Surbhi Sidana, MD, Assistant Professor of Medicine (Blood and Marrow Transplantation and Cellular Therapy), Stanford University, Stanford, California, discusses a phase 2 study of the combination regimen MGTA-145 plus plerixafor for same-day hematopoietic stem cell (HSC) mobilization for autologous transplant in patients with multiple myeloma (MM); these data were presented at the virtual 2021 American Society of Clinical Oncology (ASCO) Annual Meeting.

Transcript

Hi, I'm Surbhi Sidana. I'm an assistant professor at Stanford University.

Stem cell transplant is an important therapy in patients with multiple myeloma. As part of stem cell transplant we need to, as the first step, collect adequate stem cells. Currently, it's collected 2 ways, either by using G-CSF with plerixafor, either on demand or in every patient, or using chemotherapy-based mobilization.

Chemotherapy-based mobilization can take several weeks, 2 to 3 weeks, and even with G-CSF based methods it can take anywhere from 5 to 8 days. We have this new drug called MGTA-145, which has very strong preclinical data and data in healthy volunteers which shows that we can collect stem cells on the same day as we give them.

This is field changing.

So far, we've had to have patients mobilize with several days of G-CSF and then go to collection. The idea that we can mobilize on the same day and collect that afternoon is quite novel. Because we had strong preclinical and healthy volunteer data, we decided to go ahead and design this trial in patients with multiple myeloma.

This is phase II study with a combination of MGTA-145, which is an investigational drug, with plerixafor to mobilize stem cells rapidly in patients with myeloma. This was for same day mobilization and collections. Patients receive plerixafor followed 2 hours later by MGTA-145 as an infusion over 3 to 10 minutes. This was followed by apheresis within 30 minutes. Patients could come back for a second day of mobilization and collection. In the first day, collection was less than 6 million CD34+ cells per kg. Then, they went on to transplant for routine institutional guidelines and were followed for up to 100 days.

What we found in the study was, and this is preliminary data, that 100 percent of the patients met the primary endpoint of collecting enough cells to proceed with the transplant, which is 2 million CD34+ cells per kg. Ninety percent of patients met the secondary endpoint of collecting 4 million CD34+ cells per kg. 80 percent of patients met the endpoint of collecting 6 million CD34+ cells per kg.

MGTA-145 was very well tolerated in combination with plerixafor. The most common side effect was acute onset bone pain, which happened a few minutes after MGTA-145, lasted about 5 to 6 minutes, and resolved without intervention in all patients.

What we found is this that this is a regimen which effective with preliminary data—the study's still ongoing—and safe. Therefore, once we complete the study, if the results hold out, the next step would be to develop this into an advanced stage clinical trial and compare it with standard of care regimens.

When we see the results of that, this could potentially be a G-CSF-free regimen for both autologous as well as allogeneic stem cell transplant. We need to see the results of this bear out as the study completes and then compare them to standard of care regimens.

The trial is currently ongoing, but we are close to finishing accrual. Once that happens, we will decide our next step in terms of an advanced trial or accruing more patients to a phase 2 trial.

This is a very exciting drug for our patients because the main thing this is trying to overcome is, one, the time that patients spend in a hospital. A lot of patients are referred to our transplant center, which can be several hours from home. This can cut down the time they're away from home by several days. The second is there's a lot of other side effects associated with current mobilization regimens. Even with G-CSF based regimen it can lead to pain and especially patients that are collecting for 5 to 8 days a significant portion of patients can have a lot of bone pain associated with it.

If we can decrease that and shorten the time that patients need to be at a referral center, this could be a major advance.