Iomab-B–led Allogeneic HSCT Leads to Durable Response in Relapsed, Refractory AML

In the phase III SIERRA trial, Iomab-B (¹³¹I-apamistamab)-led allogeneic hematopoietic stem cell transplantation (HSCT) led to an improved response compared with conventional care (CC) in older patients with active relapsed or refractory acute myeloid leukemia (AML). The findings were presented at the Society of Hematologic Oncology 2024 Annual Meeting.

In the multicenter SIERRA trial, patients were randomized 1:1 to Iomab-B–led allogeneic HSCT or the physician’s choice of CC. The study included patients aged ≥55 years. Patients received CC or Iomab-B with fludarabine and total body irradiation followed by allogeneic HSCT. The primary endpoint was durable complete response (dCR), which was defined as remission lasting at least 180 days from initial CR.

All 66 patients who received Iomab-B underwent allogeneic HSCT, compared with 14 patients who received CC. In the group of evaluable patients, 59 received Iomab-B and 64 received CC. Of that group, 44 (76.4%) patients in the Iomab-B group achieved an initial CR, compared with 4 (6.3%) in the CC group. The dCR rates were 22% versus 0% in the Iomab-B and CC groups, respectively (95% CI, 12.29–34.73; P<0.0001).

Median follow-up periods were 36.6 months and 43.6 months in the primary and subsequent cutoffs. At the January 2024 data cutoff, median overall survival rates in the Iomab-B and CC groups were 6.3 months (95% CI, 5.1–7.9) and 4.0 months (95% CI, 3.0–5.1), respectively (hazard ratio, 0.69; 95% CI, 0.49–0.97; P=0.0314).

Among the 13 evaluable patients who achieved dCR in the Iomab-B group, the 12-month and 24-month survival rates were 92.3% and 69.2%. The investigators reported that Iomab-B was well tolerated and led to lower rates of sepsis and mucositis than that observed in patients who received standard allogeneic HSCT.

“The Iomab-B–led regimen was well tolerated and provided access to potentially curative [allogeneic HSCT] in a patient population traditionally considered ineligible for transplant,” the investigators concluded.

Reference

Seropian S, Gyurkocza B, Nath R, et al. Long-term follow-up demonstrates ongoing efficacy benefit of ¹³¹I-apamistamab–led allogeneic hematopoietic cell transplantation in older patients with active, R/R AML in the phase 3 SIERRA trial. Abstract #AML-545. Society of Hematologic Oncology 2024 Annual Meeting; Sept. 4-7, 2024; Houston, Texas.