Efficacy and Safety of LTG-321 Compared with Placebo in Patients with Osteoarthritis of the Knee

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What is this study about?

The condition being examined is Osteoarthritis of the knee, a common joint problem that causes the cartilage in the knee to wear down, leading to pain, stiffness, and difficulty moving. The medication tested is a coated tablet called LTG-321, taken by mouth at a dose of 150 mg. A matching inactive tablet, known as placebo, is also used for comparison.

The purpose of the study is to see whether LTG-321 reduces knee pain better than the placebo. This phase‑2 trial is randomized, meaning participants are assigned to treatment order by chance, and double‑blind, so neither the participants nor the study staff know which tablet is being taken at any time. It uses a crossover design, so each participant receives both the active tablet and the placebo in two separate periods lasting about two weeks each, with a short break in between. Throughout the study, participants keep a daily pain diary and complete the WOMAC questionnaire, which asks about pain, stiffness, and ability to perform daily activities. Safety checks include regular measurements of vital signs, an ECG (a simple heart rhythm test), and basic laboratory tests.

1 randomization and receipt of study medication

after enrollment, the study assigns the participant to receive either ltg-321 tablet (150 mg oral) or matched placebo for the first treatment period. the assigned medication is provided in identical coated tablets.

the participant receives written instructions on how to take the tablet once daily.

2 baseline assessments

on day 1, before the first dose, the participant completes a pain questionnaire (womac pain subscale) and records pain levels in a daily diary.

vital signs, an electrocardiogram (ecg), and laboratory tests are performed to establish baseline health status.

3 treatment period 1 – daily dosing

starting on day 1, the participant takes one tablet (either ltg-321 tablet or matched placebo) by mouth each day for 14 consecutive days.

the participant continues to fill out the daily pain diary each evening, noting average and worst pain scores.

4 mid‑study visit

on day 14, the participant returns for a study visit. the womac pain, physical function, and stiffness subscales are repeated, and the participant’s assessment of the study drug (pga) is recorded.

blood is drawn to measure plasma concentrations of ltg-321 (if the active drug was taken) and to check safety laboratory values.

5 washout period

from day 15 through day 27, no study medication is taken. the participant continues the pain diary to monitor any changes without treatment.

6 treatment period 2 – crossover dosing

on day 28, the participant begins the second treatment period, receiving the medication opposite to that taken in period 1 (if the active drug was taken first, the participant now receives matched placebo, and vice versa).

one tablet is taken orally each day for another 14 days, continuing to record daily pain scores.

7 final visit

on day 41, the participant completes the final study visit. the same womac subscales and pga are assessed, and a second set of blood samples is taken to evaluate plasma levels of ltg-321 (if applicable).

the participant returns any remaining study tablets and completes the rescue medication usage log.

8 study completion

after the day 41 visit, the participant’s involvement in the trial ends. all study data are compiled for analysis of efficacy and safety.

Who Can Join the Study?

Be between 40 and 80 years old when you sign the study consent form.
If you are a woman who could become pregnant, you must be willing and able to follow the study’s birth‑control rules.
If you are a man who has a partner who could become pregnant, you must be willing and able to follow the study’s birth‑control rules.
Sign the informed consent form, agreeing to follow all study requirements and restrictions.
Be able to attend scheduled visits, follow the treatment plan, do required lab tests, follow birth‑control rules if needed, keep a study diary, and talk with study staff in the local language.
Stop taking any medicines for knee osteoarthritis (such as opioids, NSAIDs, COX‑2 inhibitors, topical treatments, and duloxetine) until the final study visit.
Take only the medicines allowed by the study from the start of the diary period through the final visit.
Have a confirmed diagnosis of knee osteoarthritis based on radiographs (X‑ray images) of both knees taken in a specific view, meeting the American College of Rheumatology (ACR) clinical and X‑ray criteria, and showing a Kellgren‑Lawrence (KL) grade of 2 or 3 as read centrally.
Have experienced knee pain on most days for at least three months before screening.
Report pain in the target knee of at least 4 out of 10 on a 0‑10 scale at both screening visits.
Have target‑knee pain at least 2 points higher than the other knee on the same scale at screening and on the first day before taking the study drug.
Have a WOMAC pain subscale score of at least 4 out of 10 for the target knee at both screening and the day‑1 assessment (the WOMAC questionnaire measures pain, stiffness, and function in osteoarthritis).
During the diary run‑in period, record pain scores on at least 6 of 7 days, and the average daily pain score must be between 5 and 9 on a 0‑10 Numeric Pain Rating Scale (NPRS).
The variation (standard deviation) of daily pain scores during the diary run‑in must be 1.5 or less.
Have a body mass index (BMI) of 38 or lower at screening.

Who Cannot Join the Study?

