An Early Phase 1 interventional study of CS-121 in Familial Chylomicronemia Syndrome (FCS), sponsored by CorrectSequence Therapeutics Co., Ltd. Recruiting at 1 site in China. Open to participants aged 18 Years to 55 Years. Per ClinicalTrials.gov, last updated 2026-02-11.
Sponsored by CorrectSequence Therapeutics Co., Ltd · Early Phase 1, Interventional, and Treatment
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).
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.
324 studies on the registry are indexed under Hypertriglyceridemia; 38 are open to participants now.
This study's planned enrollment of 15 is below the median of 66 across 288 interventional studies indexed under Hypertriglyceridemia.
Browse Hypertriglyceridemia studies →CorrectSequence Therapeutics Co., Ltd is the lead sponsor of 9 studies on the registry; 7 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
or AST ≥3 × Total ≥1.5 × ULN \<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) ≥9%
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Reproductive potential
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Washout period
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this arm will receive a single low dose of CS-121.
Biological: CS-121
Participants in this arm will receive a single middle dose of CS-121.
Biological: CS-121
Participants in this arm will receive a single high dose of CS-121.
Biological: CS-121
Participants in this arm will receive a single lower dose 1 of CS-121.
Biological: CS-121
Participants in this arm will receive a single lower dose 2 of CS-121.
Biological: CS-121
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).
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.
Time frame: From the start of dosing through approximately 10 months of follow-up
Dose-Limiting Toxicities (DLTs)
Within 14 days after CS-121 infusion
Time frame: 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
Change from Baseline in Fasting Serum Triglycerides (TG)
Absolute and relative change in fasting serum triglyceride levels compared with baseline values.
Time frame: 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.
Time frame: Baseline through approximately 10 months after dosing
Peak Concentration (Cmax) of CS-121 Components
Maximum observed concentration of CS-121 components following intravenous infusion.
Time frame: 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
Time frame: 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
Time frame: From dosing through approximately 1 month after infusion.
Plan to share: Undecided
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Studies of the drug tested here: CS-121
CorrectSequence Therapeutics Co., Ltd