https://www.fda.gov/media/73667/download?utm_medium=email&utm_source=govdelivery
G. Biodistribution, Persistence, and Integration Analysis
Plasmid biodistribution, persistence and integration studies were initially recommended
to examine whether subjects in DNA vaccine trials were at heightened risk from the long-
term expression of the encoded antigen, either at the site of injection or an ectopic site,
and/or plasmid integration. Theoretical concerns regarding DNA integration include the
risk of tumorigenisis if insertion reduces the activity of a tumor suppressor or increases
the activity of an oncogene. In addition, DNA integration may result in chromosomal
instability through the induction of chromosomal breaks or rearrangements.
A typical biodistribution/persistence study assesses the presence of plasmid collected
from a panel of tissues at multiple time points ranging from a few days to several months
post administration. The panel of tissues typically includes the blood, heart, brain, liver,
kidney, bone marrow, ovaries/testes, lung, draining lymph nodes, spleen, muscle at the
site of administration and subcutis at the injection site. Plasmid levels are typically
evaluated using a quantitative real time polymerase chain reaction assay (Q-PCR)
validated for sensitivity, specificity and the absence of inhibitors. We recommend that
the sensitivity of this assay be sufficient to quantify <100 copies of plasmid per
microgram of host DNA. A claim of “non-persistence” requires that the amount of
plasmid at each site falls below this limit of quantification.