The combination regimen of MGTA-145 plus plerixafor for same-day hematopoietic stem cell (HSC) mobilization for autologous transplant in multiple myeloma had 100% efficacy, according to research presented at the ASCO21 Virtual Scientific Program.

The phase 2, single-center study is evaluating HSC mobilization with MGTA-145 (GroβT), a CXCR2 agonist, plus plerixafor and same-day apheresis in patients with multiple myeloma. Investigators reported their interim analysis of 10 patients, including a safety cohort of the first 6 patients who completed the transplant.

Participants received plerixafor 0.24 mg/kg (0.16 mg/kg if renal dysfunction was present) subcutaneously, followed by 2 hours of MGTA-145 (0.03 mg/kg) IV for 3 to 10 minutes and apheresis within 30 minutes. Mobilization was repeated for a second day if the day 1 yield was <6 × 106 CD34+ cells/kg. The primary endpoint was collection of 2 × 106 CD34+ cells/kg.


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Participants’ median age was 63 years (range, 46-68), and 50% were female. Induction therapy was bortezomib, lenalidomide, and dexamethasone (VRD) in 7 patients and daratumumab plus VRD in 3 patients. The median induction duration was 4 months (range, 3-6 months) and the median lenalidomide exposure was 6 cycles.

The median total stem cell yield (CD34+ cells/kg × 106) was 7.1 (range, 3-16.2). The day 1 yield was 5.4 (range, 1.1-16.2) and the yield per apheresis session was 4 (range, 1.1-16.2).

The researchers found that 100% of patients met the primary endpoint of collecting adequate HSCs in <2 days of mobilization with apheresis to proceed to transplant (2 × 106 CD34+ cells/kg). The secondary endpoints of 4 and 6 × 106 CD34+ cells/kg in <2 days were met in 90% and 80% of participants, respectively.

MGTA-145 was well tolerated, according to the study authors. About 90% of patients had at least 1 adverse event (AE), 20% had grade 2 AEs, and 20% had grade 3 AEs, including worsening of baseline grade 3 anemia and hypocalcemia, all of which resolved.

The 6 patients in the safety cohort completed the transplant with melphalan 200 mg/m2. The patients had a median of 4.1 × 106 CD34+ cells/kg infused (range, 3.4-5.6 × 106 CD34+ cells/kg), and all engrafted timely, the researchers noted. The median time to neutrophil engraftment was 12 days, and the median time to platelet engraftment was 17 days.

Grafts with MGTA-145 with plerixafor demonstrated high enrichment for CD90+CD45RA in CD34+ cells, a CD34 subset of long-term engrafting HSCs (median 31% of CD34+ cells), according to the investigators. In addition, 67% of grafts were minimal residual disease–negative with next generation flow cytometry.

Disclosures: Some of the study authors declared affiliations with pharmaceutical companies. Please see the original reference for a full list of disclosures.

Read more of Hematology Advisor’s coverage of the 2021 ASCO Annual Meeting by visiting the conference page.

Reference

Sidana S, Bankova A, Hosoya H, et al. Phase 2 study of MGTA-145 + plerixafor for rapid and reliable hematopoietic stem cell (HSC) mobilization for autologous transplant in multiple myelomaJ Clin Oncol. 2021;39(suppl 15; abstr 8023). doi:10.1200/JCO.2021.39.15_suppl.8023