded) or serotonin noradrenaline reuptake inhibitor (SNRI) within the licensed prescribing dose range. Subjects must have been on a stable dose for at least 3 months prior and through Screening, with the intent to remain on the same dose through to Week 16.
As needed (PRN) use of benzodiazepines (BZD) at a frequency not exceeding 2 days per week in the 3 months prior to Screening. The total dose must not exceed 30 mg/day in diazepam equivalents.
Subjects not currently receiving psychotherapy except long term supportive counseling or subjects that have received intensive regular psychotherapy for a minimum of three months prior to Screening.
Females of childbearing potential must have a negative serum pregnancy. Females not of childbearing potential must be postmenopausal. Sterilized male patients must be at least 1 year post-vasectomy to be considered of non-child bearing potential. Females and males of childbearing potential must agree to use two effective methods of contraception.

Key Exclusion Criteria

Current and ongoing exposure to the trauma that caused the PTSD.
Failed more than three trials of antidepressant medication(s) prescribed for the treatment of PTSD. Each trial must have lasted at least 6 weeks to be considered a failed attempt. A trial that was terminated due to intolerability or side effects does not constitute a failed attempt.
The use of psychiatric medications within 2 weeks of Screening except for SSRIs, SNRIs or limited PRN BZD use as per inclusion criterion 4. Restricted psychiatric medications include (but are not limited to) antidepressants not allowed by inclusion criterion 4, antianxiety drugs (except limited BZD use per inclusion criterion 4), mood stabilizers, stimulants, antipsychotics, hypnotics and acetylcholinesterase inhibitors.
History of significant traumatic brain injury.
Depression as measured by Montgomery-Äsberg depression scale (MADRS) rating > 23.
Bipolar and psychotic disorders as identified at Screening using the MINI International Neuropsychiatry Interview (V7.0) (M.I.N.I).
A score ≥ 7 on the McLean Screening Instrument for Borderline Personality Disorder (MSI-BPD) at Screening.
History of seizure disorders, uncontrolled sleep apnoea or severe neurologic disease.

Increased risk of suicide, defined as:

Any previous suicide attempt disclosed by the participant at Screening using the Columbia Suicide Severity Rating Scale (C-SSRS).
Any suicidal ideation with intent (yes to item 4 and / or 5) or suicidal behavior in the past year, as captured at Screening using the C-SSRS.
A score > 4 on item 10 of the MADRS at Screening.
The use of alprazolam or flunitrazepam within 3 months of Screening.
Any clinically significant abnormalities in laboratory test results, vitals signs, or ECG at Screening.
Positive result for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), or hepatitis C (HCV) at Screening.
Any moderate to severe substance use disorder (any type) in the 12 months prior to Screening as identified by the DSM-5 using the M.I.N.I (V7.0).
Current Australian serving Defense personnel or any member of the US military currently serving on active duty.
Participants involved with ongoing insurance or workplace claims that in the opinion of the Investigator are likely to have an impact on the mental health, presentation or capacity of the patient to engage in the study.