How a peptide is made, in plain English
Published October 26, 2026. General explainer based on a 2025 review and a 2026 manufacturer note, cited below.
Quick take: peptides are built one building block at a time, then cleaned up. Every step can leave impurities, which is why purity reports exist.
The idea
A peptide is a short chain of amino acids. In the 1950s, solid phase peptide synthesis made large scale production practical: the chain is built step by step while anchored to a solid support, then released at the end.
Why longer chains get harder
The manufacturer note says chains of more than 50 amino acids lose yield in conventional solid phase synthesis, so makers use fragment based routes. It also says scarce building blocks and purification can become bottlenecks. In one program it describes, rebuilding an 87 step synthesis from fragments raised overall yield from under 0.1% to 3%. That is company reported.
| Stage | What can go wrong |
|---|---|
| Building | Missing or extra pieces in the chain |
| Release | Leftover chemicals |
| Purification | Impurities not fully removed |
| Storage | Slow breakdown over time |
What it means for buyers
A lab report shows how much of a sample is the target compound, and mass spectrometry helps confirm identity. See how to read a COA.
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Common questions
What is solid phase peptide synthesis?
A method that builds a peptide chain step by step on a solid support.
Why do impurities occur?
Each building step and the purification can leave small amounts of unwanted material.
What does a purity report show?
The share of the sample that is the target compound.
Sources
- Xiao et al., Advance in peptide-based drug development, Signal Transduction and Targeted Therapy (2025)
- WuXi AppTec press release via GlobeNewswire: Peptide manufacturing trends, how oral dosing raises API demand (Oct 21, 2026, company sourced)
Summarised in my own words. Read the originals for the full detail.