Safety, Tolerability and Effect of RBD4059 Injection in Adults with Prior VTE After Anticoagulant Therapy and Cancer Patients at High Risk of VTE

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What is this study about?

The trial includes two groups of participants: people who have previously experienced a blood clot called Venous Thromboembolism and have finished their initial blood‑thinner treatment, and people with cancer who have a high chance of developing a clot. The medication being tested is named vortosiran and is given as a small subcutaneous injection, which means a shot placed just under the skin. This medication is compared with an inactive solution (placebo) to see how it works.

The purpose of the study is to evaluate the safety, tolerability, and effect of the medication on the activity of a clot‑helping protein known as Factor XI after eight weeks. Participants will receive a few injections over several weeks and will attend brief visits for simple check‑ups, including blood tests and basic heart monitoring, to track any side effects and how the drug behaves in the body.

1 randomization

after you join the study, you will be randomly assigned to receive either vortosiran, the investigational drug, or a placebo that looks the same but does not contain the active medication.

2 baseline assessments

before the first injection, you will undergo a series of baseline checks. these include blood tests to measure your current FXI activity and other laboratory values, a physical examination, measurement of vital signs such as blood pressure and heart rate, and a 12‑lead ECG (electrocardiogram) to record the electrical activity of your heart.

3 first injection

you will receive a single subcutaneous injection (injection under the skin). if you are in the investigational group, the injection contains vortosiran at the dose defined by the study protocol. if you are in the placebo group, the injection contains a phosphate buffer solution with a small amount of vitamin b2 added only for colour. the exact amount of medication is specified by the study and is not disclosed in this summary.

4 follow‑up visits and monitoring

after the injection, you will return for scheduled follow‑up visits. during each visit, the study team will check for any side effects, repeat blood tests to monitor changes in FXI activity, and perform other safety evaluations such as vital signs and, when required, another ECG. the primary safety and efficacy evaluation occurs at week 8 after the first dose.

5 final assessment

at the end of the trial period, you will have a final visit that includes a comprehensive safety review, repeat laboratory testing, and a final measurement of FXI activity. any remaining study medication will be accounted for, and you will receive information about the overall study results.

Who Can Join the Study?

Adult men or women who are at least 18 years old.
Women who could become pregnant must agree to use a highly effective form of birth control.
For participants in Cohort A: You must have had a confirmed blood clot in a lower‑leg vein (deep vein thrombosis) at the popliteal vein or higher, or a confirmed clot that traveled to the lungs (pulmonary embolism), shown by medical imaging.
For participants in Cohort A: You must have finished 3 to 12 months of standard blood‑thinner (anticoagulant) treatment for that clot, and this treatment must have ended at least 2 weeks before you are randomly assigned to a study group.
For participants in Cohort A: You must not have had another clot during the first 3 to 12 months of blood‑thinner treatment.
For participants in Cohort A: Your doctors must be uncertain (clinical equipoise) about whether you should stay on blood thinners long‑term, and stopping the medication must follow usual care practices.
For participants in Cohort A: You must be stable in terms of blood pressure and heart function at the screening visit and be able to be followed as an outpatient.
For participants in Cohort B: You must be starting a new course of chemotherapy that is given throughout the whole body (systemic chemotherapy) and is planned to last at least 3 months.
For participants in Cohort B: You must have a newly diagnosed cancer or a worsening of an existing cancer.
For participants in Cohort B: Your overall health and ability to perform daily activities must be rated as 0‑2 on the Eastern Cooperative Oncology Group (ECOG) performance status scale, meaning you are fully active to able to care for yourself but may not be able to do strenuous work.
For participants in Cohort B: You must have an intermediate‑high risk of another blood clot, measured by a Khorana score of 2 or higher at the screening visit.

Who Cannot Join the Study?

Pregnancy or breastfeeding: You cannot be pregnant or nursing a baby during the study.
Active significant bleeding or very high risk of bleeding: You must not have any current serious bleeding or conditions that make bleeding very likely.
Severe uncontrolled high blood pressure: Blood pressure that is very high and not controlled by medication disqualifies you.
High risk of bleeding (for certain study groups): If you have conditions that make bleeding likely, you cannot join.
Liver disease with clotting problems: Having liver disease that affects the blood’s ability to clot excludes you.
Certain cancers not allowed: If you only have basal cell or squamous cell skin cancer, acute leukemia, or a myeloproliferative neoplasm, you cannot participate.
Planned stem cell transplant: If you are planning to receive a stem cell transplant, you are not eligible.
Active infection with hepatitis B, hepatitis C, or HIV: Any current infection with these viruses at the time of screening excludes you.
Planned surgery that could change clot or bleeding risk, or recent surgery: If you plan to have surgery that might affect clotting or bleeding risk, or had surgery within the last two weeks, you cannot join.
Serious medical, psychiatric, or social condition that the doctor thinks would interfere with your participation, ability to follow study rules, or interpretation of results.
Kidney function (eGFR) less than 30 mL/min: A low estimated glomerular filtration rate, which measures how well the kidneys filter blood, makes you ineligible.
Need for long‑term blood thinner (anticoagulant) therapy: If you require ongoing anticoagulation for any reason, you cannot take part.
Absolute reason not to continue blood thinners, such as recent life‑threatening bleeding, bleeding inside the brain (intracranial hemorrhage), or major spinal or eye surgery that still carries bleeding risk.
Use of other blood‑thinning medicines that could interfere with the study’s measurements or greatly increase bleeding risk.
Abnormal lab results at screening:
- Hemoglobin (a protein that carries oxygen in the blood) less than 10 g/dL.
- Platelet count (cells that help stop bleeding) less than 100,000 per microliter.
- Alanine aminotransferase (ALT) or Aspartate aminotransferase (AST) (liver enzymes) more than 1.5 times the normal upper limit.
- Total bilirubin (a substance processed by the liver) more than 1.5 times the normal upper limit.
These lab values make you ineligible.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

