PSA-Targeted Alpha-, Beta-, and Positron-Emitting Immunotheranostics in Murine Prostate Cancer Models and Nonhuman Primates
- 12 January 2021
- journal article
- research article
- Published by American Association for Cancer Research (AACR) in Clinical Cancer Research
- Vol. 27 (7), 2050-2060
- https://doi.org/10.1158/1078-0432.CCR-20-3614
Abstract
Purpose: Most patients with prostate cancer treated with androgen receptor (AR) signaling inhibitors develop therapeutic resistance due to restoration of AR functionality. Thus, there is a critical need for novel treatment approaches. Here we investigate the theranostic potential of hu5A10, a humanized mAb specifically targeting free PSA (KLK3). Experimental Design: LNCaP-AR (LNCaP with overexpression of wildtype AR) xenografts (NSG mice) and KLK3_Hi-Myc transgenic mice were imaged with Zr-89- or treated with Y-90- or Ac-225-labeled hu5A10; biodistribution and subcellular localization were analyzed by gamma counting, PET, autoradiography, and microscopy. Therapeutic efficacy of [Ac-225]hu5A10 and [Y-99]hu5A10 in LNCaP-AR tumors was assessed by tumor volume measurements, time to nadir (TTN), time to progression (TTP), and survival. Pharmacokinetics of [Zr-89]hu5A10 in nonhuman primates (NHP) were determined using PET. Results: Biodistribution of radiolabeled hu5A10 constructs was comparable in different mouse models. Specific tumor uptake increased over time and correlated with PSA expression. Treatment with [Y-90]/[Ac-225]hu5A10 effectively reduced tumor burden and prolonged survival (P <= 0.0054). Effects of [Y-98]hu5A10 were more immediate than [Ac-225]hu5A10 (TTN, P < 0.0001) but less sustained (TTP, P < 0.0001). Complete responses were observed in 7 of 18 [Ac-225]hu5A10 and 1 of 9 mice [Y-90]hu5A10. Pharmacokinetics of [Zr-89]hu5A10 were consistent between NHPs and comparable with those in mice. [Zr-89]hu5A10-PET visualized the NHP- prostate over the 2-week observation period. Conclusions: We present a complete preclinical evaluation of radiolabeled hu5A10 in mouse prostate cancer models and NHPs, and establish hu5A10 as a new theranostic agent that allows highly specific and effective downstream targeting of AR in PSA-expressing tissue. Our data support the clinical translation of radiolabeled hu5A10 for treating prostate cancer.Keywords
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Funding Information
- NIH (P30 CA008748, S10 RR020892-01, S10 RR028889-01)
- Commonwealth Foundation for Cancer Research, the Experimental Therapeutics Center
- Radiochemistry & Molecular Imaging Probe Core (P50-CA086438)
- NIH (R01CA166078, R01CA55349, P30CA008748, P01CA33049, F31CA167863)
- NCI (R01CA201035, R01CA240711, R01CA229893)
- MSKCC (P30 CA008748)
- SPORE in Prostate Cancer (P50 CA092629)
- Swedish Cancer Society (CAN 2017/559)
- Swedish Research Council (2016-02974)
- NCI (R01CA201035, R01CA240711, R01CA229893)
- DOD (W81XWH-18-1-0223)
- Prostate Cancer (P50 CA092131)
- NIH (P30 CA016042)
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