Discovery of Novel, Orally Bioavailable, Antileishmanial Compounds Using Phenotypic Screening

Leishmaniasis is a parasitic infection that afflicts approximately 12 million people worldwide. There are several limitations to the approved drug therapies for leishmaniasis, including moderate to severe toxicity, growing drug resistance, and the need for extended dosing. Moreover, miltefosine is currently the only orally available drug therapy for this infection. We addressed the pressing need for new therapies by pursuing a two-step phenotypic screen to discover novel, potent, and orally bioavailable antileishmanials. First, we conducted a high-throughput screen (HTS) of roughly 600,000 small molecules for growth inhibition against the promastigote form of the parasite life cycle using the nucleic acid binding dye SYBR Green I. This screen identified approximately 2,700 compounds that inhibited growth by over 65% at a single point concentration of 10 μM. We next used this 2700 compound focused library to identify compounds that were highly potent against the disease-causing intra-macrophage amastigote form and exhibited limited toxicity toward the host macrophages. This two-step screening strategy uncovered nine unique chemical scaffolds within our collection, including two previously described antileishmanials. We further profiled two of the novel compounds for in vitro absorption, distribution, metabolism, excretion, and in vivo pharmacokinetics. Both compounds proved orally bioavailable, affording plasma exposures above the half-maximal effective concentration (EC50) concentration for at least 12 hours. Both compounds were efficacious when administered orally in a murine model of cutaneous leishmaniasis. One of the two compounds exerted potent activity against trypanosomes, which are kinetoplastid parasites related to Leishmania species. Therefore, this compound could help control multiple parasitic diseases. The promising pharmacokinetic profile and significant in vivo efficacy observed from our HTS hits highlight the utility of our two-step phenotypic screening strategy and strongly suggest that medicinal chemistry optimization of these newly identified scaffolds will lead to promising candidates for an orally available anti-parasitic drug

PRL3-zumab, a first-in-class humanized antibody for cancer therapy

Novel, tumor-specific drugs are urgently needed for a breakthrough in cancer therapy. Herein, we generated a first-in-class humanized antibody (PRL3-zumab) against PRL-3, an intracellular tumor-associated phosphatase upregulated in multiple human cancers, for unconventional cancer immunotherapies. We focused on gastric cancer (GC), wherein elevated PRL-3 mRNA levels significantly correlated with shortened overall survival of GC patients. PRL-3 protein was overexpressed in 85% of fresh-frozen clinical gastric tumor samples examined but not in patient-matched normal gastric tissues. Using human GC cell lines, we demonstrated that PRL3-zumab specifically blocked PRL-3(+), but not PRL-3(–), orthotopic gastric tumors. In this setting, PRL3-zumab had better therapeutic efficacy as a monotherapy, rather than simultaneous combination with 5-fluorouracil or 5-fluorouracil alone. PRL3-zumab could also prevent PRL-3(+) tumor recurrence. Mechanistically, we found that intracellular PRL-3 antigens could be externalized to become “extracellular oncotargets” that serve as bait for PRL3-zumab binding to potentially bridge and recruit immunocytes into tumor microenvironments for killing effects on cancer cells. In summary, our results document a comprehensive cancer therapeutic approach to specific antibody-targeted therapy against the PRL-3 oncotarget as a case study for developing antibodies against other intracellular targets in drug discovery

Understanding the journeys of patients with an asthma exacerbation requiring urgent therapy at a primary care clinic

Background: Asthma is a significant health issue in primary care. We examined the journeys of patients with asthma exacerbations requiring urgent therapy at a primary care clinic in Singapore. Methods: Face-to-face semi-structured interviews were conducted with patients who received urgent therapy for asthma exacerbation at a primary care clinic. Data collected was used to construct themes. Results: Fifteen multi-ethnic adult patients were recruited. Participants cited treatment cost, underuse of preventer medication, difficulties attending routine asthma care due to work, and stigma as barriers to asthma control. Reasons for delay in seeking urgent care for asthma were: inability to access medical care out of hours, competing priorities, perception that an exacerbation was ‘not serious enough’, difficulty recognizing symptoms of asthma exacerbation, and being tired or despondent. Participants were triggered to seek care due to failure of reliever inhalers, duration of symptoms, sleep disturbance, inability to work, or advice from others. During an exacerbation, participants often initiated other self-management measures besides using reliever medication. This included over-the-counter medications and non-pharmacological interventions (e.g. drinking water). Of the 15 patients interviewed, only one stepped up preventer inhaler adequately, according to their Asthma Action Plan (AAP). Conclusions: In caring for patients with asthma, primary care providers should address patients’ asthma self-management skills, such as recognizing symptoms of asthma exacerbations and regular preventer use, and provide clear instructions on how to respond to asthma symptoms (AAP). Minimizing direct (medication and consultation fees) and indirect costs (loss of earnings and adverse impact on employment prospects) are also important considerations.Ministry of Health (MOH)Nanyang Technological UniversityNational Medical Research Council (NMRC)Published versionThis research was supported by funding from the NHG-LKCMedicine Clinician-Scientist Preparatory Programme (Reference Code: CSPP-18003); the Singapore Ministry of Health’s National Medical Research Council under the Centre Grant Programme (Reference No. NMRC/CG/C019/2017)

