Flublok
influenza vaccine, recombinant hemagglutinin · Influenza HAAntigen content of quadrivalent product matched licensed trivalent vaccine plus a second B strain; no separate dose-finding
The public FDA and EMA reviews of Gardasil 9 don't say how the first human dose was chosen. That rationale is in the IND, which is confidential, so it is missing for most approved products.
HNSTD/STD10 is the method used for anticancer drugs in patients: the start dose is one-sixth of the highest non-severely toxic dose (HNSTD) in non-rodents, or one-tenth of the dose severely toxic to 10% of rodents (STD10), scaled by body surface area. The aim is a dose that is pharmacologically active yet reasonably safe.
NOAEL / key findings: No NOAEL stated; only immune-response and injection-site effects in rats (EMA assessment report, p. 24)