Toray Creates Next-Generation Opioid Analgesic Candidate Compound "KSB-200" with Expected Reduced Side Effect Risks

Toray Industries, Inc. (Headquarters: Chuo-ku, Tokyo; President and CEO: Mitsuo Ohya; hereinafter "Toray") has created a candidate compound, "KSB-200," which has shown analgesic effects and improved separation between analgesic and sedative effects in exploratory non-clinical evaluations targeting postoperative pain and other conditions. KSB-200 is a compound with agonist activity at the opioid kappa (κ) receptor (hereinafter "κ receptor") and is expected to be developed as a new analgesic drug with low side effect risks and oral administration capability.

Until now, for the treatment of postoperative pain, analgesics acting via the opioid mu (μ) receptor (hereinafter "μ receptor") have been primarily used as drugs with high analgesic efficacy for severe pain. However, μ receptor agonists can cause serious side effects such as respiratory depression and dependence, creating a demand for the development of safer analgesics.

Furthermore, while existing κ receptor agonists have a low risk of respiratory depression and dependence, they required the reduction of central side effects such as sedation and dysphoria to be developed as analgesics. Toray has leveraged its research and development experience and unique knowledge of the compound TRK-820 (generic name: nalfurafine hydrochloride, brand name: Remitch®), which has agonist activity at the κ receptor and has been approved for the treatment of intractable pruritus in dialysis patients and patients with chronic liver disease, to pursue the creation of a novel κ receptor agonist expected to achieve both reduction of central side effects and efficacy (analgesia).

KSB-200 is a novel compound designed with a focus on bias in κ receptor signaling, aiming to selectively elicit the analgesic effects of κ receptor agonists while suppressing central side effects as much as possible. In a mouse postoperative pain model, KSB-200 demonstrated analgesic effects upon oral administration, and an improved separation between analgesic and sedative effects was suggested compared to TRK-820, an existing compound with agonist activity at the κ receptor.

Toray plans to present these research results at the International Narcotics Research Conference 2026 (Location: Denver, Colorado, USA; Dates: July 13-16, 2026). Moving forward, starting with the presentation at this conference, Toray will seek development partners under an early partnership strategy. Through collaboration with partners, Toray aims to commercialize KSB-200 and contribute to the advancement of medical care.