Efficacy of intra‑articular allogeneic peripheral blood mononuclear cells induced to an early apoptotic state versus placebo in adults with primary knee osteoarthritis

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What is this study about?

Knee Osteoarthritis is a joint condition in which the cartilage that cushions the ends of the thigh bone and shin bone wears away, leading to pain, stiffness, and difficulty moving the knee. The study is testing Allocetra-OTS, a preparation made from donor blood cells that have been programmed to begin dying early, given directly into the knee using an intra-articular injection. Some participants will receive a placebo instead of the active product to allow comparison.

The purpose of the study is to determine whether the injection can reduce knee pain and improve function compared with the placebo. Participants will receive a single injection and then be asked to complete simple questionnaires about how their knee feels, how much it hurts, and how well they can perform daily activities. These questionnaires include the Western Ontario and McMaster Universities Arthritis Index (WOMAC), which scores pain, stiffness and functional ability on a scale from 0 to 100. Over the following months, researchers will also keep an eye on any adverse events or side effects and may take routine lab tests to check safety.

1 baseline assessment

after enrollment, you will undergo a baseline assessment that records your medical history, current knee condition, and initial scores on the western ontario and mcmaster universities arthritis index (womac).

the assessment establishes a reference point for later comparisons during the trial.

2 random assignment

you will be randomly assigned, in a double‑blind manner, to receive either allocetra‑ots or a matching placebo. the randomization process ensures that neither you nor the investigators know which treatment you receive.

3 intra‑articular injection

a single intra‑articular injection will be performed in the study knee joint.

if assigned to the active group, the injection contains allocetra‑ots at a dose of 200 million cells in a solution for injection; if assigned to the control group, the injection contains the matching placebo solution.

the injection is administered by a qualified professional directly into the joint space.

4 post‑injection observation

following the injection, you will be observed for a short period to monitor any immediate reactions or adverse events.

clinical staff will check vital signs and ask about any discomfort.

5 3‑month follow‑up visit

approximately three months after the injection, you will return for a follow‑up visit.

during this visit, you will complete the womac questionnaire again, reporting pain, function, and overall joint status.

the study team will also assess any adverse events and may perform safety laboratory tests.

6 6‑month follow‑up visit

approximately six months after the injection, a second follow‑up visit will be scheduled.

you will repeat the womac assessment and provide information on any adverse events that have occurred since the previous visit.

additional safety laboratory values may be collected to evaluate longer‑term safety.

7 ongoing safety monitoring

throughout the six‑month period, you are asked to report any new or worsening symptoms, known as adverse events, to the study staff.

these reports help determine the safety profile of the treatment.

Who Can Join the Study?

Be at least 64 years old when screened for the study.
Have a confirmed diagnosis of primary femorotibial knee osteoarthritis (the main type of knee arthritis that affects the thigh‑bone and shin‑bone) using the American College of Rheumatology (ACR) clinical and radiographic criteria and have experienced knee osteoarthritis symptoms for at least 3 months before randomisation, with the study knee being the most painful.
Show a specific level of arthritis on an x‑ray of the study knee: a Kellgren‑Lawrence grade 2 or 3 (moderate changes seen on a weight‑bearing x‑ray taken with the knee in a fixed position). The x‑ray may have been done up to 6 months before screening.
Have tried and been unable to benefit from at least two different treatments for knee osteoarthritis because of side‑effects or lack of relief. These treatments can include simple pain relievers such as paracetamol, non‑steroidal anti‑inflammatory drugs (NSAIDs), steroid injections, stopping activities that cause pain, exercise programs, weight‑loss plans, physical therapy, or removal of excess fluid from the knee (joint aspiration).
Meet all of the following pain‑related requirements for the study knee:
- Report a typical knee pain level of 4 out of 10 or higher when not taking medication, as assessed by the doctor at the first visit.
- Score at least 40 out of 100 on the WOMAC Pain questionnaire (a survey that measures pain) after stopping pain medicines for at least 48 hours (long‑acting medicines may require a longer washout period).
- Score at least 40 out of 100 on the WOMAC Function questionnaire (a survey that measures how pain affects daily activities) after the same medication washout.
- Keep a daily pain diary for 7 days and have an average pain rating of 4.5 to 9.0 on a 0‑10 scale, with no single day reaching a score of 10. At least 4 days of data must be recorded.
- Have a consistency of pain scores over those 7 days where the standard deviation (a measure of how much the scores vary) is no greater than 1.5.
Be willing to keep any allowed background medicines stable and agree not to use any prohibited drugs or treatments (such as other injections into the knee) during the trial.
If you are a woman, you must be postmenopausal (no natural periods for at least 12 months) or have had permanent surgical sterilisation (such as tubal ligation, removal of both ovaries, or hysterectomy).
If you are a man and your partner could become pregnant, you must not have had a vasectomy (surgical sterilisation) and must agree to use condoms with spermicide together with your partner’s birth‑control method from the time you are randomised until 90 days after the last study dose.
Be able to understand the study information, give written informed consent, and follow all study procedures, including attending scheduled visits, completing questionnaires, and allowing necessary assessments such as imaging.

Who Cannot Join the Study?