No sites found in this category

Other Sites

Site Name	City	Country
Zachodniopomorskie Centrum Onkologii	Szczecin	Poland
Hopital Beaujon	Clichy	France
Mazowiecki Szpital Wojewodzki Im. Sw. Jana Pawła II W Siedlcach Sp. z o.o.	Siedlce	Poland
Nordica Medica Sp. z o.o	Sopot	Poland
Sienna Clinic Medycyna Specjalistyczna Sp. z o.o.	Warsaw	Poland
CHU de Grenoble – Hôpital Michallon	La Tronche	France
Pole Sante Leonard De Vinci	Chambray Les Tours	France
Tokuda Hospital	Sofia	Bulgaria
Multiprofile Hospital For Active Treatment Pazardzik AD	Pazardzhik	Bulgaria
Specialized Hospital For Active Cardiology Treatment Medica Kor EAD	Ruse	Bulgaria
Ssvoxvvuup Syzrjavv Swpfah	Suceava	Romania
Ckctsjl Phmecvbg Sculzf	Sibiu	Romania
Iaiyruno dj Ccsezafqdhkb Hbogzxeoqvr Uduagbvigxmzg dh Seqsl Eqxhftg (tzcqnej	Saint Priest En Jarez	France
Gued Mcqmtca Ssetpw	Bucharest	Romania
Ajwlblq Sap z ooef	Poznan	Poland
Nqglbmlo Ikdfxjbb Ozlluttke Icf Mhtjw Stboeauabjjamgyvmnxrhcoxqvxw Iizpvqsm Bfktbcuy	Cracow	Poland
Srovgb Jfeeuydo Dm Umxitjx Srsl Mrlk	Satu Mare	Romania
Sxvfbsan Cqmmjv Juqavtcz Mqiaa	Targu Mures	Romania
Sttxftlnebj Plztbsnam Skszwjtwwgcslrl Suwmffp Zetdoors Iwgpygfynq Pjeio Iq	Grodzisk Mazowiecki	Poland
Ixnmezmkqk Dy Brek Ccloxbarlrlpcad Trcilmkeg	Timisoara	Romania
Efwxygphh Iiqganpek Fgu Cwjwxdiwccrtxv Dmtlfdzl Aog Tohlhhndoe	Targu Mures	Romania
Krjmbsjyw Sjjokbm Sbnwlsuvyyvpwvs ib Jbfy Plfqu Iz	Cracow	Poland
Lww Mgd Squ z owbz	Warsaw	Poland
Mlekqatks Hjfomvach Shkqpu	Bucharest	Romania
Umuninbfgu Myqnjdhtlath Hhkjvozb Fso Ajljcj Tlzwhynpp Asf Ehocflatr Mimlnqwh N I Plftiar	Sofia	Bulgaria
Mkhrwhsmnfbi Rtinsptb Hzbsfewp Fxr Ankgsr Trjiuwqfr Dgo Sqewhv Cyvoalxen At	Veliko Tirnovo	Bulgaria
Mklf Notcptce Hstne Hhdwsbqa Epx	Sofia	Bulgaria
Dzuycujantcirbupunypyxb chbwqi “fenzztkikshdcgy Eznc	Sofia	Bulgaria

Trial status

Country	Status	Recruitment Start
Bulgaria	Not yet recruiting	24.10.2026
France	Not yet recruiting	24.10.2026
Poland	Not yet recruiting	24.10.2026
Romania	Not yet recruiting	24.10.2026

Trial locations

Investigated Drugs:

Rbd4059

RBD4059 is an investigational medicine, also known as vortosiran, that is being tested to see if it can safely lower the activity of a blood protein called Factor XI. Lowering Factor XI may help prevent new blood clots from forming in people who have had a clot before or in cancer patients who are at high risk for clots. In the study, participants receive the medicine as a subcutaneous injection (a shot under the skin). Researchers are watching how well the medicine works to reduce Factor XI levels and are also checking for any side effects.

Investigated Diseases:

Embolism venous

Venous Thromboembolism – Venous thromboembolism is a condition in which blood clots develop in the veins. It often begins as a deep vein thrombosis in the leg and may grow larger or break loose. When a clot travels to the lungs, it causes a pulmonary embolism, which can lead to symptoms such as shortness of breath and chest discomfort.

Trial ID:

2026-525479-15-00

Protocol code:

RC03T003

Trial Phase:

Therapeutic exploratory (Phase II)

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Safety, Tolerability and Effect of RBD4059 Injection in Adults with Prior VTE After Anticoagulant Therapy and Cancer Patients at High Risk of VTE

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?