Draft: ICH Q1 consolidated stability guideline (replaces Q1A–F and Q5C once final)

In short: This is a draft. ICH endorsed the Q1 stability draft at Step 2 on 11 April 2025 for public consultation. The adopted Q1A(R2) and the other current guidelines remain the texts to follow until a final version is adopted.

What changed (proposed)

The ICH Q1 draft is a consolidated revision. Its own introduction says it will supersede Q1A–Q1F and Q5C once final. ICH states the draft is at Step 2, was released for consultation, and may change before adoption, so it should not be treated as final.

Scope: synthetic and biological drug substances and drug products, including chemically synthesised substances, therapeutic proteins, conjugates such as antibody-drug conjugates, vaccines, allergenics and adjuvants, cell and gene therapy products, the drug part of drug-device combinations, co-packaged diluents and natural health products regulated as drugs. It applies to registration submissions, post-approval changes and, where relevant, master files.

The draft has 18 chapters and three annexes:

• Development stability studies under stress and forced-degradation conditions
• Protocol design for formal studies, including lifecycle stability protocols and risk management
• Selection of batches, container closure, testing frequency
• Storage conditions for room temperature, refrigerated and frozen products
• Photostability (forced photodegradation and confirmatory studies)
• Processing and holding times for intermediates, short-term storage conditions and in-use stability
• Reference materials, novel excipients and vaccine adjuvants
• Data evaluation: statistics, extrapolation and stability modelling, defined scenarios by accelerated and intermediate results, and multi-factor designs
• Labelling and excursions outside a labelling claim
• Commitment, ongoing and product-lifecycle stability studies, and new dosage forms or strengths
• Annex 1 reduced stability protocol designs, Annex 2 stability modelling, Annex 3 stability of advanced therapy medicinal products (ATMPs)

Who it affects

Anyone planning or running stability programmes for drug substances and products, including biotechnological products now under Q5C, will be affected once a final guideline is adopted. Until then, the adopted guidelines still apply.

Key dates

• 11 April 2025: Step 2 draft endorsed for consultation (the draft states this date).
• Final adoption (Step 4): no date is given in the draft.

What to do now

• Keep following Q1A(R2) and the related guidelines for filings.
• Read the draft to see how it may affect protocols (example in-house approach: list questions for your stability and regulatory teams, but do not change protocols based on a draft).
• Watch ich.org for the final text.

Related reading: Bracketing and Matrixing Designs for Stability Study (ICH Q1D), Why Stability Testing is So Important.

Official source

• ICH Q1 Stability Testing of Drug Substances and Drug Products, Step 2 draft — ICH, 2025-04-11. Link