Study on the Safety and Effects of SYN321 Injections for Patients with Knee Osteoarthritis

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What is this study about?

This clinical trial is focused on studying knee osteoarthritis, a condition that causes pain and stiffness in the knee joint. The study will test a new treatment called SYN321, which is a solution for injection designed to provide pain relief, reduce inflammation, and potentially improve joint movement. The treatment will be administered as a single injection directly into the knee joint.

The purpose of the study is to evaluate the safety and tolerability of SYN321 in patients with knee osteoarthritis. Participants will receive one of three different dose levels of SYN321 or a placebo. The study will monitor how the body responds to the treatment and any side effects that may occur. Participants will be asked to report their pain levels and any changes in their knee function throughout the study.

The study will take place over several weeks, during which participants will have regular check-ups to assess their health and the effects of the treatment. The goal is to gather information on how well SYN321 works in relieving symptoms of knee osteoarthritis and to ensure it is safe for use. Participants will be closely monitored by healthcare professionals throughout the study period.

1 baseline assessment and randomization

after joining the study you attend a baseline visit where medical information is confirmed, the condition of the knee is evaluated, and routine tests such as vital signs, electrocardiogram (ecg), and blood work are performed.

based on the study design you are randomly assigned to receive either a single dose of syn321 or a placebo consisting of a sodium chloride solution.

2 single intra‑articular injection

the assigned product is injected directly into the study knee (intra‑articular injection).

the injection is a one‑time administration; no repeated dosing is required during the trial.

if you receive syn321 the exact dose level (low, medium, or high) is determined by the randomization schedule; if you receive the placebo the injection contains only sodium chloride.

3 post‑injection observation

after the injection you remain in the clinic for a short observation period during which vital signs are monitored and any immediate reactions are noted.

the clinical staff checks the injection site for any signs of discomfort or swelling before you are discharged.

4 daily self‑reporting of pain and function

starting the day after the injection you record your knee pain each day using a numeric rating scale (nrs) from 0 (no pain) to 10 (worst pain).

you also complete the Knee Injury and Osteoarthritis Outcome Score (koos) questionnaire to track function and quality of life.

these entries are made daily until day 56 of the study.

5 scheduled safety and efficacy visits

during the 56‑day follow‑up period you attend several clinic visits where vital signs, electrocardiogram (ecg), and laboratory tests (blood and urine) are repeated to evaluate safety.

the visits also allow collection of any adverse event information and assessment of the injected knee.

6 final study visit

on day 56 a final assessment is performed, including the last pain and function questionnaires, a final set of safety tests, and a review of any rescue medication you may have used during the trial.

Who Can Join the Study?

