The FDA granted Fast Track designation to 4Moving Biotech's 4P004 in late April 2026 — a single intra-articular injection of liraglutide delivered directly into the knee joint for osteoarthritis. This is a different way to use a GLP-1 peptide: not systemic weekly dosing for weight loss, but one local shot into the synovium and cartilage. Coverage rolled out across rheumatology and pain trade press May 8-11, putting GLP-1 joint use back in the news cycle alongside existing data on semaglutide and retatrutide.
Research-context information only. Liraglutide is the active ingredient in FDA-approved products for type 2 diabetes and chronic weight management; 4P004 (intra-articular liraglutide) is investigational and not FDA-approved. Doses, delivery routes, and outcomes reported below come from published trials and the company's clinical-trial filings. This article reports what has been documented in the clinical-trial pipeline, not what should be done. Consult a licensed physician for personal medical decisions.
What the FDA Actually Approved
Fast Track designation is not marketing approval. It is a procedural status the FDA gives to drug candidates targeting a serious condition with unmet medical need. The agency commits to more frequent meetings, rolling NDA review, and eligibility for Accelerated Approval and Priority Review if criteria are met later.
4P004's Fast Track scope is narrow: knee osteoarthritis in patients with synovitis (inflammation of the joint lining) who have not responded to at least two prior pharmacological therapies. That's the second- or third-line OA patient — someone who has already tried NSAIDs, intra-articular steroids, or hyaluronic acid and is still in pain.
The supporting data is the Phase 1 LASARE trial (ClinicalTrials.gov NCT05419856), conducted at three Belgian sites and reported by 4Moving Biotech in June 2024. LASARE enrolled patients with Kellgren-Lawrence grade 2-4 knee OA, tested single intra-articular doses of 4P004 from 0.3 mg to 3.0 mg, and confirmed safety and tolerability without serious treatment-emergent adverse events versus placebo. The trial identified a pharmacologically active dose but was not powered for efficacy.
The follow-on Phase 2a trial INFLAM MOTION (NCT07225829) is now enrolling approximately 129 patients aged 40-80 with Kellgren-Lawrence grade 2-4 disease plus synovitis. The primary endpoint is change from baseline to week 4 in WOMAC pain subscale score after a single intra-articular injection. Topline data is expected in early 2027.
Why a Local GLP-1 Shot Instead of the Weekly One
The mechanistic case is real, even if the clinical case still needs a Phase 2 readout. Liraglutide directly suppresses cartilage breakdown in preclinical osteoarthritis models. A 2022 paper in Scientific Reports (PMID 35091584) showed liraglutide dose-dependently reduced NO, PGE2, IL-6, and MMP-3/MMP-13 secretion in primary chondrocytes — the matrix-degrading enzymes that drive cartilage loss. The same paper documented analgesic, anti-inflammatory, and anti-degradative effects in animal models.
The case for putting it directly in the joint rather than under the skin is concentration. Systemic liraglutide reaches chondrocytes via the bloodstream at low local concentrations, and most of the dose is metabolized peripherally for its appetite and glycemic effects. An intra-articular injection puts the peptide where it's needed — synovium, cartilage, subchondral bone — at higher local levels with less systemic exposure. The trade-off is that you get a single-shot pharmacology problem (how long does it work?) instead of a steady-state pharmacology problem.
Systemic GLP-1 use has now generated supportive human data in knee OA without specifically targeting the joint:
- STEP-9 (NEJM 2024, PMID 39476339) — semaglutide 2.4 mg weekly in 407 obese adults with moderate knee OA produced a -41.7 point change in WOMAC pain score at 68 weeks versus -27.5 with placebo. Weight loss was -13.7% versus -3.2%. The pain benefit tracked with but was not fully explained by weight loss.
- TRIUMPH-4 (Eli Lilly, December 2025) — retatrutide 9-12 mg weekly in 445 adults with obesity plus knee OA produced 75.8% pain reduction on WOMAC and 12-14% of patients completely pain-free at 68 weeks. Weight loss reached 28.7% at 12 mg.
- Earlier liraglutide RCT (PMID 33471039) — 156 patients on liraglutide 3.0 mg after a 4-month diet-induced weight loss did not show pain superiority over placebo (group difference 0.9 points on KOOS pain, p=0.71). This is the negative result that 4P004's intra-articular delivery is trying to solve.
So the existing systemic-GLP-1 case for knee OA is mixed: strong for semaglutide and retatrutide, weak for daily liraglutide. 4P004's bet is that route of delivery, not the wrong peptide, was the limitation.
What This Means for Buyers
For someone with knee pain considering peptides today, 4P004 changes very little in the short term and clarifies something in the long term.
Short term. 4P004 is in Phase 2a. Even if INFLAM MOTION reads out positive in early 2027, a pivotal Phase 2b/3 and FDA review push commercial availability to 2029-2030 at the earliest. People with knee OA who want to act this year should look at systemic semaglutide or retatrutide based on the human RCT data, not 4P004. Compare current vendor pricing and COA testing here:
- Best semaglutide vendors — STEP-9 used 2.4 mg weekly
- Best retatrutide vendors — TRIUMPH-4 used 9-12 mg weekly
- Best liraglutide vendors — for systemic GLP-1 protocols only
- All vendor discount codes — current coupons across all peptides
Long term. The Fast Track signal raises the probability that GLP-1 receptor agonism, not weight loss alone, is the mechanism driving the OA pain reduction seen in STEP-9 and TRIUMPH-4. If INFLAM MOTION delivers a Phase 2a hit, the conclusion is that you don't need 13-28% body weight loss to get joint benefit — local GLP-1 activation is enough. That reshapes how clinicians and patients think about lean-but-painful OA patients, who currently don't have a great pharmacological option.
One thing not to do. Do not interpret 4P004 news as a green light to inject research-grade liraglutide into your knee. 4P004 uses a specialized intra-articular formulation, ultrasound or fluoroscopic guidance, and a clinical-trial sterile field. Self-injecting research peptide into a joint risks septic arthritis — a rapidly progressive infection that can destroy cartilage in days. The systemic subcutaneous protocols described in our liraglutide dosing guide are the only documented research-use route.
