Therapeutic and Transmission-Blocking Efficacy of Dihydroartemisinin/Piperaquine and Chloroquine against Plasmodium vivax Malaria, Cambodia

Genomic complexity of parasites and vectors challenges malaria control in Southeast Asia

Southeast Asia is a uniquely complex region of malaria transmission that maintains an astounding level of species diversity among potential malaria vectors and also generates drug-resistant and quickly diverging populations of malaria parasites. All five human malaria species circulate in Southeast Asia with over 50 Anopheles species that vary in their ability to transmit these pathogens. The intricate relationships of these parasites and vectors are not well-understood. Human activity in Southeast Asian countries has created an increasingly fragmented landscape, bringing humans and mosquitoes into more frequent contact, sustaining malaria transmission in a region where few control tools are effective. Genomic shifts at the species, population, and individual level in parasites and vectors introduce variation that has produced drug- and insecticide resistance. The goal of this review is to highlight genomic studies of Southeast Asian malaria parasites and vectors that demonstrate how diversity in these organisms presents unique challenges and opportunities for global malaria control and eradication efforts.

Teles CB, Medeiros JF, Pereira DB, Vinetz JM, Gazzinelli RT, Araújo MS. Transmission-blocking activity of antimalarials for Plasmodium vivax malaria in Anopheles darlingi

Malaria is caused by parasite of the genus Plasmodium and is still one of the most important infectious diseases in the world. Several biological characteristics of Plasmodium vivax contribute to the resilience of this species, including early gametocyte production, both of which lead to efficient malaria transmission to mosquitoes. This study evaluated the impact of currently used drugs on the transmission of P. vivax. Participants received one of the following treatments for malaria: i) chloroquine [10 mg/kg on day 1 and 7.5 mg/kg on day 2 and 3] co-administered with Primaquine [0.5 mg/kg/day for 7 days]; ii) Chloroquine [10 mg/kg on day 1 and 7.5 mg/kg on day 2 and 3] co-administered with one-dose of Tafenoquine [300 mg on day 1]; and iii) Artesunate and Mefloquine [100 mg and 200 mg on day 1, 2 and 3] co-administered with Primaquine [0.5 mg/kg/day for 14 days]. Patient blood was collected before treatment and 4 h, 24 h, 48 h and 72 h after treatment. The blood was used to perform a direct membrane feeding assay (DMFA) using Anopheles darlingi mosquitoes. The results showed 100% inhibition of the mosquito infection after 4 h using ASMQ+PQ, after 24 h for the combination of CQ+PQ and 48 h using CQ+TQ. The density of gametocytes declined over time in all treatment groups, although the decline was more rapid in the ASMQ+PQ group. In conclusion, it was possible to demonstrate the transmission-blocking efficacy of the malaria vivax treatment and that ASMQ+PQ acts faster than the two other treatments.

Therapeutic efficacy of dihydroartemisinin-piperaquine for the treatment of uncomplicated Plasmodium vivax malaria in Seacha area, Arbaminch Zuria District, South West Ethiopia

BACKGROUND

Declining efficacy of chloroquine against Plasmodium vivax malaria has been documented in Ethiopia. Thus, there is a need to assess the efficacy of alternative schizontocidal anti-malarials such as dihydroartemisinin-piperaquine (DHA-PPQ) in P. vivax malaria-infected patients. This study was conducted to evaluate the therapeutic efficacy of DHA-PPQ drug in South West Ethiopia.

METHODS

This is a single-arm, prospective therapeutic efficacy study in patients with uncomplicated P. vivax malaria. The study was conducted from May 2021 to August 2021, based on the standard World Health Organization study protocol for surveillance of anti-malarial therapeutic efficacy. The study endpoint was adequate clinical and parasitological response on day 42.

RESULTS

A total of 86 patients with uncomplicated vivax malaria were enrolled. Of these, 79 patients completed the scheduled follow up; all showing adequate clinical and parasitological responses to day 42, with a successful cure rate of 100% (95% CI 96-100). Parasitaemias were cleared rapidly (86% by day 1 and 100% by day 3), as were clinical symptoms (100% by day 1). Gametocyte carriage decreased from 44% on Day 0 to 1% on day 1 and 0% on Day 2. Mean haemoglobin concentrations increased between day 0 (mean 12.2 g/dL) and day 42 (mean 13.3 g/dL). Treatment was well tolerated and no severe adverse events were observed.

CONCLUSION

In summary, treatment with DHA-PPQ demonstrated excellent efficacy for uncomplicated P. vivax, with no recurrences to day 42, and no safety concerns. This treatment, which is also effective against P. falciparum, appears to be an ideal alternative for P. vivax as part of the malaria elimination programme.

