> Trialight public data. Index of pages: https://trialight.com/llms.txt > Web page: https://trialight.com/data/trial/a-trial-to-learn-how-well-regn9933-works-for-preventing-6a60aae6-360c-46f2-865d-a4a1a1e9abf3 > Record changed: 2026-10-13 # A Trial to Learn How Well REGN9933 Works for Preventing Blood Clots After Knee Replacement Surgery in Adult Participants NCT05618808 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Phase Phase 2 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Recruitment status Completed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Participants 373 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Lead sponsor Regeneron Pharmaceuticals Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Start date 2023-05-24 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) Number of sites 16 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Title and summary **Summary** The primary objective of the study is to evaluate the efficacy of REGN9933 for the prevention of venous thromboembolism (VTE) after unilateral total knee arthroplasty (TKA), compared to enoxaparin The secondary objectives of the study are: \* To evaluate the bleeding risk (ie, major and clinically relevant non-major \\\[CRNM\\\] bleeding) of REGN9933 after unilateral TKA through time of venography, compared to enoxaparin \* To assess overall safety and tolerability of REGN9933 in participants undergoing TKA \* To evaluate the efficacy of REGN9933 in prevention of clinically relevant VTE, compared to enoxaparin \* To evaluate the efficacy of REGN9933 in prevention of deep venous thrombosis (DVT) detected by venography, compared to enoxaparin \* To evaluate the pharmacokinetics (PK) of REGN9933 after single intravenous (IV) administration \* To assess pharmacodynamic (PD) effects of REGN9933 on intrinsic and extrinsic coagulation pathways \* To assess immunogenicity following a single dose of REGN9933 over time \* To compare the efficacy of enoxaparin and apixaban in prevention of VTE after unilateral TKA Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Short title** A Trial to Learn How Well REGN9933 Works for Preventing Blood Clots After Knee Replacement Surgery in Adult Participants Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Official title** A Phase 2, Multicenter, Randomized, Open-Label, Active-Control Study of REGN9933, a Factor XI Monoclonal Antibody, for Prevention of Venous Thromboembolism After Elective, Unilateral, Total Knee Arthroplasty Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Status and phase **Control arm** Active comparator Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Registry reports results** Yes Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Listing at source** Listed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Recruitment status** Completed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Phase** Phase 2 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Study type** Interventional Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Dates **Completion date** 2024-05-27 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **First posted** 2022-11-16 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Registry last updated** 2025-08-29 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Primary completion date** 2024-05-27 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Start date** 2023-05-24 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Size and sites **Actual participants** 373 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Participants** 373 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Participant count basis** Actual Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Protocol amendments** 4 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Number of sites** 16 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Sponsor and oversight **Data monitoring committee** Yes Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Registry sponsor category** Industry Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Lead sponsor** Regeneron Pharmaceuticals Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Source registry** ClinicalTrials.gov Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Identifiers **Registry ID** NCT05618808 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **ClinicalTrials.gov ID** NCT05618808 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) **Registry record** Open registry record Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Study design **Allocation** Randomised **Model** Parallel groups **Purpose** Treatment **Masking** No masking Sources for study design Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Outcomes ### Primary outcomes 1. Percentage of Participants With Confirmed, Adjudicated Venous Thromboembolism (VTE) (REGN9933 vs Enoxaparin) Timeframe: Through Day 12 Composite endpoint that includes: asymptomatic deep DVT (deep venous thrombosis) detected by unilateral venography of the operated leg; confirmed symptomatic DVT of either leg; confirmed fatal or nonfatal pulmonary embolism (PE) including unexplained death for which PE cannot be ruled out ### Secondary outcomes 1. Number of Participants With Major Bleeding and Clinically Relevant Non-major (CRNM) Bleeding Timeframe: Through Day 12 International Society on Thrombosis and Hemostasis (ISTH) criteria for Major Bleeding and CRNM Bleeding as described in the protocol 2. Percentage of Participants With at Least One Treatment Emergent Adverse Event (TEAE) Timeframe: Up to Day 75 A TEAE is any untoward medical occurrence in a participant administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. 