Having osteoarthritis in other major joints (like the other knee) that could make it hard to measure pain in the study knee.
Having had a non‑diagnostic arthroscopy (a small camera procedure) on the study knee within the last 180 days, or a diagnostic arthroscopy on the study knee within the last 90 days.
Having received an injection into the study knee joint (called an intraarticular injection) in the past 12 weeks, or an injection into any other joint in the past 6 weeks.
Using opioids (strong pain medicines, including tramadol) two or more times per week during any week in the 4 weeks before screening.
Showing signs of serious heart disease in the past 6 months, such as blocked arteries (ischemic heart disease), poor blood flow in the limbs (peripheral arterial disease), or problems with brain blood vessels (like stroke or mini‑stroke).
Having an active cancer or a cancer history within the past 5 years, except for completely removed skin cancers (basal or squamous cell).
Being pregnant, breastfeeding, or planning to become pregnant while taking part in the study.
Being allergic to sodium channel blockers or the rescue medication allowed in the study.
Needing a walker or wheelchair to move around (walking sticks are allowed).
Having ever had an opioid use disorder (OUD), meaning a long‑term problem with opioid use.
Having a substance use disorder (SUD) other than OUD in the past 2 years.
Having another joint disease besides osteoarthritis that could affect the study knee, such as rheumatoid arthritis, Paget’s disease, ankylosing spondylitis, psoriasis arthritis, or other systemic illnesses.
Having thought about or planned suicide in the past 2 years, or currently having suicidal thoughts.
Having a serious mental health condition that could interfere with reporting pain accurately.
Having an untreated sleep problem with ongoing insomnia that could affect pain reporting.
Having moderate or severe liver problems (called hepatic impairment) based on the doctor’s judgment or specific blood tests (ALT and AST).
Having previously taken Journavx (suzetrigine) or any other drug that blocks the NaV1.8 sodium channel.
Currently taking a strong or moderate CYP3A4 inhibitor or inducer (a type of medication that changes how drugs are processed) that cannot be stopped, or being unable to follow study medication rules.
Taking medicines known to cause a dangerous heart rhythm problem called Torsade de Pointes or that may lengthen the QT interval, unless the dose is stable and not being changed.
Using other experimental drugs or devices that cannot be stopped, or being unable to follow the study’s medication restrictions.
Having taken part in a previous study of LTG‑321.
Having taken part in any other experimental study within the last 30 days (or 90 days for biologic drugs).
Having osteoarthritis or another serious joint problem that is rapidly getting worse.
Having a heart ECG measurement (QTcF) longer than 450 ms for men or 470 ms for women, or longer than 430 ms if taking medicines that can lengthen the QT interval.
Having abnormal lab test results or ECG findings that the doctor thinks make participation unsafe.
Having a kidney function estimate (eGFR) below 45 mL/min/1.73 m² at screening.
Having liver enzyme levels (ALT or AST) more than 1.5 times the normal upper limit.
Having any other abnormal lab results that suggest a serious medical disease, according to the doctor.
Having a positive urine drug test for illegal substances (except for prescribed medicines that are allowed).
Being a close relative of the study’s investigators, research staff, pharmacists, or coordinators at the site.
Having any illness or condition that the doctor believes could confuse the study results or add extra risk.
Having any lifestyle, medication, or other restriction that conflicts with the study rules.
Having a hip dislocation or congenital hip dysplasia with joint degeneration.
Having gout with recent painful attacks (less than 6 months) or uncontrolled uric acid levels. (Pseudogout is allowed if there has been no flare in the past 6 months and NSAIDs are not needed.)
Having any other chronic pain condition besides osteoarthritis that required medication in the past year, such as nerve pain, complex regional pain syndrome, widespread pain (like fibromyalgia), chronic low back pain, or migraine.
Having had a major knee, hip, or shoulder injury (like a fracture inside the joint) or major surgery (other than injections or arthroscopy) in the past year.
Planning to have major surgery or another major invasive procedure while in the study.
Having had heart artery surgery or a stent placed for coronary artery disease in the past 6 months.

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	01.07.2026

Trial locations

LTG-321 is an experimental oral tablet being tested to see if it can reduce knee pain caused by osteoarthritis. In this study, participants take the tablet in a coated form, and researchers compare how well it works against a placebo. The goal is to find out whether LTG-321 can safely relieve pain and improve joint function for people with knee osteoarthritis.

Osteoarthritis of the knee – A condition where the cartilage that cushions the ends of the knee joint gradually wears away. As the cartilage thins, the bones may rub together, causing stiffness and aching that often worsens with activity. Over time the joint can develop small bone growths and the space between joint surfaces becomes narrower. The symptoms typically start as occasional discomfort and may progress to more frequent pain and reduced movement in the knee.

Trial ID:

2026-525966-22-00

Protocol code:

LTG-321-018

Trial Phase:

Therapeutic exploratory (Phase II)

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Efficacy and Safety of LTG-321 Compared with Placebo in Patients with Osteoarthritis of the Knee

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?