Pfizer's Accord For A Healthier World Program Challenges Stability Study Norms

A conversation with Paul Gerst, Lina Niu, and Jennifer L. Brown — Pfizer

Many lower income countries are found closer to the equator with extreme tropical climates. There is a lack of stability testing for these often under-served parts of the world that has historically limited access to quality medicines and vaccines.

Pfizer’s Accord for a Healthier World program, an initiative aimed at addressing healthcare disparities, offers the company’s full portfolio on a not-for-profit basis to 45 lower-income countries where more than a billion people live. But for many drugs, that means reevaluating stability in the context of warmer, more humid environments.

Among the International Council for Harmonisation’s (ICH) five stability zones, Zone IVa and Zone IVb present the greatest challenges with the highest heat and humidity conditions. Stability data for Zone IVa (30 degrees C/65%RH) and Zone IVb (30 degrees C/75%RH) is often lacking. Without this data, regulatory approval and safe distribution in these regions become difficult, if not impossible.

To address this, Pfizer’s scientists have developed a novel statistical approach that leverages existing long-term data from Zone II conditions (25 degrees C/60%RH) and short-term accelerated data (40 degrees C/75%RH). This method would allow for a scientifically sound estimation of shelf life in Zone IV markets without the need for new long-term studies.

The World Health Organization’s stability guidance provides the prevailing instruction for testing requirements for chemical and biological drugs in Zones III and IV. The WHO also says that alternative approaches may be used if they are scientifically justified. This flexibility can be valuable for initiatives, like the Accord, that seek to increase access to medicines.

Pfizer Senior Director, Global Regulatory Affairs, CMC Jennifer Brown and Associate Director, Statistics Lina Niu are presenting on the approach at the International Society for Pharmaceutical Engineering’s 2025 ISPE Annual Meeting & Expo.

Along with their colleague Senior Principal Scientist, Paul Gerst, they offered to give us a quick preview of the talk and an overview of their approach.

Please explain briefly the purpose of Pfizer's Accord for a Healthier World program.

Pfizer believes that where you live shouldn’t impact the quality of your healthcare. Accord for a Healthier World is part of Pfizer’s comprehensive approach to expand access to medicines and vaccines for all people and is intended to help close the health equity gap. Through the Accord, Pfizer is offering the full portfolio of medicines and vaccines for which it has global rights, on a not-for-profit basis to 1.2 billion people living in 45 lower-income countries around the world. To make sure these medicines reach those in need and to support long-term sustainable impact, Pfizer is working together with governments, the global health community, and others who share our commitment to advancing health equity, to understand and better address system-level barriers that can limit or prevent patient access.

Why do Zone IV markets pose such a specific challenge?

Zone IV markets have been challenging for the Accord because many of the products in the Pfizer Accord portfolio are older products that have not previously been available in Zone IV markets. Therefore, long-term stability studies at Zone IV conditions (Zone IVa, 30 degrees C/65%RH, and Zone IVb, 30 degrees C/75%RH) were never conducted.  

How does your novel approach account for higher temperature and humidity conditions without new long-term studies?

Our novel statistical approach evaluates available long-term Zone II (25 degrees C/60%RH) and short-term accelerated (40 degrees C/75%RH) data and interpolates the expiry at Zone IV conditions using the Arrhenius model relationship between the two conditions. This approach takes into consideration all stability-limiting attributes for each product and the probability of breaching the specified limits. The first set of products to which we are applying this model does not have variable humidity exposure; therefore, temperature is the only attribute considered.

How do you balance prediction model innovation with the need for global regulatory acceptance?

Conferences such as this allow for greater discussion, review, and suggestions from peers prior to engaging with regulatory agencies. We hope with the feedback we receive we can better position the science, while maintaining focus on the safety and efficacy of the products.

Is it possible to validate your model in real-world networks?

Our presentation will provide two product examples that applied the approach and compared against available Zone IV data.

Finally, do you see this model applied more broadly someday, beyond Pfizer's portfolio?

Yes, we think that it is feasible to perhaps apply this model more broadly and perhaps save on sample and testing resources.