Identification of a non-competitive inhibitor of Plasmodium falciparum aspartate transcarbamoylase.

Aspartate transcarbamoylase catalyzes the second step of de-novo pyrimidine biosynthesis. As malarial parasites lack pyrimidine salvage machinery and rely on de-novo production for growth and proliferation, this pathway is a target for drug discovery. Previously, an apo crystal structure of aspartate transcarbamoylase from Plasmodium falciparum (PfATC) in its T-state has been reported. Here we present crystal structures of PfATC in the liganded R-state as well as in complex with the novel inhibitor, 2,3-napthalenediol, identified by high-throughput screening. Our data shows that 2,3-napthalediol binds in close proximity to the active site, implying an allosteric mechanism of inhibition. Furthermore, we report biophysical characterization of 2,3-napthalenediol. These data provide a promising starting point for structure based drug design targeting PfATC and malarial de-novo pyrimidine biosynthesis.

Systematic Evaluation of Osimertinib Population Pharmacokinetic Models in a Cohort of Dutch Adults with Non-Small Cell Lung Cancer.

BACKGROUND AND OBJECTIVE: Several population pharmacokinetic (popPK) studies have been reported that can guide the prediction of osimertinib plasma concentrations in individual patients. It is currently unclear which popPK model offers the best predictive performance and which popPK models are most suitable for nonadherence management and model-informed precision dosing. Therefore, the objective of this study was to externally validate all osimertinib popPK models available in the current literature. METHODS: Published popPK models for osimertinib were constructed using NONMEM version 7.4.4. The predictive quality of the identified models was assessed with goodness-of-fit (GoF) plots, conditional weighted residuals (CWRES) plots and a prediction-corrected visual predictive check (pcVPC) for osimertinib and its active metabolite AZ5104. A subset from the Dutch OSIBOOST trial, where 11 patients with low osimertinib exposure were included, was used as evaluation cohort. RESULTS: The population GoF plots for all four models poorly followed the line of identity. For the individual GoF plots, all models performed comparable and were closely distributed among the line of identity. CWRES of the four models were skewed. The pcVPCs of all four models showed a similar trend, where all observed concentrations fell in the simulated shaded areas, but in the lower region of the simulated areas. CONCLUSION: All four popPK models can be used to individually predict osimertinib concentrations in patients with low osimertinib exposure. For population predictions, all four popPK models performed poorly in patients with low osimertinib exposure. A novel popPK model with good predictive performance should be developed for patients with low osimertinib exposure. Ideally, the cause for the relatively low osimertinib exposure in our evaluation cohort should be known. CLINICAL TRIALS REGISTRATION: NCT03858491.

Osimertinib Plasma Trough Concentration in Relation to Brain Metastases Development in Patients With Advanced EGFR-Mutated NSCLC.

Introduction: Brain metastases (BM) are common in patients with advanced EGFR-mutated (EGFRm+) NSCLC. Despite good BM-related outcomes of osimertinib, several patients still experience intracranial progression. A possible explanation is pharmacologic failure due to low plasma trough levels (Cmin,SS) and consequently limited intracranial osimertinib exposure. We investigated the relation between osimertinib Cmin,SS and BM development or progression. Methods: A prospective multicenter cohort study, including patients receiving osimertinib for advanced EGFRm+ NSCLC. At osimertinib start, patients were allocated to the BM or no or unknown BM cohort and were further divided into subgroups based on osimertinib Cmin,SS (low, middle, and high exposure). Cumulative incidence of BM progression or development and overall survival were determined for each group. Results: A total of 173 patients were included, with 49 (28.3%) had baseline BM. Of these patients, 36.7% experienced BM progression, of which 16.7% in the low (<159.3 ng/mL), 40.0% in the middle, and 47.1% in the high (>270.7 ng/mL) Cmin,SS subgroups. After 12 months, the cumulative incidence of BM progression for the BM cohort was 20% (95% confidence interval [CI] 2.6-49.0), 31% (95% CI:10.6-53.9), and 31% (95% CI:10.8-54.5) per Cmin,SS subgroup, respectively. After 20 months, this was 20% (95% CI:2.6-49.0), 52% (95% CI:23.8-74.2), and 57% (95% CI:24.9-79.7), respectively. For the no or unknown BM cohort, 4.0% developed BM without differences within Cmin,SS subgroups. Conclusions: No relation was found between osimertinib Cmin,SS and BM development or progression in patients with advanced EGFRm+ NSCLC. This suggests that systemic osimertinib exposure is not a surrogate marker for BM development or progression.

