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Rapid Reduction of Peripheral Blasts in Older Patients with Refractory Acute Myeloid Leukemia (AML) Using Re-Induction with Single Agent Anti-CD45 Targeted Iodine (131I) Apamistamab [Iomab-B] Radioimmunotherapy in the Phase III SIERRA Trial.


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Rapid reduction of peripheral blasts in older patients with refractory acute myeloid leukemia (AML) using reinduction with single agent anti-CD45 targeted iodine (131I) apamistamab [Iomab-B] radioimmunotherapy in the phase III SIERRA trial.

Benjamin Tomlinson1, Vijay Reddy2, Mark S. Berger2, Jennifer Spross2, Renee Lichtenstein2, Boglarka Gyurkocza3

1 University Hospitals Case Medical Center, Cleveland, OH, 2Actinium Pharmaceuticals, New York, NY, 3 Memorial Sloan Kettering Cancer Center, New York, NY

Poster Number: AML-287

2019 SOHO Annual Meeting

September 11 – 14, 2019

Houston, Texas

The SIERRA trial is a prospective, randomized, phase 3, open-label, ongoing multicenter trial for patients aged ≥55 years with active, relapsed/refractory (R/R) AML evaluating allogeneic hematopoietic cell transplantation (HCT) versus conventional care (CC). Recent preliminary data demonstrated robust donor engraftment in all patients treated with Iomab-B (Agura et al, Blood 2018 132:1017) despite active disease.  Rapid peripheral blast clearance is predictive of CR and RFS after cytotoxic chemotherapy for AML (Elliot et al, Blood 2007 110:4172; Gianfaldoni et al, BJH 2006 134:54).  In the present study we characterize the anti-leukemic effect and rate of peripheral disease reduction by single-agent Iomab-B.

We hypothesize that successful engraftment following HCT may be related to myeloablation and anti-leukemic activity by single agent Iomab-B prior to RIC.

Patients are randomized to receive Iomab-B and HCT or to a CC therapy including approved targeted agents followed by HCT if in remission. Majority of patients (79%) in the CC arm did not achieve CR and the study allowed crossover to receive Iomab-B.

Data were evaluated for the first 25% of patients (N = 38).  29 patients received Iomab-B, either directly (N = 19) or via crossover (N = 10). Median baseline marrow blasts were 30% (4-74) for Iomab-B and 24% (6-70%) for CC, which increased to 45% (10-70%) at crossover. Peripheral blast data was available in 16 patients (Iomab-B 7, Crossover 9). By day 3 post-Iomab-B, blasts were reduced by 98% with 100% reduction by day 8 (assuming 0% blasts due to lack of differential at WBC 0.1).  All patients engrafted with ANC at a median of 13 days (9-22 days). Patients treated with hydroxyurea versus without were analyzed together as well as separately and showed similar results. One patient received hydroxyurea post-Iomab-B therapeutic infusion.

•Targeted radioimmunotherapy with single-agent Iomab-B rapidly decreases peripheral blasts by 98% by day 3 in chemotherapy refractory AML.
•Iomab-B conditioning leads to myeloablation in older patients with active disease (up to a median of 45% blasts in the marrow) as demonstrated by engraftment in all patients.
•Successful engraftment after Iomab-B and HCT benefits patients who had prolonged neutropenia due to active and refractory disease prior to transplant.
•While efficacy data is not yet available for these patients, rapid peripheral blast reduction is encouraging as prior studies utilizing cytotoxic chemotherapy suggest a relationship between the rate of disease reduction and disease response. Enrollment is ongoing.

For Questions or Comments Relating to the SIERRA Trial, Please Contact: [email protected]

For more information about the SIERRA Trial, Please Visit:   www.sierratrial.com


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