The purpose of this study is to determine the safety and efficacy of HB-1, versus placebo in male and female adult patients aged 18 to 65 years, inclusive, with Post-Traumatic Stress Disorder (PTSD).

This is a flexible-dose, multi-centre, double-blind, placebo-controlled trial for adults with Post Traumatic Stress Disorder (PTSD).

This study will enrol approximately 200 (up to 500) adults patients diagnosed with PTSD, without severe neuropsychiatric or medical co-morbidities.

Participants will be recruited from multiple sites in Australia and/or the United States.

Patients will be treated for 12 weeks followed by a safety follow up visit one week after their last dose of study treatment. Safety will be assessed by monitoring of treatment emergent adverse events (TEAEs), vital signs, questionnaires, ECG and clinical labs.

Inclusion Criteria:

• Male or female aged 18 to 65 years old, inclusive, at the time of informed consent.
• Meets DSM-V Criteria for PTSD.
• Minimum CAPS-5 score of at least 26 (based on the optimal diagnostic correspondence in the definitive CAPS-5 psychometric validation study).
• Clinically stable on current medication and/or therapy regimen for at least 2 months, as determined by Investigator.
• Willing to remain on current doses of other psychiatric medications throughout the length of the trial.
• Willing and able to safely stop any medications that are contraindicated to be taken together with HB-1, as determined by Investigator.
• Fluent in English.
• Willing to take HB-1.
• Willing and able to provide informed consent indicating an understanding of the requirements of the study and a willingness to comply with scheduled visits and all study procedures.
• Female subjects must be surgically sterile (or have a monogamous partner who is surgically sterile) or be at least 2 years postmenopausal or agree to commit to use acceptable forms of birth control (defined as the use of an intrauterine device, a barrier method with spermicide, condoms, any form of hormonal contraceptives, or abstinence) for the duration of the study. Investigator shall use discretion and familiarity with subject's preferred and usual lifestyle to understand if reporting of abstinence may be trusted to achieve 100% effectiveness. Male subjects must be sterile (biologically or surgically) or commit to the use of a reliable method of birth control (condoms with spermicide) for the duration of the study and for 4 months following the last dose of study treatment. Individuals who are involved exclusively in same-sex relationships are exempt from the birth control requirements but must agree to abide by the recommendations if they do engage in a heterosexual relationship.
• Female subjects who are women of childbearing potential (WOCBP) must have a negative pregnancy test at Screening within 7 days of dosing with study treatment.

Exclusion Criteria:

• Any ongoing concomitant disease, condition, or treatment that could interfere with the conduct of the study, or that would, in the opinion of the Investigator or Sponsor, pose an unacceptable risk to the participant in the study or interfere with the interpretation of study data.
• Ongoing treatment with benzodiazepines (e.g. alprazolam, diazepam, clonazepam, lorazepam) or opiates (e.g., codeine, morphine) as assessed by clinical interview and urine toxicology testing.
• Ongoing treatment with any medication that has a clinically significant drug-drug interaction with either telmisartan or verapamil, per the verapamil SR and telmisartan FDA labels and per standard drug interaction compendia. These include but are not limited to: Inhibitors or inducers of cytochrome P450 (CYP)3A4 (including certain β-hydroxy β-methylglutaryl-CoA [HMG-CoA] reductase inhibitors), Ivabradine, Antihypertensive Agents (including Beta Blockers), Antiarrhythmic Agents, Lithium, Carbamazepine, Rifampin, Phenobarbital, cyclosporin, theophylline, Inhalation Anesthetics, Neuromuscular Blocking Agents, Telithromycin, mTOR inhibitors as well as strong P-glycoprotein inhibitors (e.g., macrolides, ritonavir, itraconazole, ketoconazole, cyclosporin, ritonavir, and ivermectin).
• Diagnosis of Severe Substance Use Disorder, Obsessive-Compulsive Disorder (OCD), Bipolar I, Bipolar II disorder, or Psychotic disorder (per SCID-V) or Borderline Personality Disorder (per Short-Bord).
• Active suicidal ideation and behavior (Columbia-Suicide Severity Rating Scale [C-SSRS] score ≥ 4 at Screening, or who has made a serious suicide attempt in the last 3 months).
• Severe uncontrolled cardiac disease within 6 months of Screening, including but not limited to: severe uncontrolled hypertension, hypotension (below 90/60 mmHg); unstable angina; myocardial infarction (MI) or cerebrovascular accident (CVA).
• Any clinically significant electrocardiogram (ECG) abnormalities at screening.
• Inadequate hepatic function defined as total bilirubin > 1.5 × the upper limit of normal (ULN) ranges of each institution, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) > 3 × the ULN range of each institution.
• Inadequate renal function defined as serum creatinine > 1.5 × the ULN range of each institution and/or estimated glomerular filtration rate (eGFR) < 60 mL/min.
• Any clinically significant abnormalities in clinical laboratory assessments as assessed by the Investigator.
• Already on treatment with either telmisartan or verapamil or both.
• Documented contraindication to taking telmisartan or verapamil: (eg, prior drug allergy, Duchenne's muscular dystrophy, myasthenia gravis).
• Pregnant or breastfeeding.
• Participation in another current clinical trial or prior trial within the last three months.
• Urinalysis evidence of exposure to substances that may interfere with HB-1 testing (per investigator discretion).

An unblinded pharmacist will be utilized to assign bottles to each patient using an interactive voice response system (IVRS) central randomization system.

Study treatment or placebo will be dispensed to patients in blinded bottles.