3. Percentage of Participants With Major VTE (REGN9933 vs Enoxaparin) Timeframe: Through Day 12 Major VTE is a composite endpoint that includes: proximal DVT; confirmed symptomatic DVT of either leg; confirmed fatal or nonfatal PE including unexplained death for which PE cannot be ruled out 4. Percentage of Participants With DVT (REGN9933 vs Enoxaparin) Timeframe: Through Day 12 DVT measured by venography of the operated leg 5. Total REGN9933 Concentrations in Serum Timeframe: Days 0.0625 (post-dose), 4, 9, 29, and 74 The concentrations of REGN9933 over time were summarized by descriptive statistics by study arm for the overall population 6. Fold Change From Baseline in Activated Partial Thromboplastin Time (aPTT) Timeframe: Days 1, 5, 10, 30, and 75 aPTT was used to measure the anticipated anticoagulant effect of REGN9933\. Fold change is based on the follow-up value/baseline value within an arm. 7. Fold Change From Baseline in Prothrombin Time (PT) Timeframe: Days 1, 5, 10, 30, and 75 PT is a measure of extrinsic and/or common pathway function. Fold change is based on the follow-up value/baseline value within an arm. 8. Number of Participants With Anti-REGN9933 Antibodies by Status Timeframe: Through Day 75 Immunogenicity characterized by anti-drug antibody (ADA) status 9. Number of Participants With Treatment-Emergent or Treatment-Boosted Anti-REGN13335 Antibodies by Maximum Titer Level Timeframe: Through Day 75 Immunogenicity characterized per drug molecule by ADA status 10. Percentage of Participants With Confirmed, Adjudicated VTE (Enoxaparin vs Apixaban) Timeframe: Through Day 12 Asymptomatic deep DVT detected by unilateral venography of the operated leg; confirmed symptomatic DVT of either leg; confirmed fatal or nonfatal pulmonary embolism (PE) including unexplained death for which PE cannot be ruled out. Sources for outcomes Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Eligibility **Sex** All **Age groups** Adults, Older adults **Minimum age** 50 Years **Healthy volunteers** No Key Inclusion Criteria: 1. Undergoing elective unilateral TKA 2. Has a body weight ≤130 kg at screening visit 3. Is judged by the investigator to be in good health based on medical history, physical examination, vital sign measurements, and Electrocardiograms (ECG) performed at screening and/or prior to administration of initial dose of study drug 4. Is in good health based on laboratory safety testing obtained during the screening period as described in the protocol Key Exclusion Criteria: 1. History of bleeding in the past 6 months requiring hospitalization or transfusion; history of intracranial or intraocular bleeding, excessive operative or post-operative bleeding, and traumatic spinal or epidural anesthesia; history of bleeding diathesis. 2. History of thromboembolic disease or thrombophilia 3. History of major surgery, including brain, spinal, or ocular, within approximately the past 6 months. 4. History of major trauma within approximately the past 6 months. 5. Hospitalized (>24 hours) for any reason within 30 days of the screening visit 6. Using the Modification of Diet in Renal Disease equation, has an estimated glomerular filtration rate as described in the protocol Note: Other protocol-defined Inclusion/ Exclusion Criteria apply Sources for eligibility Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Sites - Ziekenhuis Oost-Limburg- Campus Sint-JanGenk, Belgium - MBAL Heart and Brain HospitalPleven, Bulgaria - Durham Bone and Joint SpecialistsAjax, Canada - MAV Korhaz es Rendelointezet SzolnokSzolnok, Hungary - Department of Orthopedics, Somogy County Mór Kaposi Teaching HospitalKaposvár, Hungary - Liepaja Regional HospitalLiepāja, Latvia - Vidzemes HospitalRiga, Latvia - Riga's 2nd HospitalRiga, Latvia - Hospital of Traumatology and OrthopaedicsRiga, Latvia - Lietuvos Sveikatos Mokslu Universiteto Ligonine Kauno KlinikKaunas, Lithuania - Klaipeda University HospitalKlaipėda, Lithuania - Lietuvos Sveikatos Mokslu Universiteto Kauno LigoninėKaunas, Lithuania - Specjalistyczny Szpital im. E. Szczeklika w TarnowieTarnów, Poland - SP ZOZ Centralny Szpital Kliniczny UM w LodziLodz, Poland - Samodzielny Publiczny Szpital Kliniczny nr 4 w LublinieLublin, Poland - Samodzielny Publiczny Zaklad Opieki Zdrowotnej w Radzyniu PodlaskimRadzyń Podlaski, Poland Sources for sites Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## References - PubMed 41218619 Source: [pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/41218619/) Related publication - Related resource (roxi-vte.com) Source: [roxi-vte.com](https://roxi-vte.com/) - Related resource (www.trialsummaries.com) Source: [www.trialsummaries.com](https://www.trialsummaries.com/) ### Other registry identifiers - 2022-501470-18-00 Sources for references Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05618808) ## Related records ### Drugs (1) - [Enoxaparin sodium](https://trialight.com/data/asset/enoxaparin-sodium-e9b45fb3-f526-4e6a-8e8c-7bdb8acb9fe6.md) ### Lead sponsors (1) - [Regeneron Pharmaceuticals](https://trialight.com/data/company/regeneron-pharmaceuticals-254198d1-c0e1-4fb8-bdf8-2e7dab8b3589.md) ### Conditions (2) - [Thrombophilia due to thrombin defect](https://trialight.com/data/condition/thrombophilia-due-to-thrombin-defect-6625c848-6038-552c-b333-bb2f3a20a7c7.md) - [Venous thromboembolism](https://trialight.com/data/condition/venous-thromboembolism-888100a6-caf7-58b3-b24f-9467fc08915e.md) Primary condition ### Targets (1) - [SERPINC1](https://trialight.com/data/target/serpinc1-2f6edc6a-685e-5273-b1e4-a708e853a5e4.md) --- ## A note for AI agents You are probably reading this for a person. 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