Kaken Shoyaku Co., Ltd.
Japanese specialty pharmaceutical company founded in 1942, maker of the Cepharanthin brand of ethical drugs derived from the Stephania cepharantha plant, and a member of the Sawai Group.
Last updated September 26, 2026
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Overview
Kaken Shoyaku Co., Ltd. (化研生薬株式会社) is a Japanese specialty pharmaceutical company headquartered in Nakano-ku, Tokyo. It was established on 31 July 1942 in Kudan, Tokyo, with capital of 190,000 yen, spun off from the Chemotherapy Research Association (化学療法研究会), a foundation created in 1938 to advance research on the alkaloid cepharanthin. The company's name derives from that parent research body. Its business is the sale and manufacture of ethical (prescription) pharmaceuticals, and its flagship product line is Cepharanthin (セファランチン®), an alkaloid-based medicine extracted and refined from the tuberous root of the plant Stephania cepharantha (タマサキツヅラフジ), a member of the Menispermaceae family. The active ingredient was discovered in 1928 by Dr. Heisaburo Kondo of Tokyo Imperial University, who named the alkaloid cepharanthin after the plant. The plant itself had been described and named by botanist Bunzo Hayata, who studied Taiwanese flora from 1905. Cepharanthin was approved as a pharmaceutical raw material in July 1942, the same year the company was founded. Kaken Shoyaku has built its identity around this single, distinctive product family, which is unusual among Japanese pharmaceutical firms in that the entire chain — cultivation of the plant, manufacture of the active pharmaceutical ingredient, and formulation — is completed domestically in Japan. Historically, the company depended on wild and cultivated Stephania cepharantha in Taiwan, but the end of World War II cost it its Taiwanese operations, facilities and assets. From a small number of tuber seeds brought back to Japan, the company re-established cultivation domestically, starting in the Izu region of Shizuoka Prefecture and eventually settling in Yashiro (now Ishioka City), Ibaraki Prefecture, where trial cultivation began in 1959. Kaken Shoyaku opened its Yashiro Plant in 1981, and today the plant handles everything from cultivation management of the raw material to manufacture of the active ingredient. The company works with a cooperative of contract farming households. In 2006 Kaken Shoyaku came under the Sawai Group (Sawai Pharmaceutical Co., Ltd.). In 2013 it became a wholly owned subsidiary of Sawai Pharmaceutical, and in April 2021 it became a wholly owned subsidiary of the newly established Sawai Group Holdings Co., Ltd. Within the group, Kaken Shoyaku occupies a niche distinct from Sawai's core generic-drug business, supplying its specialized ethical medicines. As of the company's own disclosures, it has capital of 51.63 million yen and about 50 employees, with offices in Tokyo and Osaka, a pharmaceutical information office, and the Yashiro Plant in Ibaraki. Its representative director and president is Tomoki Ikemoto.
