GLP-1 manufacturing challenges: peptide synthesis, formulation, and supply chain

GLP-1 manufacturing challenges have become the binding constraint on one of the most successful drug classes in history. Demand for semaglutide and tirzepatide outran the industry’s ability to make them, triggering years of shortages and the largest manufacturing buildout pharma has ever attempted. The difficulty runs through three linked problems: synthesizing complex peptides at scale, formulating and filling them, and building a supply chain that can keep up.

Why manufacturing became the bottleneck

For most of pharmaceutical history, the hard part was finding a drug that worked. With GLP-1 agonists, the science arrived first, and the factories could not keep up. Demand for semaglutide and tirzepatide rose faster than any blockbuster precedent; the drugs spent years on official shortage lists, and for a time, compounding pharmacies filled the gap. The constraint was not the molecule but the capacity to make it.

The response has been historic in scale. Manufacturers have committed billions of dollars to expanding production, including multibillion-dollar plant buildouts and one drugmaker’s purchase of a contract manufacturer for 16.5 billion dollars simply to secure fill-finish capacity. That level of capital spending, unusual even by pharma standards, is the clearest signal of how binding the manufacturing constraint became.

Manufacturing now sits alongside biology and the pipeline as a defining force in the wider story of GLP-1 and metabolic disease. The drugs that win may be the ones that can be made at scale.

How are GLP-1 peptides actually made?

Most GLP-1 drugs are peptides produced by solid-phase peptide synthesis, in which the chain is built one amino acid at a time on a solid resin. Semaglutide, at 31 amino acids, and tirzepatide, at 39, sit near the upper limit of what this method handles comfortably, each requiring 30 to 40 or more coupling cycles, followed by cleavage, purification, and the chemical modifications that give these molecules their long duration of action.

To push past the limits of pure solid-phase work, manufacturers increasingly use hybrid approaches that combine solid-phase and solution-phase steps, along with continuous manufacturing and recombinant production of the peptide backbone. The molecular design that makes these peptides effective, including the fatty-acid acylation that extends their half-life, is the subject of how GLP-1 receptor biology became a drug-discovery platform. Manufacturing has to reproduce that design exactly, at a scale of hundreds of kilograms or more.

The hidden cost of peptide synthesis

Peptide synthesis is expensive and wasteful in ways that surprise people used to small-molecule drugs. By one analysis, solid-phase synthesis can generate on the order of 13,000 kilograms of waste for every kilogram of peptide, raw materials account for the majority of production cost, and purification can take longer than the synthesis itself. A single commercial-scale plant can cost more than 500 million dollars to build.

Those economics explain much of the industry’s behavior. They are why manufacturers are investing in greener, aqueous synthesis to cut solvent use, why continuous manufacturing is replacing batch production, and why the capital barrier to entry is so high that the field has been dominated by a small number of players. The table below sets out how the main production routes compare.

Table 1. How GLP-1 drugs are produced, by modality

A peptide is straightforward to make once; making it a billion times over is a problem of engineering, economics, and logistics.

What makes formulation and delivery so hard?

Synthesizing the peptide is only half the job; getting it into a stable, deliverable product introduces its own bottlenecks. For the injectables that still dominate the class, the constraint is sterile fill-finish, the filling of the drug into pens and syringes under aseptic conditions. Building a new sterile line can take years, and even ordering filling equipment carries long lead times, which is why fill-finish capacity, not chemistry, is often the true ceiling on supply.

Oral delivery is harder still for a peptide. Because peptides are digested, the oral form of semaglutide relies on an absorption enhancer and still reaches the bloodstream at only about 0.8 percent bioavailability, meaning far more active ingredient must be made for each effective dose. Formulation, in other words, can multiply the manufacturing burden rather than ease it.

The small-molecule disruption

The arrival of orforglipron changes the manufacturing calculus more than any capacity expansion. Because it is a small molecule rather than a peptide, it is made by conventional chemical synthesis, which is cheaper, simpler, and far more scalable than solid-phase peptide production. It needs no peptide reactors and, as a pill, sidesteps the sterile fill-finish bottleneck entirely. One manufacturer has committed billions to a dedicated oral-drug plant and stockpiled roughly 1.5 billion dollars of the product ahead of launch.

This does not end peptide manufacturing, which will carry the majority of GLP-1 volume for years, but it reframes the competition. A molecule that is easier and cheaper to make can reach more patients at lower cost, even if it delivers somewhat less weight loss than the leading injectables. Manufacturability is becoming a competitive weapon, not just an operational concern.

The molecule that is easiest to make may beat the molecule that works best.

What does the GLP-1 supply chain look like now?

The acute shortages have eased. US regulators declared the semaglutide injection shortage resolved in early 2025, and compounding of copies was wound down soon after. But the supply chain remains tight and structurally fragile, with intermittent backorders and demand still running far above historical levels. Resolution reflected an enormous, ongoing investment rather than a return to slack capacity.

Behind the headline drugs sits a complex web of pressure points. Manufacturers are building captive capacity and booking contract manufacturers years in advance, while raw-material sourcing, skilled labor, and capital intensity all constrain how fast the system can grow. The table below maps the main pressures.

Table 2. GLP-1 supply-chain pressure points

Quality and analytics: the other half of the problem

Making a peptide at scale is inseparable from proving that what comes out is correct, pure, and consistent batch after batch. Every synthesis route generates closely related impurities, and every formulation and scale-up step has to be controlled and verified, which makes analytical science the constant companion of manufacturing. That work, the chromatography, mass spectrometry, and impurity profiling that confirm identity and purity, is a discipline in its own right, covered on the analytical side in the analytical science of measuring and characterizing these peptides.

The strategic point for a manufacturing program is that capacity and quality are not separable goals. Adding a plant, switching a synthesis route, or moving production to a contract manufacturer all create analytical and regulatory work, because the new output must be shown to match the old. The fastest expansions are the ones that plan the analytical and quality strategy from the start rather than bolting it on later.

What should drug discovery and strategy watch?

Several forces will shape GLP-1 manufacturing over the next few years. The shift toward oral small molecules is the most consequential because it could lower cost and expand access in a way that no amount of peptide capacity can match. Greener and continuous synthesis will gradually reshape the economics and environmental footprint of the peptides that remain. And the approaching patent cliff, with semaglutide exclusivity ending around the end of the decade, will bring generic entrants and a wave of technology transfer to new manufacturers and regions.

Underneath all of it sits a simple strategic truth. With class sales projected to run into the hundreds of billions, manufacturing capacity is not a back-office concern but a determinant of who captures the market. Raw-material dependence, sterile capacity, and a strained skilled workforce will continue to set the pace, and the companies that solve manufacturing will be as important as the ones that discover the next molecule.

This article was produced under Drug Discovery News’ AI Editorial Guidelines.