Semaglutide traces back to a 1983 discovery in a genetics lab, where researchers found a gut hormone that would take over three decades of chemical engineering to turn into a usable drug. The story involves sequencing a gene, identifying a short-lived hormone, and then painstakingly redesigning its molecular structure so it could survive in the human body long enough to be useful. It’s a case study in how a basic science finding becomes a blockbuster medication.
The 1983 Discovery That Started Everything
In 1983, Joel Habener and his colleagues at Massachusetts General Hospital sequenced the gene responsible for producing glucagon, a hormone that raises blood sugar. Inside that gene, they found something unexpected: the blueprint for a second, previously unknown hormone. Groups working with researchers Graeme Bell and Linda Lopez confirmed and named it GLP-1, short for glucagon-like peptide-1.
GLP-1 turned out to do something remarkable. Working with biochemist Svetlana Mojsov, Habener showed that a trimmed version of GLP-1 was a powerful trigger for insulin release in rat pancreas tissue. Bernard Kreymann quickly confirmed the same effect in humans. The implication was clear: here was a natural hormone that could help control blood sugar in people with type 2 diabetes.
There was one major problem. Natural GLP-1 breaks down in the bloodstream within about two minutes. An enzyme called DPP-IV chews it apart almost immediately, and the kidneys filter out whatever remains. Injecting pure GLP-1 into patients was essentially useless because it vanished before it could do much. The challenge for the next two decades was figuring out how to make it last.
Building Liraglutide: The First Long-Acting Version
Scientists at Novo Nordisk in Måløv, Denmark, led by researcher Lotte Bjerre Knudsen, took on the engineering challenge. Their strategy was elegant: attach a fatty acid chain to the GLP-1 molecule so it would stick to albumin, the most abundant protein in blood. Albumin acts like a bodyguard, shielding the hormone from both the breakdown enzyme and kidney filtration.
The team started by systematically replacing each amino acid in the GLP-1 chain, one at a time, with alanine (a simple amino acid) to map which positions were essential for the hormone to work. This “alanine scan” revealed that the front end of the molecule and a couple of positions near the back were critical for binding to its receptor. Those spots couldn’t be touched. The scan also identified one substitution, at position 8, that made the molecule resistant to DPP-IV without sacrificing its ability to activate the GLP-1 receptor.
Next came the fatty acid attachment. The team tested various fatty acid chains at different positions along the molecule. Attaching the chain near the front end killed the drug’s potency, so they focused on the back end, where a naturally occurring lysine at position 26 provided a convenient anchor point. They settled on palmitate, a 16-carbon fatty acid, connected through a small chemical spacer. The other lysine in the molecule, at position 34, was swapped out for arginine to simplify manufacturing.
The result was liraglutide, approved in 2010 as a once-daily injection for type 2 diabetes. It was a significant advance, but “once daily” still meant a needle every morning. The Novo Nordisk team wanted something patients would only need once a week.
Engineering Semaglutide for Weekly Dosing
Semaglutide built directly on the liraglutide blueprint but pushed the chemistry further. The core idea remained the same: use a fatty acid chain to hitch a ride on albumin in the bloodstream. But the team needed the molecule to bind albumin more tightly and resist breakdown even longer.
They kept the position 8 modification that protected against DPP-IV and the position 34 arginine swap from liraglutide. The key change was upgrading the fatty acid attachment. Instead of a 16-carbon palmitate chain, semaglutide uses an 18-carbon fatty diacid connected through a longer, more elaborate chemical spacer. This stronger albumin binding dramatically extended the drug’s half-life, meaning it stays active in the body long enough to require only one injection per week.
The injectable version won FDA approval in December 2017 under the brand name Ozempic, initially for type 2 diabetes at doses up to 1 mg weekly.
Making a Pill From an Injectable Hormone
Protein-based drugs like semaglutide normally can’t survive the stomach. Acid and digestive enzymes destroy them before they reach the bloodstream, which is why most biologics require injection. Getting semaglutide into a pill was a separate engineering challenge altogether.
The solution came from pairing semaglutide with an absorption enhancer called SNAC (salcaprozate sodium). This compound works through three mechanisms simultaneously. First, it acts as a local buffer, neutralizing the acid immediately surrounding the tablet and protecting semaglutide from stomach enzymes. Second, it prevents semaglutide molecules from clumping together, which would block absorption. Third, it temporarily loosens the cell membranes lining the stomach wall, allowing semaglutide to pass through individual cells and into the bloodstream without disrupting the tight seals between cells.
The result was Rybelsus, approved in 2019 as the first oral GLP-1 drug for type 2 diabetes. Patients take it on an empty stomach with a small sip of water and wait at least 30 minutes before eating, giving the SNAC time to do its work before food disrupts the process.
The Pivot to Weight Loss
Weight loss had been an observed side effect of GLP-1 drugs from early on. GLP-1 receptors exist not just in the pancreas but also in brain regions that regulate appetite and fullness. Patients taking semaglutide for diabetes consistently lost weight, which prompted Novo Nordisk to test whether a higher dose could work as a dedicated obesity treatment.
The STEP clinical trial program tested 2.4 mg weekly injections (more than double the standard diabetes dose) in thousands of people with overweight or obesity. The results were striking. Across the major trials, participants without diabetes lost an average of 14.9% to 17.4% of their body weight over 68 weeks. Between 69% and 79% of participants lost at least 10% of their weight, compared to 12% to 27% on placebo. In a longer trial running to 104 weeks, the average loss held at 15.2%. For people who also had type 2 diabetes, weight loss was somewhat lower at 9.6%, reflecting the metabolic complexity of that condition.
These numbers were unprecedented for a pharmaceutical weight loss treatment. The FDA approved the 2.4 mg dose as Wegovy in June 2021 for chronic weight management in adults with obesity or overweight with at least one weight-related health condition.
From Gene Sequence to Global Phenomenon
The timeline from discovery to impact spans almost 40 years. GLP-1 was identified in 1983. Liraglutide proved the fatty acid strategy could work in 2010. Semaglutide refined that chemistry for weekly dosing by 2017, broke the oral barrier in 2019, and became a weight loss treatment in 2021. Each step required solving a distinct scientific problem: finding the hormone, keeping it alive in the body, getting it through the stomach, and recognizing its potential beyond diabetes.
The 2024 Lasker Award for clinical research honored the scientists behind GLP-1 therapeutics, recognizing the chain of work stretching from Habener and Mojsov’s early hormone research through to the drug development at Novo Nordisk. Semaglutide wasn’t a single eureka moment. It was a long sequence of incremental chemistry decisions, each one building on the last, that turned a two-minute hormone into a once-weekly medicine.