Viagra and Plerixafor Bone Marrow Trasplants?

A study published today in the journal Stem Cell Reports suggests that a combination of two clinically approved drugs – Viagra and Plerixafor – efficiently and rapidly mobilizes blood stem cells from the bone marrow into the bloodstream in a mouse model.1

Hematopoietic stem cell transplantation

Each year, over 25,000 hematopoietic stem cell transplantations (HSCTs) are performed as a curative treatment for conditions such as lymphoma, leukemia, hemoglobinopathies, myelodysplastic and myeloproliferative syndromes.2 HSCs are characterized by their ability to self-renew and differentiate into all mature blood lineages. Their transplantation to treat the aforementioned syndromes involves replacing abnormal blood-forming stem cells with healthy cells.

As HSCs reside in the bone marrow, collecting them for transplants traditionally involved drilling into the hip bone and using a needle to extract cells directly. In modern medicine, it is now more common to obtain the cells from whole blood, using drugs to coax the stem cells to migrate from the bone marrow into the bloodstream.

The current regimen used to encourage stem cell mobilization is multi-day injections of the pharmacological agent granulocyte-colony stimulating factor, or G-CSF, prior to stem cell collection. Whilst this approach has proven effective in most cases, it is limited by adverse side effects such as fatigue, bone pain and nausea, and is expensive. Certain subpopulations of patients are also unable to tolerate this drug regimen, for example individuals who have undergone chemotherapy, elderly frail patients or individuals with sickle cell disease. Unfortunately, this means that bone marrow transplantation is not a viable option for them.

A second pharmacological agent, Plerixafor (AMD3100), also used to mobilize HSCs. However, used as a single agent, it is limited in its efficacy, and is commonly adopted as a salvaging agent when the G-CSF regimen fails.

Scientists are therefore directing research efforts towards improving the harvesting protocols for HSCs. Professor Camilla Forsberg, a stem cell biologist from the University of California Santa Cruz says, "Better harvesting protocols would significantly improve the success rate for current indications and open curative hematopoietic cell therapies to a wider spectrum of disorders."

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