Stability Testing Explained: How a Peptide’s Shelf Life Is Determined

Where a shelf-life number comes from

ICH Q1A(R2), the core guideline for new drug substances and products, gives the purpose of stability testing as “to provide evidence on how the quality of a drug substance or drug product varies with time under the influence of a variety of environmental factors such as temperature, humidity, and light, and to establish a re-test period for the drug substance or a shelf life for the drug product and recommended storage conditions.” The number is an output of measurement, tied to stated conditions.

The design is specific. Long-term testing of a drug substance “should cover a minimum of 12 months’ duration on at least three primary batches at the time of submission and should be continued for a period of time sufficient to cover the proposed re-test period”, with testing normally every three months in the first year, every six months in the second and annually after that. The material is studied in a container closure system “that is the same as or simulates the packaging proposed for storage and distribution”.

The guidance is being rewritten. In April 2025, ICH endorsed a Step 2 draft, Q1 Stability Testing of Drug Substances and Drug Products, which the US Food and Drug Administration describes as “a consolidated revision of the ICH Q1A(R2), Q1B, Q1C, Q1D, Q1E, and Q5C series of stability guidances”. Consultation ran from April to September 2025, and ICH’s February 2026 work plan targets Step 4 for November 2026. Until then, the texts quoted here remain the adopted versions.

What stability testing measures

A study is only as sensitive as its methods. Q1A(R2) says that “The testing should cover, as appropriate, the physical, chemical, biological, and microbiological attributes”, and that “Validated stability-indicating analytical procedures should be applied.” A stability-indicating method is one that can see the change: it separates degradation products from the intact molecule and measures them, instead of counting them as part of the main signal.

Stress testing is how a method earns that label. Q1A(R2) explains that stressing a drug substance “can help identify the likely degradation products, which can in turn help establish the degradation pathways and the intrinsic stability of the molecule and validate the stability indicating power of the analytical procedures used.” A method never challenged with degraded material has not shown that it can detect degradation.

For peptides, the changes to look for are well catalogued. Lai and Topp’s review lists the major solid-state reactions as “deamidation, peptide bond cleavage, oxidation, the Maillard reaction, beta-elimination, and dimerization/aggregation”, and our guide to how peptides degrade explains the main pathways, including isomers with the same mass as the parent peptide. A purity method has to separate those products to report them, which is what our page on HPLC purity methods covers. ICH Q5C, written for biotechnological products, adds a caution that applies by analogy: “there is no single stability-indicating assay or parameter that profiles the stability characteristics” of such a product.

ICH storage conditions in plain English

Q1A(R2) defines a small set of standard storage conditions. For a drug substance in the general case, the applicant chooses 25 °C or 30 °C for the long-term study; the other conditions follow from that choice and from the intended storage.

Three details matter for peptides, since manufacturers such as Bachem recommend frozen long-term storage. First, “significant change” for a drug substance is defined as failure to meet its specification, so “stable” means “still within specification”, not “unchanged”. Second, a freezer study has no accelerated arm; Q1A(R2) instead asks for “testing on a single batch at an elevated temperature (e.g., 5°C ± 3°C or 25°C ± 2°C)” to address “the effect of short term excursions outside the proposed label storage condition, e.g., during shipping or handling.” Third, substances “intended for storage below -20°C should be treated on a case-by-case basis”, so there is no standard ICH condition behind a −80 °C claim.

Accelerated data and its limits

Q1A(R2) defines accelerated testing as studies “designed to increase the rate of chemical degradation or physical change” through “exaggerated storage conditions”, whose data can help “assess longer term chemical effects at non-accelerated conditions”. The same definition ends with a warning: “Results from accelerated testing studies are not always predictive of physical changes.”

The usual bridge from hot to cold is the Arrhenius equation, k = A e^−E_a/RT. The IUPAC Gold Book describes it as “An equation that represents the dependence of the rate constant k of a reaction on the absolute temperature T”, and notes that in its original form A and E_a “are considered to be temperature-independent”. Projecting from 40 °C to −20 °C would therefore assume that the same reaction, with the same activation energy, dominates across a 60-degree span. That assumption can fail. In solids, moisture matters as well as heat: González-González and colleagues write that “the use of only the classical Arrhenius equation is not enough” and describe a “humidity-corrected Arrhenius equation”. A different mechanism can take over when it is hot: modelling antibody solutions, Kuzman and colleagues report findings that suggest “at higher temperatures additional mechanisms of fragmentation are present”, and cite earlier work in which Arrhenius behaviour held from 5 to 40 °C but not above. For peptides, González-González and colleagues note that accelerated predictive studies “for peptides and biological products are very limited”.

