カリスト

Callisto Inc. (カリスト株式会社) is a Tokyo-based company that builds and supplies medical imaging datasets for medical AI development and clinical research. Working with Japanese hospitals and clinics, it assembles radiology images, pathology images, clinical information and molecular data at scales ranging from tens to millions of cases, and handles the full chain of processing: de-identification/anonymization, case selection, standardization, quality control and annotation by specialist physicians. Datasets are delivered after passing institutional procedures and are described as already in use for training and evaluating AI medical devices, regulatory submissions, clinical research, drug evidence generation and marketing activities.

The company operates two named lines: "Callisto DataHub," a medical image data platform of datasets ready for medical-AI and drug-discovery-AI R&D, and "Callisto CustomAI," contract development and technical consulting that applies AI to datasets on the platform or to data held by client companies and research institutions. In drug discovery it targets applications such as applying AI to pathology images, CT and MRI for toxicity and efficacy assessment of compounds and histopathological evaluation in clinical trials; in medical AI it targets noise reduction, organ segmentation and disease classification/detection for diagnostic and surgical support. Stated vision and mission are a society where everyone lives healthily and a goal of becoming a hub for medical datasets worldwide.

Callisto is a University of Tokyo-originated startup founded on 2022-06-27 and headquartered at Shinjuku Sumitomo Building 18F, Nishi-Shinjuku, Shinjuku-ku, Tokyo (earlier registered in Toshima-ku). It reported 23 people including officers, interns and contractors as of August 2025, and capital of JPY 210 million including capital reserves. Governance comprises CEO Han Changhee (Kallis) as representative director and Yumi Katogi as outside director; earlier filings listed directors Takahito Honda and Yuta Mitsuhashi. Advisory roles include a technical advisor from the National Institute of Informatics' Research Center for Medical Big Data (appointed 2024) and a medical advisor from Ofuna Chuo Hospital's radiation therapy center (appointed 2022).

Founding story

The company was founded on 2022-06-27 by Han Changhee (known as Kallis), who entered the University of Tokyo at age 16, holds a doctorate in information science and technology, and has worked on medical AI for over a decade, with first-author papers cited more than 2,000 times. His research focused on addressing medical image data scarcity through AI-based data augmentation, unsupervised anomaly detection and cross-institution generalization. Concluding that medical AI progress required a distribution infrastructure for usable, high-quality data rather than algorithms alone, and after serving as assistant to the CEO of LPIXEL, he established Callisto to build that infrastructure. He was formerly a visiting researcher at Cambridge, the Technical University of Munich, the University of Milano-Bicocca, the Research Center for Medical Big Data and the National Center for Global Health and Medicine hospital, and concurrently holds appointments as invited associate professor at Osaka University, specially appointed associate professor at Nagasaki University and director of the Japanese Society of Digital Pathology.

Business model

Callisto sells de-identified, standardized and expert-annotated medical image datasets to AI companies, medical device manufacturers and pharmaceutical companies through its DataHub platform, and additionally undertakes contract development and technical consulting for drug-discovery AI and medical AI (Callisto CustomAI) using platform or client data. A portion of revenue is returned to the medical institutions that supply data, and to annotators, with the stated aim of a self-sustaining data ecosystem.

Revenue comes from dataset sales/licensing to industry customers and from fee-based custom AI development and consulting engagements; part of dataset revenue is shared with partner medical institutions and annotators.

Traction

More than 20 customers in the US, Europe, South Korea and Japan; millions of medical images accessible through partnerships with medical institutions including Kameda Medical Center, Kurashiki Central Hospital and Kasumi Clinic. Datasets are reported in use for AI medical device training and evaluation, regulatory submissions, clinical research and evidence generation. At the time of the 2023 seed round the company cited 16 team members and five university hospitals engaged in data provision and joint medical AI research (including planned). Later milestones include the DataHub launch in 2024, joint research on medical image generative AI with Hiroshima University Hospital, headcount of 23 as of August 2025, and a 2026 capital and business alliance with Towns.

Latest developments

In July 2026 Callisto announced a capital and business alliance with Towns Co., Ltd. to build medical data infrastructure and AI utilization platforms. In March 2026 it began free distribution of annotated Japan-sourced lung-cancer-suspected X-ray and prostate cancer MRI datasets for AI and clinical research, and it exhibited at ITEM (held with JRC) in April 2026, CARS in July 2026, and the Japanese Society of Digital Pathology and AI (JSDP) meeting in August 2026.