Abstract 5329: Pt(IV)-M13, a blood-brain-barrier penetrant macrocyclic peptide-platinum(IV) conjugate, leads to enhanced drug uptake and efficacy in murine glioblastoma models
Authors: Jimenez-Macias Jorge-Luis , Lee Yen-Chun , Finkelberg Tomer , Berger Gilles , Nowicki Michal , Cho Choi-Fong , Fedeles Bogdan , Loas Andrei , Penetelute Brad , Lawler Sean E. 
Published: June 2022

INTRODUCTION. Glioblastoma is the most aggressive primary malignant brain tumor and has a median survival of approximately 15 months. Treatment is hindered by the blood-brain barrier (BBB) that restricts entry of the vast majority of cancer therapeutics to the brain. We have designed a peptide-drug conjugate, (Pt(IV)-M13), comprised of M13, a perfluoroaryl-stapled cell-penetrating peptide, covalently linked to Pt(IV) via an amide bond. Upon intracellular reduction the Pt(IV) prodrug releases active cisplatin eliciting DNA damage and cell death. To investigate the properties of Pt(IV)-M13 in detail, we determined in vitro cell killing, platinum brain accumulation, biodistribution, and efficacy in mouse models.

METHODS. Pt(IV)-M13 tumor cytotoxicity was assessed in vitro using standard approaches. In vivo platinum levels were measured in the brain by ICP-MS, and BBB penetration assessed through a multicellular 3D in vitro BBB model, and biodistribution to peripheral organs was determined. Toxicity from bi-weekly injections of the Pt(IV)-M13 platinum conjugate was monitored from 5mg/kg to 30mg/kg. Animal survival was determined in a glioblastoma xenograft model. DNA damage was quantified by γH2AX staining.

RESULTS. Pt(IV)-M13 possesses in vitro tumor cell killing effects similar to cisplatin and Pt(IV) alone. Pt(IV)-M13 showed increased BBB penetration when compared to cisplatin in our in vitro BBB spheroid model (&gt;20-fold), in brain tissue (7-fold) and glioblastoma tumor-bearing mice (8-fold). Five hours after intravenous injection, biodistribution of platinum delivered by Pt(IV)-M13 was higher than cisplatin in the spleen, but lower in the heart. Bi-weekly injections of Pt(IV)-M13 were well-tolerated in nude mice to at least 15mg/kg, three times the reported cisplatin MTD. Finally, Pt(IV)-M13 treatment increased survival in a murine glioblastoma xenograft model (median survival= 33 days for Pt(IV)-M13 vs. 22.5 days for cisplatin and 24 days Pt(IV) alone. Elevated γH2AX foci were observed in Pt(IV)-M13 treated mice providing direct support for the improved delivery of cisplatin to brain tumors using this approach.

CONCLUSION. Pt(IV)-M13 leads to enhanced BBB penetration and cisplatin accumulation in glioblastoma models, with consequent animal survival benefit. Overall, our data support further investigation and development of Pt(IV)-M13 for glioblastoma treatment. Future studies will include additional glioblastoma models, and further optimization of this approach.

Citation Format: Jorge-Luis Jimenez-Macias, Yen-Chun Lee, Tomer Finkelberg, Gilles Berger, Michal Nowicki, Choi-Fong Cho, Bogdan Fedeles, Andrei Loas, Brad Penetelute, Sean E. Lawler. Pt(IV)-M13, a blood-brain-barrier penetrant macrocyclic peptide-platinum(IV) conjugate, leads to enhanced drug uptake and efficacy in murine glioblastoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5329.