Targeting PARP-1 with Alpha-Particles Is Potently Cytotoxic to Human Neuroblastoma in Preclinical Models

Molecular Cancer Therapeutics

July 1, 2019
Makvandi M, Lee H, Puentes LN, Reilly SW, Rathi KS, Weng CC, Chan HS, Hou C, Raman P, Martinez D, Xu K, Carlin SD, Greenberg RA, Pawel BR, Mach RH, Maris JM, Pryma DA



Alpha-emitters can be pharmacologically delivered for irradiation of single cancer cells, but cellular lethality could be further enhanced by targeting alpha-emitters directly to the nucleus. PARP-1 is a druggable protein in the nucleus that is overexpressed in neuroblastoma compared with normal tissues and is associated with decreased survival in high-risk patients. To exploit this, we have functionalized a PARP inhibitor (PARPi) with an alpha-emitter astatine-211. This approach offers enhanced cytotoxicity from conventional PARPis by not requiring enzymatic inhibition of PARP-1 to elicit DNA damage; instead, the alpha-particle directly induces multiple double-strand DNA breaks across the particle track. Here, we explored the efficacy of [211At]MM4 in multiple cancers and found neuroblastoma to be highly sensitive in vitro and in vivo Furthermore, alpha-particles delivered to neuroblastoma show antitumor effects and durable responses in a neuroblastoma xenograft model, especially when administered in a fractionated regimen. This work provides the preclinical proof of concept for an alpha-emitting drug conjugate that directly targets cancer chromatin as a therapeutic approach for neuroblastoma and perhaps other cancers.