By Peter A. McCullough, MD, MPH
Biohackers and podcasters have been discussing peptides in recent years given the many hopes of what molecular biology can bring to the human body. Because they are not carbon-based small molecules the stigma of a “drug” doesn’t land with the public—yet they are still used as drugs. What many of them don’t know is the 100-year history of peptides in pharmaceutical development and the roughly 80–100 FDA-approved therapeutic peptides are currently on the U.S. market used as drugs. If you broaden to “peptide-based drugs” globally (including peptide conjugates, radiopharmaceuticals, and peptidomimetics), the number climbs closer to 150+.
🔬 Introduction: The Small Molecule That Changed Medicine
Peptides—short chains of amino acids, the biological middle ground between free amino acids and full proteins—have quietly transformed modern medicine. Unlike the small-molecule drugs that dominated 20th-century pharmacology, peptides offer something extraordinary: biological specificity. They can be designed to bind almost any target with surgical precision, act as hormones, signaling molecules, and therapeutic agents, and do it all with a metabolic footprint that the body already understands.
But delivering them has always been the problem. Peptides are fragile, rapidly degraded, and—crucially—recognizable as foreign. The history of parenteral (injected) peptide therapy is therefore a story of two parallel battles: the fight to synthesize and deliver these molecules effectively, and the fight against the body’s own immune system trying to destroy them.
