Biodistribution and PK of ⁹⁰Y-DOTA–biotin using CD38-bispecific PRIT. Athymic nude mice (n = 5 per group) bearing H929 (MM) xenografts (10⁷ cells injected in the right flank) were injected at −24 hours with 2.8 nM pretargeting Ab (either CD38 bispecific = 028-C825, or control bispecific [targeting CD20] = 2H7-C825), then at −1 hour with CA, and at 0 hours with ⁹⁰Y-DOTA–biotin. (A) Blood, tumor, and normal organ specimens were taken 24 hours after radioactivity injections. (B-C) Comprehensive tissue biodistributions were obtained at sequential time points 6, 24, 48, and 120 hours after ⁹⁰Y-DOTA–biotin injection, using (B) CD38 or (C) control bispecific PRIT. The panel C description also applies to nontarget tissues in panel B. Error bars = 1 SEM.