Abstract B44: Optimization and IND enabling investigations of MVT-2163 (89Zr-DFO-5B1) leading to First-in-Human readiness

Abstract

Abstract Rationale: MVT-2163 (89Zr-DFO-5B1) — an anti-CA19.9 human monoclonal antibody formed via conjugation of the chelator desferoxamine (DFO) and radiolabeling with zirconium-89 (89Zr) — was recently reported to have excellent ability to delineate CA19-9 positive malignancies via PET imaging, including pancreatic cancer.(1) Additionally, preclinical studies have shown the antibody has antitumor properties alone(2) and, more recently, in combination with frontline chemotherapies such as nab-Paclitaxel and gemcitabine. Herein, we report the preclinical optimization and characterization of MVT-2163 that led to the recent approval of an IND application for first-in-human trials in patients with metastatic pancreatic cancer. Methods: The conditions for appending the chelator DFO to MVT-5873 (5B1) were optimized by screening various combinations of reaction pH, stoichiometric ratios of chelate to antibody, buffer type, and incubation times. The optimized conjugation strategy was used to prepare clinical grade DFO-5B1 that was subsequently radiolabeled with 89Zr to yield MVT-2163 for use in human subjects. The biodistribution was determined in healthy female, athymic nude mice at 1, 24, 48, 72, and 120h via gamma counting of resected tissues and comparison to standards. The normal-organ radiation doses were estimated for the 70-kg Standard Adult anatomic model using the time-dependent organ activity concentrations and total-body activities, and the Standard Adult mean organ dose and effective dose were calculated using OLINDA. The stability of MVT-2163 in formulation buffer and in human serum at 37°C was assessed (24, 48, 96, 120, and 168h) via thin layer chromatography and size exclusion chromatography. Additionally, the remaining immunoreactive fraction was determined at the same time points using an in vitro cellular binding assay with BxPC3 cells. Results: We found that the optimal conjugation strategy was to buffer exchange MVT-5873 into 100mM sodium bicarbonate buffer (pH9) prior to letting the DFO react at 32.5°C for 90m. Unincorporated DFO was removed by buffer exchanging the reaction mixture into 1M ammonium acetate (pH7) buffer. The final MVT-7686 (DFO-5B1) product was stored in long term storage at -80°C. Biodistribution of the MVT-2163 indicated tissue retentions that were within expected norms for a 89Zr-labeled antibody. The highest uptake at 120h in terms of percent injected dose per gram of tissue (%ID/g) was found in the bone, which is common for osteophilic radiometals such as 89Zr. Dosimetry calculations based on the biodistribution results predicted a total absorbed dose of 8.1 rem when accounting for the proposed accompanying low-dose CT scan. The absorbed doses to all organs were within acceptable limits at the proposed human study dose (5 mCi), and the absorbed dose in red marrow — which is often the dose-limiting factor — was within ranges predicted and observed with other 89Zr-radiolabeled antibodies in humans. The radiochemical purity data indicate that the tracer remains intact in formulation buffer up to 120 hours. Cell binding assays performed with multiple lots of the same material showed that the immunoreactivity remains above 75% when stored up to 120h at room temperature, indicating exemplary stability. The stability and immunoreactivity were slightly lower when incubated in human serum at 37°C. However, the data shows that the immunoreactivity is maintained in human serum for more than up to 168h. Conclusions: The stability studies in both formulation buffer and human serum indicate that MVT-2163 maintains sufficient radiochemical purity and immunoreactivity. The results of the reported studies support the proposed specifications and the excellent performance has resulted in MVT-2163 being accepted for first in human trials at MSKCC, which are set to begin in Q2 2016. 1. Viola-Villegas NT, et al. J Nucl Med. 2013;54(11):1876-82. 2. Sawada R, et al. Clin Cancer Res. 2011;17(5):1024-32. Citation Format: Jacob L. Houghton, Serge K. Lyashchenko, Ritsuko Sawada, Pat Zanzonico, Scott Rudge, Wolfgang W. Scholz, Paul Maffuid, Jason S. Lewis.{Authors}. Optimization and IND enabling investigations of MVT-2163 (89Zr-DFO-5B1) leading to First-in-Human readiness. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B44.