Reaction hijacking inhibition of Plasmodium falciparum asparagine tRNA synthetase

Malaria poses an enormous threat to human health. With ever increasing resistance to currently deployed drugs, breakthrough compounds with novel mechanisms of action are urgently needed. Here, we explore pyrimidine-based sulfonamides as a new low molecular weight inhibitor class with drug-like physical parameters and a synthetically accessible scaffold. We show that the exemplar, OSM-S-106, has potent activity against parasite cultures, low mammalian cell toxicity and low propensity for resistance development. In vitro evolution of resistance using a slow ramp-up approach pointed to the Plasmodium falciparum cytoplasmic asparaginyl-tRNA synthetase (PfAsnRS) as the target, consistent with our finding that OSM-S-106 inhibits protein translation and activates the amino acid starvation response. Targeted mass spectrometry confirms that OSM-S-106 is a pro-inhibitor and that inhibition of PfAsnRS occurs via enzyme-mediated production of an Asn-OSM-S-106 adduct. Human AsnRS is much less susceptible to this reaction hijacking mechanism. X-ray crystallographic studies of human AsnRS in complex with inhibitor adducts and docking of pro-inhibitors into a model of Asn-tRNA-bound PfAsnRS provide insights into the structure-activity relationship and the selectivity mechanism.

Reaction hijacking inhibition of Plasmodium falciparum asparagine tRNA synthetase

Malaria poses an enormous threat to human health. With ever increasing resistance to currently deployed drugs, breakthrough compounds with novel mechanisms of action are urgently needed. Here, we explore pyrimidine-based sulfonamides as a new low molecular weight inhibitor class with drug-like physical parameters and a synthetically accessible scaffold. We show that the exemplar, OSM-S-106, has potent activity against parasite cultures, low mammalian cell toxicity and low propensity for resistance development. In vitro evolution of resistance using a slow ramp-up approach pointed to the Plasmodium falciparum cytoplasmic asparaginyl tRNA synthetase (PfAsnRS) as the target, consistent with our finding that OSM-S-106 inhibits protein translation and activates the amino acid starvation response. Targeted mass spectrometry confirms that OSM-S-106 is a pro-inhibitor and that inhibition of PfAsnRS occurs via enzyme-mediated production of an Asn-OSM-S-106 adduct. Human AsnRS is much less susceptible to this reaction hijacking mechanism. X-ray crystallographic studies of human AsnRS in complex with inhibitor adducts and docking of pro-inhibitors into a model of Asn-tRNA-bound PfAsnRS provide insights into the structure activity relationship and the selectivity mechanism.

Multistage and transmission-blocking tubulin targeting potent antimalarial discovered from the open access MMV pathogen box

The development of resistance to current antimalarial therapies remains a significant source of concern. To address this risk,newdrugswithnoveltargetsin distinct developmental stages ofPlasmodiumparasites are required. In the current study,we have targetedP. falciparumTubulin(PfTubulin)proteins which represent some of thepotentialdrug targetsfor malaria chemotherapy. PlasmodialMicrotubules (MTs) play a crucial role during parasite proliferation, growth, and transmission, which render them highlydesirabletargets for the development ofnext-generation chemotherapeutics. Towards this,we have evaluated the antimalarial activity ofTubulintargetingcompounds received from theMedicines for Malaria Venture (MMV)"Pathogen Box"against the human malaria parasite,P. falciparumincluding 3D7 (chloroquine and artemisinin sensitive strain), RKL-9 (chloroquine-resistant strain), and R539T (artemisinin-resistant strain). At nanomolar concentrations, the filtered-out compounds exhibitedpronouncedmultistage antimalarialeffects across the parasite life cycle, including intra-erythrocytic blood stages, liver stage parasites, gametocytes, and ookinetes. Concomitantly, these compoundswere found toimpedemale gamete ex-flagellation, thus showingtheir transmission-blocking potential. Target mining of these potent compounds, by combining in silico, biochemical and biophysical assays,implicatedPfTubulinas their moleculartarget, which may possibly act bydisruptingMT assembly dynamics by binding at the interface of α-βTubulin-dimer.Further, the promising ADME profile of the parent scaffold supported its consideration as a lead compound for further development.Thus, our work highlights the potential of targetingPfTubulin proteins in discovering and developing next-generation, multistage antimalarial agents against Multi-Drug Resistant (MDR) malaria parasites.

