2,4-Diamino-6-methylpyrimidines for the potential treatment of Chagas' disease.

Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, affects 8-10 million people across the Latin American population and is responsible for around 12,500 deaths per annum. The current frontline treatments, benznidazole and nifurtimox, are associated with side effects and lack efficacy in the chronic stage of the disease, leading to an urgent need for new treatments. A high throughput screening campaign against the physiologically relevant intracellular form of the parasite identified a series of 2,4-diamino-6-methylpyrimidines. Demonstrating the series did not work through the anti-target TcCYP51, and was generally cytocidal, confirmed its suitability for further development. This study reports the optimisation of selectivity and metabolic stability of the series and identification of a suitable lead for further optimisation.

Short-course combination treatment for experimental chronic Chagas disease.

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects millions of people in the Americas and across the world, leading to considerable morbidity and mortality. Current treatment options, benznidazole (BNZ) and nifurtimox, offer limited efficacy and often lead to adverse side effects because of long treatment durations. Better treatment options are therefore urgently required. Here, we describe a pyrrolopyrimidine series, identified through phenotypic screening, that offers an opportunity to improve on current treatments. In vitro cell-based washout assays demonstrate that compounds in the series are incapable of killing all parasites; however, combining these pyrrolopyrimidines with a subefficacious dose of BNZ can clear all parasites in vitro after 5 days. These findings were replicated in a clinically predictive in vivo model of chronic Chagas disease, where 5 days of treatment with the combination was sufficient to prevent parasite relapse. Comprehensive mechanism of action studies, supported by ligand-structure modeling, show that compounds from this pyrrolopyrimidine series inhibit the Qi active site of T. cruzi cytochrome b, part of the cytochrome bc1 complex of the electron transport chain. Knowledge of the molecular target enabled a cascade of assays to be assembled to evaluate selectivity over the human cytochrome b homolog. As a result, a highly selective and efficacious lead compound was identified. The combination of our lead compound with BNZ rapidly clears T. cruzi parasites, both in vitro and in vivo, and shows great potential to overcome key issues associated with currently available treatments.

Identification and development of a series of disubstituted piperazines for the treatment of Chagas disease.

Approximately 6-7 million people around the world are estimated to be infected with Trypanosoma cruzi, the causative agent of Chagas disease. The current treatments are inadequate and therefore new medical interventions are urgently needed. In this paper we describe the identification of a series of disubstituted piperazines which shows good potency against the target parasite but is hampered by poor metabolic stability. We outline the strategies used to mitigate this issue such as lowering logD, bioisosteric replacements of the metabolically labile piperazine ring and use of plate-based arrays for quick diversity scoping. We discuss the success of these strategies within the context of this series and highlight the challenges faced in phenotypic programs when attempting to improve the pharmacokinetic profile of compounds whilst maintaining potency against the desired target.

Custody early warning scores; Do they predict patient deterioration in police custody?

This paper analyses the results of a three month trial based in a police custody suite, where we assigned a value; using the recently developed Custody Early Warning Score, to detainees arriving into police custody, as part of their 'booking in' process. We then compared this to the more established National Early Warning Scoring system and then looked at the predictive accuracy of these two systems and how they correlated to one another, when applied to three different clinical groups of detainees in police custody. Police Custody Sergeants and Custody Detention Officers continue to experience difficulties in identifying those detainees with health care needs; be they subtle, emerging or more evident. The introduction of a 'track and trigger' physiological scoring system has been seen to reduce morbidity in health care settings and so the adoption of an altered custodial version of such a system is an effort by some police forces to do likewise. Recent innovations in police custody have focussed on identifying and appropriately referring those detainees with mental health needs. There is a lack of research that examines the physical health needs of the custodial population and the risks that they might present. With detainee deaths and serious adverse events continuing to occur in police custody, forces are looking at ways to identify risk early on in the custodial process, to reduce such high profile occurrences. Police use of the Custody Early Warning Score system, is one effort to try and identify and reduce this risk, early on in the custodial process. OBJECTIVE: In an increasing number of police custody suites, the Custody Early Warning Score system has been, added to the normal, standardised police risk assessment process. This 'track & trigger' system has been adapted to the custody environment and is conducted by non-medical detention staff upon detainee arrival, in order to identify detainee morbidity and mortality risk. We wanted to test the predictive accuracy of this system at identifying detainee health need and prioritisation. We also wanted to know how well this tool correlated to another well-established monitoring tool and how accurate these two systems are at pre-empting the medical emergencies and hospital referrals that occur in police custody. RESULTS: 1'163 detainees were assessed by medical staff over a three month period, with staff blinded to the assigned scoring. 276 of these were identified as requiring further clinical assessment following this scoring with 29 of the 33 patients referred to hospital by medical staff, also scored, with some declining assessment or were serious enough to abandon scoring. Whilst we found a small correlation between increased scores and referral to hospital; we found that there was little correlation between assessment scores in general and the need for referral to hospital. We also found that most clinical risk was associated with lower or low scores. CONCLUSIONS: The scoring systems that we assessed were not sensitive enough to identify health need in the detainee population, due to frequent, altered physiological parameters. Life threatening conditions have low assessment scores, not reflective of the seriousness of medical conditions, nor the potential for rapid deterioration. Such scoring systems add little to the risk assessment process, with low scores allowing for complacency and a false reassurance, when using a system designed for very different circumstances.

Identification of Trypanocidal Activity for Known Clinical Compounds Using a New Trypanosoma cruzi Hit-Discovery Screening Cascade.

Chagas disease is a significant health problem in Latin America and the available treatments have significant issues in terms of toxicity and efficacy. There is thus an urgent need to develop new treatments either via a repurposing strategy or through the development of new chemical entities. A key first step is the identification of compounds with anti-Trypanosoma cruzi activity from compound libraries. Here we describe a hit discovery screening cascade designed to specifically identify hits that have the appropriate anti-parasitic properties to warrant further development. The cascade consists of a primary imaging-based assay followed by newly developed and appropriately scaled secondary assays to predict the cidality and rate-of-kill of the compounds. Finally, we incorporated a cytochrome P450 CYP51 biochemical assay to remove compounds that owe their phenotypic response to inhibition of this enzyme. We report the use of the cascade in profiling two small libraries containing clinically tested compounds and identify Clemastine, Azelastine, Ifenprodil, Ziprasidone and Clofibrate as molecules having appropriate profiles. Analysis of clinical derived pharmacokinetic and toxicity data indicates that none of these are appropriate for repurposing but they may represent suitable start points for further optimisation for the treatment of Chagas disease.