How long do research peptides last? Lyophilised and in-solution stability

Last reviewed 9 August 2026

The question is usually asked as though a vial carried one number. It carries two, because over its life the vial holds two different materials: a dry solid before reconstitution and an aqueous solution afterwards. The chemistry of the second is not the chemistry of the first running faster, and the published rate data separate the two states by orders of magnitude rather than by a factor.

What follows is what the handling literature and the stability guidelines specify. One point is fixed at the outset, because most of the confusion in this topic runs through it: shelf life and re-test period are defined terms, and neither is a property of a molecule. Both are conclusions drawn from a stability study, on defined batches, in a defined container, under defined conditions.

Shelf life and re-test period are not the same term

ICH Q1A(R2) defines a re-test period as the period of time during which the drug substance is expected to remain within its specification and, therefore, can be used in the manufacture of a given drug product, provided that the drug substance has been stored under the defined conditions. Material past the corresponding re-test date is examined again rather than discarded; a batch can be re-tested multiple times as long as it continues to comply. Shelf life is the parallel term for a finished product, running to the approved shelf life specification under the conditions defined on the container label. The guideline adds one sentence that matters here: For most biotechnological/biological substances known to be labile, it is more appropriate to establish a shelf life than a re-test period.

Two consequences follow from the definitions rather than from anyone’s opinion of them. A date is inseparable from the storage condition and the container closure system the study ran in — Q1A requires packaging that is the same as, or simulates, the packaging proposed for storage and distribution. And significant change for a substance is defined simply as failure to meet its specification, so a date encodes an analytical limit, not a moment of visible spoilage.

The storage vocabulary is compendial, not colloquial

USP General Chapter ⟨659⟩ defines the terms that appear on storage statements. They are narrower than ordinary usage, and one of them is deliberately not a temperature at all.

ICH Q1A(R2) goes further, instructing that in a storage statement terms such as ‘ambient conditions’ or ‘room temperature’ should be avoided. Read against the ⟨659⟩ entry the reason is plain: one term describes wherever the article happens to be, the other is a specified range with a mean kinetic temperature attached.

Why the dry solid is the stable form

Lai and Topp (1999) reviewed the reactions available to peptides and proteins in the solid state and named them: deamidation, peptide bond cleavage, oxidation, the Maillard reaction, β-elimination, and dimerisation or aggregation. They also named the governing variables — temperature, moisture content, excipients, and whether the formulation is amorphous or crystalline; Chang and Pikal (2009) review the same ground from the drying and formulation side. Three primary studies put numbers on it.

• Li and colleagues (2005) studied deamidation of two model peptides, Gly-Gln-Asn-Gly-Gly and Val-Tyr-Pro-Asn-Gly-Ala, at 50 °C in pH 7 buffer and as solids lyophilised from those solutions. They reported that the peptides degraded 2- to 80-fold more slowly in the solid formulations of sucrose and mannitol than in 5% solutions of these carbohydrates, and that the mannitol solids developed ordered, crystalline-like structure during storage while the sucrose solids stayed amorphous.
• DeHart and Anderson (2012) examined the asparaginyl peptide Gly-Phe-L-Asn-Gly in amorphous lyophilised solids containing hypromellose at 40 °C. They reported that increases in water content, as relative humidity was varied from 33% to 75%, produced orders-of-magnitude increases in the rate constants for succinimide formation and hydrolysis with both becoming nearly constant at high water contents.
• Oliyai and colleagues (1994) studied lyophilised formulations of the hexapeptide Val-Tyr-Pro-Asp-Gly-Ala in a factorial design, and reported that the pH of the starting solution had no significant effect while moisture level, temperature and the type of bulking agent did.

The variable common to all three is water — as a reactant, and as the medium that permits molecular mobility in an amorphous solid. That is why the handling guidance is about sealing and desiccation rather than about cold alone, and why the appearance of the cake is worth reading before anything is added to it, which the article on lyophilisation and cake appearance takes up.