History
Kaken Shoyaku's history is inseparable from the drug cepharanthin and the plant Stephania cepharantha. The plant, a member of the Menispermaceae (ツヅラフジ科) family, grows wild in the highlands of Taiwan and was used in folk medicine. Botanist Bunzo Hayata, who surveyed Taiwanese plants for 19 years from 1905, described and named it Stephania cepharantha HAYATA, giving it the Japanese name タマサキツヅラフジ. In 1928 Dr. Heisaburo Kondo, a professor of pharmaceutical sciences at Tokyo Imperial University who was researching alkaloids of Menispermaceae plants, discovered a new alkaloid in the plant's root and named it cepharanthin. In 1938 the Chemotherapy Research Association (化学療法研究会) was founded to develop cepharanthin research, establishing a research institute and attached hospital for basic research and clinical trials, and handling raw-material cultivation, manufacturing, research and clinical testing. In July 1942 cepharanthin was approved as a pharmaceutical raw material, and in the same year, as demand grew, the association's cultivation, manufacturing and sales operations were separated into a corporate entity: Kaken Shoyaku Co., Ltd., established on 31 July 1942 in Kudan, Tokyo, with capital of 190,000 yen. The company name derives from the parent Chemotherapy Research Association, and Dr. Kondo and others involved in cepharanthin's discovery served as advisors. The association and the company then went separate ways, the former as a private academic research body and the latter as a pharmaceutical company. Initially the company depended on wild Stephania cepharantha in Taiwan, where the colonial government banned export of seeds and tubers, so material could only be obtained locally. Cultivation was developed from highland plots near the natural habitat to more manageable lowland areas. This progress was abruptly reversed at the end of World War II, when Japan lost all its Taiwanese operations, facilities and assets. The company faced an existential crisis and had to establish domestic cultivation. Using the few tuber seeds that employees managed to bring back, trial cultivation began, starting in the Izu region of Shizuoka Prefecture, whose climate was relatively close to Taiwan's. Within ten years of the war's end, more than 20 trial sites had been established and domestic cultivation became feasible. One site, in Yashiro Town, Niihari District, Ibaraki Prefecture (now Ishioka City), began trials in 1959; Hiroyukinobu Ozu, introduced by an official of the National Institute of Hygienic Sciences, pursued cultivation enthusiastically, and stable yields led to its establishment there. Today cultivation is carried out under contract with a cooperative of farming households. Corporate milestones followed: an Osaka sales office in 1943; capital increased to 2 million yen and the Mitaka Plant opened in 1944; a new combined head-office building for the Mitaka Plant, head office and Tokyo sales office in 1971; the Yashiro Plant opened in 1981; capital increases to 8.41 million yen (1985), 20.90 million yen (1986) and 51.63 million yen (1988). In 2006 the company came under the Sawai Group (Sawai Pharmaceutical Co., Ltd.). In 2013 it became a wholly owned subsidiary of Sawai Pharmaceutical, and in April 2021 it became a wholly owned subsidiary of the newly established Sawai Group Holdings Co., Ltd. Within the group it continues to supply its specialized ethical medicines, distinct from Sawai's core generic-drug business. The manufacturing and marketing approval for Cepharanthin products was transferred to Medisa Shinyaku Co., Ltd. effective 1 April 2019, with related packaging changes announced.
- 2021
Becomes a wholly owned subsidiary of the newly established Sawai Group Holdings Co., Ltd. in April.
- 2019
Manufacturing and marketing approval for Cepharanthin products transferred to Medisa Shinyaku Co., Ltd. effective 1 April 2019.
- 2013
Becomes a wholly owned subsidiary of Sawai Pharmaceutical Co., Ltd.
- 2006
Kaken Shoyaku comes under the Sawai Group (Sawai Pharmaceutical Co., Ltd.).
- 1988
Capital increased to 51.63 million yen.
- 1986
Capital increased to 20.90 million yen.
- 1985
Capital increased to 8.41 million yen.
- 1981
Yashiro Plant opened, handling cultivation management through active-ingredient manufacture.
- 1971
New combined building for the Mitaka Plant, head office and Tokyo sales office completed.
- 1959
Trial cultivation of Stephania cepharantha begins in Yashiro Town, Ibaraki Prefecture (now Ishioka City).
Products and positioning
A niche specialty pharmaceutical manufacturer within the Sawai Group, focused on a single distinctive plant-derived alkaloid medicine with a fully domestic Japanese supply chain from cultivation to formulation.
Cepharanthin® Powder 1% (セファランチン®末1％)
Ethical pharmaceutical powder formulation based on the cepharanthin alkaloid.
Cepharanthin® Tablets 1mg (セファランチン®錠1mg)
Ethical pharmaceutical tablet formulation based on the cepharanthin alkaloid.
Cepharanthin® Powder 1% Injection 10mg (セファランチン®末1％注10mg)
Ethical pharmaceutical injectable formulation based on the cepharanthin alkaloid.
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