China Stroke Primary Prevention Trial 2 for Participants With H-type Hypertension and MTHFR 677 CC/CT Genotype (CSPPT2-CC/CT)

This study consists of 3 periods: Screening, Run-in, and Randomized treatment. Period I: Screening (V0) The purpose of Period I is to obtain informed consent and screen for eligible participants. After obtaining written informed consent, at the first screening visit (V0), participants will complete a face-to-face interview, and clinical evaluation and measurements. Their biological samples will be collected for laboratory analyses. Collectively, these information will help to determine eligibility for inclusion in the study. Period II: Run-in Period (VD) The purpose of Run-in is to assess participants' compliance for the amlodipine treatment regimen as well as to observe participants' tolerance to amlodipine, so as to screen out those with poor compliance or intolerance to amlodipine treatment. The run-in phase lasted 2 to 4 weeks, during which oral administration of Amlodipine tablets (5 mg) was given once daily. Period III: Randomized Treatment (V1-V21) This is a randomized, double-blind, double-dummy, controlled treatment with a total of 5-years. At each of the participating centers, participants who remain eligible for participation at V1 will first be stratified by MTHFR genotypes: CC vs. CT. Within each genotype stratum, participants will then be randomized into 2 treatment groups: either an amlodipine-only tablet (5mg/d) with a dummy tablet or an amlodipine folic acid tablet (5.8mg/d) with a dummy tablet in a 1:1 ratio, using randomization and trial supply management (RTSM) platform. During the treatment period, other antihypertensive drugs can be added to achieve the target blood pressure control (BP≤140/90mmHg), including Valsartan (80mg/d), or/and Indapamide (1.5mg/ d), or/and metoprolol tartrate tablets (25mg/d). Participants will be followed every 3 months during the five-year treatment period, and the treatment drugs will be distributed at each visit. A total of 32,000 participants will be randomly assigned to one of the two treatment groups: Group A: amlodipine 5.0mg (n=16,000) and Group B: amlodipine-folic acid 5.8mg (n=16,000). Based on published data from CSPPT (Huo et al, JAMA, 2015), the 5-year cumulative incidence of ischemic stroke is around 2.9%. Assuming the 5-year cumulative incidence of ischemic stroke is 2.5% in the amlodipine-only group, this trial has 80% power to detect a 20% difference between group A and group B in the observed hazard ratio (HR) for incident ischemic stroke (HR ≤0.80), at a two-sided significance level of α=0.05. If instead, the 5-year cumulative incidence of ischemic stroke in the amlodipine-only group is 3.5%, this trial has 80% power to detect a 16% difference between group A and group B (HR ≤0.84). There are two planned interim analyses, one at the end of the third year, and another at the end of the fourth year. The O'Brien-Fleming alpha-spending function will be used to define the significance level of each interim analysis to ensure that the final overall two-sided significance level of α=0.05 is met.