By Ellen Verhavert, Head of GMP Production Facility, SGS
The race to replicate infection and accelerate innovation
In vaccine development, speed and certainty are everything. Controlled Human Infection Model (CHIM) studies have redefined that race: enabling researchers to test efficacy early, in small groups of healthy volunteers, under controlled conditions. But CHIM studies depend on one crucial ingredient: a safe, potent and well-characterized challenge agent.
For Respiratory Syncytial Virus (RSV), that task has defeated most who tried. At SGS, we now hold one of the only GMP-manufactured, infective RSV-A challenge agents in existence – the result of scientific resilience, quality control, adaptability and collaboration in overcoming demanding obstacles.
The risk and complexity of RSV challenge agent development
Developing an RSV challenge agent from scratch is a costly endeavor. It also requires regulatory approval at every stage and takes years before a usable product emerges. The technical failure rate is high and there are only few qualified CDMOs worldwide with the know-how to manufacture a stable respiratory challenge agent under GMP conditions.
Even then, success is not guaranteed or predictable. A challenge agent must infect at least 75% of healthy volunteers to be a viable asset in CHIM studies. Anything less, years of investment may never reach a single clinical trial. Biology of challenge agents can be uncertain and variable – success depends on achieving a consistent infection rate in humans, something no preclinical test can fully forecast.
As a result, the risk-to-reward ratio is daunting.
The science keeps moving
Circulation of RSV strains keep evolving, which means challenge agents must reflect viral characteristics that remain relevant for today’s development programs. Our RSV-A challenge agent, which is the first in its kind worldwide, is derived from a recent clinical isolate and represents a meaningful addition to the field.
This recent isolate means a closer match to currently circulating viruses, resulting in more relevant infection profiles for modern vaccine and antiviral candidates. Yet, staying scientifically current also means continuous surveillance, testing and continuous reinvestment.
Why collaboration is the only way forward
No single organization can master every part of a CHIM program. Our partnership with the University of Antwerp (UAntwerp) and the Antwerp University Hospital (UZA) combines manufacturing with clinical and academic excellence. This collaboration ensures our RSV agent is not only clinically validated but also scientifically characterized down to the molecular level.
Building Europe’s CHIM hub
The outcome is more than a virus – it is capacity. By uniting GMP manufacturing, CHIM operations and academic partnerships in one ecosystem, we’ve built Europe’s largest platform for human challenge research. Belgium now stands as Europe’s emerging CHIM hub.
Our Clinical Pharmacology Unit in Edegem (Antwerp), offers 46 BSL-2+ quarantine beds, GMP-certified production and multidisciplinary clinical expertise (virologists, pharmacists, data scientists, infectious disease specialists). This ecosystem enables faster go/no-go decisions for RSV vaccine and antiviral candidates.
Curious why Antwerp has evolved into Europe’s CHIM hotspot? We unpack the structural, regulatory and scientific drivers in a separate article.
Closing thought
Perhaps it is unsurprising that only two RSV challenge models exist globally – and SGS owns the most recent one. Developing an RSV challenge agent is a test of endurance, precision and conviction.
It demands stamina to withstand many challenges, the technical and scientific expertise to produce a safe, infective virus, and above all, the collaborative mindset to bring it all together.
Beyond RSV, SGS has established challenge models for influenza, rhinovirus and malaria, further broadening our CHIM portfolio.
