Pharmacokinetic Study of Rectal Artesunate in Children with Severe Malaria in Africa

Artesunate-Nanoliposome-TPP, a Novel Drug Delivery System That Targets the Mitochondria, Attenuates Cisplatin-Induced Acute Kidney Injury by Suppressing Oxidative Stress and Inflammatory Effects

Background

Acute kidney injury (AKI) is a syndrome, posing a substantial healthcare burden. The pathological basis of AKI is associated with inflammation and oxidative stress which cause additional damage to mitochondria. Artesunate (ATS) is a derivative of artemisinin isolated from Artemisia annua L. that is an effective treatment for malaria and favored for the prevention and treatment of kidney diseases. However, there are still challenges related to its efficacy, including poor water solubility, limited oral bioavailability and short half-life. Liposome-based nanoparticles are used for drug delivery due to their ideal biocompatibility and their ability to improve the bioavailability of specific drugs and enhance drug efficacy.

Methods

In this study, a novel TPP-based natural ATS-nanoliposome, namely T-A-Ls, was applied for the treatment of AKI. ATS was encapsulated with or without triphenylphosphonium (TPP)-modified nanoliposomes. AKI was induced by cisplatin in C57BL/6J mice and a cisplatin-induced injury model was generated in HK-2 cells in vitro. Blood urea nitrogen (BUN), serum creatinine (Scr) measurements and section staining were utilized to assess renal protective effect of T-A-Ls. Inflammatory-related factors and proteins were quantified via Elisa, Immunofluorescence and Western Blot (WB). The anti-mitochondrial oxidative stress effect of T-A-Ls was determined by ROS, JC-1 and oxygen consumption rate (OCR) kits. Immunohistochemistry and WB were conducted to measure associated protein expressions. In vivo biodistribution and the concentration of T-A-Ls in kidney were also explored.

Results

T-A-Ls exhibited good oxidative resistance, preferential renal uptake, mitochondrial targeting, and it ameliorated kidney injury in cisplatin-induced AKI mice. Mitochondrial dysfunction, ATP production and respiratory capacity were improved in damaged HK-2 cells; ROS content decreased while mitochondrial membrane potential recovered. T-A-Ls exerted renal protection by inhibiting inflammation and reducing oxidative stress; these effects were mediated by a downregulation in the expression of RAGE and iNOS and an upregulation in both Nrf2 and HO-1.

Conclusion

T-A-Ls could improve the delivery of ATS to the kidney, offering a promising avenue to treat AKI.

Evidence Based Optimal Dosing of Intravenous Artesunate in Children with Severe Falciparum Malaria

The majority of deaths from malaria are in young African children. Parenteral artesunate (ARS) is the first-line treatment for severe falciparum malaria. Since 2015, the World Health Organization has recommended individual doses of 3 mg/kg for children weighing < 20 kg. Recently, the US Food and Drug Administration (FDA) has challenged this recommendation, based on a simulated pediatric population, and argued for a lower dose in younger children (2.4 mg/kg). In this study, we performed population pharmacokinetic (PK) modeling of plasma concentration data from 80 children with severe falciparum malaria in the Democratic Republic of Congo who were given 2.4 mg/kg of ARS intravenously. Bayesian hierarchical modeling and a two-compartment parent drug-metabolite PK model for ARS were used to describe the population PKs of ARS and its main biologically active metabolite dihydroartemisinin. We then generated a virtual population representative of the target population in which the drug is used and simulated the total first-dose exposures. Our study shows that the majority of younger children given the lower 2.4 mg/kg dose of intravenous ARS do not reach the same drug exposures as older children above 20 kg. This finding supports withdrawal of the FDA's recent lower ARS dose recommendation as parenteral ARS is an extremely safe and well-tolerated drug and there is potential for harm from underdosing in this rapidly lethal infection.

Rectal artesunate suppositories for the pre-referral treatment of suspected severe malaria

In this Policy Forum article, James A. Watson and colleagues discuss recent guidelines relating to pre-referral treatment of suspected severe malaria with rectal artesunate suppositories in remote areas.

The CARAMAL study could not assess the effectiveness of rectal artesunate in treating suspected severe malaria

CARAMAL was a large observational study which recorded mortality in children with suspected severe malaria before and after the roll-out of rectal artesunate in Nigeria, Uganda and the Democratic Republic of the Congo. The results of CARAMAL have had a huge impact on public health policy leading to a World Health Organization moratorium on the roll-out of rectal artesunate. The conclusion reported in the abstract uses strong causal language, stating that "pre-referral RAS [rectal artesunate suppositories] had no beneficial effect on child survival". We argue that this causal interpretation of the study results is not justified. Data from the CARAMAL study inform chiefly on the strengths and weaknesses of referral systems in these three countries and do not inform reliably as to the beneficial effect of providing access to a known life-saving treatment.

Pioneer Use of Antimalarial Transdermal Combination Therapy in Rodent Malaria Model

We have previously reported 1,2,6,7-tetraoxaspiro [7.11]nonadecane (N-89) as a promising antimalarial compound. In this study, we evaluated the effect of transdermal therapy (tdt) of N-89 in combination (tdct) with other antimalarials as an application for children. We prepared ointment formulas containing N-89 plus another antimalarial drug, specifically, mefloquine, pyrimethamine, or chloroquine. In a 4-day suppressive test, the ED50 values for N-89 alone or combined with either mefloquine, pyrimethamine, or chloroquine were 18, 3, 0.1, and 3 mg/kg, respectively. Interaction assays revealed that N-89 combination therapy showed a synergistic effect with mefloquine and pyrimethamine, but chloroquine provoked an antagonistic effect. Antimalarial activity and cure effect were compared for single-drug application and combination therapy. Low doses of tdct N-89 (35 mg/kg) combined with mefloquine (4 mg/kg) or pyrimethamine (1 mg/kg) gave an antimalarial effect but not a cure effect. In contrast, with high doses of N-89 (60 mg/kg) combined with mefloquine (8 mg/kg) or pyrimethamine (1 mg/kg), parasites disappeared on day 4 of treatment, and mice were completely cured without any parasite recurrence. Our results indicated that transdermal N-89 with mefloquine and pyrimethamine provides a promising antimalarial form for application to children.

