On October 5, 2026, Japan’s Pharmaceuticals and Medical Devices Agency (PMDA) published an early-consideration guidance on developing companion diagnostics (CDx) in parallel with cancer drugs. Japan already expects a CDx and its matching drug to be filed at about the same time. The purpose of the guidance is to explain how drug and diagnostic developers can plan for that from the clinical trial stage.
Drug developers should decide early whether a CDx test is essential for selecting patients, setting the dose, or stopping treatment. They should base that decision on the biomarker’s link to the drug’s mechanism and on whether pivotal trials use the test to select patients. The CDX used in the pivotal drug clinical trial should normally become the CDx that is approved in Japan. If a different test will be used with the drug after launch, a concordance study must show the two give equivalent results.
The PMDA asks CDx developers to consult the agency no later than the PMDA consultation on pivotal trial design. They should bring the rationale for the CDx, test performance data, and its approval status overseas. In principle, the CDx should be covered by insurance by the time the drug is listed on the National Health Insurance (NHI) price list, so drug and diagnostic developers need to align their timelines closely. CDx reimbursement has its own reimbursement path in Japan, which is different than medical device reimbursement.
Written by: Ames Gross – President and Founder, Pacific Bridge Medical (PBM)
Mr. Gross founded PBM in 1988 and has helped hundreds of medical companies with regulatory and business development issues in Asia. He is recognized nationally and internationally as a leader in the Asian medical markets. Mr. Gross has a BA degree, Phi Beta Kappa, from the University of Pennsylvania and an MBA from Columbia University.