Inclusion Criteria  Male or female aged 18 to 60 years old, inclusive, at the time of informed consent. Meets DSM-5 Criteria for Panic Disorder. Documented moderate to severe levels of symptoms at baseline (Panic Disorder Severity Scale of 13 or above) Medically stable on current medication regimen for at least 3 months (including PRN medications), as determined by Investigator. Willing to remain on current doses of other psychiatric medications throughout the length of the trial (unless a dose reduction is warranted due to improvement in symptoms). Willing and able to safely stop any of the following medications prior to study trial: Inhibitors or inducers of CYP3A4 (erythromycin, ritonavir, telithromycin, rifampin), HMG-CoA Reductase Inhibitors (Simvastatin, Lovastatin, Atorvastatin), Beta Blockers (Timolol eyedrops, Metoprolol), Neuromuscular Blocking Agents (curare-like and depolarizing), Antihypertensive Agents (Prazosin and vasodilators, angiotensin-converting enzyme inhibitors, diuretics, beta blockers), Inhalation Anesthetics, Disopyramide, Flecainide, Quinidine, Cimetidine, Lithium, Carbamazepine, Phenobarbital, Cyclosporine, Digitalis, Aliskiren, Ramipril and Ramiprilat, aspirin. Fluent in English. Willing to take HB-1 or placebo. 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 patients must be surgically sterile (or have a monogamous partner who is surgically sterile) or be least 2 years postmenopausal or commits to use 2 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 and for 4 months following the last dose of study treatment. Male patients 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 patients 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:  Severe uncontrolled cardiac disease within 6 months of Screening, including but not limited to uncontrolled hypertension, hypotension (defined as below 90/60); 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 eGFR <60. Any clinically significant abnormalities in clinical laboratory assessments as assessed by the Investigator. Any other systemic conditions or organ abnormalities that in the opinion of the Investigator may interfere with the conduct and/or interpretation of the current study. Unable to complete neuropsychological testing. Diagnosis of Bipolar I, Bipolar II disorder or Schizophrenia. History of suicidal behaviors including ideation. Current treatment with doses of benzodiazepines that are outside the FDA-approved prescriber's information. Already on treatment with either telmisartan or verapamil or both. Documented prior drug allergy to either telmisartan or verapamil. Documented contraindication to taking telmisartan or verapamil: (eg, Duchenne's muscular dystrophy, myasthenia gravis). Documented moderate to severe substance abuse within the last 6 months (recreational cannabis use is allowed). Pregnant or breastfeeding.