Repurposing of antitumor drug candidate Quisinostat lead to novel spirocyclic antimalarial agents

Antimalarial chemotherapies endowed with effectiveness against drug-resistant parasites and good safety are urgently required in clinical. Our previous research revealed that clinical phase Ⅱ antitumor drug Quisinostat was a promising antimalarial prototype by inhibiting the activity of Plasmodium falciparum (P. falciparum) histone deacetylase (PfHDAC). Herein, 30 novel spirocyclic linker derivatives were designed and synthesized based on Quisinostat as lead compound, and then their antimalarial activities and cytotoxicity were systematically evaluated. Among them, compounds 8 and 27 could effectively eliminate wild-type and multi-drug resistant P. falciparum parasites, and display weakened cytotoxicity and good metabolic stability. Western blot assay demonstrated that they could inhibit PfHDAC activity like Quisinostat. In addition, both 8 and 27 showed certain antimalarial efficacy in rodent malaria model, and the animal toxicity of 8 was significantly improved compared with Quisinostat. Overall, 8 and 27 were structurally novel PfHDAC inhibitors and provided prospective prototype for further antimalarial drug research.