Abstract 6029: 225Ac/89Zr labeled anti nectin 4 radioimmunoconjugates as theranostics against nectin 4 positive triple negative breast cancer

Abstract

Abstract Nectin4 (N4) is a biomarker that is overexpressed in ~62% of triple negative breast cancer (TNBC) and its lack of expression in normal tissues makes it an ideal target for the therapy and PET imaging of TNBC. Methods: We developed a fully human antibody against nectin 4 (anti N4) using phage display. Anti N4 was radiolabeled with 89Zr & 225Ac, respectively, for imaging & radiotherapy using TNBC xenograft & syngeneic mouse models. TNBC murine 4T1 cells were transduced with human N4 and N4 expression was confirmed by FACS. Biodistribution & PET imaging of 89Zr anti N4 radioimmunoconjugate (RIC) was studied in mice bearing N4 positive xenografts. Dosimetry of 225Ac anti N4 was studied in healthy mice & the therapeutic efficacy was evaluated for 90 days in mice bearing MDA MB 468 xenograft & transduced 4T1 syngeneic models. Mice were treated with 2 doses of 350 nCi administered at 10 days apart. Tumor growth was monitored by a digital caliper. Results: The pharmacokinetic profile of 89Zr-anti-N4 RIC showed biphasic distribution with a moderate elimination of 63 h. PET imaging & biodistribution of 89Zr anti N4 in mice bearing MDA MB 468 xenograft showed high tumor uptake of 13.2 ± 1.12 %IA/g at 120 h. 225Ac anti N4 was effectively internalized in MDA MB 468 and was cytotoxic to the cells with IC50 of 1.2 kBq/mL. Treatment with 225Ac anti N4 led to complete tumor remission in all mice bearing MDA MB 468 xenografts and 4T1 syngeneic model by day 20 and 28, respectively. Conclusions: 89Zr anti N4 was an effective PET imaging probe with specific uptake in tumor. 225Ac anti N4 was effective as a therapeutic agent resulting in complete remission of tumors in both mouse xenograft & syngeneic models. These results are promising for the development of anti-N4 RICs as theranostics for TNBC. Citation Format: Hanan Babeker, Fabrice Njotu, Jessica Ketchmen, Florence Tikum, Alireza Doroudi, Emmanuel Nwangele, Maruti Uppalapati, Humphrey Fonge. 225Ac/89Zr labeled anti nectin 4 radioimmunoconjugates as theranostics against nectin 4 positive triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6029.