Introduction to Regulatory Considerations
According to the document issued by the Pharmaceuticals and Medical Devices Agency (PMDA) on March 9, 2026, Japan has outlined key considerations for the clinical development of radiopharmaceuticals used in PSMA-PET imaging for prostate cancer. PSMA-PET has demonstrated superior diagnostic performance compared to conventional imaging modalities such as CT, MRI, and bone scintigraphy, and is already recommended in major international clinical guidelines. However, such radiopharmaceuticals are not yet approved in Japan, and early introduction into clinical practice is anticipated.
Clinical Performance Requirements (Sensitivity and Specificity)
As with other diagnostic radiopharmaceuticals, the clinical performance of PSMA-PET agents should generally be demonstrated through adequate sensitivity and specificity for their intended use. This remains the fundamental requirement for regulatory evaluation in Japan.
Use of Overseas Data and Reduced Development Burden
The document highlights that some PSMA-PET radiopharmaceuticals have already been approved and widely used in the US and Europe based on exploratory evaluations. For such products, accumulated overseas clinical experience and guideline recommendations may support the assumption of established diagnostic performance.
Furthermore, if no clinically meaningful differences in pharmacokinetics are identified between Japanese and non-Japanese populations, efficacy and safety in Japanese patients may be evaluated primarily based on foreign clinical data. This reflects a flexible approach aligned with global development strategies.
Applicability of Conditional Approval Pathway
PSMA-PET radiopharmaceuticals may qualify for Japan’s conditional approval system if the following conditions are met:
Sponsors are encouraged to utilize PMDA consultations to discuss eligibility for this pathway, which can accelerate patient access.
Limited Japanese Clinical Experience and Bridging Measures
Given that domestic clinical experience may be limited at the time of development, the guidance recommends:
These measures aim to ensure appropriate clinical use in Japan despite limited local data.
Future Use as Companion Diagnostics
PSMA-PET radiopharmaceuticals are expected to be used not only for diagnosis but also for selecting patients eligible for specific therapies. However, using multiple agents depending on purpose may be operationally challenging in clinical settings.
Therefore, PMDA suggests that developers consider parallel development as a companion diagnostic alongside its use for staging and recurrence detection.
Conclusion
This PMDA “Early Consideration” document signals a pragmatic and globally aligned regulatory approach for PSMA-PET radiopharmaceuticals in Japan. By allowing reliance on foreign clinical data, enabling conditional approval, and proposing practical bridging measures, Japan aims to accelerate access to advanced diagnostic technologies while maintaining scientific rigor.
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