Last year, a long-anticipated change finally happened for stability testing. On 11 April 2025, the International Council for Harmonization (ICH) published for consultation the draft version of ICH Q1 “Stability Testing of Drug Substances and Drug Products”. This new guideline is a full consolidation of everything that came before it (Q1A–F and Q5C), and it’s set to reshape how we think about stability studies for small molecules, biologics, and novel therapies such as oligonucleotides or advanced therapies (ATMPs).
While the guideline is currently in its draft phase for public consultation, it is expected to officially enter into force between 2026 and 2027. However, the industry is already in a transition period; beginning to align protocols now is essential to ensure future compliance.
At Kymos Group, stability studies have long been one of our core strengths. And with our growing focus on biologics, and our work with advanced therapies, this new guideline arrived at the perfect time to guide future strategies. So, what’s inside ICH Q1? And more importantly, what does it mean for our clients? Let’s break it down.
ICH Q1: A Single Harmonized Guideline
Until recently, stability guidelines were split between Q1A–F for traditional synthetic drugs and Q5C for biologics. This division made sense in the past, but it created grey areas for hybrid products and added complexity to global regulatory submissions. The new Q1 finally brings it all under one same document. You can view the full draft of the guideline here: ICH Q1 Draft Guideline 2025.
Small molecules, biologics, vaccines, gene therapies, and even drug–device combinations are now covered by a single harmonized document. That includes oligonucleotides, plasma-derived products, ATMPs, novel excipients, and co-packaged solvents. This broader and expanded scope matches today’s pipeline reality: more complex molecules, more hybrid formats, and a shift toward personalized medicine. If your product doesn’t fall into a “classic” category, Q1 is your reference.
A Lifecycle and Risk-Based Approach
Another major change is how the guideline treats the lifecycle of a product. Instead of focusing stability requirements only around submission, Q1 encourages a continuous, risk-based strategy from early development to post-approval changes.
This means:
- Development stability studies (e.g., stress or forced degradation) are emphasized early on.
- Primary studies must be robust (typically three batches, covering full shelf life) with reduced designs allowed only if well justified.
- Ongoing and commitment studies become part of the long-term regulatory picture.
- Stability modeling and prior knowledge can be used to streamline studies, especially when supported by solid science.
At Kymos, we already use this kind of logic when helping clients define matrixed or reduced study designs. With Q1, this scientific flexibility is not only allowed, it’s also encouraged.
For Biologics: More Structure, More Expectation
The Q1 draft brought clarity but also higher expectations for biologics. If you’re working with therapeutic proteins, peptides, vaccines, or biosimilars, there are key takeaways:
- You’ll generally need three primary batches of stability data (unless justified otherwise) that match your proposed shelf life.
- Accelerated conditions can be used to build product knowledge, but not to justify shelf life.
- Data should address the unique degradation risks of biologics: temperature sensitivity, oxidation, shear, and more.
- Analytical procedures need to demonstrate that they can detect subtle changes over time including changes in potency and purity.
For our biologic clients at Kymos, this is very much aligned with what we already do. But Q1 gives it a formal structure and allows us to better justify modern, leaner approaches.
Advanced Therapies Finally Get Their Spotlight
Perhaps one of the most exciting developments remains Annex 3, a dedicated section on Advanced Therapy Medicinal Products (ATMPs). These include cell and gene therapies: fast-growing segments that face unique stability challenges such as cryopreservation or viability after thaw.
The guideline includes:
- The importance of functional viability (not just physical appearance or potency).
- The role of frozen and fresh storage strategies.
- The complexity of defining a meaningful shelf life for products that may be shipped thawed or administered immediately.
With clear regulatory guidance available, we’re in a strong position to support future ATMP clients as we expand into this area.
What About Modeling and Reduced Protocols?
Q1 includes two annexes that many companies will find helpful:
- Annex 1 covers reduced designs (e.g., matrixing or bracketing) still allowed, but requiring strong scientific rationale.
- Annex 2 covers stability modeling, expanding on previous linear regression models and encouraging more sophisticated approaches.
These tools are powerful when applied correctly, and they’re part of our daily thinking at Kymos. We work with clients to ensure their models aren’t just statistically sound, but also regulatory-ready.
What Should You Do Now?
Given the 2026–2027 implementation window, we are currently in a vital phase of preparation. If you’re developing a new biologic or preparing a variation submission, you should be reviewing your stability strategies considering the Q1 draft. While this draft is likely to evolve, its core structure and principles are here to stay.
Here’s how we can help:
- We design ICH-compliant stability studies for biologics, with full support for modeling, bracketing, and forced degradation.
- We offer guidance for lifecycle-based stability planning including commitment and ongoing studies post-approval.
As we move into the ATMP space, we are developing the capabilities to support viability studies, cryostability, and function-based protocols.
Final Thoughts
The draft ICH Q1 wasn’t just a new document, it was a signal. The regulatory world is adapting to a more complex, biologically driven landscape, and stability testing is evolving accordingly.
At Kymos, we’re ready for the 2026 transition. Our services already align with many of Q1’s new expectations, and we’re working closely with clients to future-proof their stability programs.
If you’re unsure how the guideline affects your products or want to ensure your current stability protocols are aligned, our team is here to help. Let’s make your next submission or lifecycle update a stable one. You can contact us at https://kymos.com/contact/ or email us at commercial@kymos.com
