Familial Chylomicronemia Syndrome (FCS)Early Phase 1NCT07176923
CS-121 APOC3 Base Editing in FCS
A Early Phase 1 study testing CS-121 in people with Familial Chylomicronemia Syndrome (FCS), run by CorrectSequence Therapeutics Co., Ltd at 1 site in China.
Trial summary
This is an open-label, single-arm, dose-escalation Phase I clinical trial to evaluate the safety, tolerability, pharmacodynamics (PD), and pharmacokinetics (PK) of CS-121, an in vivo base editing therapy delivered by lipid nanoparticles targeting APOC3, in adult participants (18-55 years) with familial chylomicronemia… Read more about this study
- Who is it for?
- Ages 18 to 55 years
- Conditions the study is for
- Familial Chylomicronemia Syndrome (FCS)
- What is being tested?
- CS-121
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 15 participants
- Where
- 1 siteChina
- Study dates
- 15 Oct 2025to Dec 2026
- Phase
- Early Phase 1
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 55 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- 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).
Who cannot join
- Currently participating in another interventional clinical study, or last use of another investigational product with a washout period of less than 5 half-lives or 30 days (whichever is longer).
- Use of APOC3-targeted antisense oligonucleotides (ASO) or siRNA lipid-lowering agents within 6 months prior to dosing.
- History of acute pancreatitis within 3 months before dosing.
- History of acute coronary syndrome (ACS) within 6 months before dosing, such as myocardial infarction or unstable angina, or prior coronary revascularization (e.g., coronary artery bypass grafting, angioplasty, or stent implantation).
- In the investigator's judgment, receipt of major surgery within 3 months before dosing that would make the participant unsuitable for this study drug or unable to tolerate possible cytokine-release events.
- Any of the following laboratory abnormalities at screening:
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- ALT or AST ≥3 × ULN Total bilirubin ≥1.5 × ULN eGFR <30 mL/min/1.73 m² Random urine albumin-to-creatinine ratio (UACR) >30 mg/g LDL-C >130 mg/dL (3.4 mmol/L) HbA1c ≥9%
- Coagulation abnormalities deemed by the investigator to make CS-121 administration unsuitable.
- Positive at screening for HBsAg, HCV antibody and RNA, HIV, or Treponema pallidum (syphilis).
- Known major organ disease, psychiatric disorders, Cushing's syndrome, or malignancy that, in the investigator's judgment, would make the participant unsuitable for the study or unable to tolerate possible cytokine-release-like events.
- Concomitant medications or treatments judged by the investigator to affect lipid metabolism, hepatic or renal function, or coagulation, or to interfere with the evaluation of study drug efficacy, including but not limited to: systemic glucocorticoids, anabolic steroids, antiretroviral agents used within 4 weeks prior to dosing, plasma exchange, blood donation, or blood loss >200 mL.
- Planning pregnancy, currently pregnant, or breastfeeding.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
China1 site, 1 recruiting
- Recruiting
The First Affiliated Hospital of Anhui Medical University
Hefei, Anhui
Huan Zhou, +8613665527160, zhouhuanbest@vip.163.com
Huan Zhou
About this study
Official title: A Clinical Study to Evaluate the Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of CS-121, an In Vivo Base Editing Therapy Delivered by Lipid Nanoparticles Targeting APOC3, in Adults With Familial Chylomicronemia Syndrome
This is an open-label, single-arm, dose-escalation Phase I clinical trial to evaluate the safety, tolerability, pharmacodynamics (PD), and pharmacokinetics (PK) of CS-121, an in vivo base editing therapy delivered by lipid nanoparticles targeting APOC3, in adult participants (18-55 years) with familial chylomicronemia syndrome (FCS).
Read the detailed description
Familial chylomicronemia syndrome (FCS) is a rare, autosomal recessive lipid metabolism disorder characterized by impaired clearance of triglyceride-rich lipoproteins due to deficiencies in lipoprotein lipase or its cofactors. Patients experience severe hypertriglyceridemia, recurrent episodes of acute pancreatitis, abdominal pain, and other complications that significantly reduce quality of life and may be life-threatening. Despite strict dietary restrictions and conventional lipid-lowering therapies, many patients fail to achieve adequate triglyceride control, highlighting a major unmet medical need.
CS-121 is an investigational, in vivo base editing therapy delivered by lipid nanoparticles (LNPs) targeting the APOC3 gene in the liver. By introducing precise base edits at specific APOC3 loci, CS-121 is intended to mimic naturally occurring protective mutations that reduce ApoC3 expression, thereby restoring triglyceride clearance pathways and lowering pancreatitis risk. Preclinical studies in transgenic mouse and non-human primate models demonstrated dose-dependent APOC3 editing, reductions in serum ApoC3 protein and triglyceride levels, and acceptable safety profiles, supporting advancement into first-in-human evaluation.
This Phase I study uses an adaptive, dose-escalation design to investigate multiple dose levels of CS-121 in adults with genetically and clinically confirmed FCS. The design incorporates dynamic dose adjustment based on emerging safety, pharmacokinetic (PK), and pharmacodynamic (PD) data, consistent with regulatory guidance for rare disease trials.
