Donald Metcalf: The Scientist Who Discovered G-CSF
Donald Metcalf and the Mysterious Molecule That Made Blood Stem Cell Donation Possible
On July 1st, 2011 — my first day at WEHI — the third person I met was Don Metcalf, right after Rosie the receptionist, who'd called my then-supervisor Ben to come pick me up. Ben introduced me to Don as a new postdoc from South Korea. Don asked me "whereabouts," meaning what region of South Korea I was from. I must have been so nervous that I completely misunderstood the question — as if he'd asked me where South Korea was — and I just repeated it back: "Where is South Korea?"Both Ben and Don burst out laughing.
That was my first encounter with the man whose legacy this story is really about. Professor Donald Metcalf AC (26 February 1929 – 15 December 2014) was an outstanding medical researcher whose discovery of colony-stimulating factors has benefited more than 20 million people worldwide.
Most people who register as a blood stem cell donor never think much about the small daily injections that make modern donation possible. But behind that simple pre-donation routine sits one of the great detective stories in twentieth-century medicine — a decades-long hunt for an invisible signal that tells the body to make more white blood cells. That signal is called granulocyte colony-stimulating factor, or G-CSF, and its discovery quietly transformed both cancer treatment and the entire practice of stem cell transplantation.
An Odd Observation in a Petri Dish
The story begins in Melbourne, Australia, in 1965. A researcher named Ray Bradley, working at the University of Melbourne, noticed something odd while growing bone marrow cells in agar culture: under certain conditions, the cells didn't just sit there — they organized themselves into distinct colonies. It wasn't what he set out to find, but it was a clue that something in the culture environment was actively instructing these cells to grow and multiply.
That observation caught the attention of Donald Metcalf, a researcher at the Walter and Eliza Hall Institute of Medical Research (WEHI) who would go on to be described as the father of modern haematology. Metcalf abandoned his existing research on the thymus and devoted essentially the rest of his career to chasing down the mysterious factors responsible for this colony-forming behavior. Around the same time, on the other side of the world, researchers Yasuo Ichikawa, Dov Pluznik, and Leo Sachs at the Weizmann Institute of Science in Israel were independently converging on similar findings.
Naming the Family
Through the late 1960s and 1970s, Metcalf and colleagues at WEHI established that the substances driving this cell growth — dubbed colony stimulating factors (CSFs) — were present in the blood and urine, and that their levels rose during infection. This was itself an important insight: it suggested the body has a built-in feedback system for ramping up white blood cell production exactly when it's needed most, such as when fighting off an infection.
Over time, researchers characterized several distinct members of this CSF family, each nudging different blood cell lineages to grow: M-CSF, GM-CSF, multi-CSF, and G-CSF. Isolating and purifying any one of them from biological fluids was a punishing task — the factors existed in vanishingly small quantities, and years of painstaking biochemistry were needed just to get workable amounts for study. GM-CSF was the first to be purified, in 1977, after roughly eleven years of effort. Then, in 1983, a research team led by Nicos Nicola within Metcalf's WEHI lab isolated the specific factor that stimulated neutrophil-forming colonies — G-CSF itself.
From the Lab Bench to the Clinic
The real turning point came with the ability to clone the G-CSF gene, which allowed the factor to be mass-produced using recombinant DNA technology rather than painstakingly extracted from natural sources. Cloned GM-CSF and G-CSF became available around 1984, and clinical trials followed quickly. One of the earliest and most publicized recipients of CSF therapy, in 1987, was the world-renowned tenor José Carreras, who was fighting acute myeloid leukemia at the time.
What made G-CSF (marketed under brand names like Neupogen, using the drug name filgrastim) so clinically valuable was straightforward: cancer chemotherapy tends to wipe out the bone marrow's ability to produce white blood cells, leaving patients dangerously vulnerable to infection. G-CSF could coax the bone marrow into rebuilding that supply faster, shortening the most dangerous window of a patient's treatment. It remains, decades later, one of the most widely used supportive-care drugs in all of oncology.
An Unexpected Second Act: Mobilizing Stem Cells
G-CSF's story might have ended there, as a valuable but fairly narrow tool for boosting neutrophil counts after chemotherapy. Instead, it took on a second, arguably even more consequential role.
Researchers discovered that G-CSF doesn't just stimulate the bone marrow to produce more blood cells locally — it also has the ability to coax hematopoietic stem cells, the master cells that give rise to all blood cell types, out of the bone marrow and into the general bloodstream. This phenomenon, called mobilization, works in part by suppressing a signaling molecule (CXCL12) that normally keeps stem cells anchored inside the marrow.
At WEHI, physician-researcher George Morstyn, working with Uli Dührsen, made a discovery in this space that quietly changed bone marrow transplantation worldwide: that peripheral blood, once flooded with mobilized stem cells, could serve as a source for stem cell collection in its own right — no bone marrow harvest required.
How Peripheral Blood Stem Cell Donation Works Today
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This discovery is the reason that most stem cell donations today don't involve a surgical bone marrow harvest at all. Instead, the process — known as a peripheral blood stem cell (PBSC) donation — typically looks like this:
- Mobilization. For about four to six days before donation, the donor receives daily injections of G-CSF (filgrastim), usually self-administered or given at a clinic. This drives hematopoietic stem cells out of the bone marrow and into general circulation.
- Apheresis. On the day of donation, the donor is connected to a cell-separator machine through a needle in each arm. Blood is drawn from one arm, passed through the machine, which spins out and collects the stem cells, and the remaining blood components are returned to the donor through the other arm. The whole session typically takes several hours and may be repeated over one or two days if needed.
- Recovery. The body replenishes the collected stem cells naturally within a couple of weeks. Common side effects of the G-CSF injections include bone pain, headache, and muscle aches, usually manageable with over-the-counter pain relief and resolving quickly after donation.
Because PBSC donation avoids general anesthesia and a surgical procedure, it has become the dominant method of stem cell collection for transplantation worldwide, largely displacing traditional bone marrow harvesting from the hip bone for adult donors — though marrow donation is still used in some circumstances, including for certain pediatric recipients.
A Discovery That Keeps Paying Dividends
What's striking about the G-CSF story is how far it traveled from its starting point. A researcher noticing an odd pattern in a petri dish in 1965 led, decades later, to a drug that helps cancer patients survive chemotherapy, and — almost as a side effect of understanding how that drug worked — to an entirely new, far gentler way of collecting the stem cells that make bone marrow and blood cancer transplants possible. It's a good reminder that some of medicine's biggest practical breakthroughs begin as basic scientists simply following an unexpected observation wherever it leads.
This post is for general informational purposes and isn't medical advice. Anyone considering stem cell donation, or currently receiving G-CSF as part of cancer treatment, should talk with their own healthcare team about what to expect.