Severe knee arthritis shown on X‑ray (end‑stage osteoarthritis, KL grade 4) or bone directly touching bone in the study knee.
Rapidly worsening arthritis or any lower‑leg joint replacement (partial or total) in either leg within 6 months before enrollment, or any previous replacement of the study knee at any time.
Other joint problems that could change how you walk or need surgery during the study, such as painful back, hip, ankle or foot arthritis; very loose ligaments; nerve problems in the lower body; or conditions that would make you use a wheelchair or stay in bed.
Very painful arthritis in the other knee (pain score ≥ 40) that could affect the results, or widespread pain conditions like fibromyalgia, complex regional pain syndrome, severe pain anxiety, long‑COVID, or needing prescription pain medication for anything other than the study knee.
Body weight that gives a Body Mass Index (BMI) higher than 40 kg/m² (very obese).
Medical problems that make the study drug unsafe, including:
- Uncontrolled diabetes (blood sugar not well‑controlled).
- Uncontrolled high blood pressure.
- Serious heart, brain‑blood‑vessel, clotting, or lung diseases (e.g., heart failure, irregular heartbeat, recent heart attack, unstable chest pain, severe asthma or lung disease).
- History of organ transplant.
- Cancer diagnosed in the past 5 years (except fully treated skin cancers).
- Regular use of blood thinners, clotting disorders, or medicines that increase bleeding risk.
- Weak immune system or taking strong immune‑suppressing drugs (e.g., steroids >5 mg prednisone daily, biologics, methotrexate) within the past 4 months.
- Regular use of strong opioid pain medicines, certain nerve‑pain drugs (e.g., pregabalin, gabapentin) or muscle relaxants.
- Any active infection anywhere in the body or a live vaccine within one month.
- Known HIV infection, or active hepatitis B or C.
- Any other uncontrolled serious disease (liver, kidney, blood, nerve, hormone, or mental health) that could threaten safety or affect study results.
Laboratory test results that are far outside normal limits, such as very low hemoglobin, very low or very high white blood cells, low platelets, high creatinine (kidney), high bilirubin (liver), very high liver enzymes (AST/ALT), or abnormal clotting time (INR > 1.2).
Women who are pregnant, breastfeeding, or could become pregnant (women of child‑bearing potential).
Severe psychiatric or social issues that could make participation unsafe or unreliable, such as major depression or anxiety (PHQ‑9 score ≥ 15), thoughts of suicide, substance abuse, being in prison, or an active workers’ compensation claim.
Known severe allergies, especially to the study drug components (e.g., dimethyl sulfoxide [DMSO]), or a history of allergic reactions that required hospitalization, multiple drug allergies, severe eczema/urticaria, or any situation the doctor thinks puts you at high risk of a serious allergic reaction.
Being in another clinical trial or having received another experimental drug within the past 60 days (or 5 half‑lives of that drug).
Having been treated with the study drug Allocetra before.
Specific problems in the study knee that could interfere with evaluation, such as:
- Meniscus tear that needs surgery.
- Loose fragments of bone or cartilage inside the joint.
- Large or changing Baker’s cyst (fluid‑filled swelling behind the knee).
- Locking or sudden blockage feeling in the knee.
- Ligament damage or osteochondritis dissecans (a bone‑cartilage condition).
- Any new knee injury within the past 6 months.
Any condition that the doctor believes could confuse the study results or place you at undue risk.
Past or current joint infection (septic arthritis) or skin infection at the injection site.
Major cartilage surgeries on the study knee within the past year (e.g., autologous chondrocyte implantation, osteochondral autograft) or minor cartilage procedures within the past 6 months (e.g., microfracture).
Any ligament repair, bone‑realignment surgery, arthroscopy, osteotomy, large meniscus removal, or knee replacement done on the study knee within the past 6–12 months (as specified for each procedure).
Knee swelling that required fluid removal (aspiration) within the past 3 months, or large swelling expected to need aspiration during the study.
Steroid injection into the study knee within the past 3 months.
Hyaluronic‑acid (viscosupplement), platelet‑rich plasma, bone‑marrow or tissue/cell injections into the study knee within the past 6 months.
Any inflammatory joint disease or crystal‑related arthritis in the knee (e.g., rheumatoid arthritis, gout, pseudogout), major joint deformities, severe misalignment (>10° varus/valgus), significant ligament instability, serious inherited bone/cartilage disorders, or any tumor in the knee.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Sanos A/S	Gandrup	Denmark

Trial status

Country	Status	Recruitment Start
Denmark	Recruiting	23.04.2026

Trial locations

Investigated drugs:

Allogeneic Peripheral Blood Mononuclear Cells Induced To An Early Apoptotic State

Allocetra-OTS is a treatment made from donor blood cells that have been prepared to enter an early stage of natural cell death. These cells are injected directly into the knee joint. The idea is that the dying cells can help calm the immune system and reduce inflammation in the joint, which may relieve pain and improve function for people with knee osteoarthritis.

Knee Osteoarthritis – Knee osteoarthritis is a condition where the protective cartilage in the knee joint gradually wears away. As the cartilage thins, the joint surfaces rub together, causing stiffness and a feeling of grinding. The loss of cartilage can lead to small bone growths called osteophytes that may further limit movement. Over time, the surrounding tissues can become inflamed, making the knee feel swollen and tender. People often notice increasing difficulty with activities such as walking, climbing stairs, or standing for long periods. The changes in the joint typically develop slowly and become more noticeable as the condition progresses.

Trial ID:

2025-524668-39-00

Protocol code:

ENX-CL-05-002

Trial Phase:

Therapeutic exploratory (Phase II)

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Efficacy of intra‑articular allogeneic peripheral blood mononuclear cells induced to an early apoptotic state versus placebo in adults with primary knee osteoarthritis

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?