plerixafor
Meaning of plerixafor: A drug that works by cutting a tether, so stem cells released from the marrow can simply be drawn off through a vein.
Definition of plerixafor
Plerixafor is a drug given to push blood-forming stem cells out of the bone marrow and into the bloodstream, where they can be collected for a transplant. It works by blocking CXCR4, a receptor on the surface of those cells that acts as their anchor. It is given by injection under the skin, alongside a growth factor, and its effect appears within hours.
Why move stem cells into the blood?
A stem cell transplant needs a supply of the cells that rebuild blood, and those cells normally live packed inside the bone marrow. Harvesting them from there means an operation under anesthesia, with repeated needle punctures into the back of the hip bone. Collecting them from a vein instead is far gentler: blood is drawn through a machine that keeps the wanted cells and returns everything else. The only obstacle is that stem cells do not ordinarily circulate in useful numbers, so they must first be coaxed out.
How does it release them?
Marrow cells display a protein that stem cells grip through the CXCR4 receptor, and that grip is what keeps them at home. The drug occupies the receptor so the grip cannot form, the cells lose their hold and drift into the circulation. It is given the evening before collection, after several days of a growth factor that has already expanded the pool of stem cells available to move. The two are used together because each acts differently, and the combination frees far more cells than either alone.
Who is it used for?
| Setting | Reason it is added |
|---|---|
| Lymphoma before a transplant | Growth factor alone often yields too few cells |
| Myeloma before a transplant | Earlier chemotherapy has left the marrow slow to respond |
| A rare inherited immune disorder | The same receptor is overactive, trapping white cells in marrow |
Cells gathered this way are frozen, then returned after high-dose treatment has emptied the marrow, in what is called an autologous bone marrow transplantation even though the collection came from a vein. The harvested product is described as a peripheral stem cell graft for that reason. Reported effects are mostly mild and short lived: stinging at the injection site, loose stools, nausea and a light-headed feeling.
Used in a sentence
Plerixafor was added the night before collection after the first attempt yielded too few cells.
Good to know
Plerixafor mobilizes stem cells rather than treating cancer itself, and it is given with a growth factor rather than instead of one, because the two release cells by different routes.