Screening the pandemic response box identified benzimidazole carbamates, Olorofim and ravuconazole as promising drug candidates for the treatment of eumycetoma

Eumycetoma is a chronic subcutaneous neglected tropical disease that can be caused by more than 40 different fungal causative agents. The most common causative agents produce black grains and belong to the fungal orders Sordariales and Pleosporales. The current antifungal agents used to treat eumycetoma are itraconazole or terbinafine, however, their cure rates are low. To find novel drugs for eumycetoma, we screened 400 diverse drug-like molecules from the Pandemic Response Box against common eumycetoma causative agents as part of the Open Source Mycetoma initiative (MycetOS). 26 compounds were able to inhibit the growth of Madurella mycetomatis, Madurella pseudomycetomatis and Madurella tropicana, 26 compounds inhibited Falciformispora senegalensis and seven inhibited growth of Medicopsis romeroi in vitro. Four compounds were able to inhibit the growth of all five species of fungi tested. They are the benzimidazole carbamates fenbendazole and carbendazim, the 8-aminoquinolone derivative tafenoquine and MMV1578570. Minimal inhibitory concentrations were then determined for the compounds active against M. mycetomatis. Compounds showing potent activity in vitro were further tested in vivo. Fenbendazole, MMV1782387, ravuconazole and olorofim were able to significantly prolong Galleria mellonella larvae survival and are promising candidates to explore in mycetoma treatment and to also serve as scaffolds for medicinal chemistry optimisation in the search for novel antifungals to treat eumycetoma.

MalDA, Accelerating Malaria Drug Discovery

The Malaria Drug Accelerator (MalDA) is a consortium of 15 leading scientific laboratories. The aim of MalDA is to improve and accelerate the early antimalarial drug discovery process by identifying new, essential, druggable targets. In addition, it seeks to produce early lead inhibitors that may be advanced into drug candidates suitable for preclinical development and subsequent clinical testing in humans. By sharing resources, including expertise, knowledge, materials, and reagents, the consortium strives to eliminate the structural barriers often encountered in the drug discovery process. Here we discuss the mission of the consortium and its scientific achievements, including the identification of new chemically and biologically validated targets, as well as future scientific directions.

MAIP: a web service for predicting blood-stage malaria inhibitors

Malaria is a disease affecting hundreds of millions of people across the world, mainly in developing countries and especially in sub-Saharan Africa. It is the cause of hundreds of thousands of deaths each year and there is an ever-present need to identify and develop effective new therapies to tackle the disease and overcome increasing drug resistance. Here, we extend a previous study in which a number of partners collaborated to develop a consensus in silico model that can be used to identify novel molecules that may have antimalarial properties. The performance of machine learning methods generally improves with the number of data points available for training. One practical challenge in building large training sets is that the data are often proprietary and cannot be straightforwardly integrated. Here, this was addressed by sharing QSAR models, each built on a private data set. We describe the development of an open-source software platform for creating such models, a comprehensive evaluation of methods to create a single consensus model and a web platform called MAIP available at https://www.ebi.ac.uk/chembl/maip/ . MAIP is freely available for the wider community to make large-scale predictions of potential malaria inhibiting compounds. This project also highlights some of the practical challenges in reproducing published computational methods and the opportunities that open-source software can offer to the community.

Estimating local need for mental healthcare to inform fair resource allocation in the NHS in England: cross-sectional analysis of national administrative data linked at person level

BACKGROUND

Equitable access to mental healthcare is a priority for many countries. The National Health Service in England uses a weighted capitation formula to ensure that the geographical distribution of resources reflects need.

AIMS

To produce a revised formula for estimating local need for secondary mental health, learning disability (intellectual disability) and psychological therapies services for adults in England.

METHOD

We used demographic records for 43 751 535 adults registered with a primary care practitioner in England linked with service use, ethnicity, physical health diagnoses and type of household, from multiple data-sets. Using linear regression, we estimated the individual cost of care in 2015 as a function of individual- and area-level need and supply variables in 2013 and 2014. We sterilised the effects of the supply variables to obtain individual-need estimates. We aggregated these by general practitioner practice, age and gender to derive weights for the national capitation formula.