Participants will undergo screening to confirm eligibility, including fasting triglyceride measurements, North American FCS score (NAFCS), genetic and laboratory testing, and imaging studies. Eligible participants will receive a single intravenous infusion of CS-121 and will be observed in-clinic immediately post-dose for early safety monitoring. Extended follow-up visits will be conducted for up to 10 months, with evaluations of clinical safety parameters, ApoC3 protein and triglyceride levels, drug exposure (sgRNA/mRNA), and exploratory endpoints such as pancreatitis incidence and imaging of hepatic lipid accumulation.
The study is designed to establish a dose range, identify an optimal biological dose (OBD), and provide first-in-human safety, tolerability, PK, and PD data for CS-121 in FCS. Findings from this trial will inform the future development of base editing therapies in severe hypertriglyceridemia and related rare metabolic disorders.
- Conditions
- Familial Chylomicronemia Syndrome (FCS)
- Being tested
- CS-121
- Keywords
- Familial Chylomicronemia Syndrome (FCS), Severe Hypertriglyceridemia, Acute Pancreatitis, Apolipoprotein C3 (APOC3), In Vivo Base Editing, Lipid Nanoparticles (LNP), Gene Editing Therapy, First-in-Human Study, Rare Metabolic Disorder
- Medical subject headings
- Familial hyperchylomicronemia syndrome, Hypertriglyceridemia, Pancreatitis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
CS-121Biological
CS-121 is a in vivo base editing therapy formulated in lipid nanoparticles for targeted editing of the APOC3 gene in hepatocytes. In this study, participants receive a single intravenous infusion of CS-121 at escalating dose levels. The investigational product is designed to reduce ApoC3 protein expression and serum triglyceride levels in adults with familial chylomicronemia syndrome (FCS).
| Study group | Role | What they receive |
|---|---|---|
| Single Low Dose CS-121 | Experimental | Participants in this arm will receive a single low dose of CS-121. Receives: Biological: CS-121 |
| Single Middle Dose CS-121 | Experimental | Participants in this arm will receive a single middle dose of CS-121. Receives: Biological: CS-121 |
| Single High Dose CS-121 | Experimental | Participants in this arm will receive a single high dose of CS-121. Receives: Biological: CS-121 |
| Single Lower Dose 1 of CS-121 | Experimental | Participants in this arm will receive a single lower dose 1 of CS-121. Receives: Biological: CS-121 |
| Single Lower Dose 2 of CS-121 | Experimental | Participants in this arm will receive a single lower dose 2 of CS-121. Receives: Biological: CS-121 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Treatment-Emergent Adverse Events (TEAEs)
Incidence, nature, and severity of treatment-emergent adverse events (TEAEs), including serious adverse events (SAEs), adverse events of special interest (AESIs), and abnormalities in clinical symptoms, vital signs, physical examinations, laboratory tests, and electrocardiograms (ECGs). Severity will be graded according to NCI CTCAE version 5.0.
Measured: From the start of dosing through approximately 10 months of follow-up
Dose-Limiting Toxicities (DLTs)
Within 14 days after CS-121 infusion
Measured: Number and type of dose-limiting toxicities (DLTs), defined as CTCAE grade ≥3 adverse events considered possibly, probably, or definitely related to CS-121 and persisting ≥7 days, or other adverse events/laboratory abnormalities that lead to suspension o
Secondary outcomes (5)
Change from Baseline in Fasting Serum Triglycerides (TG)
Absolute and relative change in fasting serum triglyceride levels compared with baseline values.
Measured: Baseline through approximately 10 months after dosing
Change from Baseline in Serum ApoC3 Protein Levels
Absolute and relative change in serum ApoC3 protein concentrations compared with baseline values.
Measured: Baseline through approximately 10 months after dosing
Peak Concentration (Cmax) of CS-121 Components
Maximum observed concentration of CS-121 components following intravenous infusion.
Measured: From dosing through approximately 1 month after infusion.
Time to Maximum Concentration (Tmax) of CS-121 Components
Time to reach maximum observed concentration of CS-121 components following intravenous infusion
Measured: From dosing through approximately 1 month after infusion
Area Under the Curve (AUC) of CS-121 Components
Area under the Curve of CS-121 components to characterize systemic exposure
Measured: From dosing through approximately 1 month after infusion.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Sep 2025
- Study start15 Oct 2025
- Primary completionDec 2026 (estimated)
- Study completionDec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Familial Chylomicronemia Syndrome (FCS)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Early Phase 1
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Model description
- About 3-15 participants with NAFCS ≥45 and fasting triglycerides ≥10 mmol/L will be enrolled. The study follows an adaptive design with three ascending dose levels and up to two de-escalation cohorts if needed. Each cohort includes 1-3 participants; escalation proceeds after ≥14 days of safety, PK, and PD review. A single intravenous infusion of CS-121 is given, followed by 5 days of inpatient monitoring and \~10 months of follow-up to assess safety, tolerability, PK, PD, and exploratory efficacy including triglyceride reduction and pancreatitis incidence.
- Masking
- None (open label)
- Enrolment
- 15 participants (estimated)
Sponsor and investigators
- Lead sponsor
- CorrectSequence Therapeutics Co., Ltd
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- The First Affiliated Hospital of Anhui Medical University
- Responsible party
- Sponsor
- Investigators
- YALIANG LI, Study director, CorrectSequence Therapeutics (Shanghai) Co., Ltd
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07176923
- Sponsor's protocol ID
- CS-121-01
- Status last verified
- Feb 2026
- First submitted
- 30 Aug 2025
- Last updated
- 11 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided