CHANGING TIDES OF CHEMOTHERAPY OF MALARIA

Lead Optimization of Dehydroemetine for Repositioned Use in Malaria

Drug repositioning offers an effective alternative to de novo drug design to tackle the urgent need for novel antimalarial treatments. The antiamoebic compound emetine dihydrochloride has been identified as a potent in vitro inhibitor of the multidrug-resistant strain K1 of Plasmodium falciparum (50% inhibitory concentration [IC₅₀], 47 nM ± 2.1 nM [mean ± standard deviation]). Dehydroemetine, a synthetic analogue of emetine dihydrochloride, has been reported to have less-cardiotoxic effects than emetine.

Drug repositioning offers an effective alternative to de novo drug design to tackle the urgent need for novel antimalarial treatments. The antiamoebic compound emetine dihydrochloride has been identified as a potent in vitro inhibitor of the multidrug-resistant strain K1 of Plasmodium falciparum (50% inhibitory concentration [IC₅₀], 47 nM ± 2.1 nM [mean ± standard deviation]). Dehydroemetine, a synthetic analogue of emetine dihydrochloride, has been reported to have less-cardiotoxic effects than emetine. The structures of two diastereomers of dehydroemetine were modeled on the published emetine binding site on the cryo-electron microscopy (cryo-EM) structure with PDB code 3J7A (P. falciparum 80S ribosome in complex with emetine), and it was found that (−)-R,S-dehydroemetine mimicked the bound pose of emetine more closely than did (−)-S,S-dehydroisoemetine. (−)-R,S-dehydroemetine (IC₅₀ 71.03 ± 6.1 nM) was also found to be highly potent against the multidrug-resistant K1 strain of P. falciparum compared with (−)-S,S-dehydroisoemetine (IC₅₀, 2.07 ± 0.26 μM), which loses its potency due to the change of configuration at C-1′. In addition to its effect on the asexual erythrocytic stages of P. falciparum, the compound exhibited gametocidal properties with no cross-resistance against any of the multidrug-resistant strains tested. Drug interaction studies showed (−)-R,S-dehydroemetine to have synergistic antimalarial activity with atovaquone and proguanil. Emetine dihydrochloride and (−)-R,S-dehydroemetine failed to show any inhibition of the hERG potassium channel and displayed activity affecting the mitochondrial membrane potential, indicating a possible multimodal mechanism of action.

Medicinal plants and Malaria: an historical case study of research at the London School of Hygiene and Tropical Medicine in the twentieth century

Interest in medicinal plants has increased in recent years. This article examines the history of medicinal plant research through a case study of the London School of Hygiene and Tropical Medicine (LSHTM) over the past 100 years. Papers published by members of the School and documents in the School archives show a fluctuating but continuous interest in plants as sources of medicine. Research interests of individual scientists, changes in the School structure and the changing role of research affected research into medicinal plants at LSHTM. As important were external developments, including the supply of plant resources, especially during wartime, the development of drug-resistance, advances in science and technology, knowledge exchange between both disciplines and cultures, the increased influence of global organizations on policy, as well as pressure groups particularly those involved in conservation. With the revival of interest in plants and the increasing variety of influences on research, it is important to have a better understanding of how debates and subsequent policy impact at the research level, and how research in turn impacts upon policy.

Long-term results of trigone-preserving orthotopic substitution enterocystoplasty for interstitial cystitis

PURPOSE

Interstitial cystitis is a chronic debilitating condition mainly affecting women. Conservative treatment often produces unsatisfactory results and the identification of the best surgical treatment modality is difficult. We evaluate retrospectively the long-term results of trigone-preserving cystectomy followed by orthotopic substitution enteroplasty for women suffering from interstitial cystitis.

MATERIALS AND METHODS

The study comprised 18 women with a mean age of 55.9 years. All surgical interventions were performed by 1 surgeon. All patients completed a voiding log and were interviewed about symptoms. Renal ultrasonography was done to evaluate the upper urinary tract. Followup data also comprised blood chemistry studies, including vitamin B12 blood levels and blood gas analysis. Pain and lower urinary tract problems were measured using a validated self-assessment symptom index.

RESULTS

Ileocoecal augmentation was performed in 10 women and ileal substitute was done in 8. After a mean followup of 57 months 14 patients are completely pain-free, 12 void spontaneously and 15 report complete resolution of dysuria. Three patients perform intermittent self-catheterization and 1 woman prefers a suprapubic catheter for control of urinary hypercontinence. These 4 patients underwent ileoplasty. Surgery failed to relieve symptoms in 2 of the 18 patients. Surgery achieved a statistically highly significant improvement of diurnal and nocturnal voiding frequencies, functional bladder capacity and symptom index score.

CONCLUSIONS

Substitution enterocystoplasty is a valuable and safe therapeutic option for patients with intractable interstitial cystitis resistant to conservative therapy. In our series use of the ileocecal bowel segment showed better functional results.

The effects of diaphenylsulfone (DDS) against chloroquine-resistant Plasmodium falciparum

In view of the problems caused by the chloroquine-resistance of some strains of Plasmodium falciparum, the authors have investigated the effectiveness of diaphenylsulfone against two such resistant strains, from Malaya and Viet-Nam. They found that diaphenylsulfone given during acute attacks of malaria had a blood schizontocidal activity against the Malayan resistant strain but was not rapidly effective in terminating acute attacks in non-immune persons, and that, when the drug was given prophylactically in relatively small doses, it was substantially effective in preventing patency of mosquito-induced infection with the same strain. The protective effect of diaphenylsulfone is that of a clinical prophylactic or suppressive drug; it does not appear to be a true causal prophylactic. It was also found that the protective effect is vitiated by the concurrent administration of paraaminobenzoic acid.These studies indicate a need for further assessment of the antimalarial value of sulfones and sulfonamides, both alone and in combination with other drugs, for prevention and cure.