Acute myelogenous leukemia (AML) currently kills the majority of afflicted patients despite treatment with combination chemotherapy and allogeneic stem cell transplantation (SCT). Radiolabeled anti-CD45 monoclonal antibodies (Ab) have been shown to improve outcomes for AML in the setting of SCT, but toxicity remains high and cure rates are suboptimal. The objective of this research proposal is to maximize the cure rate of AML using a novel approach employing pretargeted radioimmunotherapy (PRIT) with genetically engineered bispecific antibodies.
In Aim 1, we will engineer, express, and purify anti-CD45 x anti-ligand bispecific Abs (scFv2-iFabs) that bind covalently and irreversibly to radiometal ligands.
In Aim 2, we will assess the binding characteristics of anti-CD45 x anti-ligand bispecific Abs (scFv2-iFabs) for CD45 antigen and for radiometal ligand chelates in vitro.
In Aim 3, we will compare and contrast the pharmacokinetics and biodistributions of pretargeted radioimmunotherapy using the novel molecularly engineered anti-CD45 x anti- ligand bispecific Abs (scFv2-iFabs) with our current gold standard method of PRIT using a streptavidin-biotin pretargeting method. Comparisons will be made in both an AML xenograft model and in a disseminated model of AML.
In Aim 4, we will compare and contrast the therapeutic efficacy of pretargeted RIT using the streptavidin-biotin approach with the novel bispecific anti-CD45 x anti-ligand bispecific antibody approach in both xenograft and disseminated AML models.
In Aim 5, we will investigate the toxicity and efficacy of combination therapy using anti-CD45 bispecific Ab pretargeting, with and without cytotoxic chemotherapy, in a disseminated model of human AML in SCID mice. We hypothesize that the novel bispecific """"""""pretargeted"""""""" RIT strategy defined in this proposal will amplify the amount of radiation delivered to AML cells, decrease the radiation delivered to the liver, lungs, and other normal organs, improve remission and cure rates, prolong survival, and markedly attenuate toxicities compared to conventional RIT and to streptavidin-biotin PRIT. We anticipate rapid translation of the results of these preclinical experiments into our clinical RIT program for AML.

Public Health Relevance

Acute myelogenous leukemia (AML) develops in 13,290 Americans and kills 8,820 of them each year despite treatment with chemotherapy and stem cell transplantation. In this project, we plan to improve the cure rate of AML by targeting radionuclides to the CD45 antigen expressed on AML using a new method called pretargeted radioimmunotherapy using bispecific antibodies. Although this grant is specifically focused on AML, the treatment being developed can also be applied to other CD45- expressing malignancies, including other types of leukemia, myelodysplasia, and non-Hodgkin's lymphoma, that affect a total of more than 120,000 Americans each year. We anticipate that this approach will cure more patients and cause fewer toxicities than currently available therapies.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Radiation Therapeutics and Biology Study Section (RTB)
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Merritt, William D
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Fred Hutchinson Cancer Research Center
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Green, Damian J; O'Steen, Shyril; Lin, Yukang et al. (2018) CD38-bispecific antibody pretargeted radioimmunotherapy for multiple myeloma and other B-cell malignancies. Blood 131:611-620
Green, Damian J; Press, Oliver W (2017) Whither Radioimmunotherapy: To Be or Not To Be? Cancer Res 77:2191-2196
O'Steen, Shyril; Green, Damian J; Gopal, Ajay K et al. (2017) Venetoclax Synergizes with Radiotherapy for Treatment of B-cell Lymphomas. Cancer Res 77:3885-3893
Orozco, Johnnie J; Kenoyer, Aimee; Balkin, Ethan R et al. (2016) Anti-CD45 radioimmunotherapy without TBI before transplantation facilitates persistent haploidentical donor engraftment. Blood 127:352-9
Green, Damian J; Frayo, Shani L; Lin, Yukang et al. (2016) Comparative Analysis of Bispecific Antibody and Streptavidin-Targeted Radioimmunotherapy for B-cell Cancers. Cancer Res 76:6669-6679
Frost, Sofia H L; Frayo, Shani L; Miller, Brian W et al. (2015) Comparative efficacy of 177Lu and 90Y for anti-CD20 pretargeted radioimmunotherapy in murine lymphoma xenograft models. PLoS One 10:e0120561
Miller, Brian W; Frost, Sofia H L; Frayo, Shani L et al. (2015) Quantitative single-particle digital autoradiography with ?-particle emitters for targeted radionuclide therapy using the iQID camera. Med Phys 42:4094-105
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Green, Damian J; Shadman, Mazyar; Jones, Jon C et al. (2015) Astatine-211 conjugated to an anti-CD20 monoclonal antibody eradicates disseminated B-cell lymphoma in a mouse model. Blood 125:2111-9
Orozco, Johnnie J; Balkin, Ethan R; Gooley, Ted A et al. (2014) Anti-CD45 radioimmunotherapy with 90Y but not 177Lu is effective treatment in a syngeneic murine leukemia model. PLoS One 9:e113601

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