Structure and pharmacokinetics

Two amino acid swaps that made a hormone into a drug

Natural alpha-MSH is potent but fragile, rapidly degraded and short-acting. 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 trials could dose every 60 days despite an apparent half-life of about 15 hours.