Willing and able to give written informed consent for participation in the study and willing and able to participate in all procedures and follow-up evaluations necessary to complete the study.
Patients without contraindications for treatment with diclofenac (a type of pain medication).
Male or female patient clinically diagnosed with knee osteoarthritis (KOA), no later than 3 months prior to the first visit. The KOA diagnosis should be confirmed in the patient’s medical record.
Dominant pain in one knee due to KOA with weight-bearing pain between 4 and 8 inclusive on the NRS scale (0-10) at the time of inclusion (checked at screening and confirmed at the second visit, pain during the last 7 days). The NRS scale is a way to measure pain where 0 means no pain and 10 means the worst pain possible.
Age between 40 to 79 years, inclusive, at the time of the first visit.
BMI (Body Mass Index) between 18.5 and less than 35.0 kg/m².
Patients without abnormal clinically significant medical history, physical findings, vital signs, hypotension (low blood pressure), cardiovascular disease, ECG (a heart test), and laboratory values at the time of the screening visit, as judged by the Investigator.
Patient is willing to discontinue all pain medication (such as COX-2 inhibitors, NSAIDs, and opioid analgesics) at least 10 days before study drug administration and for the study duration. Paracetamol (a pain reliever) will be allowed as rescue medication up to a maximum of 4000 mg/day (except for 24 hours prior to visiting the study site).
Patient agrees not to take additional knee symptom-modifying drugs (e.g., glucosamine, collagen, HA) at least 10 days before study drug administration and for the study duration.
WOCBP (Women of Child-Bearing Potential) must practice abstinence from heterosexual intercourse (only allowed when this is the preferred and usual lifestyle of the patient) or agree to use a highly effective method of contraception with a failure rate of less than 1% to prevent pregnancy from at least 2 weeks prior to the administration of the study drug to 4 weeks after the last administration of the study drug. In addition, any male partner of a female patient must, unless he has undergone vasectomy, agree to use a condom from the first administration of the study drug until 4 weeks after the last administration of the study drug. The following are considered highly effective methods of contraception: combined hormonal contraception (oral, intravaginal, transdermal), progestogen-only hormonal contraception (oral, injectable, implantable), intrauterine device (IUD), or intrauterine hormone-releasing system (IUS). WOCBP must refrain from donating eggs from the first administration of the study drug until 3 months after the last administration of the study drug. WOCBP are pre-menopausal females who have undergone any of the following surgical procedures: hysterectomy, bilateral salpingectomy, or bilateral oophorectomy, or who are post-menopausal defined as 12 months of no menstrual periods (in questionable cases a blood sample with detection of follicle stimulating hormone [FSH] greater than 25 IU/L is confirmatory). Male patients must be willing to use a condom or be vasectomized or practice sexual abstinence from heterosexual intercourse (only allowed when this is the preferred and usual lifestyle of the patient) to prevent pregnancy and drug exposure of a partner and refrain from donating sperm from the first administration of the study drug until 3 months after the last administration of the study drug. Any female partner of a non-vasectomized male patient who is of child-bearing potential must use contraceptive methods with a failure rate of less than 1% to prevent pregnancy from at least 2 weeks prior to the first administration of the study drug to 4 weeks after the last administration of the study drug.

Who Cannot Join the Study?

Patients who have had a knee replacement surgery.
Patients with an active infection in the knee.
Patients who have received another investigational drug within the last 30 days.
Patients with a known allergy to the study medication or its ingredients.
Patients with severe heart, liver, or kidney disease.
Patients who are pregnant or breastfeeding.
Patients with a history of cancer in the last 5 years, except for skin cancer that is not melanoma.
Patients with a history of drug or alcohol abuse in the last year.
Patients who are unable to comply with the study procedures.

Where you can join this trial?

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Verified Sites

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Other Sites

Site Name	City	Country	Status
CTC Clinical Trial Consultants AB	Uppsala	Sweden

Trial status

Country	Status	Recruitment Start
Sweden	Not recruiting	18.08.2025

Trial locations

Investigated drugs:

SYN321 is a medication being tested in this clinical trial for its potential to help people with knee osteoarthritis, a condition that causes pain and stiffness in the knee joint. The trial is looking at how safe and tolerable this medication is when injected directly into the knee joint. Researchers are also interested in understanding how the body processes the medication and whether it can help improve symptoms of knee osteoarthritis. The study involves giving patients a single injection of SYN321 and observing its effects.

Knee Osteoarthritis – Knee osteoarthritis is a degenerative joint disease characterized by the breakdown of cartilage in the knee joint. As the cartilage wears away, bones begin to rub against each other, causing pain and stiffness. Over time, the joint may become swollen and lose its normal shape, leading to decreased mobility. The condition often progresses slowly, with symptoms worsening over years. It can lead to the formation of bone spurs and a reduction in the joint space. The disease primarily affects older adults, but can also occur in younger individuals due to injury or repetitive stress on the knee.

Trial ID:

2024-517920-21-00

Protocol code:

SYN321-01

Trial Phase:

Human Pharmacology (Phase I) – Other

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Study on the Safety and Effects of SYN321 Injections for Patients with Knee Osteoarthritis

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?