Validated extended multiplexed LC-MS/MS assay for the quantification of adagrasib and sotorasib in human plasma, together with four additional SMIs.

Recently, two small molecular inhibitors (SMIs) -adagrasib and sotorasib- have been introduced for targeting Kirsten rat sarcoma (KRAS) p.G12C mutations in patients with non-small cell lung cancer (NSCLC). In order to support pharmacokinetic research as well as clinical decision making, we developed and validated a simple and accurate liquid chromatography-tandem mass spectrometry method for the multiplexed quantification of adagrasib and sotorasib. This assay was co-validated with the quantification for brigatinib, lorlatinib, pralsetinib and selpercatinib. Methanol was used for single-step protein precipitation. Chromatographic separation was performed using an Acquity® HSS C18 UPLC column, with an elution gradient of ammonium formate 0.1 % v/v in water and acetonitrile. In K2-EDTA plasma, adagrasib was found to be stable for at least seven days at room temperature and 4 °C, and at least 3 months at -80 °C. Sotorasib was found to be stable for at least three days at room temperature, seven days at 4 °C and at least 3 months at -80 °C. The method was validated over a linear range of 80-4000 ng/mL for adagrasib and 25-2500 ng/mL for sotorasib. The assay is therefore well-equipped for determining plasma concentrations in clinical practice.

Thiosulfate sulfurtransferase prevents hyperglycemic damage to the zebrafish pronephros in an experimental model for diabetes.

Thiosulfate sulfurtransferase (TST, EC 2.8.1.1), also known as Rhodanese, was initially discovered as a cyanide detoxification enzyme. However, it was recently also found to be a genetic predictor of resistance to obesity-related type 2 diabetes. Diabetes type 2 is characterized by progressive loss of adequate ß-cell insulin secretion and onset of insulin resistance with increased insulin demand, which contributes to the development of hyperglycemia. Diabetic complications have been replicated in adult hyperglycemic zebrafish, including retinopathy, nephropathy, impaired wound healing, metabolic memory, and sensory axonal degeneration. Pancreatic and duodenal homeobox 1 (Pdx1) is a key component in pancreas development and mature beta cell function and survival. Pdx1 knockdown or knockout in zebrafish induces hyperglycemia and is accompanied by organ alterations similar to clinical diabetic retinopathy and diabetic nephropathy. Here we show that pdx1-knockdown zebrafish embryos and larvae survived after incubation with thiosulfate and no obvious morphological alterations were observed. Importantly, incubation with hTST and thiosulfate rescued the hyperglycemic phenotype in pdx1-knockdown zebrafish pronephros. Activation of the mitochondrial TST pathway might be a promising option for therapeutic intervention in diabetes and its organ complications.

Unraveling the role of thiosulfate sulfurtransferase in metabolic diseases.

Thiosulfate sulfurtransferase (TST, EC 2.8.1.1), also known as Rhodanese, is a mitochondrial enzyme which catalyzes the transfer of sulfur in several molecular pathways. After its initial identification as a cyanide detoxification enzyme, it was found that its functions also include sulfur metabolism, modification of iron­sulfur clusters and the reduction of antioxidants glutathione and thioredoxin. TST deficiency was shown to be strongly related to the pathophysiology of metabolic diseases including diabetes and obesity. This review summarizes research related to the enzymatic properties and functions of TST, to then explore the association between the effects of TST on mitochondria and development of diseases such as diabetes and obesity.