Dihydroartemisinin alleviates steatosis and inflammation in nonalcoholic steatohepatitis by decreasing endoplasmic reticulum stress and oxidative stress

Nonalcoholic steatohepatitis (NASH) is a severely inflammatory subtype of nonalcoholic fatty liver. Endoplasmic reticulum stress (ERS) and oxidative stress (OS) cause metabolic abnormalities, promote liver steatosis and inflammation, and are central to the development of NASH. Dihydroartemisinin (DHA) is a compound extracted from Artemisia annua that is often used in the treatment of malaria. Recent studies have shown that DHA also has a wide range of pharmacological effects, acting on various organs throughout the body to exert anti-inflammatory, antioxidant, and anti-fibrotic effects. In this study, we demonstrated in vitro that the anti-inflammatory effect of DHA is effective against NASH and reduces liver steatosis. DHA treatment decreased the synthesis of lipids, such as cholesterol and free fatty acids, and the expression of nuclear factor kappa-B. This is accomplished by inhibiting the unfolded protein response and reducing the production of reactive oxygen species, thereby inhibiting OS and ERS. This study reveals DHA's therapeutic effect and potential mechanism in NASH, implying that DHA could be a new and promising candidate for NASH therapy.

Structure-activity relationship study of dihydroartemisinin C-10 hemiacetal derivatives as Toll-like receptor 4 antagonists

Dihydroartemisinin (DHA), a natural product isolated from the traditional Chinese herb Artemisia annua and one of the clinical frontline drugs against malarial infections, has recently been discovered as a Toll-like Receptor 4 (TLR4) antagonist. However, the TLR4 antagonistic activity of DHA is modest and it exhibits cellular toxicity. In this work, the structure-activity relationship (SAR) of DHA as TLR4 antagonist was explored. Since destroying the sesquiterpene endoperoxide scaffold substantially compromised the TLR4 antagonistic activity and molecular dynamics analysis showed that the C-10 hydroxyl group formed a hydrogen bond with E72 of myeloid differentiation factor 2 (MD2) to prevent it moving deeper into MD2, SAR of DHA was focused on the C-10 hemiacetal position. With extending the length of the linear alkane chain at C10 position, the TLR4 antagonistic activity of DHA analogs increased first and then decreased with the best TLR4 antagonism occurring at the length of the carbon chain of 3-4 carbons. In contrast, the cellular toxicity of DHA analogs was raised with the increasing length of the linear alkane chain. The TLR4 antagonistic activity of DHA derivatives with substituted halogen as the terminal functional group decreased with the decrease of electronegativity of the substituted halogen, which implies the electron-rich functional group at the end of the alkane chain appears preferred. Therefore, DHA derivative 2k with alkynyl as the end functional group, exhibited 14 times more potent TLR4 antagonistic activity than DHA. Moreover, 2k showed less cellular toxicity than DHA. Cellular signaling characterizations indicated that 2k inhibited LPS-induced TLR4 dimerization and endocytosis and suppressed LPS-induced NF-κB but not MAPKs activation, culminating in blocking LPS-induced TLR4 signaling downstream pro-inflammatory factors NO and IL-1β. Further, 2k was active in vivo; it significantly increased and prolonged morphine analgesia. Collectively, this study provides a structural guidance to reposition DHA derivatives as TLR4 antagonists.

Safety of treatment with chloroquine and hydroxychloroquine: A ten-year systematic review and meta-analysis

OBJECTIVE

To estimate the incidence rate ratio (IRR) of adverse events (AE) in chloroquine or hydroxychloroquine users.

METHODS

We systematically reviewed randomized controlled trials (RCTs), using MEDLINE (2010-2020) and EMBASE (2010-2020) databases, reporting AE in chloroquine or hydroxychloroquine users during treatment for lupus, rheumatoid arthritis, malaria and COVID-19. The protocol for this systematic review is registered at the PROSPERO database (CRD42020197938). The quality of the included studies was assessed using the Cochrane risk-of-Bias tool and relevant data were extracted though a customized data collection form, independently, by two authors. The IRR of AE was estimated using a random-effect model meta-analysis and heterogeneity was evaluated by T² and I². Subgroup analysis was performed, and publication bias was assessed by funnel-plot.

RESULTS

Forty-six RCTs met our eligibility criteria and were included in our analysis (23132 patients). There was not a single death attributed to chloroquine or hydroxychloroquine use in the included RCTs. The IRR of general AE during antimalarial use was 1.15 [CI 95% 1.01-1.31]. COVID-19 patients treated with either antimalarial presented an 83% and 165% higher risk of developing general and gastrointestinal AE, respectively, in comparison with controls. The use of antimalarial increased the risk of developing dermatological AE by 92% in malarial studies and reduced by 65% in lupus studies. We did not find a significatively higher risk of cardiovascular nor ophthalmological AE in antimalarial users.

CONCLUSIONS

Our data reinforces that chloroquine and hydroxychloroquine have a good safety profile though caution is advised when using higher than usual doses in hospitalized COVID-19 patients.

