Hiroshima University and Sanyo Chemical launch silk-elastin clinical trial for meniscus injuries

A research group led by Sanyo Chemical Industries, Ltd. (President and CEO: Akinori Higuchi) and Professor Nobuo Adachi from the Department of Orthopedic Surgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Professor Masakazu Ishikawa from the Faculty of Medicine, Kagawa University (who was affiliated with Hiroshima University at the time of the research) announced on October 31 that they have begun a corporate clinical trial to verify the efficacy and safety of "silk-elastin" (SE) in patients with meniscus injuries. Patient recruitment will begin soon, and the trial will be conducted at Hiroshima University Hospital and seven other facilities. The goal is to obtain regulatory approval by fiscal year 2027 and to achieve insurance coverage and market launch by fiscal year 2028. The research is anticipated to contribute to preventing knee osteoarthritis and extending healthy life expectancy.

Knee osteoarthritis is caused by damage to the knee joint cartilage and meniscus that occurs with aging or sports. An estimated 30 million people in Japan have knee osteoarthritis, of whom 10 million are estimated to experience symptoms such as pain and difficulty walking. Knee osteoarthritis is the leading cause of needing support and significantly reduces healthy life expectancy, with estimated annual economic losses of approximately 5 trillion yen. The meniscus functions as a cushion in the knee and helps the knee move smoothly. Meniscus injuries are treated with either repair surgery or resection surgery in which the meniscus itself is removed. While meniscus injuries are common in elderly people, they also frequently occur in younger people due to sports-related trauma.

However, 30 to 40 percent of repair surgeries require reoperation, and resection surgery leads to the onset and progression of knee osteoarthritis due to impaired knee function. The meniscus consists of two regions: the outer and inner. The success of repair surgery depends on blood flow, and surgery is not applicable to injuries in the inner avascular zone. Therefore, treating the avascular zone has been a challenge for healing.

In contrast, the current clinical trial involves both repair surgery and placement of SE at the tear site for injuries in the avascular zone.

SE is a recombinant protein biosynthesized by introducing repeating sequences of silk fibroin (a silk-derived protein) and elastin (an elastic protein found in human skin) into Escherichia coli. It has already received regulatory approval in April of this year as a wound healing material for refractory skin ulcers and is scheduled to begin sales in the spring of next year.

The SE obtained through extraction and purification has a cotton-like texture. Previous basic research has confirmed features such as activation of cell migration and enhanced collagen production, and its high safety has been verified given it is not derived from animals.

In this clinical trial, repair surgery is performed arthroscopically, and a SE aqueous solution is injected and put in place. The SE transforms into a gel that serves as a scaffold for cell proliferation, helping the meniscus to heal.

The two parties began joint research in 2017 and have continued the research with support from AMED since 2018.

Following preclinical trials in small and large animals, an investigator-initiated clinical trial was conducted in 2022 with eight patients. Meniscus preservation through healing was successful in six of the eight cases, with good results obtained even in cases that were difficult to treat with conventional methods. Based on this confirmation of safety and efficacy, a corporate clinical trial is now being conducted.

The corporate clinical trial targets consenting patients aged 8 years or older, who have been diagnosed with meniscus injuries involving the avascular zone through MRI (occurring either alone or in combination with anterior cruciate ligament injury), who have mechanical symptoms caused by meniscus injury, whose pain has not improved with conservative treatment such as exercise therapy or pain medication, and who have an IKDC score of 55 or below.

The observation period in the clinical trial is 365 days from repair surgery and SE injection and placement, with arthroscopic examinations conducted at weeks 1, 2, 12, and 24 to examine the state of healing.

The primary endpoint is an IKDC score of 69 or above, with secondary endpoints including changes over time and whether reoperation was required.

The clinical trial is scheduled to end in March 2027. The aim is to obtain FDA approval in parallel with regulatory approval in Japan. There are high expectations worldwide for meniscus preservation.

The clinical trial will be conducted at Hiroshima University Hospital, Kagawa University Hospital, Kanto Rosai Hospital, Kofu National Hospital, JCHO Osaka Hospital, Hirosaki University Hospital, Sapporo Maruyama Orthopedics Hospital, and Hyogo Prefectural Central Rehabilitation Hospital. Adachi will act as the coordinating investigator.

Journal Information
Publication: Scientific Reports
Title: First-in-human exploratory trial assessing safety, feasibility, and efficacy of artificial protein (silk-elastin) in promoting healing in patients with meniscus injuries
DOI: 10.1038/s41598-025-88616-x