Leonard Thompson was 14 years old when doctors diagnosed him with diabetes. It was a death sentence at the time. His only treatment: a starvation diet of 450 calories daily. When admitted to Toronto General Hospital in December 1921, he weighed 65 pounds and drifted into diabetic comas.

In December 1921, his father consented to the experimental extract. The first dose on January 11, 1922 triggered a severe reaction due to impurity. On January 23, biochemist James Collip provided a purified version that changed everything.

Leonard's blood sugar dropped to near-normal in one day. Medical records noted: "The boy became brighter, more active, looked better and said he felt stronger."

Leonard Thompson lived another 13 years on insulin. Far longer than anyone with Type 1 diabetes had survived before.

Banting, Best, and their colleagues sold the insulin patent to the University of Toronto for one dollar each. Banting explained flatly:

Insulin does not belong to me. It belongs to the world.

By October 1923, manufacturers shipped commercial insulin. That same month, Banting and J.J.R. Macleod won the Nobel Prize in Physiology or Medicine. Banting shared his prize money with Best. Macleod shared his with Collip. They had built something bigger than themselves.

Scientists quickly realized insulin had siblings. The body produced hundreds of molecular signals. Chains of amino acids that told cells how to behave.

The first map: Sanger's 12-year obsession (1950s). Frederick Sanger wanted to see insulin's shape. Not imagine it. See it. He spent 12 years identifying the exact position of every amino acid in the insulin molecule. Fifty-one amino acids arranged across two chains. In 1958, he won the Nobel Prize in Chemistry for work that most chemists thought was impossible.

Sanger showed what was possible. He showed the body's signals could be mapped. Understood. Copied.

Building on the map: Bigger peptides discovered (1953 onwards). Now that the insulin map existed, other scientists chased other peptides. Vincent du Vigneaud synthesized oxytocin. Nine amino acids governing labor, bonding, and connection. Nobel Prize in 1955. Roger Guillemin and Andrew Schally proved the brain speaks to the body in peptides: TRH, GnRH, somatostatin.

These discoveries showed that peptides were not insulin's quirk. They were the body's operating system.

The 1970s brought a stunning detail. Researchers extracted peptides from 500,000 sheep brains to isolate a single hormone signal. This was grinding, invisible work. This was the foundation everything rested on.

In the 1960s, scientists noticed a puzzle. Oral glucose generated roughly twice the insulin response as identical glucose delivered directly into the bloodstream.

The exact same sugar should trigger the exact same insulin release. Yet the gut somehow amplified the signal. This made no sense.

Researchers labeled these mystery amplification factors "incretins," literally "secreted by the intestine." They spent 20 years chasing this anomaly. 20 years of experiments. 20 years before isolating the mechanism.

The body was keeping secrets. Science was learning to listen.

In 1982, Joel Habener's lab at Massachusetts General Hospital discovered an anomaly: the glucagon gene coded for three peptides instead of one.

The team named the two new peptides Glucagon-Like Peptide-1 (GLP-1) and Glucagon-Like Peptide-2 (GLP-2).

But here is where the story narrows to one person's work.

Svetlana Mojsov, a peptide chemist who joined MGH in 1983, faced a specific challenge: Which of the two new peptides mattered? The one that actually worked?

She synthesized GLP-1(7-37), created antibodies to locate it, and searched human tissue. She found the peptide in the intestine. She proved that exactly 30 amino acids, arranged in one specific sequence, controlled blood sugar regulation.

In September 1986, Mojsov and colleagues published. GLP-1 originated in the intestine and flowed into the blood in response to food.

In early 1987, Mojsov, Habener, and Gordon Weir demonstrated something remarkable: tiny concentrations of GLP-1(7-37) stimulated insulin release six-fold in isolated rat pancreas tissue. The full-length form had zero effect. A few atoms mattered. A specific shape mattered. Precision mattered.

Mojsov had found the key. But the key was broken.

GLP-1 had a half-life of exactly 2 minutes. An enzyme circulating in the blood called DPP-4 chopped the peptide in half almost instantly. DPP-4 destroys roughly 80 to 90% of GLP-1 before it reaches the pancreas. Other enzymes finish the job in transit.

As a raw drug, GLP-1 failed completely. It degraded before it could work.

For nearly a decade, this seemed like a dead end. Scientists could see the mechanism. They could prove it worked. They could not keep it alive long enough to be a drug.

Then nature provided a solution. In an unexpected place.

John Eng, an endocrinologist at the Bronx VA Medical Center, had an unconventional idea. He screened venomous lizards for bioactive compounds.

He ordered dried Gila monster venom from a Utah serpentarium and ran his tests.

In 1992, he found exendin-4. The peptide mirrored human GLP-1 perfectly. It bound to the same targets in the human pancreas. But the lizard peptide carried something human GLP-1 lacked: built-in chemical armor.

The tail end of exendin-4 had a physical shape that completely blocked DPP-4 from snipping the molecule. Where human GLP-1 degraded in 2 minutes, the lizard version survived circulating for hours.

Eng patented his discovery after the VA initially declined to claim it. He pitched the concept at an American Diabetes Association meeting in 1996. Andrew Young from Amylin Pharmaceuticals recognized the potential immediately.

The Gila monster eats 5 to 10 times per year while maintaining stable blood glucose regulation. Eng found the key inside its saliva. For millions of humans who could not regulate blood sugar on their own, the answer had been hidden in the desert for millennia.

Once scientists understood the problem (DPP-4 degradation) and had a working solution (exendin-4 armor), the innovation accelerated.

2005: Exenatide (Byetta). The synthetic lizard peptide became the first FDA-approved GLP-1 drug. But it had a catch: twice-daily injections. The armor helped, but it was not perfect.

2010: A new armor strategy. Liraglutide (Victoza) arrived. Instead of copying the lizard's shape, researchers attached a fatty acid to human GLP-1. The fatty acid allowed the drug to hitch a ride on albumin proteins circulating through the blood. This shielded the peptide from DPP-4, extending the half-life to 13 hours. Once daily became possible.

2014: Bigger shield, less frequent dosing. Dulaglutide hit the market. Drug makers bound GLP-1 to a larger molecule to slow destruction further and enable once-weekly dosing. Same signal, different armor.

2017: Optimization complete. Semaglutide (Ozempic/Wegovy) combined the fatty acid strategy with direct structural modifications that blocked DPP-4. The half-life stretched to 7 days. Once weekly. Optimal.

2019: The oral breakthrough. Scientists developed Rybelsus, an oral peptide engineered to endure stomach acid and absorb directly through the intestine. The same signal. A new delivery method.

Each breakthrough represented the same insight: copy what the body already does, armor the molecule against destruction, and adjust the delivery. No magic. No new biology. Just chemistry, iteration, and engineering.

The initial patents for GLP-1 listed Joel Habener as the sole inventor. Mojsov fought successfully for co-inventor status. But only after MGH had already issued and licensed the patents to Novo Nordisk.

For decades, major scientific prizes ignored her entirely. The Lasker Award finally recognized her in 2024. Thirty-eight years after her foundational work.

This is peptide history. Decades of grinding work. Invisible contributors. Breakthroughs that look instantaneous only to outsiders. Every major peptide required accidental observation, years of refinement, brutal engineering, and finally a drug.

Insulin. Oxytocin. Somatostatin. GLP-1. All clear this exact bar.

Leonard Thompson received the first crude extract. He weighed 65 pounds. Over a century later, millions of people use the highly engineered descendants of that original vial.

Scientists did not invent entirely new magic drugs. They learned how to armor molecules that already existed. They learned to see what the body was doing. They learned to copy it better.