ICH Q1E writes those cautions into its rules. Extrapolation “assumes that the same change pattern will continue to apply beyond the period covered by long-term data.” Even when long-term and accelerated data show little change and little variability, a proposed period “can be up to twice, but should not be more than 12 months beyond, the period covered by long-term data”; for refrigerated storage the limit is “up to one-and-a-half times, but should not be more than 6 months beyond”. Any period granted by extrapolation “should always be verified by additional long-term stability data as soon as these data become available.”

Retest period versus shelf life

Q1A(R2) has two words for the result. A re-test period is the time during which a drug substance “is expected to remain within its specification”; after it, a batch “should be re-tested for compliance with the specification and then used immediately”. A shelf life is the period during which a drug product “is expected to remain within the approved shelf life specification, provided that it is stored under the conditions defined on the container label.” For most labile biotechnological substances, the guideline adds, “it is more appropriate to establish a shelf life than a re-test period.” How these become dates on a label, and what each date asks of you, is covered in our explainer on retest dates versus expiry dates.

How to read a storage claim

Take a line that might appear on a listing or a certificate: “stable for 24 months at −20 °C”. Measured against the drug framework, each part implies something you can ask about.

• The period. For freezer storage, Q1E says the period “should be based on long-term data”, so a pharmaceutical 24-month freezer claim should rest on measurements made at −20 °C, not on a projection from warmer conditions.
• The condition. In Q1A(R2), −20 °C means −20 °C ± 5 °C. A freezer that warms during defrost, or a day on the bench, can fall outside the studied condition.
• The word “stable”. It means a specification was met. Without the specification and the method, the word cannot be interpreted.
• The container. Studies use the intended container closure, so a claim for a sealed vial says nothing about material once it has been opened, weighed or dissolved.
• The wording. Q1A(R2) says “Terms such as ‘ambient conditions’ or ‘room temperature’ should be avoided” in storage statements; neither phrase defines a temperature.
• The batches. One batch is a weaker basis than the three primary batches Q1A(R2) asks for.

So the honest answer to “how long do peptides last?” is: as long as a study on that material, in that container and under those conditions, has shown, and only while storage since has matched it. Bachem puts the sequence-dependence plainly: “Peptides containing Asn, Gln, Met, Cys, and/or Trp have limited shelf lives.” The manufacturer guidance we reviewed gives temperatures and warnings like that one, not study data, and in preparing this article we found no published stability study behind the research-peptide shelf-life figures we looked at. Regard a printed period as a claim to ask about. We are a supplier too, so the same questions are fair to put to anything we print.

What’s established and what isn’t

Practical storage for Canadian labs

Health Canada implemented ICH Q1A(R2) and Q1E on September 25, 2003, and Q5C on January 5, 2001, stating that in implementing these guidelines it “endorses the principles and practices described therein.” They are drug frameworks. For a laboratory, the useful lesson is to keep material inside the conditions a claim assumes, and to keep the records that show you did.

• Store sealed vials at the recommended temperature and keep them sealed until needed; the peptide storage guide covers temperatures and handling.
• Keep the lot number, certificate and receiving date together, so any question about stability can be tied to one batch.
• Log the freezer. A minimum–maximum thermometer or a data logger shows whether storage stayed within the band a claim assumes.
• Plan deliveries around the season. Our guide to shipping research peptides through a Canadian winter covers transit and arrival.
• Ask before relying on a date. If a printed period matters to your work, ask the supplier what data support it; for our products, contact us.

Lyophilized research peptides

Every research peptide below ships as a lyophilized powder, the form that keeps best when stored cold, dry and sealed. Janoshik test reports for all four are listed on our Lab Testing page.

BPC-15715-amino-acid research peptideView product GHK-CuCopper tripeptideView product TB-500Thymosin beta-4 research peptideView product EpithalonLyophilized tetrapeptideView product

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