The routes, and the residues that carry them

Deamidation at asparagine is the best-characterised route. Patel and Borchardt (1990) followed Val-Tyr-Pro-Asn-Gly-Ala by HPLC and reported marked dependence on pH, temperature and buffer composition: between pH 5 and 12 it deamidated via a cyclic imide intermediate giving both aspartyl and isoaspartyl products, while at acidic pH the route was direct hydrolysis of the side-chain amide. Robinson and Robinson (2001) reported a procedure for predicting those rates from structure; oxidation mechanisms are reviewed by Li, Schöneich and Borchardt (1995), and protein pharmaceutical stability more broadly by Manning and colleagues (2010).

Bachem’s handling guidance names the residues whose presence shortens a solid’s usable life: Peptides containing Asn, Gln, Met, Cys, and/or Trp have limited shelf lives. Its frequently asked questions page gives the same set for lyophilised material and adds one residue for material held in solution: Peptides containing Asn, Gln, Cys, Met, Trp, Tyr tend to be less stable. The handling guidance notes separately that peptides carrying a free thiol are oxidised to disulfides above pH 7. That list is checkable against a sequence, and the answer differs sharply between two compounds held under identical conditions.

Neither column states how long either material lasts. Each states which of the documented routes a sequence has the chemistry to run. Sequence and formula are printed in the identification table of every library entry, so the same check can be made for any of them.

Material in solution

Bachem’s position is unambiguous: Peptides should not be stored in solution (even sterile and oxygen-free solution) because they may slowly undergo chemical degradation. Frozen solutions may be kept for a few weeks. Where a solution is held it is divided into aliquots and kept frozen below −15 °C, with pH 5 to 7 given as the range of best stability and long-term storage of solutions described as not recommended. Short-term refrigerated holding is the 2 °C to 8 °C band defined at ⟨659⟩, which ICH Q1A expresses as a set point and tolerance, 5 °C ± 3 °C. ICH Q5C states the regulatory counterpart for a formulated product: the stability of a freeze-dried product after reconstitution should be demonstrated for the conditions and the maximum storage period specified — demonstrated for that product, not inferred from the class.

The twenty-eight-day figure that circulates in this category answers a different question. It is a property of a preserved diluent and its closure, derived from antimicrobial effectiveness testing and a beyond-use convention for an entered container, and it says nothing about chemical degradation of a dissolved solute. The comparison of the two diluents sets out where the number comes from.

Loss that is not degradation

Grohganz, Rischer and Brandl (2004) examined adsorption of the decapeptide cetrorelix to container surfaces. They reported a Langmuir isotherm reaching a plateau at 0.4 µg/cm², adsorption decreasing in the rank order glass > polypropylene = polyethylene > polytetrafluoroethylene, and mitigation raising the HPLC response up to five times. Material lost to a wall is not degraded; it is simply no longer in the liquid, and at low concentration the two are indistinguishable by assay alone.

Freezing and thawing

Cao and colleagues (2003) studied freeze denaturation of three model enzymes — lactate dehydrogenase, alcohol dehydrogenase and catalase — in dilute aqueous solution without cryoprotectants, under controlled rates. They reported that slow freezing at about 1 °C/min with fast thawing above 10 °C/min produced higher activity recovery, while fast freezing above 20 °C/min with slow thawing caused more severe damage, and attributed the pattern to the ice–liquid interfacial area created during freezing and to recrystallisation during thawing.

The model class matters. These are folded enzymes assayed by activity recovery, not short synthetic sequences, and the mechanism described is interfacial and buffer-mediated rather than sequence-specific. What transfers is the reason the handling literature recommends aliquoting: dividing a solution so each container is thawed once removes the variable rather than tuning it.

Light

Kerwin and Remmele (2007) reviewed photodegradation of protein biologics and describe photo-oxidation at tryptophan, tyrosine, phenylalanine and cysteine residues — two of which, tryptophan and cysteine, also sit on the list that limits solid-state shelf life. Whether a given material is affected is established by testing it: ICH Q1B sets the confirmatory exposure at not less than 1.2 million lux hours and an integrated near ultraviolet energy of not less than 200 watt hours/square meter, using either a D65/ID65 daylight source or a cool white lamp combined with a near-UV lamp emitting between 320 and 400 nm. Where no photostability study exists for a particular sequence, that is an absence of data, not a finding that light has no effect.

