Vivos Inc (RDGL)

[SC8]

I seem to recall FDA has raised or is raising standards on verifying radioactive device dosimetry to target area. So wouldn't be surprised if prior animal containment verification work was done to an earlier standard as you're suggesting. Likely the complication here requiring a detailed test plan for FDA review before starting test is animal testing protocol acceptable to FDA will vary between devices and isotopes employed. An injectable radioactive gel that hardens at typical mammal body temperatures is a rather unique device. Also in this case, with Y90 decay to stable Zr90, most of the decay mechanism is single electron emission, which makes for a very short 5-6mm kill zone around the Radiogel, but there is a very minor decay path that includes positron emission. So the Radiogel will show up nicely on a PET scan even before F18 labeled glucose is used to "light up" the tumors on a PET scan. Then as the treated tumor dies, it will no longer "light up" via F18 labeled glucose, and containment of the Radiogel vs. initial position can be monitored for a couple weeks (5 half-lives) if needed. I'm pretty sure one of the things FDA will be on lookout for is does animal body begin removing necrotic cancer tissue and commence Radiogel absorption process within ~5 half-lives, and if so, how far does the remaining y90 migrate, how is it eliminated, etc.