RESULTS

Higher costs were associated with: being 30-50 years old, compared with 20-24; being Irish, Black African, Black Caribbean or of mixed ethnicity, compared with White British; having been admitted for specific physical health conditions, including drug poisoning; living alone, in a care home or in a communal environment; and living in areas with a higher percentage of out-of-work benefit recipients and higher prevalence of severe mental illness. Longer distance from a provider was associated with lower cost.

CONCLUSIONS

The resulting needs weights were higher in more deprived areas and informed the distribution of some 12% (£9 bn in 2019/20) of the health budget allocated to local organisations for 2019/20 to 2023/24.

Structure-Guided Identification of Resistance Breaking Antimalarial N‑Myristoyltransferase Inhibitors

The attachment of myristate to the N-terminal glycine of certain proteins is largely a co-translational modification catalyzed by N-myristoyltransferase (NMT), and involved in protein membrane-localization. Pathogen NMT is a validated therapeutic target in numerous infectious diseases including malaria. In Plasmodium falciparum, NMT substrates are important in essential processes including parasite gliding motility and host cell invasion. Here, we generated parasites resistant to a particular NMT inhibitor series and show that resistance in an in vitro parasite growth assay is mediated by a single amino acid substitution in the NMT substrate-binding pocket. The basis of resistance was validated and analyzed with a structure-guided approach using crystallography, in combination with enzyme activity, stability, and surface plasmon resonance assays, allowing identification of another inhibitor series unaffected by this substitution. We suggest that resistance studies incorporated early in the drug development process help selection of drug combinations to impede rapid evolution of parasite resistance.

Open-source discovery of chemical leads for next-generation chemoprotective antimalarials

To discover leads for next-generation chemoprotective antimalarial drugs,we tested more than 500,000 compounds for their ability to inhibit liver-stage development of luciferase-expressing Plasmodium spp. parasites (681 compounds showed a half-maximal inhibitory concentration of less than 1micromolar).Cluster analysis identified potent and previously unreported scaffold families as well as other series previously associated with chemoprophylaxis. Further testing through multiple phenotypic assays that predict stage-specific and multispecies antimalarial activity distinguished compound classes that are likely to provide symptomatic relief by reducing asexual blood-stage parasitemia from those which are likely to only prevent malaria. Target identification by using functional assays, in vitro evolution, or metabolic profiling revealed 58 mitochondrial inhibitors but also many chemotypes possibly with previously unidentified mechanisms of action.

A discovery and development roadmap for new endectocidal transmission-blocking agents in malaria

Reaching the overall goal of eliminating malaria requires halting disease transmission. One approach to blocking transmission is to prevent passage of the parasite to a mosquito, by preventing formation or transmission of gametocytes. An alternative approach, pioneered in the veterinary field, is to use endectocides, which are molecules that render vertebrate blood meals toxic for the mosquito vector, also killing the parasite. Field studies and modelling suggest that reducing the lifespan of the mosquito may significantly reduce transmission, given the lengthy maturation process of the parasite. To guide the development of new endectocides, or the reformulation of existing molecules, it is important to construct a framework of the required attributes, commonly called the target candidate profile. Here, using a combination of insights from current endectocides, mathematical models of the malaria transmission dynamics, and known impacts of vector control, a target candidate profile (TCP-6) and a regulatory strategy are proposed for a transmission reducing agent. The parameters chosen can be used to assess the potential of a new medicine, independent of whether it has classical endectocide activity, reduces the insect and parasite lifespan or any combination of all three, thereby constituting an ‘endectocidal transmission blocking’ paradigm.

