From Life-Saving Discovery to Drug Target: The Story of GM-CSF
๐ Available in: English | ํ๊ตญ์ด
From Life-Saving Discovery to Drug Target
The Story of GM-CSF
⏱ In 30 Seconds
- ✓ GM-CSF was first discovered as a growth factor that supports the production and function of white blood cells.
- ✓ It later became clear that GM-CSF also changes how macrophages, monocytes and other immune cells behave during inflammation.
- ✓ This led scientists to develop antibodies that block GM-CSF or its receptor in diseases such as rheumatoid arthritis.
- ✓ The story shows how the same biological pathway can help patients in one setting but become a therapeutic target in another.
When Australian scientist Professor Don Metcalf and his colleagues first discovered granulocyte-macrophage colony-stimulating factor (GM-CSF), together with other colony-stimulating factors such as G-CSF, they believed they had identified another growth factor involved in white blood cell production.
For years, that assumption appeared to be correct. GM-CSF was viewed primarily as a molecule that stimulated the bone marrow to produce granulocytes and macrophages, helping patients recover their immune cells after chemotherapy or bone marrow transplantation.
Its clinical potential was striking. World-renowned tenor Josรฉ Carreras recovered from leukaemia after participating in a pioneering clinical trial involving GM-CSF, illustrating how a discovery in blood-cell biology could become part of life-saving medical care.
But science rarely follows a straight line. As researchers continued studying GM-CSF, they began to notice something unexpected.
In many inflammatory diseases, the problem was not just the number of immune cells. Their behaviour had also changed.
They survived longer, produced more inflammatory cytokines, recruited additional immune cells and helped sustain chronic inflammation. Researchers gradually realised that GM-CSF was doing more than supporting immune-cell production. It was also changing how those cells behaved during inflammation.
That realisation changed the scientific story of GM-CSF completely.
The Master Switch of Inflammation
GM-CSF does far more than activate a single immune pathway. It can reshape the behaviour of macrophages, monocytes, dendritic cells and neutrophils, coordinating a much broader inflammatory response.
Rather than acting as one soldier on the battlefield, GM-CSF behaves more like a battlefield commander. It can promote immune-cell survival, increase inflammatory cytokine production and strengthen communication between different parts of the immune system.
During infection or tissue injury, this response can be protective. But when GM-CSF activity becomes excessive or persists for too long, the same immune machinery can begin damaging healthy tissue.
Once scientists understood this, an obvious question emerged.
What if GM-CSF could simply be switched off?
Rheumatoid Arthritis Led the Way
One of the first diseases to seriously test this idea was rheumatoid arthritis (RA).
Patients with RA often have high concentrations of GM-CSF inside inflamed joints. Researchers found that GM-CSF can continually activate macrophages, causing them to release inflammatory cytokines such as TNF, IL-1 and IL-6.
Over time, these inflammatory signals contribute to the destruction of cartilage and bone. If GM-CSF sits upstream of several of these pathways, blocking it might interrupt the inflammatory cascade before much of the downstream damage occurs.
Instead of treating only the consequences of inflammation, doctors might be able to intervene closer to its source.
Building Anti-GM-CSF Medicines
Few discoveries in biomedical science have followed such an unexpected path. GM-CSF was first used to stimulate the immune system. Decades later, scientists began testing whether blocking the same molecule could treat inflammatory disease.
This idea led to the development of monoclonal antibodies designed either to neutralise GM-CSF itself or to block its receptor.
Several candidates progressed through preclinical research, including studies using carefully selected mouse models, before entering clinical trials, including:
- Namilumab — targeting GM-CSF
- Otilimab — targeting GM-CSF
- Lenzilumab — targeting GM-CSF
- Mavrilimumab — targeting the GM-CSF receptor
Not every development programme progressed to regulatory approval. Even so, these studies demonstrated that blocking GM-CSF could reduce inflammation in several immune-mediated diseases and helped establish the pathway as a legitimate therapeutic target.
Then Came COVID-19
The COVID-19 pandemic unexpectedly placed GM-CSF back in the global spotlight. Doctors observed that some critically ill patients were harmed not only by viral infection, but also by an immune response that had become dangerously overactivated.
This overwhelming inflammatory state was often described as a cytokine storm, and GM-CSF was identified as one of several cytokines that could contribute to this process.
Anti-GM-CSF antibodies therefore moved rapidly into clinical trials to test whether dampening the pathway could reduce severe lung inflammation. The results varied across different studies and patient groups.
Nevertheless, the pandemic demonstrated how decades of basic immunology research could be mobilised quickly during a global health emergency.
A Connection Back to WEHI
Years before the COVID-19 pandemic, researchers at the Walter and Eliza Hall Institute of Medical Research (WEHI) had already begun exploring this pathway in another inflammatory disease.
The findings suggested that abnormal GM-CSF production was not limited to rheumatoid arthritis or severe viral inflammation. It could also help explain why immune activation continues in some people after the original Group A Streptococcus infection has disappeared.
The study also found that hydroxychloroquine, a drug already used in inflammatory diseases such as rheumatoid arthritis, could suppress parts of this pathway in laboratory experiments.
These findings did not establish hydroxychloroquine as a treatment for acute rheumatic fever. They did, however, identify a possible direction for future drug-repurposing research and showed that the IL-1ฮฒ–GM-CSF pathway could be modified pharmacologically.
From Discovery to Therapy
When Don Metcalf discovered GM-CSF, few imagined that scientists would one day try to block the very molecule he had helped identify.
Yet this apparent contradiction reflects how biomedical science evolves. A comparable journey from fundamental biology to a targeted medicine can be seen in the Australian discovery story behind Venetoclax.
In some settings, increasing GM-CSF activity can be useful. In others, persistent GM-CSF signalling can contribute to disease.
That difference in context is what eventually turned a growth factor into a therapeutic target.
A Personal Note
Over the years, I have seen certain cytokines rise and fall in prominence in immunology. When a cytokine was found to have an important role in one disease, researchers naturally began looking for the same pathway in the diseases they studied. For a while, it could sometimes seem as though almost every immune-mediated disease was being explained by the same cytokine. IFN-ฮณ is one example I remember well.
I was therefore cautious when GM-CSF began attracting increasing attention as an inflammatory cytokine in autoimmune diseases. But in our study of acute rheumatic fever, we found a particularly strong GM-CSF response, including an IL-1ฮฒ-mediated expansion of GM-CSF-producing CD4 T cells.
That finding was what made GM-CSF personally interesting to me—not because it was the cytokine attracting attention at the time, but because our own data had unexpectedly pointed us in the same direction.
Continue Reading
- Donald Metcalf: The Scientist Who Discovered G-CSF
- How Australian Scientists Discovered a New Immune Pathway in Rheumatic Heart Disease
- WEHI's Three Lasker Award Winners: Discoveries That Changed Medicine
- How WEHI Scientists Are Helping Defeat Malaria: From Fundamental Discovery to New Treatments
This article is intended for general educational purposes. It does not provide medical advice, and the clinical status of individual therapies should be checked using current regulatory and trial information.
Comments
Post a Comment