Synthesis and Characterization of Transferrin Receptor-Targeted Peptide Combination SN-38 and Rucaparib Conjugate for the Treatment of Glioblastoma

<b>Background/Objectives:</b> Glioblastoma represents a particularly aggressive and fatal type of brain tumor. Peptide-drug conjugates, which offer the promise of traversing the blood-brain barrier to selectively accumulate in tumor tissues and precisely target cancer cells, are an active area of research. We present the synthesis and characterization of the T7 peptide (HAIYPRH) as a targeting ligand for the transferrin receptor, which is highly expressed on both the blood-brain barrier and glioma cells. <b>Methods</b>: Using the T7 peptide, the synthesis, characterization, and biological evaluation of a transferrin receptor-targeted, combination SN-38 and rucaparib peptide drug conjugate (T7-SN-38-rucaparib) are described. <b>Results</b>: The T7 peptide drug conjugate readily cleaved in the presence of exogenous cathepsin B, releasing the active drug payloads. In vitro experiments demonstrated potent cytotoxic effects of the T7 peptide drug conjugate on glioblastoma cells (IC₅₀ = 22.27 nM), with reduced toxicity to non-cancerous HEK 293 cells (IC₅₀ = 115.78 nM), indicating selective toxicity toward cancer cells. Further investigations revealed that blocking transferrin receptors with drug-free T7 peptide significantly reduced the conjugate's cytotoxicity, an effect that could be reversed by introducing exogenous cathepsin B to the cells. <b>Conclusions</b>: These findings highlight the potential of glioblastoma-targeted delivery of SN-38 and rucaparib based on specific recognition of the transferrin receptor for transport across the blood-brain barrier, offering the prospect of reduced toxicity and selective killing of cancer cells. Additionally, since rucaparib does not cross the blood-brain barrier, this work is significant to facilitate the use of rucaparib for the treatment of brain tumors.