Hi, I'm Jack Khouri. I'm a hematologist at the Cleveland Clinic in Cleveland, Ohio, and I'm here to talk to you about a phase two study that we participated in on a novel stem cell mobilizer called burixafor, in combination with a drug called propranolol and G-CSF for mobilization of stem cells before stem cell transplant for multiple myeloma.
Many of you know that stem cell transplant is still standard of care for multiple myeloma treatment. Currently, what we do before we go to stem cell transplant is we have to mobilize the stem cells. We have to get them out of the bone marrow into the bloodstream so that we can use a machine to collect them before the transplant itself.
The way we do that is with medications, currently injections. We have G-CSF, which is a growth factor for stem cells, and we have a class of medications called CXCR4 inhibitors that we use in combination with G-CSF.
We currently have two available medications from that class. There are burixafor, which we’ve had for a long time, and a new medication called motixafortide. They both do the same thing: they allow the stem cells to leave the bone marrow and get into the bloodstream so that we can collect them with a machine.
So far, the CXCR4 inhibitors that we have on the market are given the day before or the evening before we start collecting stem cells, which can be a little inconvenient for patients because they have to get an injection at 4 or 5 p.m., go home, and then start collecting the next morning. So that can be a little inconvenient.
The other thing is, the current stem cell mobilizers cause some side effects like diarrhea and infusion-related reactions, mostly with the most recent CXCR4 inhibitor, which is motixafortide. So we were still looking for safer, better tolerated alternatives from that class of medications.
The third point is that most of the medications we’re using right now for stem cell mobilization were not studied in the era of frontline daratumumab therapy. Many patients with myeloma now receive frontline daratumumab for induction before transplant. The drugs available for stem cell mobilization were not studied in this patient population, and some studies suggest that daratumumab may actually decrease stem cell mobilization, reducing the stem cell yield before transplant.
We wanted to study a novel agent called burixafor, which blocks CXCR4 in the bone marrow, in the era of frontline daratumumab. The cool thing about this drug is that mobilization of stem cells happens within the first hour after administration. It's given intravenously on the same day as collection, not the day before like current medications. One IV dose is given, and then 45 minutes later, collection starts, so patients don’t have to come the night before. The time burden is lower, and the kinetics of stem cell mobilization are faster.
We combined this drug in the study with a pill called propranolol, which is a beta blocker, commonly used for heart conditions. We also used G-CSF, which is a cornerstone of stem cell mobilization.
We enrolled 19 patients in this study and found that close to 90% collected enough stem cells—meaning 2 million or more—to proceed to transplant, in just two sessions of collection. More than 85% of patients who received frontline daratumumab were also able to collect enough stem cells to proceed to transplant.
The majority of patients were able to collect successfully without needing another mobilization and collection phase. The drug was really well tolerated. We did not see major infusion-related reactions. Only one patient had an infusion-related reaction, and only one patient had diarrhea, which is commonly seen with other CXCR4 inhibitors. The majority of side effects were low grade and not deemed related to the study drug.
This combination is novel: a pill, an injection, and an IV. More than 90% of patients achieved the needed number of stem cells to proceed with transplant. The safety profile was great, and the drug is given on the same day as cell collection, not the night before, making it more convenient for patients.
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HealthTree • December 20, 2025