The wrongful indictment of pre-referral rectal artesunate further delays the roll-out of this lifesaving drug

Administering rectal artesunate suppositories to patients with severe malaria before they receive parenteral and oral consolidation therapy was found to reduce mortality more than a decade ago. The roll-out of rectal artesunate could combat the current global increase in malaria deaths. Instead, on Jan 27, 2022, WHO recommended a moratorium on the deployment of rectal artesunate and in doing so stopped the roll-out of a lifesaving intervention. This decision was based mainly on the results from an observational study that is part of a larger project being conducted in Nigeria, Uganda, and DR Congo. The Community Access to Rectal Artesunate for Malaria (CARAMAL) project was not set up to provide patient transport to referral health-care centres for parenteral artesunate administration or logistic support to assure the availability of parenteral and oral antimalarial consolidation therapy. Using a before-after study design, which is known to be prone to bias, the study found that case fatality rates of severe malaria increased instead of decreased after the roll-out of rectal artesunate. However, the study and its analysis have methodological flaws that provide an alternative explanation for study findings. Instead of further delaying the roll-out of rectal artesunate, there is an urgent need for a concerted effort to provide rectal artesunate as originally intended, where and when it is needed.

Pre-referral intranasal artesunate powder for cerebral malaria: a proof-of-concept study

Background

Malaria still kills young children in rural endemic areas because early treatment is not available. Thus, the World Health Organization recommends the administration of artesunate suppositories as pre-referral treatment before transportation to the hospital in case of severe symptoms with an unavailable parenteral and oral treatment. However, negative cultural perception of the rectal route, and limited access to artesunate suppositories, could limit the use of artesunate suppositories. There is, therefore, a need for an alternative route for malaria pre-referral treatment. The aim of this study was to assess the potential of intranasal route for malaria pre-referral treatment.

Methods

The permeability of artesunate through human nasal mucosa was tested in vitro. The Transepithelial Electrical Resistance (TEER) of the nasal mucosa was followed during the permeation tests. Beside, regional deposition of artesunate powder was assessed with an unidose drug delivery device in each nostril of a nasal cast. Artesunate quantification was performed using Liquid Chromatography coupled to tandem Mass Spectrometry.

Results

The experimental model of human nasal mucosa was successfully implemented. Using this model, artesunate powder showed a much better passage rate through human nasal mucosa than solution (26.8 ± 6.6% versus 2.1 ± 0.3%). More than half (62.3%) of the artesunate dose sprayed in the nostrils of the nasal cast was recovered in the olfactory areas (44.7 ± 8.6%) and turbinates (17.6 ± 3.3%) allowing nose-to-brain and systemic drug diffusion, respectively.

Conclusion

Artesunate powder showed a good permeation efficiency on human nasal mucosa. Moreover it can be efficiently sprayed in the nostrils using unidose device to reach the olfactory area leading to a fast nose-to-brain delivery as well as a systemic effect. Taken together, those results are part of the proof-of-concept for the use of intranasal artesunate as a malaria pre-referral treatment.

Loss of pro-apoptotic Bax and Bak increases resistance to dihydroartemisinin-mediated cytotoxicity in normoxia but not in hypoxia in HCT116 colorectal cancer cells

Tumor hypoxia is a major biological factor that drives resistance to chemotherapy and radiotherapy. We previously demonstrated that the pro-oxidative drug dihydroartemisinin (DHA) efficiently targeted normoxic and hypoxic cancer cells. Although well studied in normoxia, the mechanism behind DHA-mediated cytotoxicity in hypoxia is insufficiently explored. Here, we analyzed the effect of DHA in HCT116 wild type (wt) cells and in HCT116 Bax^-/-Bak^sh cells with a defective intrinsic apoptosis pathway. Normoxic HCT116 wt cells underwent apoptosis shortly after treatment with DHA. Autophagy-associated cell death contributes to short-term cytotoxicity of DHA in normoxia. These cells switched to an apoptosis- and autophagy-independent cell death after treatment with DHA in hypoxia and displayed similar long-term survival in response to DHA in normoxia and hypoxia. In HCT116 Bax^-/-Bak^sh cells, DHA induced cell cycle arrest shortly after treatment irrespective of oxygen levels. Later, HCT116 Bax^-/-Bak^sh cells induced a delayed cell death after treatment with DHA in hypoxia followed by return to normoxia, while treatment with DHA in normoxia was hardly toxic. We identified lower glutathione levels in hypoxic HCT116 cells which correlated with higher lipid peroxidation after treatment with DHA. Moreover, insufficient expression of Bax/Bak counteracted hypoxia-mediated downregulation of mitochondrial function, thereby adding to DHA-induced ROS production and lipid peroxidation in hypoxia. In summary, DHA-mediated cytotoxicity in normoxia depended on Bax/Bak expression, while cytotoxicity after treatment with DHA in hypoxia was regulated independently of Bax/Bak in HCT116 colorectal cancer cells.