Chagas disease, caused by infection with the protozoan parasite Trypanosoma cruzi (T. cruzi), is responsible for a large health burden with around 6-8 million people infected globally. The current drug development pipeline is sparsely populated and there is an urgent need for new treatments. In this paper we describe the identification of a series of benzodiazepinediones with antiparasitic activity, and the platform we utilised to demonstrate that they act via a novel mechanism of action. Two distinct sub-series were identified, and the medicinal chemistry program identified compounds from both with pIC50's >6.4 which were progressed to a T. cruzi washout assay. This assay showed that neither sub-series was suitable for further development. This work demonstrated the value of a robust Chagas disease discovery platform for focusing the limited resources available for neglected disease drug discovery onto the most promising series.

There is an urgent need for new treatments for Chagas disease, a parasitic infection which mostly impacts South and Central America. We previously reported on the discovery of GSK3494245/DDD01305143, a preclinical candidate for visceral leishmaniasis which acted through inhibition of the Leishmania proteasome. A related analogue, active against Trypanosoma cruzi, showed suboptimal efficacy in an animal model of Chagas disease, so alternative proteasome inhibitors were investigated. Screening a library of phenotypically active analogues against the T. cruzi proteasome identified an active, selective pyridazinone, the development of which is described herein. We obtained a cryo-EM co-structure of proteasome and a key inhibitor and used this to drive optimization of the compounds. Alongside this, optimization of the absorption, distribution, metabolism, and excretion (ADME) properties afforded a suitable compound for mouse efficacy studies. The outcome of these studies is discussed, alongside future plans to further understand the series and its potential to deliver a new treatment for 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.

There is an urgent need for new treatments for visceral leishmaniasis (VL), a parasitic infection which impacts heavily large areas of East Africa, Asia, and South America. We previously reported on the discovery of GSK3494245/DDD01305143 (1) as a preclinical candidate for VL and, herein, we report on the medicinal chemistry program that led to its identification. A hit from a phenotypic screen was optimized to give a compound with in vivo efficacy, which was hampered by poor solubility and genotoxicity. The work on the original scaffold failed to lead to developable compounds, so an extensive scaffold-hopping exercise involving medicinal chemistry design, in silico profiling, and subsequent synthesis was utilized, leading to the preclinical candidate. The compound was shown to act via proteasome inhibition, and we report on the modeling of different scaffolds into a cryo-EM structure and the impact this has on our understanding of the series' structure-activity relationships.

AbstractThe SCAL linker, a safety catch linker, is amongst the most versatile linkers for solid phase synthesis. It was originally described in 1991 by Pátek and Lebl. Yet, its application has been hindered by the low yields of published synthetic routes. Over time, the exceptional versatility of this linker has been demonstrated in several applications of advanced solid phase synthesis of peptides and peptidomimetics. Recently, an updated synthesis of the original linker has also been presented at the 22nd American Peptide Symposium, comprising 10 steps. Herein, the design and synthesis of a next generation SCAL linker, SCAL‐2, is reported. SCAL‐2 features a simplified molecular architecture, which allows for a more efficient synthesis in 8 steps with superior yields. Both linkers, SCAL and SCAL‐2 are compared in terms of their cleavage properties adding valuable information on how to best utilize the versatility of these linkers for solid phase synthesis.

A well-documented obstacle in the synthesis of functionalized rhodamine dyes is the generation of regioisomers which are difficult to separate. These isomers occur due to the use of unsymmetrical anhydride reagents, which possess two potential points of reactivity where condensation with meta-aminophenols can take place. In this report we describe a method which eliminates this problem by using phthalaldehydic acids as anhydride replacements. These reagents provide only one point of reactivity for the aminophenol, thus allowing direct access to single isomer tetramethylrhodamines and avoiding isomer generation altogether. A range of functionalities are shown to be tolerated at the 5- and 6-position of the dye compounds which are prepared in up to gram quantities using our method. The scope of the method is further demonstrated by the preparation of additional rhodamine family members Rhodamine B and X-Rhodamine.

The first example of an inhibitor of the kinase TAK1 that binds in the DFG-out conformation is disclosed. These preliminary studies used kinase-targeted screening and structure-based drug design to create a molecule with dual pharmacological inhibition of p38 and TAK1 that demonstrated significant activity in a cell-based, anti-inflammatory assay.

This paper describes the identification and optimization of a novel series of DFG-out binding p38 inhibitors as inhaled agents for the treatment of chronic obstructive pulmonary disease. Structure based drug design and "inhalation by design" principles have been applied to the optimization of the lead series exemplied by compound 1a. Analogues have been designed to be potent and selective for p38, with an emphasis on slow enzyme dissociation kinetics to deliver prolonged lung p38 inhibition. Pharmacokinetic properties were tuned with high intrinsic clearance and low oral bioavailability in mind, to minimize systemic exposure and reduce systemically driven adverse events. High CYP mediated clearance and glucuronidation were targeted to achieve high intrinsic clearance coupled with multiple routes of clearance to minimize drug-drug interactions. Furthermore, pharmaceutical properties such as stability, crystallinity, and solubility were considered to ensure compatibility with a dry powder inhaler. 1ab (PF-03715455) was subsequently identified as a clinical candidate from this series with efficacy and safety profiles confirming its potential as an inhaled agent for the treatment of COPD.

Small molecule fluorometric boron dipyrromethene probes were developed to bind hepatitis C virus-encoded NS5A protein and aid subcellular distribution studies. These molecules did not co-locate with NS5A, therefore alternative ‘silent’ azide reporters were used to obtain a more relevant picture of their distribution. Following pre-incubation with replicon cells, click chemistry was used to append a fluorophore to the azide that confirmed the co-localisation of the small molecule with the NS5A protein, thus providing greater insight into the antiviral mode of action of this chemotype.

The SAR of a series of novel pyrido[3,4-d]pyramid-4-ylamine mGluR1 antagonists is described. The multiple of the unbound Ki in cerebrospinal fluid necessary to give morphine like analgesic effects in an electromyograph pinch model in rodents is determined and the effect of structure on CNS penetration examined.

COPD is a major cause of mortality in the western world. A(2A) agonists are postulated to reduce the lung inflammation that causes COPD. The cardiovascular effects of A(2A) agonists dictate that a compound needs to be delivered by inhalation to be therapeutically useful. A strategy of minimizing side-effect liability by maximizing systemic clearance was followed and pharmacological and pharmacokinetic SAR of a series of inhaled A(2A) agonists described. A sevenfold improvement in potency and 150-fold reduction in side-effect liability over the lead compound CGS-21680, were obtained.

A series of novel mGluR1 antagonists have been prepared. Incorporation of fragments derived from weak lead matter into a library led to enhanced potency in a new chemical series. A chemistry driven second library iteration, covering a greatly enhanced area of chemical space, maintained good potency and introduced metabolic stability.