Excursions in transit

ICH Q1A(R2) frames a short warm period as a bounded, measurable challenge rather than an unknown. Its glossary states that accelerated data can be used to assess longer term chemical effects at non-accelerated conditions and to evaluate the effect of short term excursions outside the label storage conditions such as might occur during shipping. For substances intended for freezer storage, where no accelerated condition exists, it directs testing of a single batch at an elevated temperature, giving 5 °C ± 3 °C or 25 °C ± 2 °C as examples, to address the effect of short term excursions outside the proposed label storage condition, e.g., during shipping or handling.

The quantity doing the work is mean kinetic temperature: a single derived temperature that, if maintained over a defined period of time, affords the same thermal challenge… as would be experienced over a range of both higher and lower temperatures for an equivalent defined period, higher than the arithmetic mean because it takes the Arrhenius equation into account. USP ⟨659⟩ applies the same logic to controlled room temperature, permitting spikes to 40 °C provided they do not exceed 24 h and the mean kinetic temperature stays at or below 25 °C. Time at temperature and integrated exposure are the variables, not peak alone. Bachem’s guidance is consistent: short-term storage at 4 °C is described as sufficient and lyophilised material may be shipped at room temperature. A fuller account sits in the article on ambient shipping.

What accelerated data can and cannot establish

ICH Q1A(R2) permits limited extrapolation beyond the observed range but states that it assumes that the same degradation relationship will continue to apply beyond the observed data, and warns that results from accelerated testing studies are not always predictive of physical changes. ICH Q5C is stronger, stating that expiration dating should be based on real-time/real-temperature data and that the accelerated and stress conditions of the parent guideline may not be appropriate for biotechnological/biological products.

One scope point should be stated rather than glossed. Q5C applies to well-characterised proteins and polypeptides, their derivatives and products of which they are components, and which are isolated from tissues, body fluids, cell cultures, or produced using rDNA technology. A peptide made by solid-phase chemical synthesis falls outside that description. Q5C is cited here for the principle it articulates about extrapolation, not as a rule governing this class of material.

Handling that follows from the chemistry

1. Allow a cold container to reach ambient temperature in a desiccator before opening it. Peptide solids are hygroscopic, and Bachem notes that uptake of atmospheric water reduces the overall peptide content and may decrease stability. Opening a cold vessel in room air condenses water onto the solid.
2. Weigh quickly, reseal tightly, and keep the container dry rather than relying on temperature alone. Moisture was significant in Oliyai’s factorial analysis, and relative humidity moved rate constants by orders of magnitude in DeHart and Anderson’s solids.
3. Divide solutions into aliquots rather than re-entering one container, use degassed buffer below pH 7 for sequences carrying a free thiol, and wear a dust respirator when handling larger quantities of lyophilisate.

Two things this category consistently gets wrong

1. “It lasts twenty-eight days once mixed.” Twenty-eight days is a preservative and container figure. Chemical degradation of a dissolved solute is a separate question with separate kinetics, and no antimicrobial preservative acts on it.
2. “No study found, so it is stable.” This literature is built on model sequences and recombinant proteins chosen because they are analytically tractable. For most sequences sold as research material there is no published stability programme at all, and the correct description of that is an absence of data.

What this page does not establish

Every figure above is a property of a substance, a container or a rule. None of it is a stability programme for a particular sequence in a particular vial, and the two are not interchangeable. Where no such programme exists, no date derived from one exists either. What a certificate does and does not establish is set out in the certificate literacy article; what research-grade material is not manufactured to is set out in the article on research-grade specification.

