Japanese regulation and approval process for medical artificial intelligence (AI) as software as a medical device (SaMD): Current status and emerging challenges.

The rapid expansion of artificial intelligence (AI) in healthcare has led to increasing adoption of AI-based software as a medical device (SaMD). This paper reviews the current regulatory and approval framework for AI-based SaMD in Japan and discusses emerging challenges associated with generative and adaptive AI technologies. Under the Pharmaceuticals and Medical Devices Act (PMD Act), software intended for diagnosis, treatment, or prevention is regulated as a medical device when classified as Class II or higher, and its clinical utility, performance, and safety are evaluated. While the number of approved AI-based SaMDs has increased, most existing products are task-specific systems supporting clinical decision-making within defined scopes. Recent advances in generative AI introduce novel regulatory issues, including difficulties in defining intended use, evaluating reliability of natural language outputs, and managing continuously evolving performance after market entry. These characteristics challenge conventional regulatory paradigms based on fixed product specifications. In light of ongoing international regulatory developments, key issues include clarifying scope of regulated functions, strengthening lifecycle and change management approaches, enhancing transparency, and improving user literacy. Developing adaptive regulatory frameworks that balance innovation, patient safety, and regulatory clarity will be essential for responsible integration of generative AI into healthcare.