Antimalarial efficacy of MMV390048, an inhibitor of Plasmodium phosphatidylinositol 4-kinase

As part of the global effort toward malaria eradication, phenotypic whole-cell screening revealed the 2-aminopyridine class of small molecules as a good starting point to develop new antimalarial drugs. Stemming from this series, we found that the derivative, MMV390048, lacked cross-resistance with current drugs used to treat malaria. This compound was efficacious against all Plasmodium life cycle stages, apart from late hypnozoites in the liver. Efficacy was shown in the humanized Plasmodium falciparum mouse model, and modest reductions in mouse-to-mouse transmission were achieved in the Plasmodium berghei mouse model. Experiments in monkeys revealed the ability of MMV390048 to be used for full chemoprotection. Although MMV390048 was not able to eliminate liver hypnozoites, it delayed relapse in a Plasmodium cynomolgi monkey model. Both genomic and chemoproteomic studies identified a kinase of the Plasmodium parasite, phosphatidylinositol 4-kinase, as the molecular target of MMV390048. The ability of MMV390048 to block all life cycle stages of the malaria parasite suggests that this compound should be further developed and may contribute to malaria control and eradication as part of a single-dose combination treatment.

Modelling mosquito infection at natural parasite densities identifies drugs targeting EF2, PI4K or ATP4 as key candidates for interrupting malaria transmission

Eradication of malaria requires a novel type of drug that blocks transmission from the human to the mosquito host, but selection of such a drug is hampered by a lack of translational models. Experimental mosquito infections yield infection intensities that are substantially higher than observed in natural infections and, as a consequence, underestimate the drug effect on the proportion of mosquitoes that become infected. Here we introduce a novel experimental and computational method to adequately describe drug efficacy at natural parasite densities. Parameters of a beta-binomial infection model were established and validated using a large number of experimental mosquito infections at different parasite densities. Analyses of 15 experimental and marketed drugs revealed a class-specific ability to block parasite transmission. Our results highlight the parasite's elongation factor EF2, PI4 kinase and the ATP4 sodium channel as key targets for interruption of transmission, and compounds DDD107498 and KAE609 as most advanced drug candidates.

Quantitative proteomic analysis of HER2 expression in the selection of gastric cancer patients for trastuzumab treatment

Background

A wide range of response rates have been reported in HER2-positive gastric cancer (GC) patients treated with trastuzumab. Other HER2-targeted therapies for GC have yet to show efficacy in clinical trials. These findings raise question about the ability of standard HER2 diagnostics to accurately distinguish between GC patients who would and would not benefit from anti-HER2 therapies.

Patients and methods

GC patients (n = 237), including a subset from the Trastuzumab in GC (ToGA) trial were divided into three groups based on HER2 status and history of treatment with standard chemotherapy or chemotherapy plus trastuzumab. We applied mass spectrometry-based proteomic analysis to quantify HER2 protein expression in formalin-fixed tumor samples. Using HER2 expression as a continuous variable, we defined a predictive protein level cutoff to identify which patients would benefit from trastuzumab. We compared quantitated protein level with clinical outcome and HER2 status as determined by conventional HER2 diagnostics.

Results

Quantitative proteomics detected a 115-fold range of HER2 protein expression among patients diagnosed as HER2 positive by standard methods. A protein level of 1825 amol/µg was predicted to determine benefit from the addition of trastuzumab to chemotherapy. Trastuzumab treated patients with HER2 protein levels above this cutoff had twice the median overall survival (OS) of their counterparts below the cutoff (35.0 versus 17.5 months, P = 0.011). Conversely, trastuzumab-treated patients with HER2 levels below the cutoff had outcomes similar to HER2-positive patients treated with chemotherapy. (Progression-free survival = 7.0 versus 6.5 months: P = 0.504; OS = 17.5 versus 12.6 months: P = 0.520). HER2 levels were not prognostic for response to chemotherapy.

Conclusions

Proteomic analysis of HER2 expression demonstrated a quantitative cutoff that improves selection of GC patients for trastuzumab as compared with current diagnostic methods.

Characterization of Novel Antimalarial Compound ACT-451840: Preclinical Assessment of Activity and Dose-Efficacy Modeling

BACKGROUND

Artemisinin resistance observed in Southeast Asia threatens the continued use of artemisinin-based combination therapy in endemic countries. Additionally, the diversity of chemical mode of action in the global portfolio of marketed antimalarials is extremely limited. Addressing the urgent need for the development of new antimalarials, a chemical class of potent antimalarial compounds with a novel mode of action was recently identified. Herein, the preclinical characterization of one of these compounds, ACT-451840, conducted in partnership with academic and industrial groups is presented.

