The purpose of this study is to evaluate the biodistribution, safety and tolerability of a single dose of [18F]GTP1 as a tau targeted radiopharmaceutical in healthy Japanese participants.

Key inclusion criteria:

• Healthy with no clinically relevant finding on physical examination at screening and prior to radiopharmaceutical administration
• Female participants must be willing to avoid pregnancy and refrain from donating eggs during the treatment period and for 30 days after the final dose
• Male participants with partners of childbearing potential must commit to the use of two methods of contraception for the study duration and 90 days after the last dose
• Male participants must not donate sperm for the duration of the study and 90 days after the last dose
• Participants must have both Japanese parents and all Japanese grandparents

Key exclusion criteria:

• Participants with any significant medical disorder or disease expected to interfere with the study
• Current or prior history (within a six-month period) of exposure to nicotine products
• History of drug or alcohol abuse within 12 months prior to screening
• Prior participation in other research protocols or clinical care in the last year, such that radiation exposure combined with that from the present study exceeds an effective dose of 50 millisievert (mSv), the allowable annual limit for research participants as established by the US Federal Guidelines
• Use of any prescription drugs, herbal supplements, within 4 weeks prior to initial dosing
• Use of over the counter (OTC) medication, dietary supplements, or vitamins, within 2 weeks prior to initial dosing
• Known hypersensitivity to any component of the formulation of [18F]GTP1 or related compounds
• Major surgery, or donation or loss of 400 mL or more of blood within 4 weeks prior to initial dosing
• History of immunodeficiency diseases, including positive human immunodeficiency virus (HIV) test
• Positive for Hepatitis B surface antigen (HBsAg) or Hepatitis C antibody
• Women who are pregnant, lactating or breastfeeding
• Unsuitable veins for repeated venipuncture

Qualified researchers may request access to individual patient level data through the clinical study data request platform (www.vivli.org). Further details on Roche's criteria for eligible studies are available here (https://vivli.org/ourmember/roche/). For further details on Roche's Global Policy on the Sharing of Clinical Information and how to request access to related clinical study documents, see here (https://www.roche.com/research\_and\_development/who\_we\_are\_how\_we\_work/clinical\_trials/our\_commitment\_to\_data\_sharing.htm).

Baseline up to 5 days