A 4-week, Randomized, Placebo-Controlled, Double-Blind, Efficacy and Safety Study of HS-25 in Adults With Primary Hypercholesterolemia

Inclusion Criteria: * Men, or women using a highly effective birth control method or not of child-bearing potential, who are 18 to 65 years of age at Visit 1 (screening visit). * LDL-C 130 to 189 mg/dL (inclusive) on a cholesterol lowering diet but no lipid modifying drug treatment for at least 6 weeks. A qualifying LDL-C value must be obtained at the beginning and end of the placebo run-in (Visit 2 and Visit 3) and the Visit 3 value must be within 15% of the value at Visit 2, higher or lower; the average of both qualifying values must be in the range of 130 to 189 mg/dL (inclusive) for inclusion in the study. * TG ≤ 350 mg/dL on a cholesterol lowering diet but no lipid modifying drug treatment for at least 6 weeks and TG levels must be ≤ 350 mg/dL at both Visit 2 and Visit 3 * Compliance of 80% to 120% with assigned study drug regimen during a 2 week placebo run-in phase. Exclusion Criteria: * Women who are pregnant or breast feeding. * History of stroke, myocardial infarction, unstable angina, heart failure or any arterial revascularization procedure (eg, carotid, coronary, aorta, peripheral arterial). * History of diabetes or glycosylated hemoglobin (HbA1c) \> 6.5. * History of moderate to severe lactose intolerance (eg, unable to drink a glass of milk). * History of hospitalization for treatment of a major psychiatric disorder. * History of drug or alcohol abuse as defined by the Diagnostic and Statistical Manual (DSM-5) within the prior 12 months. * History of regular alcohol consumption exceeding 7 drinks/week for females or 14 drinks/week for men (1 drink = 5 ounces of wine or 12 ounces of beer or 1.5 ounces of hard liquor) within 6 months prior to screening. * Hospitalization for a duration \> 24 hours for any reason within the prior 3 months that, in the opinion of the investigator, may affect adherence to study procedures. * History of a positive test for human immunodeficiency virus, hepatitis B or hepatitis C. * History of cancer with the exception of well-treated basal cell or squamous cell carcinoma of skin, or in-situ cervical carcinoma. * Presence of any condition which, in the opinion of the investigator, is likely to compromise completion of this trial or not be in the best interest of the subject. * History of intolerance to ezetimibe. * Participation in a prior study of HS 25. * Participation in a study of an investigational drug or device within the prior 3 months unless subject has documentation of placebo administration in a placebo-controlled drug treatment trial only. * Treatment with a fibric acid derivative (eg, fenofibrate, gemfibrozil), probucol, warfarin, systemic corticosteroid, cyclosporine or other immunosuppressant agent within the prior 12 weeks. * Anticipated need or frequent use of acetaminophen (\> 2 gm/day, that is required \> 4x/week). * Vitamins, herbal and dietary supplements must be discontinued at screening unless subject has been on a long-term daily regimen and agrees to continue this regimen during the study. * Alanine aminotransferase (ALT) \> 1.0 × upper limit of normal (ULN) at Visit 1, Visit 2 or Visit 3. * Aspartate aminotransferase (AST) \> 1.0 × ULN at Visit 1, Visit 2 or Visit 3. * Unexplained (not due to exercise or strenuous activity) creatinine kinase increase \> 2 × ULN at Visit 1, Visit 2 or Visit 3. * Estimated glomerular filtration rate (Modification of Diet in Renal Disease) \< 60 mL/min/1.73m2 at Visit 1, Visit 2 or Visit 3. * Thyroid stimulating hormone outside of the normal range. * Prisoners or subjects who are compulsorily detained (involuntarily incarcerated) for treatment of either a psychiatric or physical disease (eg, infectious disease) must not be enrolled. * Any other laboratory abnormality considered by the investigator to be clinically significant. * Any subject with an electrocardiogram (ECG) having a QTc interval ≥ 450 msec, or any other abnormality considered by the investigator to be clinically significant at the end of placebo run-in (Visit 3) should not be enrolled.