Anthim
obiltoxaximab · B. anthracis PASingle-dose clinical escalation supported by monkey AUC margin: 10 mg/kg AUC ~50,000 µg·hr/mL vs human AUC 10,000 at 114 mg
The public FDA and EMA reviews of Vyepti 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.
Find the highest dose with no adverse effects (NOAEL) in each animal species, convert it to a human equivalent dose, usually by body surface area, pick the most appropriate species, then divide by a safety factor (default 10) to get the maximum recommended starting dose.
NOAEL / key findings: No adverse effects; NOAEL 100 mg/kg/week (rat 4-week) and 150 mg/kg every 2 weeks (monkey 6-month) (FDA pharmacology/toxicology review, p. 8)