METHOD AND FINDINGS

The properties of ACT-451840 are described, including its spectrum of activities against multiple life cycle stages of the human malaria parasite Plasmodium falciparum (asexual and sexual) and Plasmodium vivax (asexual) as well as oral in vivo efficacies in two murine malaria models that permit infection with the human and the rodent parasites P. falciparum and Plasmodium berghei, respectively. In vitro, ACT-451840 showed a 50% inhibition concentration of 0.4 nM (standard deviation [SD]: ± 0.0 nM) against the drug-sensitive P. falciparum NF54 strain. The 90% effective doses in the in vivo efficacy models were 3.7 mg/kg against P. falciparum (95% confidence interval: 3.3-4.9 mg/kg) and 13 mg/kg against P. berghei (95% confidence interval: 11-16 mg/kg). ACT-451840 potently prevented male gamete formation from the gametocyte stage with a 50% inhibition concentration of 5.89 nM (SD: ± 1.80 nM) and dose-dependently blocked oocyst development in the mosquito with a 50% inhibitory concentration of 30 nM (range: 23-39). The compound's preclinical safety profile is presented and is in line with the published results of the first-in-man study in healthy male participants, in whom ACT-451840 was well tolerated. Pharmacokinetic/pharmacodynamic (PK/PD) modeling was applied using efficacy in the murine models (defined either as antimalarial activity or as survival) in relation to area under the concentration versus time curve (AUC), maximum observed plasma concentration (Cmax), and time above a threshold concentration. The determination of the dose-efficacy relationship of ACT-451840 under curative conditions in rodent malaria models allowed prediction of the human efficacious exposure.

CONCLUSION

The dual activity of ACT-451840 against asexual and sexual stages of P. falciparum and the activity on P. vivax have the potential to meet the specific profile of a target compound that could replace the fast-acting artemisinin component and harbor additional gametocytocidal activity and, thereby, transmission-blocking properties. The fast parasite reduction ratio (PRR) and gametocytocidal effect of ACT-451840 were recently also confirmed in a clinical proof-of-concept (POC) study.

Pyrazoleamide compounds are potent antimalarials that target Na+ homeostasis in intraerythrocytic Plasmodium falciparum

The quest for new antimalarial drugs, especially those with novel modes of action, is essential in the face of emerging drug-resistant parasites. Here we describe a new chemical class of molecules, pyrazoleamides, with potent activity against human malaria parasites and showing remarkably rapid parasite clearance in an in vivo model. Investigations involving pyrazoleamide-resistant parasites, whole-genome sequencing and gene transfers reveal that mutations in two proteins, a calcium-dependent protein kinase (PfCDPK5) and a P-type cation-ATPase (PfATP4), are necessary to impart full resistance to these compounds. A pyrazoleamide compound causes a rapid disruption of Na⁺ regulation in blood-stage Plasmodium falciparum parasites. Similar effect on Na⁺ homeostasis was recently reported for spiroindolones, which are antimalarials of a chemical class quite distinct from pyrazoleamides. Our results reveal that disruption of Na⁺ homeostasis in malaria parasites is a promising mode of antimalarial action mediated by at least two distinct chemical classes.

Novel antimalarial drugs are urgently needed to combat parasite drug resistance. Here, Vaidya et al. describe a new chemical class of potent antimalarial compounds that act by disrupting the parasite's sodium homeostasis.

EBV & HHV6 reactivation is infrequent and not associated with MS clinical course

BACKGROUND

Among the environmental factors associated with multiple sclerosis (MS) causation, some of the strongest associations are with Epstein-Barr virus (EBV), and to a lesser extent human herpesvirus 6 (HHV6). Associations with clinical course are less conclusive, however.

METHODS

We evaluated serum anti-EBV-EA-R IgG and anti-HHV6 IgM, and EBV and HHV6 viral load (VL) for their associations with relapse, disability, and progression in disability in a prospective cohort of 198 participants with clinically definite MS.

RESULTS

Anti-EBV-EA-R IgG was detected in 81.8% of cases at study entry, and titers remained essentially unchanged during the study. Anti-HHV6 IgM was detected in only one participant, and EBV-VL (29%) and HHV6-VL (1.8%) were detected in a minority of samples, and where detected levels were low. Our previously demonstrated association between anti-HHV6 IgG and relapse hazard was not affected by adjustment for parameters of reactivation. We found no evidence that any of the viral markers were associated with disability or progression in disability. In relation to relapse, only EBV-VL was positively associated, although this was strongly influenced by a single individual.

