TOKYO and LONDON, February 22/PRNewswire-FirstCall/ -- Sosei Co. Ltd. (4565, Tokyo Stock Exchange MOTHERS Index) announced today that it has in-licensed an urology compound OPC-51803 (Sosei code SOU-003) from Otsuka Pharmaceutical Co., Ltd. who has already completed Phase I human studies. Sosei has been granted the rights to develop and commercialise the compound globally, except for Japan and other Asian countries where Otsuka retains the rights. Sosei also has co-promotion rights in Japan, whilst Otsuka retains a co-promotion option in the USA and Europe.

SOU-003 is an orally active small molecule with selective vasopressin V2 receptor agonist activity which increases water re-absorption in the kidneys. The safety of SOU-003 has already been confirmed in several Phase I studies with healthy volunteers and also in various types of incontinence patients by Otsuka. Sosei intends to begin a Phase II study, to select the optimal dose in nocturia and nocturnal enuresis patients, during the second half of 2005. The compound is expected to reduce the urine production rate at night which should avoid interruptions to sleep and improve the quality of life of sufferers. Nocturia is more prevalent in the elderly for whom the condition becomes increasingly more distressing and for which there is a growing medical need for treatment.

Only one treatment based on the same mechanism as SOU-003 is currently available and is mainly used to treat those who suffer from nocturnal enuresis. Known as desmopressin, an orally active peptide, it is administered either orally or via the nose. Its bioavailability as an oral tablet is very low as it is a peptide analogue. A small molecule oral treatment such as SOU-003, with higher bioavailability, is likely to provide a treatment with a more reliable effect.

SOU-003 also has the potential for other indications including diabetes insipidus. The agreement provides the right for Sosei to explore all uses which could provide further medical and commercial opportunities.

Sosei's CEO Shinichi Tamura stated "We are excited by this agreement with Otsuka Pharmaceuticals. SOU-003 adds a third urology product to our development pipeline giving us an expanded opportunity in this disease area with a growing need for new therapies. The profile of SOU-003 is very promising and we believe it will provide a valuable new treatment for patients."

Otsuka's CEO Mr. Tatsuo Higuchi commented: "The development of OPC-51803 by Sosei, a company dedicating a large part of its R&D resources to the urology area, should be promising. We expect that Sosei's advanced development capabilities will make it possible for OPC-51803 to contribute to the treatment of patients who are suffering from nocturia and nocturnal enuresis."

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