Design and Rationale of the COLT Study

NCT07432529 | Not Yet Recruiting Phase 3

• 1 other identifier: COLT123
• Study Type: interventional
• Target: 940
• Locations: 0 countries
• Sites: N/A

Brief Summary

Deep vein thrombosis (DVT) is a condition in which a blood clot forms in the deep veins of the leg and can lead to long-term problems such as leg pain, swelling, and reduced quality of life. Standard treatment with blood-thinning medication lowers the risk of complications, but some patients still develop long-term damage to the veins. Inflammation is thought to play an important role in these complications. This study will evaluate whether adding colchicine, an anti-inflammatory medication already used for other conditions, to standard anticoagulant therapy can improve outcomes in patients with acute DVT. Participants will be randomly assigned to receive either colchicine or a placebo, in addition to usual blood-thinning treatment, and will be followed for one year. The main goal of the study is to determine whether colchicine reduces the risk of developing long-term vein problems after DVT. The study will also assess the risk of new blood clots, vein recovery, quality of life, and the safety of colchicine treatment.

Conditions

Venous Thrombosis Deep (Limbs); Post-thrombotic Syndrome; Venous Thromboembolism (VTE); Venous Insufficiency

Keywords

Deep vein thrombosis; Venous thromboembolism; Post-thrombotic syndrome; Colchicine; Anticoagulation therapy; Randomized controlled trial; Inflammation

Outcome Measures

Primary Outcomes (2)

• Post-thrombotic syndrome (PTS)

  To determine whether addition of low-dose colchicine to standard anticoagulation reduces the incidence of PTS at 12 months in patients with acute proximal lower-limb DVT. PTS is defined as: chronic clinical condition that occurs after DVT, presenting with symptoms such as leg pain, heaviness, cramps, pruritus, and paresthesia, and signs such as edema, skin hyperpigmentation, venous ectasia, lipodermatosclerosis, or venous ulcer, in the previously thrombosed limb, between 3 to 12 months after the acute event, and not explained by other causes \[31\]. A Villalta score \> 5 is considered diagnostic for PTS.

  From the start of treatment to the 12-month follow-up visit

• Recurrent venous thromboembolism.

  To evaluate the effect of low-dose colchicine added to standard anticoagulation on the incidence of recurrent venous thromboembolism (VTE), defined as objectively confirmed recurrent DVT and/or pulmonary embolism (PE), within 12 months of the index event.

  From the start of treatment to the 12-month follow-up visit

Secondary Outcomes (5)

• Longitudinal evaluation of PTS severity

  From the start of treatment to the 12-month follow-up visit

• Venous healing and function on imaging

  From the start of treatment to the 12-month follow-up visit

• Change From Baseline in Health-Related Quality of Life (HRQOL) as Measured by the VEINES-QOL/Sym Questionnaire

  From the start of treatment to the 12-month follow-up visit

• Adverse event and treatment discontinuation

  From the start of treatment to the 12-month follow-up visit

• Adherence and persistence to colchicine therapy

  From the start of treatment to the 12-month follow-up visit

Study Arms (2)

Arm 1 - Colchicine + Standard Anticoagulation

EXPERIMENTAL

Participants in this arm will receive low-dose colchicine in addition to standard anticoagulant therapy for deep vein thrombosis. Colchicine will be administered as 0.5 mg twice daily for the first month, followed by 0.5 mg once daily for the subsequent five months. Participants will be monitored for safety, efficacy, and outcomes including post-thrombotic syndrome, recurrent venous thromboembolism, vein recanalization, and quality of life over a 12-month follow-up period.

Drug: Colchicine 0.5 MG Oral Tablet

Arm 2 - Placebo + Standard Anticoagulation

PLACEBO COMPARATOR

Participants in this arm will receive a matching placebo in addition to standard anticoagulant therapy for deep vein thrombosis. Placebo will be administered following the same schedule as colchicine (0.5 mg twice daily for one month, then 0.5 mg once daily for five months). Participants will be monitored for the same outcomes and safety measures over a 12-month follow-up period.

Drug: Placebo

Interventions

Colchicine 0.5 MG Oral Tablet DRUG

Low-dose colchicine added to standard anticoagulant therapy for acute proximal deep vein thrombosis. Colchicine is administered 0.5 mg twice daily for the first month, then 0.5 mg once daily for the next five months. Participants are monitored for post-thrombotic syndrome, recurrent venous thromboembolism, vein recanalization, quality of life, and safety over 12 months.

