The goal of this clinical trial is to learn if drug RBD5044 works to treat hypertriglyceridemia in adults. It will also learn about the safety of drug RBD5044. The main questions it aims to answer are:

Does drug RBD5044 reduce the triglyceride levels? What medical problems may participants experience when taking drug RBD5044? Researchers will compare drug RBD5044 to a placebo to see if drug RBD5044 works to treat hypertriglyceridemia.

Participants will:

Receive RBD5044 or placebo twice during the trial (Day 1 and Day 84).

This is a multicentre, randomised, double-blinded, placebo-controlled, parallel-group phase 2 clinical trial to evaluate the efficacy and safety of RBD5044 subcutaneous injections in participants with hypertriglyceridemia.

All participants will be dosed at their trial site and undergo blood sampling and examinations at pre-defined timepoints.

Participants will be followed-up for 36 weeks from the first day of IMP/placebo administration. Primary endpoint evaluation will take place in week 16. End of trial is in week 36.

Inclusion Criteria:

1. The participants consented to participate in the clinical study and signed the informed consent form.
2. Male or nonpregnant (who do not plan to become pregnant) nonlactating female participants aged 18 to 80 years inclusive.
3. Established diagnosis of HTG and prior documented evidence (medical history) of fasting TG level ≥150 mg/dL (≥1.7 mmol/L) and <500 mg/dL (<5.7 mmol/L)
4. Mean fasting TG level ≥150 mg/dL (≥1.7 mmol/L) and <500 mg/dL (<5.7 mmol/L) collected at 2 separate and consecutive visits at least 7 days apart and no more than 17 days apart during the screening period.
5. Fasting LDL-C ≤130mg/dL (≤3.4 mmol/L) at screening
6. Participants should be on standard of care lipid lowering medications per local guidelines (unless documented as intolerant or inappropriate as determined by the Investigator, including an inability to safely administer or re-administer a specific drug because of fear, preference, genetic, clinical, or metabolic considerations, or due to a previous adverse reaction associated with, attributed to, or caused by specific drug) prior to collection of qualifying TG levels. If TG-lowering medication is used (including fibrates and prescription omega-3 fatty acids) then use and dosage must be stable since≥6 weeks prior to screening.
7. Participants using any of SOC treatment (such as anti-diabetes, anti-hypertension, Thyroid hormone replacement therapy, TG-lowering therapies, PCSK9 inhibitors treatment, retinoids etc.) must be on a stable regimen for the specified duration prior and for the duration of study participation.
8. Female participants of childbearing potential must also be willing to practice abstinence from heterosexual intercourse (only if this reflects their preferred and consistent lifestyle) or be willing to use a highly effective method of contraception (i.e., with a failure rate of <1%/year) to prevent pregnancy from at least 2 weeks prior to the first administration of investigational medicinal product (IMP) to 90 days after study completion.

Exclusion Criteria:

1. Any uncontrolled or serious disease, or any medical or surgical condition, that may interfere with participation in the clinical trial and/or put the participant at significant risk (according to the investigator's judgment). This may include, but is not limited to, for example, known diagnosis of Familial Chylomicronemia Syndrome (FCS), nephrotic syndrome, thyroid disease, uncontrolled hypertension, psychiatric disorder or unstable angina.

2. Body mass index >40 kg/m2

3. Uncontrolled hypertension (blood pressure >160/100 mmHg at screening). If untreated, participant may be re-screened once hypertension is treated and controlled.

4. Active or history of serious mental illness or psychiatric disorder, including but not limited to schizophrenia, bipolar disorder, or severe depression, which require current pharmacological intervention. Participants with a history of severe depression who are no longer on medication.