CONCLUSION

Using a prospective cohort design, we found no convincing evidence that reactivation parameters of EBV or HHV6 were associated with subsequent MS relapse hazard or progression in disability, confirming previous findings, and indicating that herpesvirus reactivation is not an important driver of relapse or disability in this established MS population.

Case Study of Small Molecules As Antimalarials: 2-Amino-1-phenylethanol (APE) Derivatives

Antiparasitic oral drugs have been associated to lipophilic molecules due to their intrinsic permeability. However, these kind of molecules are associated to numerous adverse effects, which have been extensively studied. Within the Tres Cantos Antimalarial Set (TCAMS) we have identified two small, soluble and simple hits that even presenting antiplasmodial activities in the range of 0.4-0.5 μM are able to show in vivo activity.

Simulated air quality and pollutant budgets over Europe in 2008

Major gaseous and particulate pollutant levels over Europe in 2008 have been simulated using the offline-coupled WRFCMAQ chemistry and transport modeling system. The simulations are compared with surface observations from the EMEP stations, ozone (O3) soundings, ship-borne O3 and nitrogen dioxide (NO2) observations in the western Mediterranean, tropospheric NO2 vertical column densities from the SCIAMACHY instrument, and aerosol optical depths (AOD) from the AERONET. The results show that on average, surface O3 levels are underestimated by 4 to 7% over the northern European EMEP stations while they are overestimated by 7-10% over the southern European EMEP stations and underestimated in the tropospheric column (by 10-20%). Particulate matter (PM) mass concentrations are underestimated by up to 60%, particularly in southern and eastern Europe, suggesting underestimated PM sources. Larger differences are calculated for individual aerosol components, particularly for organic and elemental carbon than for the total PM mass, indicating uncertainty in the combustion sources. Better agreement has been obtained for aerosol species over urban areas of the eastern Mediterranean, particularly for nss-SO4(2), attributed to the implementation of higher quality emission inventories for that area. Simulated AOD levels are lower than the AERONET observations by 10% on average, with average underestimations of 3% north of 40°N, attributed to the low anthropogenic emissions in the model and 22% south of 40°N, suggesting underestimated natural and resuspended dust emissions. Overall, the results reveal differences in the model performance between northern and southern Europe, suggesting significant differences in the representation of both anthropogenic and natural emissions in these regions. Budget analyses indicate that O3 and peroxyacetyl nitrate (PAN) are transported from the free troposphere (FT) to the planetary boundary layer over Europe, while other species follow the reverse path and are then advected away from the source region.

Identification of RBCK1 as a novel regulator of FKBPL: implications for tumor growth and response to tamoxifen

FKBPL has been implicated in processes associated with cancer, including regulation of tumor growth and angiogenesis with high levels of FKBPL prognosticating for improved patient survival. Understanding how FKBPL levels are controlled within the cell is therefore critical. We have identified a novel role for RBCK1 as an FKBPL-interacting protein, which regulates FKBPL stability at the post-translational level via ubiquitination. Both RBCK1 and FKBPL are upregulated by 17-β-estradiol and interact within heat shock protein 90 chaperone complexes, together with estrogen receptor-α (ERα). Furthermore, FKBPL and RBCK1 associate with ERα at the promoter of the estrogen responsive gene, pS2, and regulate pS2 levels. MCF-7 clones stably overexpressing RBCK1 were shown to have reduced proliferation and increased levels of FKBPL and p21. Furthermore, these clones were resistant to tamoxifen therapy, suggesting that RBCK1 could be a predictive marker of response to endocrine therapy. RBCK1 knockdown using targeted small interfering RNA resulted in increased proliferation and increased sensitivity to tamoxifen treatment. Moreover, in support of our in vitro data, analysis of mRNA microarray data sets demonstrated that high levels of FKBPL and RBCK1 correlated with increased patient survival, whereas high RBCK1 predicted for a poor response to tamoxifen. Our findings support a role for RBCK1 in the regulation of FKBPL with important implications for estrogen receptor signaling, cell proliferation and response to endocrine therapy.

