Gimatecan and other camptothecin derivatives poison Leishmania DNA-topoisomerase IB leading to a strong leishmanicidal effect

Abstract

The aim of this work is the in vitro and ex vivo assessment of the leishmanicidal activity of camptothecin and three analogues used in cancer therapy: topotecan (Hycantim®), gimatecan (ST1481) and the pro-drug irinotecan (Camptosar®) as well as its active metabolite SN-38 against Leishmania infantum. The activity of camptothecin and its derivatives was studied on extracellular L. infantum infrared-emitting promastigotes and on an ex vivo murine model of infected splenocytes with L. infantum fluorescent amastigotes. In situ formation of SDS/KCl precipitable DNA-protein complexes in Leishmania promastigotes indicated that these drugs are DNA topoisomerase IB poisons. The inhibitory potency of camptothecin derivatives on recombinant L. infantum topoisomerase IB was assessed in vitro showing that gimatecan is the most active compound preventing the relaxation of supercoiled DNA at submicromolar concentrations. Cleavage equilibrium assays in Leishmania topoisomerase IB show that gimatecan changes the equilibrium towards cleavage at much lower concentrations than the other camptothecin derivatives and that this effect persists over time. Gimatecan and camptothecin were the most powerful compounds preventing cell growth of free-living L. infantum promastigotes within the same concentration range. All these compounds killed L. infantum splenocyte-infecting amastigotes within the nanomolar range. The amastigote form showed higher sensitivity to topoisomerase IB poisons (with high therapeutic selectivity indexes) than free-living promastigotes. All the compounds assayed poisoned L. infantum DNA topoisomerase IB leading to a strong leishmanicidal effect. Camptothecin derivatives are suitable for reducing the parasitic burden of ex vivo infected splenocytes. The selectivity index of gimatecan makes it a promising drug against this neglected disease

PEGylated Dendritic Polyglycerol Conjugate Delivers Doxorubicin to the Parasitophorous Vacuole in Leishmania infantum Infections

“…In free DOX treated cells, nuclei showed a 15‐fold higher fluorescence level than PG‐DOX(pH)‐PEG treated cells, confirming that our nanoparticle avoids drug deposition in the nuclei. The accumulation of free DOX in nucleus or mitochondria is a major drawback of this drug as well as of other drugs, such as the topoisomerase‐I poisoning derivatives (camptothecin derivatives and indenoisoquinolines) that have shown to be active against intracellular‐leishmania amastigotes but are highly toxic to host cells …”

Antileishmanial Activity of Semisynthetic Lupane Triterpenoids Betulin and Betulinic Acid Derivatives: Synergistic Effects with Miltefosine

“…Inhibitors of respiratory chain complexes were able to induce apoptotic cell death on the blood stream form of L. donovani [13]. Topoisomerase I poison camptothecin, promotes protein-DNA cleavable complex formation leading to apoptosis-like cell death in Leishmania donovani [14], [15]. Miltefosine, the latest antileishmanial drug introduced in the market and the first effective oral treatment of VL, was initially developed as an anticancer drug [16] and induce apoptosis-like cell death in Leishmania donovani [17].…”

Efficacy of a Binuclear Cyclopalladated Compound Therapy for Cutaneous Leishmaniasis in the Murine Model of Infection with Leishmania amazonensis and Its Inhibitory Effect on Topoisomerase 1B

“…It is well known that inhibition of DNA topoisomerases should affect mainly cell cycling cells such cancer cells (22, 56–59), but the toxicity assays performed here against the LM3 cells demonstrated that CP2 presents low selectivity for these cancer cells compared to Leishmania amastigotes, which could be indicative of the selectivity to the parasite's molecular target. It is worth noting that structural differences between human DNA topoisomerase I and Ld Topo1B might be the reason of the higher selectivity of CP2 to the parasite over the LM3 cells.…”