Structure and pharmacokinetics

Two amino acid swaps that made a hormone into a drug

Natural alpha-MSH is potent but fragile, gone from the blood in minutes. Afamelanotide keeps the potency and removes the fragility with two precise substitutions, which this unit examines residue by residue.

It then follows the molecule through the body: how the implant releases it, what the plasma levels look like, and why the tan lasts far longer than the drug itself.