Abstract P1-07-19: Mass Spectrometry Based Quantitative Analysis of the HER Family receptors in FFPE Breast Cancer Tissue

The human EGF receptor family (HER's) consists of two clinically validated drug targets (EGFR and HER2), a third (HER3) currently under investigation for its possible role in the acquisition of multidrug resistance and a fourth (HER4), the role of which is still matter of debate. Drugs inhibiting EGFR or HER2 show significant antitumor activity in the clinic, however, acquisition of resistance is a hallmark of these and most targeted therapies. In the case of EGFR and HER2, one of the emerging resistance mechanisms is the co-expression of HER3. Indeed, recent reports show that inhibition of the PI3K pathway leads to upregulation of HER3, and subsequent resistance. Clinical analysis of protein levels in formalin fixed paraffin embedded (FFPE) tissues is limited to immunohistochemistry (IHC), which is semi-quantitative and requires significant amounts of tissue. Moreover, the vast majority of research groups consider specific HER3 staining by IHC particularly challenging. However, accurate measurement of these targets is critical both for properly defining treatment groups and predicting patterns of resistance.

In order to address these issues, we used trypsin digestion mapping and stable isotope labeled peptides to develop a panel of quantitative mass spectrometric (MS) assays to measure the levels of EGFR, HER2, HER3 and other clinically relevant targets in FFPE breast cancer tissue. These quantitative MS assays were then multiplexed to analyze 1μg of tumor protein.

In this study, we multiplexed HER family analysis on 31 HER2 positive breast cancers. Tumor tissue was microdissected from FFPE sections, and subjected to quantitative MS analysis of EGFR, HER2, HER3 as well as IGF1R and cMET. Quantitation of HER2 showed a broad range of HER2 expression in these tissues. The highest expresser measured 26 fmol/ug tumor tissue, representing amplification and massive protein over expression. In contrast, five tissues showed low levels of HER2 expression, below 1 fmol/ug, similar to HER2 non-amplified cell lines. This suggests that MS quantitation can identify patients with low expression of HER2 who are unlikely to respond to trastuzumab therapy. As a matter of fact, 3 of these 5 low expressing patients had outcome data and showed no response to trastuzumab treatment.

In 28 of 31 patient tissue samples, HER3 showed low levels of expression (100–300 amol/ug tumor tissue) similar to HER3 expression in cell lines, and comparable to low expressing EGFR and HER2 cell lines. The remaining 3 patients had no detectable HER3. This study demonstrates the feasibility of measuring HER3 in multiplex in FFPE breast cancer tissue. Based on the low but widespread expression of HER3 in this cohort, it may be most useful to assess HER3 expression after initial treatment as a marker of potential resistance to targeted therapies.

Taken together, these data demonstrate that a sensitive and quantitative assay to measure oncoproteins in FFPE clinical samples may help stratify patients with variable expression of these targets. Our quantitation of oncogene expression from clinical samples uses a small amount of tissue, is clinically applicable and alleviates the problem of scoring either positive or negative for the expression of a given protein.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-19.

Identification and In-Vitro ADME Assessment of a Series of Novel Anti-Malarial Agents Suitable for Hit-to-Lead Chemistry

Triage of a set of antimalaria hit compounds, identified through high throughput screening against the Chloroquine sensitive (3D7) and resistant (Dd2) parasite Plasmodium falciparum strains identified several novel chemotypes suitable for hit-to-lead chemistry investigation. The set was further refined through investigation of their in vitro ADME properties, which identified templates with good potential to be developed further as antimalarial agents. One example was profiled in an in vivo murine Plasmodium berghei model of malaria infection.

A Divergent SAR Study Allows Optimization of a Potent 5-HT2c Inhibitor to a Promising Antimalarial Scaffold

From the 13 533 chemical structures published by GlaxoSmithKline in 2010, we identified 47 quality starting points for lead optimization. One of the most promising hits was the TCMDC-139046, a molecule presenting an indoline core, which is well-known for its anxiolytic properties by interacting with serotonin antagonist receptors 5-HT2. The inhibition of this target will complicate the clinical development of these compounds as antimalarials. Herein, we present the antimalarial profile of this series and our efforts to avoid interaction with this receptor, while maintaining a good antiparasitic potency. By using a double-divergent structure-activity relationship analysis, we have obtained a novel lead compound harboring an indoline core.