References

1. Bachem. Handling and Storage Guidelines for Peptides. Source type: manufacturer technical handling guidance. bachem.com
2. Bachem. Care and Handling of Peptides; Frequently Asked Questions. Source type: manufacturer technical handling guidance; source of the solution residue list including Tyr, the pH 5–7 optimum and the long-term storage statement. bachem.com, bachem.com/knowledge-center/faq
3. United States Pharmacopeia. General Chapter ⟨659⟩, Packaging and Storage Requirements — temperature and storage definitions. Source type: pharmacopoeial general chapter.
4. ICH. Stability Testing of New Drug Substances and Products, Q1A(R2), Step 4, 6 February 2003 — storage conditions, stress testing, evaluation, statements and labelling, and glossary. Source type: regulatory guideline. ich.org
5. ICH. Stability Testing: Photostability Testing of New Drug Substances and Products, Q1B — light sources and confirmatory study procedure. Source type: regulatory guideline. ich.org
6. ICH. Quality of Biotechnological Products: Stability Testing of Biotechnological/Biological Products, Q5C, Step 4, 30 November 1995 — scope, storage conditions, accelerated and stress conditions, stability after reconstitution of freeze-dried product. Source type: regulatory guideline. ich.org
7. Lai MC, Topp EM. Solid-state chemical stability of proteins and peptides. J Pharm Sci. 1999;88(5):489–500. Model: review of solid-state degradation chemistry. PMID 10229638. DOI 10.1021/js980374e.
8. Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–75. Model: review. PMID 20143256. DOI 10.1007/s11095-009-0045-6.
9. Chang LL, Pikal MJ. Mechanisms of protein stabilization in the solid state. J Pharm Sci. 2009;98(9):2886–908. Model: review of solid-state formulation and drying. PMID 19569054. DOI 10.1002/jps.21825.
10. Patel K, Borchardt RT. Chemical pathways of peptide degradation. II. Kinetics of deamidation of an asparaginyl residue in a model hexapeptide. Pharm Res. 1990;7(7):703–11. Model: in vitro kinetics, synthetic hexapeptide in buffer. PMID 2395797. DOI 10.1023/a:1015807303766.
11. Li B, O’Meara MH, Lubach JW, Schowen RL, Topp EM, Munson EJ, Borchardt RT. Effects of sucrose and mannitol on asparagine deamidation rates of model peptides in solution and in the solid state. J Pharm Sci. 2005;94(8):1723–35. Model: in vitro kinetics, two synthetic model peptides in solution and as lyophilised solids. PMID 15986465. DOI 10.1002/jps.20372.
12. Oliyai C, Patel JP, Carr L, Borchardt RT. Chemical pathways of peptide degradation. VII. Solid state chemical instability of an aspartyl residue in a model hexapeptide. Pharm Res. 1994;11(6):901–8. Model: in vitro kinetics, lyophilised synthetic hexapeptide, factorial design. PMID 7937533. DOI 10.1023/a:1018998312503.
13. DeHart MP, Anderson BD. Effects of water and polymer content on covalent amide-linked adduct formation in peptide-containing amorphous lyophiles. J Pharm Sci. 2012;101(9):3142–56. Model: in vitro kinetics, synthetic tetrapeptide in amorphous lyophilised solids containing hypromellose. PMID 22437444. DOI 10.1002/jps.23092.
14. Robinson NE, Robinson AB. Prediction of protein deamidation rates from primary and three-dimensional structure. Proc Natl Acad Sci U S A. 2001;98(8):4367–72. Model: computational procedure validated against proteins and haemoglobin variants. PMID 11296285. DOI 10.1073/pnas.071066498.
15. Li S, Schöneich C, Borchardt RT. Chemical instability of protein pharmaceuticals: mechanisms of oxidation and strategies for stabilization. Biotechnol Bioeng. 1995;48(5):490–500. Model: review of oxidation mechanisms. PMID 18623513. DOI 10.1002/bit.260480511.
16. Kerwin BA, Remmele RL Jr. Protect from light: photodegradation and protein biologics. J Pharm Sci. 2007;96(6):1468–79. Model: review. PMID 17230445. DOI 10.1002/jps.20815.
17. Cao E, Chen Y, Cui Z, Foster PR. Effect of freezing and thawing rates on denaturation of proteins in aqueous solutions. Biotechnol Bioeng. 2003;82(6):684–90. Model: in vitro, three model enzymes in dilute aqueous solution. PMID 12673768. DOI 10.1002/bit.10612.
18. Grohganz H, Rischer M, Brandl M. Adsorption of the decapeptide Cetrorelix depends both on the composition of dissolution medium and the type of solid surface. Eur J Pharm Sci. 2004;21(2–3):191–6. Model: in vitro, synthetic decapeptide against glass and polymer surfaces. PMID 14757490. DOI 10.1016/j.ejps.2003.10.008.
19. National Center for Biotechnology Information. PubChem Compound Summary for CID 9941957 and CID 146675088. Source type: chemical registry records; molecular formula and average mass.