Questions to Ask Your Peptide Supplier Before You Commit to a Program

Picking a peptide supplier for a single catalogue sequence is low stakes. If it goes wrong, you reorder. Committing to one for a discovery program is different. You’re betting weeks of timeline, a chunk of budget and possibly your SAR data on a partner whose limits you won’t fully see until a hard sequence lands on their bench.

The quote and the website won’t tell you much. The questions you ask before signing will. Here are the ones worth putting on the table.

Why Supplier Selection Matters More for Complex Peptides

For a short, well-behaved linear sequence, most competent suppliers will deliver something usable. The differences show up as complexity climbs: long chains, hydrophobic stretches, aggregation-prone regions, non-natural residues, cyclization, branching. Standard batch SPPS starts to struggle there, and deletion products pile up faster than purification can clean them out.

That’s exactly where most interesting programs live. A supplier that’s great at 15-mers can turn into your bottleneck on a 70-mer with three modifications, and you usually find out after the first missed delivery, not before.

Questions About Sequence Feasibility

• What’s the longest sequence you routinely deliver? Ask for the everyday number, not the record. Routine capability and a one-time achievement are very different things.
• Have you made sequences like mine? Share the real features: length, hydrophobic regions, disulfides, the specific non-natural amino acids. Ask for comparable examples.
• What happens when a synthesis fails? Do they flag difficult sequences upfront, suggest workarounds like ligation strategies, or just quote and hope?
• Can you handle the modifications I’ll need later? Think beyond this order. Staples, lipidation, PEGylation, branched or mirror-image constructs. Switching suppliers mid-program costs time.

Questions About Quality and Analytics

Purity on a certificate is only as meaningful as the method behind it.

• How is purity measured and reported? HPLC at which wavelength, and is identity confirmed by mass spec on every batch?
• Will I receive the raw data? Chromatograms and spectra, not just a number on a PDF.
• What counter-ion and salt form will I get? TFA salts can interfere with cell-based assays. Ask whether exchange to acetate or HCl is available.
• Is peptide content reported, or only purity? A 95% pure sample can still contain a surprising amount of water and salt by weight, which throws off your dosing.

Questions About Speed and Reliability

Fast quotes are easy to give. Fast deliveries are harder.

• What’s your actual on-time delivery rate? Ask for a number, and ask how they measure it.
• What’s the realistic turnaround for my sequence? Not the brochure minimum. Your sequence, at your purity spec.
• What’s your process when a timeline slips? You want early warning, not an apologetic email on the due date.

Synthesis platform plays a big role here. Flow-based methods like AFPS can couple residues in seconds to minutes rather than hours, which shortens cycle times and gives a supplier more room to retry a difficult synthesis without blowing your schedule.

Questions About Communication and Collaboration

• Who’s my scientific point of contact? A chemist who understands the sequence, or an account manager relaying messages?
• How do you report progress? Regular updates during long or complex syntheses save you a lot of chasing.
• Will you push back on my design? The best suppliers will tell you when a sequence is likely to cause trouble and suggest a smarter route. Silence isn’t a feature.

Questions About Scale, Cost, and Continuity

• Can you scale from discovery quantities to what I’ll need for later studies? Changing suppliers between stages can introduce new impurity profiles at the worst possible moment.
• How does pricing change with length, modifications and scale? Get the logic behind the quote so you can budget the next three orders, not just this one.
• Is the process reproducible batch to batch? Ask how they document methods so a resynthesis six months from now matches.
• What’s your financial and operational stability? If your program depends on one supplier, their staying power becomes your risk.

Questions About IP and Confidentiality

• Will you sign our NDA, or only your own? Either can work, but read it before sending sequences.
• Who owns process improvements made on my sequence? If they develop a better route for your molecule, make sure the agreement says who can use it.
• How is sequence data stored and who can access it? Ask about internal access controls and data retention.
• Do you work with direct competitors in my therapeutic area? Many suppliers do. What matters is how they separate projects.

Red Flags to Watch For

Some answers should slow you down. Be wary of a supplier who quotes a difficult sequence instantly without asking a single question about it, or who can’t produce raw analytical data. Vague answers on turnaround (“it depends”) with no follow-up range are another warning sign, as is a supplier who’s never said no to a sequence. Every honest chemist has.

Watch for pressure to commit to large volumes before a pilot order, and for IP terms that are loose or one-sided. If communication is slow while they’re trying to win your business, it won’t get faster once they have it.

Choose a Partner, Not Just a Vendor

The right peptide supplier shortens your program. The wrong one adds weeks you’ll never get back. Ask hard questions about feasibility, analytics, reliability, scale and IP, and pay as much attention to how a supplier answers as to what they say.

Amide Technologies, an MIT spinout based in Waltham, built its AFPS platform for the sequences that slow other suppliers down: linear synthesis up to 120 amino acids, larger proteins through ligation, and complex constructs with unnatural amino acids, branched structures and mirror-image backbones. Turnaround starts at four days, and the team reports an on-time delivery rate above 99 percent.