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CD38 bispecific antibody pretargeted radioimmunotherapy for multiple myeloma and other B cell malignancies

Damian J. Green, Shyril O'Steen, Yukang Lin, Melilssa L. Comstock, Aimee L. Kenoyer, Donald K. Hamlin, D. Scott Wilbur, Darrell R. Fisher, Margaret Nartea, Mark D. Hylarides, Ajay K. Gopal, Theodore A. Gooley, Johnnie J. Orozco, Brian G. Till, Kelly D. Orcutt, K. Dane Wittrup and Oliver W. Press

Key points

  • A novel bispecific antibody against CD38 eradicates multiple myeloma and non-Hodgkin lymphoma tumors in murine models.

  • CD38 bispecific antibody pretargeting addresses limitations associated with radioimmunotherapy.

Abstract

Pretargeted radioimmunotherapy (PRIT) has demonstrated remarkable efficacy targeting tumor antigens, but immunogenicity and endogenous biotin blocking may limit clinical translation. We describe a new PRIT approach for the treatment of Multiple Myeloma (MM) and other B cell malignancies, for which we developed an anti-CD38 bispecific fusion protein that eliminates endogenous biotin interference and immunogenic elements. In murine xenograft models of MM and non-Hodgkin lymphoma (NHL), the CD38 bispecific construct demonstrated excellent blood clearance and tumor targeting. Dosimetry calculations showed a tumor absorbed dose of 43.8 Gy per mCi injected dose of yttrium-90, with tumor-to-normal organ dose ratios of 7:1 for liver and 15:1 for lung and kidney. In therapy studies, CD38 bispecific PRIT resulted in 100% complete remissions (CR) by day 12 in MM and NHL xenograft models, ultimately curing 80% of mice at optimal doses. In direct comparisons, efficacy of the CD38 bispecific proved equal or superior to streptavidin (SA)-biotin-based CD38-SA PRIT. Each approach cured at least 75% of mice at the highest radiation dose tested (1200µCi), while at 600 and 1000µCi doses the bispecific outperformed the SA approach, curing 35% more mice overall (p < 0.004). The high efficacy of bispecific PRIT, combined with its' reduced risk of immunogenicity and endogenous biotin interference, make the CD38 bispecific an attractive candidate for clinical translation. Critically, CD38 PRIT may benefit patients with unresponsive, high-risk disease, because refractory disease typically retains radiation sensitivity. We posit that PRIT might not only prolong survival, but possibly cure MM and treatment refractory NHL patients.

  • Submitted September 26, 2017.
  • Accepted November 1, 2017.