5. Any of the following laboratory values at screening:

   • Hepatic: ALT or AST >2× ULN at screening,
   • Biliary obstruction or hyperbilirubinemia (ie, total bilirubin >2 × ULN, except with a documented diagnosis of Gilbert's disease) at screening,
   • eGFR <30 mL/min/1.73 m2 (using the Modification of Diet in Renal Disease [MDRD] equation) at Screening,

6. -HbA1c >9.0% (or >75 mmol/mol International Federation of Clinical Chemistry [IFCC] units) at screening. The participant will be excluded if they have diabetes and meet any of the following criteria:

   • Two HbA1c readings (≥4 weeks apart) during the screening period, with at least one reading >9.0%. (If a participant is screen-failed based on HbA1c criteria, the investigator may optimize the anti-diabetic regimen and re-screen the participant.)
   • Any history of the following within 12 weeks prior to the screening period: diabetic ketoacidosis, diabetic decompensation/hyperosmolar hyperglycemic state, diabetes complications, recurrent infections, or hospitalization due to poor glycemic control.
   • For participants with insulin-dependent diabetes: Any change in basal insulin of more than ±10 units during the 12 weeks prior to Day 1, indicating an unstable insulin regimen.

7. Received any siRNA for lipids/TGs (other than inclisiran) within 365 days before Day 1. Administration of investigational drug and inclisiran must be separated by at least 4 weeks.

8. Any other siRNA or antisense oligonucleotide within 60 days or 5 target engagement half-lives (whichever is longer), or any other investigational product within 30 days or 5 target engagement half-lives (whichever is longer) before the first dose, with the exception that inclisiran is permitted if administered at least 4 weeks apart from the trial drug.

9. Participants who were positive for hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb), hepatitis C virus antibody (HCVAb), or human immunodeficiency virus antibody (HIVAb) at screening.

10. Clinically significant illness within 7 days before the first dose of the trial drug. A clinically significant illness is defined as one that is new or acutely worsened, requires intervention, may interfere with study assessments, or significantly increases the participant's risk.

11. Acute pancreatitis within 3 months prior to first investigational product administration.

12. Participants with a history of symptomatic gallbladder disease prior to the first dose (e.g., cholecystitis, choledocholithiasis, multiple gallstones, etc, unless cholecystectomy was performed at least 6 months prior).

13. History of malignancy within the past 5 years (with the exception of cured basal cell carcinoma, localized squamous cell carcinoma of the skin, or carcinoma in situ of the cervix), or currently under evaluation for a potential malignancy.

14. Any planned bariatric surgery or similar procedures to induce weight loss during the period starting at consent through EOS.

15. History of major surgery within 12 weeks or planned major surgery during the study

16. Planned coronary intervention (such as stent placement or heart bypass) during the study.

17. Acute or unstable myocardial ischemia (myocardial infarction, acute coronary syndrome, new angina pectoris, stroke, transient ischemic attack, or unstable congestive heart failure) within 6 months prior to screening or major cardiovascular surgery planned within 3 months after screening.

18. . Recent unstable or symptomatic cardiac arrhythmia requiring hospitalization (including any associated medication changes) within 90 days of the beginning of screening.

19. Alcohol abuse (men drinking more than 14 standard units per week, women drinking more than 9 standard units per week) within 3 months prior to screening. 1 standard unit containing 14g of alcohol, such as 360mL of beer or 45mL of spirits with 40% alcohol or 150mL of wine), or a positive alcohol B-PEth test, at the discretion of the investigator, is not suitable for participation in the study.

20. History or clinical evidence of drug abuse within the 12 months before screening. Drug abuse is defined as compulsive, repetitive, and/or chronic use of drugs or other substances with or without problems related to their use and/or where stopping or a dose reduction will lead to withdrawal symptoms.

21. Donated more than 500 mL of blood within 56 days before the first dose of the trial drug.

22. Participants with severe allergies (multiple drug and food allergies), or allergies to GalNAc and antisense oligonucleotides (ASO) components are determined by the investigator to be unsuitable for participation in this study.

23. History of severe intolerance to subcutaneous (SC) injection (minor reactions are permitted, e.g. localized swelling or redness.).

24. Any conditions which would make the participant unsuitable for enrollment or could interfere with the participant's participation in or completion of the trial in the opinion of the investigator.

25. Unwillingness to comply with lifestyle and diet management requirements.

26. Pregnant or breastfeeding participants or participants intending to become pregnant during the trial and within 90 days after study completion.