CS-121 APOC3 Base Editing in FCS

Inclusion Criteria: * Male or female aged 18 to 55 years (inclusive) at the time of signing informed consent. * On regular standard therapy with good compliance, but fasting triglyceride (TG) levels have not been consistently reduced below 10 mmol/L (880 mg/dL); i.e., before screening, there must be records of at least three separate fasting TG values \>10 mmol/L (880 mg/dL), or the participant is intolerant to standard therapy. * North American Familial Chylomicronemia Syndrome (NAFCS) score ≥45 * Able to sign informed consent and comply with the requirements and restrictions specified in the informed consent form and the protocol, such as dietary guidance and intake restrictions. * Female participants must meet one of the following: be not of childbearing potential (e.g., documented hysterectomy, bilateral salpingectomy/sterilization, or ≥1 year postmenopausal); or, if of childbearing potential, have a negative pregnancy test at screening and be willing to use strict and effective contraception (e.g., abstinence, pharmacologic, or barrier methods) during the study. Male participants with reproductive potential must agree to use strict and effective contraception (e.g., abstinence, pharmacologic, or barrier methods) throughout the entire post-dose observation period; males without reproductive potential must provide supporting medical history (e.g., post-vasectomy). Exclusion Criteria: * Currently participating in another interventional clinical study, or last use of anot…