Lead optimization of aryl and aralkyl amine-based triazolopyrimidine inhibitors of Plasmodium falciparum dihydroorotate dehydrogenase with antimalarial activity in mice

Malaria is one of the leading causes of severe infectious disease worldwide; yet, our ability to maintain effective therapy to combat the illness is continually challenged by the emergence of drug resistance. We previously reported identification of a new class of triazolopyrimidine-based Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) inhibitors with antimalarial activity, leading to the discovery of a new lead series and novel target for drug development. Active compounds from the series contained a triazolopyrimidine ring attached to an aromatic group through a bridging nitrogen atom. Herein, we describe systematic efforts to optimize the aromatic functionality with the goal of improving potency and in vivo properties of compounds from the series. These studies led to the identification of two new substituted aniline moieties (4-SF(5)-Ph and 3,5-Di-F-4-CF(3)-Ph), which, when coupled to the triazolopyrimidine ring, showed good plasma exposure and better efficacy in the Plasmodium berghei mouse model of the disease than previously reported compounds from the series.

Adverse drug effects following oseltamivir mass treatment and prophylaxis in a school outbreak of 2009 pandemic influenza A(H1N1) in June 2009, Sheffield, United Kingdom

During the containment phase of the 2009 influenza A(H1N1) pandemic, mass treatment and prophylaxis with oseltamivir was used to control an outbreak of pandemic influenza in a primary school in Sheffield, United Kingdom, where ten cases of pandemic influenza had been laboratory confirmed over a three day period in June 2009. A subsequent cross-sectional survey showed that 51 of 297 (17%) pupils and 10 of 58 (17%) reported an influenza-like illness. The most common symptoms were headache, cough, fever, tiredness, sore throat and nausea. Fifty-three staff and 273 pupils took oseltamivir for treatment or prophylaxis. Of this group, 41% (113/273) of pupils and 47% (25/53) of staff reported adverse effects. Overall, 14% (37/273) of pupils and 20% (11/53) of staff did not complete the course of oseltamivir, primarily due to adverse effects. Nausea, vomiting and rash were statistically significantly associated with failing to complete the course of oseltamivir. Given the potential for side effects from oseltamivir, particularly among those without influenza who receive the drug for prophylaxis, our findings have two important implications. Firstly, the benefits of mass treatment in an outbreak setting must clearly be greater than the benefits of targeted treatment. Secondly, any large scale regional or state level system for distribution of antiviral drugs for treatment should ideally include a robust quantification of an individual’s probability of infection with influenza virus in order to avoid unnecessary treatment.

Adverse drug effects following oseltamivir mass treatment and prophylaxis in a school outbreak of 2009 pandemic influenza A(H1N1) in June 2009, Sheffield, United Kingdom

During the containment phase of the 2009 influenza A(H1N1) pandemic, mass treatment and prophylaxis with oseltamivir was used to control an outbreak of pandemic influenza in a primary school in Sheffield, United Kingdom, where ten cases of pandemic influenza had been laboratory confirmed over a three day period in June 2009. A subsequent cross-sectional survey showed that 51 of 297 (17%) pupils and 10 of 58 (17%) reported an influenza-like illness. The most common symptoms were headache, cough, fever, tiredness, sore throat and nausea. Fifty-three staff and 273 pupils took oseltamivir for treatment or prophylaxis. Of this group, 41% (113/273) of pupils and 47% (25/53) of staff reported adverse effects. Overall, 14% (37/273) of pupils and 20% (11/53) of staff did not complete the course of oseltamivir, primarily due to adverse effects. Nausea, vomiting and rash were statistically significantly associated with failing to complete the course of oseltamivir. Given the potential for side effects from oseltamivir, particularly among those without influenza who receive the drug for prophylaxis, our findings have two important implications. Firstly, the benefits of mass treatment in an outbreak setting must clearly be greater than the benefits of targeted treatment. Secondly, any large scale regional or state level system for distribution of antiviral drugs for treatment should ideally include a robust quantification of an individual s probability of infection with influenza virus in order to avoid unnecessary treatment.