A Phase I Trial of First-in-Human Alpha-Emitter Astatine-211-Labeled Anti-CD45 Antibody (211At-BC8-B10) in Combination with Fludarabine and TBI As Conditioning for Allogeneic Hematopoietic Cell Transplantation (HCT) for Patients with Refractory/Relapsed Leukemia or High-Risk Myelodysplastic Syndrome (MDS): Preliminary Results of Dose Escalation

Astatine-211 based radionuclide therapy: Current clinical trial landscape

Astatine-211 (²¹¹At) has physical properties that make it one of the top candidates for use as a radiation source for alpha particle-based radionuclide therapy, also referred to as targeted alpha therapy (TAT). Here, we summarize the main results of the completed clinical trials, further describe ongoing trials, and discuss future prospects.

Where do we stand with radioimmunotherapy for acute myeloid leukemia?

INTRODUCTION

Despite the approval of several new drugs, deaths from acute myeloid leukemia (AML) remain common. Because of well-defined cell surface antigens, easy accessibility, and radiosensitivity of leukemia cells, there is long-standing interest in radiolabeled antibodies (radioimmunotherapy [RIT]) to complement or replace existing treatments and improve outcomes in AML.

AREAS COVERED

Targeting primarily CD33, CD45, or CD66, early RIT efforts have focused on β-emitters, including iodine-131 (¹³¹I) and yttrium-90, mostly to intensify conditioning therapy before allogeneic hematopoietic cell transplantation (HCT). An ¹³¹I-labeled CD45 antibody (Iomab-B [apamistamab-I131]) is currently studied in the registration-type phase 3 SIERRA trial (NCT02665065) for this purpose. Of growing interest as therapeutic payloads are α-particle emitting radionuclides such as actinium-225 (²²⁵Ac) or astatine-211 (²¹¹At) since they deliver substantially higher decay energies over a much shorter distance than β-emitters, rendering them more suitable for precise, potent, and efficient target cell killing while minimizing toxicity to surrounding bystander cells, possibly allowing use outside of HCT. Clinical efforts with ²¹¹At-labeled CD45 antibodies and ²²⁵Ac-labeled CD33 antibodies (e.g. ²²⁵Ac-lintuzumab [Actimab-A]) are ongoing.

EXPERT OPINION

A first anti-AML RIT may soon become available. This might propel further work to develop RIT-based treatments for AML, with many such efforts already ongoing.

Effectiveness of allogeneic hematopoietic cell transplantation for older patients with acute myeloid leukemia

Outcomes with conventional chemotherapy for older patients with acute myeloid leukemia (AML) remain disappointing, with few cures. For younger patients with AML, allogeneic hematopoietic cell transplantation (HCT) offers the best chance for cure, but this strategy is seldomly used for older patients. With recently improved methodologies, transplantation has become increasingly safe, suggesting that its use in older patients be reconsidered. This report will address four issues: the current frequency of transplantation for AML according to patient age; the impact of patient age on transplant outcomes; the comparative outcomes of transplantation versus chemotherapy for older patients with AML; and possible methods to improve the outcome of allogeneic HCT in older patients with AML.