CynosBio Announces Last Patient Implanted in Japan Phase 3 IK-01 Trial for Knee Osteoarthritis

Study of a 3D matrix-based autologous chondrocyte therapy evaluates clinical symptoms alongside imaging, arthroscopic and histological findings

• Topline results expected in March 2028, following completion of follow-up to the primary assessment time point at 52 weeks after treatment.
• MRI, arthroscopy and histological assessment will be evaluated based on cartilage defect filling, the status of cartilage repair and cartilage tissue characteristics by biopsy, respectively.
• A global pivotal trial for traumatic focal cartilage defects is being prepared first. If results in knee osteoarthritis (OA) are positive, the Company will consider additional development opportunities with a view to the U.S. market.

TOKYO, November 5, 2026 — CynosBio Inc. (CynosBio or the Company), a regenerative medicine company developing autologous cell therapies, today announced completion of the final patient implantation on November 5, 2026, in its Japanese Phase 3 trial of IK-01, an investigational 3D matrix-based autologous chondrocyte therapy for knee osteoarthritis (OA). This study is a multicenter, randomized, controlled trial comparing IK-01 implantation with sodium hyaluronate intra-articular injection, with a target sample size of 54 patients. Ultimately, treatment was initiated in 57 patients. Follow-up is ongoing, with topline results expected in March 2028.

The study will evaluate clinical efficacy and structural repair findings in the regenerated cartilage. MRI, arthroscopy and histological assessment will be evaluated based on cartilage defect filling, the status of cartilage repair and cartilage tissue characteristics by biopsy as structural repair findings.

“Completing the final patient implantation brings us closer to a defined clinical readout and an important test of IK-01’s potential in knee osteoarthritis,” said Shinji Uga, President and Chief Executive Officer of CynosBio. “Our aim is to understand both how patients feel and function and what kind of repair tissue forms. We are building a staged international development strategy, with traumatic cartilage defects first and an additional opportunity in OA if the evidence supports it. We thank the patients, investigators and clinical and manufacturing teams who have brought this study to this milestone.”

Clinical symptoms and structural repair findings in regenerated cartilage

The Phase 3 study (jRCT2053240275) is a randomized, open-label, active-controlled, parallel-group trial in Japan. Eligibility includes adults aged 20–74 years with Kellgren–Lawrence grade 2 or 3 knee OA. The primary endpoint is the change from baseline in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score at 52 weeks after IK-01 implantation or treatment with the comparator drug. WOMAC is a patient-reported measure of pain, stiffness and physical function.

Beyond the primary clinical assessment, structural repair findings in regenerated cartilage will be evaluated as follows:

• MRI to evaluate morphological features, including cartilage defect filling.
• Arthroscopy to directly assess the status of cartilage repair, integration with surrounding normal cartilage and the appearance of the repaired cartilage.
• Histological assessment of cartilage by biopsy samples, including type II collagen expression, to evaluate hyaline cartilage formation.

Under the study protocol, MRI, arthroscopy and histological assessment will be performed for all patients in the IK-01 treatment arm. In addition to evaluating clinical outcomes, the study aims to determine how well the cartilage has regenerated.

“The goals of treating knee osteoarthritis are to relieve pain, improve physical function, and enhance quality of life. When evaluating a treatment aimed at regenerating articular cartilage, it is important to understand the structural characteristics of the regenerated cartilage alongside the clinical outcomes,” said Ryosuke Kuroda, M.D., Ph.D., Professor of Orthopaedic Surgery at Kobe University Graduate School of Medicine and medical expert for the trial. “MRI can assess cartilage defect filling, arthroscopy can examine the surface of the regenerated cartilage and its integration with surrounding tissue, and histological assessment of biopsy samples can characterize tissue features, including the presence of type II collagen. Together, these assessments allow us to evaluate whether IK-01 implantation regenerates normal hyaline cartilage. I hope that a comprehensive review of the forthcoming clinical outcomes and structural repair findings will further clarify the clinical value of this product. I sincerely hope that this product will offer a new treatment option for patients suffering from knee osteoarthritis and reach many patients as soon as possible.”

Follow-up and evaluation are continuing. Topline results are expected in March 2028.

About IK-01: designed for in vivo cartilage regeneration

IK-01 is an investigational 3D matrix-based autologous chondrocyte therapy. A patient’s own cartilage cells are embedded and cultured within a three-dimensional collagen matrix. The cell–matrix construct is designed to support cartilage tissue formation and maturation after implantation—an in vivo regeneration approach.

IK-01 can be implanted approximately two weeks after the patient’s own cartilage is collected. IK-01 combines a short culture period with a three-dimensional scaffold that supports the cells at the repair site. The clinical and biological outcomes of this design are being evaluated in the ongoing Japanese Phase 3 trial for OA.

A staged path toward international development

CynosBio is preparing a separate global pivotal trial of IK-01 for traumatic focal cartilage defects ahead of potential global OA development. If the Japanese OA Phase 3 results are positive, the Company plans to evaluate a global pivotal OA program with a view to the U.S. market, subject to regulatory discussions and development requirements.

To the Company’s knowledge, no autologous chondrocyte implantation (ACI) product is currently FDA-approved specifically for knee osteoarthritis. This area may offer a new development opportunity beyond existing indications for focal cartilage defects.

About CynosBio

CynosBio Inc. is a Japan-based regenerative medicine company focused on developing and commercializing autologous cell therapies and advancing them internationally. Its pipeline includes IK-01 for knee cartilage disorders. CynosBio is the sponsor of the Japanese IK-01 Phase 3 OA trial.

Important information

IK-01 is investigational and is not approved in Japan or the United States. This announcement reports a development milestone, not trial results or an established treatment benefit.

Forward-looking statements

This release contains forward-looking statements, including expectations for data availability, manufacturing timelines, cartilage regeneration and global development. Actual outcomes may differ materially because of clinical results, follow-up and data quality, regulatory requirements, manufacturing and logistics, financing and partnership availability. No assurance is given that trials will succeed, start as planned or result in regulatory approval. CynosBio undertakes no obligation to update these statements except as required by law.