Arm 1 - Colchicine + Standard Anticoagulation

Placebo DRUG

Matching placebo administered alongside standard anticoagulant therapy on the same schedule as colchicine. Participants are monitored for the same outcomes and safety measures.

Arm 2 - Placebo + Standard Anticoagulation

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age ≥18 years at the time of screening.
• Objectively confirmed first, symptomatic acute proximal lower-limb deep vein thrombosis (DVT), involving the popliteal vein or more proximal veins, diagnosed within the previous 48 hours.
• Planned initiation of standard anticoagulation therapy, including:
• Low-molecular-weight heparin (LMWH) bridging to vitamin K antagonists (VKA) or direct oral anticoagulants (DOACs),
• DOAC monotherapy according to local guidelines,
• Fondaparinux or other guideline-recommended regimens. Note: Standard anticoagulation regimens include dose reduction of apixaban or rivaroxaban at the sixth month, as per local practice.
• Ability and willingness to provide written informed consent and comply with all study procedures.

You may not qualify if:

• Participants meeting any of the following criteria will be excluded:
• History of prior DVT in the same limb.
• Known contraindications to anticoagulation or anticipated inability to comply with study procedures.
• Current use of colchicine or clinical indication requiring colchicine therapy.
• Known hypersensitivity or allergy to colchicine.
• Severe hepatic impairment, defined as ALT or AST \>3× upper limit of normal, or severe renal impairment (creatinine clearance \<30 mL/min).
• Active malignancy with an estimated life expectancy \<12 months.
• History of active or chronic gastrointestinal disease that may interfere with colchicine tolerance, including:
• Inflammatory bowel disease (Crohn's disease or ulcerative colitis),
• Collagenous colitis,
• Irritable bowel syndrome,
• Chronic or recurrent diarrhea.
• Recent (\<30 days) or ongoing use of systemic immunosuppressive therapy, including but not limited to corticosteroids, cyclosporine, or tumor necrosis factor-alpha inhibitors.
• Pregnancy or breastfeeding, or unwillingness to use effective contraception during the study period.
• Concomitant use of strong CYP3A4 inhibitors or P-glycoprotein inhibitors contraindicated with colchicine.

Sponsors & Collaborators

• Azienda Sanitaria Locale ASL 6, Livorno: lead

MeSH Terms

Conditions

Venous Thrombosis; Postthrombotic Syndrome; Venous Thromboembolism; Venous Insufficiency; Inflammation

Interventions

Colchicine; Tablets

Condition Hierarchy (Ancestors)

Thrombosis; Embolism and Thrombosis; Vascular Diseases; Cardiovascular Diseases; Thromboembolism; Pathologic Processes; Pathological Conditions, Signs and Symptoms

Intervention Hierarchy (Ancestors)

Alkaloids; Heterocyclic Compounds; Dosage Forms; Pharmaceutical Preparations

Central Study Contacts

Nicola Mumoli NM Dr

CONTACT

+39 0331699111; nimumoli@tiscali.it

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER GOV
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Chief of Cardiovascular Medicine Department, Busto Arsizio (VA), Italy

Model Details: This is a randomized, double-blind, placebo-controlled, parallel-group study. Participants with acute proximal deep vein thrombosis (DVT) will be randomly assigned in a 1:1 ratio to receive either low-dose colchicine or a matching placebo, in addition to standard anticoagulant therapy. The parallel design ensures that each group receives its assigned treatment concurrently, allowing for a clear comparison of outcomes between colchicine and placebo. Participants, investigators, and study staff will be blinded to treatment assignment to reduce bias. The main goal is to evaluate whether colchicine reduces the risk of post-thrombotic syndrome, recurrent venous thromboembolism, and other clinical outcomes, while monitoring safety and tolerability over a 12-month follow-up period.

Study Record Dates

• First Submitted: February 14, 2026
• First Posted: February 25, 2026
• Study Start: June 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): June 1, 2027
• Last Updated: February 25, 2026

Record last verified: 2026-02

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR, ANALYTIC CODE
• Access Criteria: Data will be available upon reasonable request to the corresponding author, following approval of a research proposal and in compliance with institutional and ethical regulations. Data will be shared in a de-identified format to protect participant confidentiality.