Rege Nephro Co., Ltd. (Headquarters: Kyoto, Japan; Chief Executive Officer: Akifumi Morinaka) announced that Tamibarotene, a novel drug candidate under development, received orphan drug designation by the Ministry of Health, Labour and Welfare (MHLW) of Japan for the treatment of Autosomal Dominant Polycystic Kidney Disease (ADPKD) on June 27th, 2025.
We are simultaneously conducting a Phase 2a clinical trial – a placebo-controlled randomized trial – of Tamibarotene (development code: RN-014), targeting Japanese ADPKD patients, and preparing for global development.
With our mission of “leveraging groundbreaking iPS cell technology to create a future where people around the world no longer suffer from disease”, we will continue to spare no effort to deliver Tamibarotene as quickly as possible, aiming to provide a new therapeutic option for ADPKD patients, a rare disease with high unmet medical needs.

About Autosomal Dominant Polycystic Kidney Disease (ADPKD)
Autosomal Dominant Polycystic Kidney Disease (ADPKD) is an inherited cystic kidney disease characterized by the gradual development and enlargement of numerous cysts in both kidneys, leading to progressive decline in renal function. It’s designated as an intractable disease by the Japanese government. As the disease progresses, the number of renal cysts increases, causing the kidneys to enlarge and leading to symptoms such as abdominal distension, hematuria, and cyst infection. Cysts can also develop in the liver. Systemic complications like hypertension and cerebral aneurysms (subarachnoid hemorrhage) occur at a higher frequency than in the general population. Tolvaptan is currently the only approved drug for ADPKD, which works to suppress cyst enlargement. However, there is currently no curative treatment. When kidney function deteriorates to kidney failure, dialysis or kidney transplantation becomes necessary.

About Tamibarotene
Tamibarotene is a synthetic retinoid that acts on retinoic acid receptors. It is expected to suppress the enlargement of renal volume and improve kidney function by inhibiting multiple signaling pathways involved in cyst growth and renal fibrosis. This mechanism of action is distinct from Tolvaptan and other ADPKD drug candidates currently under development. Given its anticipated different safety profile, if Tamibarotene’s efficacy and safety are confirmed and it is approved, it is expected to significantly broaden the range of treatment options for ADPKD.

About Orphan Drugs
Orphan drugs are designated by the Minister of Health, Labour and Welfare of Japan based on Article 77-2 of the Pharmaceuticals and Medical Devices Act. To qualify, a drug must meet criteria such as targeting a disease with fewer than 50,000 patients in Japan or a nationally designated intractable disease, treating a serious condition, and addressing a high medical need where existing approved drugs or treatments are insufficient and multiple clinical options are required.
For more details, please refer to the following website:
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000068484.html (Text in Japanese)

About RegeNephro Co., Ltd. (Headquarters: Kyoto; Chief Executive Officer: Akifumi Morinaka)
Rege Nephro is a clinical-stage drug discovery startup that leverages technology based on the research seeds of Professor Kenji Osafune at Kyoto University’s Center for iPS Cell Research and Application (CiRA). Our corporate philosophy is to revolutionize therapeutic options for intractable diseases, primarily affecting the kidneys, but also the liver and pancreas, and to create a future where people worldwide no longer suffer from illness.

Media Inquiries:
Mariko Iwamura　
Rege Nephro CO., Ltd.
TEL: +81-75-744-6858
E-mail: info@regenephro.co.jp