Cannabidiol-dihydroartemisinin conjugates for ameliorating neuroinflammation with reduced cytotoxicity

Cannabidiol (CBD) and dihydroartemisinin (DHA) can alleviate neuroinflammatory responses. However, they show cytotoxicity, which severely limits their therapeutic windows. Therefore, there is a great need to develop neuroprotective agents with improved safety. Drug-drug conjugate is an emerging approach for enhancing therapeutic index. Herein, the development, synthesis, and the pharmacological characterization of CBD-DHA conjugates were performed. Meanwhile, the combination of CBD and DHA as separate entities was also quantitatively analyzed for direct comparison with CBD-DHA conjugates. In this study, BV-2 microglial cell line was used to mimic primary microglia and the effects of CBD, DHA, the combination of CBD and DHA, as well as CBD-DHA conjugates on LPS-activated signaling molecules and pro-inflammatory factors were assessed. The interaction of CBD and DHA in inhibiting LPS-induced nitric oxide (NO) production was found to be additive. In contrast, DHA was found to synergize with CBD in inhibiting BV-2 cellular viability which implies that the combination of CBD and DHA amplifies their cytotoxicity. CBD-DHA conjugate C3D eliminated the cytotoxicity associated with single CBD/DHA use without significantly compromising the anti-neuroinflammation activity. C3D was more potent than C2D and C4D in inhibiting LPS-induced NO and mRNAs of iNOS and IL-1β, which implies that the linker length is critical for CBD-DHA conjugates' anti-inflammatory activities. Further signaling characterizations showed that C3D inhibited LPS-induced NF-κB but not MAPKs activation in BV-2 cells, therefore blocking LPS-induced neuroinflammation. This work provides a good example that conjugated drug-drug approach may improve the therapeutic index by increasing the maximum tolerated concentration/dose compared to traditional combination strategy.

Chloroquine against malaria, cancers and viral diseases

Quinoline (QN) derivatives are often used for the prophylaxis and treatment of malaria. Chloroquine (CQ), a protonated, weakly basic drug, exerts its antimalarial effect mainly by increasing pH and accumulating in the food vacuole of the parasites. Repurposing CQ is an emerging strategy for new indications. Given the inhibition of autophagy and its immunomodulatory action, CQ shows positive efficacy against cancer and viral diseases, including Coronavirus 2019 (COVID-19). Here, we review the underlying mechanisms behind the antimalarial, anticancer and antiviral effects of CQ. We also discuss the clinical evidence for the use of CQ and hydroxychloroquine (HCQ) against COVID-19.

Declining Burden of Plasmodium vivax in a Population in Northwestern Thailand from 1995 to 2016 before Comprehensive Primaquine Prescription for Radical Cure

All Plasmodium cases have declined over the last decade in northwestern Thailand along the Myanmar border. During this time, Plasmodium vivax has replaced Plasmodium falciparum as the dominant species. The decline in P. falciparum has been shadowed by a coincidental but delayed decline in P. vivax cases. This may be due to early detection and artemisinin-based therapy, species-specific diagnostics, and bed net usage all of which reduce malaria transmission but not P. vivax relapse. In the absence of widespread primaquine use for radical cure against P. vivax hypnozoites, the decline in P. vivax may be explained by decreased hypnozoite activation of P. vivax relapses triggered by P. falciparum. The observed trends in this region suggest a beneficial effect of decreased P. falciparum transmission on P. vivax incidence, but elimination of P. vivax in a timely manner likely requires radical cure.

Developments in Taste-Masking Techniques for Traditional Chinese Medicines

A variety of pharmacologically active substances, including chemotherapeutic drugs and the substances from traditional Chinese medicine (TCM), always exhibit potent bioactivities after oral administration. However, their unpleasant taste (such as bitterness) and/or odor always decrease patient compliance and thus compromise their curative efficacies in clinical application. Therefore, the developments of taste-masking techniques are of great significance in improving their organoleptic properties. However, though a variety of taste-masking techniques have been successfully used to mask the unpalatable taste of chemotherapeutic drugs, their suitability for TCM substances is relatively limited. This is mainly due to the fact that the bitter ingredients existing in multicomponent TCM systems (i.e., effective fractions, single Chinese herbs, and compound preparations) are always unclear, and thus, there is lack of tailor-made taste-masking techniques to be utilized to conceal their unpleasant taste. The relevant studies are also relatively limited. As a whole, three types of taste-masking techniques are generally applied to TCM, including (i) functional masking via sweeteners, bitter blockers, and taste modifiers; (ii) physical masking via polymer film-coating or lipid barrier systems; and (iii) biochemical masking via intermolecular interaction, β-cyclodextrin inclusion, or ion-exchange resins. This review fully summarizes the results reported in this field with the purpose of providing an informative reference for relevant readers.