Otsuka obtains regulatory approval in Japan for pharmacological treatment of ADPKD

Otsuka Pharmaceutical Co., Ltd. (Otsuka) today announced it has become the first company in the world to obtain regulatory approval for a pharmacological treatment of autosomal dominant polycystic kidney disease (ADPKD). Samsca^® (generic name: tolvaptan) has been approved in Japan in 7.5-mg and 15-mg tablet forms for extended use for the additional indication of ADPKD. Also, the new dosage form of 30-mg Samsca tablets has received approval for the indication of ADPKD.

Samsca was developed over the past 26 years by the efforts of many researchers in Otsuka's Tokushima, Japan research facility. It is currently used in 14 countries and territories around the world as an aquaretic drug, which facilitates excretion of only free water without electrolyte loss due to its antagonist action on vasopressin V₂ receptors. Upon a discovery that proliferation and enlargement of renal cysts are hindered by suppression of cAMP formation at vasopressin V₂ receptors, Otsuka launched a new effort from 2004 to develop a drug for the rare disease ADPKD, in conjunction with world specialists including Dr. Vicente E. Torres of the Mayo Clinic in the U.S. In global clinical trials (the TEMPO 3:4 trial) conducted in 15 countries on more than 1,400 patients with ADPKD, Samsca was shown to significantly suppress the rate of increase in total kidney volume by approximately 50% more than a placebo. The results of these trials were published in November, 2012 in the New England Journal of Medicine.

Taro Iwamoto, CEO of Otsuka Pharmaceutical Co., Ltd., stated, "Development of a pharmacotherapy for ADPKD, a rare disease leading to end stage renal failure, has been difficult. Lack of a fundamental therapy for this disease has over many years been a great difficulty for people with ADPKD. We are very pleased that, through this approval, we may be able to contribute something to these patients and their families. Through Samsca's completely new mode of action, development of a new category of indications was possible. While rigorously pursuing safety and effectiveness, in the future we look forward to having something to present to patients who suffer from this disease, not only in Japan but all over the world."

Eiji Higashihara, professor of nephrology at Kyorin University School of Medicine, noted, "Since there has been no drug treatment for ADPKD up to now, this recent approval is great news for these patients and their families, and also for those of us who treat them. On the other hand, physicians and other health care workers need to thoroughly know the indications of Samsca for treatment of ADPKD. We further need to keep in close touch with the patients and their families in paying attention to safe use of Samsca. It is important that, through teamwork, we carefully nurture this medicine that has been developed here in Japan."

In Europe, as of December, 2013, an application for regulatory approval of tolvaptan in ADPKD had been received and is under review. In the United States, based on a review issued by the FDA, we have continued discussions with them regarding supplementary data and the path forward for resubmission.