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131I-Apamistamab Improves Outcomes in Patients 65 Years and Older with Relapsed or Refractory AML
Abstract   Peer reviewed

131I-Apamistamab Improves Outcomes in Patients 65 Years and Older with Relapsed or Refractory AML

Rajneesh Nath, Stuart Seropian, Boglarka Gyurkocza, Hannah Choe, Mark R. Litzow, Camille Abboud, Nebu Koshy, Patrick J. Stiff, Sunil H. Abhyankar, James Foran, …
Transplantation and cellular therapy, Vol.30(2 Supplement), pp.S54-S55
02/2024
DOI: 10.1016/j.jtct.2023.12.089

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Abstract

Older patients (pts) with relapsed or refractory acute myeloid leukemia (AML) have poor outcomes which have not improved over time. Only about 30% of AML pts aged 65 and older are offered treatment and the vast majority are not eligible for curative allogeneic hematopoietic cell transplant (HCT). Age as an independent risk factor for non-relapse mortality (NRM) exists in a continuum. 131I-apamistamab (Iomab-B), an anti-CD45 radioimmunoconjugate, safely delivers targeted radiation, allowing for myeloablation and eradication of leukemic cells. Iomab-B based conditioning can provide pts ≥65 years with access to HCT. Here we present the outcome analysis for pts ≥65 years old receiving Iomab-B led HCT. SIERRA (NCT02665065) was a multi-center, randomized, controlled phase 3 study comparing the efficacy of Iomab-B based conditioning versus physician's choice of Conventional Care (CC) in pts ≥55 years of age with active, r/r AML. Pts were randomized (1:1, N=153) to CC or Iomab-B with fludarabine and total body irradiation (2 Gy) followed by HCT. Primary endpoint was durable complete remission (dCR), defined as CR/CRp ≥6 mos. Pts not achieving CR/CRp in the CC arm could crossover (CO) to Iomab-B. A total of 153 pts were randomized (CC, n=77; Iomab-B, n=76). Forty-five pts ≥65 years received Iomab-B led HCT (Iomab-B=28; CO=17) while 9 pts ≥65 years in the CC arm received standard HCT. Baseline characteristics are shown in Table 1. Iomab-B pts ≥65 years represented a very high-risk population. 73.3% were primary induction failure, more than 90% in the intermediate or adverse cytogenetic risk group and nearly 70% having failed prior targeted therapy, 45% of which with a BCL2 inhibitor. 22% were TP53 positive. The CR/CRp rate of 62.2% and the dCR rate of 13.3% were markedly better in the Iomab-B pts compared to a CR/CRp rate of 33.3% and the dCR rate of 0% in the CC pts. These rates were also similar to the overall SIERRA population. Pts receiving Iomab-B based treatment were able to achieve a notably higher 1-year survival rate of 20.1% (95% CI: 9.7, 33.1) compared to 0% for CC pts (Figure 1). Safety was similar to the overall SIERRA population. Patients 65 years and older presented with multiple high-risk features such as primary induction failure (PIF), venetoclax failure and TP53 positivity which independently portend dismal outcomes. Both PIF and TP53 for Iomab B pts were double in frequency compared to the CC patients. Iomab-B was effective in improving outcomes despite advancing age and presence of these very high-risk features. In these pts, Iomab-B produced response rates and survival that were markedly better than the CC pts and approached that of historically comparable high risk AML subjects in remission. Iomab-B based conditioning was well-tolerated and provided access to HCT with curative potential in pts irrespective of advancing age and high-risk features.

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