Reduced carboxylesterase 1 is associated with endothelial injury in methamphetamine-induced pulmonary arterial hypertension

Pulmonary arterial hypertension is a complication of methamphetamine use (METH-PAH), but the pathogenic mechanisms are unknown. Given that cytochrome P450 2D6 (CYP2D6) and carboxylesterase 1 (CES1) are involved in metabolism of METH and other amphetamine-like compounds, we postulated that loss of function variants could contribute to METH-PAH. Although no difference in CYP2D6 expression was seen by lung immunofluorescence, CES1 expression was significantly reduced in endothelium of METH-PAH microvessels. Mass spectrometry analysis showed that healthy pulmonary microvascular endothelial cells (PMVECs) have the capacity to both internalize and metabolize METH. Furthermore, whole exome sequencing data from 18 METH-PAH patients revealed that 94.4% of METH-PAH patients were heterozygous carriers of a single nucleotide variant (SNV; rs115629050) predicted to reduce CES1 activity. PMVECs transfected with this CES1 variant demonstrated significantly higher rates of METH-induced apoptosis. METH exposure results in increased formation of reactive oxygen species (ROS) and a compensatory autophagy response. Compared with healthy cells, CES1-deficient PMVECs lack a robust autophagy response despite higher ROS, which correlates with increased apoptosis. We propose that reduced CES1 expression/activity could promote development of METH-PAH by increasing PMVEC apoptosis and small vessel loss.Peer reviewe

IL-1beta Signals through the EGF Receptor and Activates Egr-1 through MMP-ADAM

<div><p>The immediate-early gene Egr-1 controls the inducible expression of many genes implicated in the pathogenesis of a range of vascular disorders, yet our understanding of the mechanisms controlling the rapid expression of this prototypic zinc finger transcription factor is poor. Here we show that Egr-1 expression induced by IL-1beta is dependent on metalloproteinases (MMP) and <u>a d</u>isintegrin <u>a</u>nd a <u>m</u>etalloproteinase (ADAM). Pharmacologic MMP/ADAM inhibitors and siRNA knockdown prevent IL-1beta induction of Egr-1. Further, IL-1beta activates Egr-1 via the epidermal growth factor receptor (EGFR). This is blocked by EGFR tyrosine kinase inhibition and EGFR knockdown. IL-1beta induction of Egr-1 expression is reduced in murine embryonic fibroblasts (mEFs) deficient in ADAM17 despite unbiased expression of EGFR and IL-1RI in ADAM17-deficient and wild-type mEFs. Finally, we show that IL-1beta-inducible wound repair after mechanical injury requires both EGFR and MMP/ADAM. This study reports for the first time that Egr-1 induction by IL-1beta involves EGFR and MMP/ADAM-dependent EGFR phosphorylation.</p> </div

ADAM17 is required for IL-1beta–inducible Egr-1 expression.

<p>(<b>A</b>) Western blotting for Egr-1, ADAM17, EGFR, IL-1RI or beta-actin using total extracts of growth-quiescent wild-type or ADAM17-deficient mEFs treated with IL-1beta for 30 or 60 min. (<b>B</b>) Interaction of ¹²⁵I-IL-1beta with ADAM17WT and ADAM17-deficient cells. Growth-quiescent ADAM17WT and ADAM17−/− mEFs (1.8×10⁴ cells/well) were incubated with increasing amounts of ¹²⁵I-IL-1beta in 1% BSA/PBS for 1 h at 4°C. The cells were washed and lysed with 1M NaOH prior to assessment of counts in an automated gamma-counter.</p

Induction of Egr-1 by IL-1beta is EGFR-dependent.

<p>Growth-quiescent SMCs were incubated with EGFR inhibitors AG1478 (5 µM) and PD153035 (5 µM) for 30 min, and exposed to IL-1beta (10 ng/ml) for another 30 min (unless indicated otherwise). (<b>A</b>) Egr-1 mRNA levels in AG1478- and PD153035-treated SMCs incubated with IL-1beta by qPCR. Data were normalized to beta-actin. (<b>B</b>) Western blotting for Egr-1 or beta-actin of total extracts of SMCs treated with AG1478 or PD153035. (<b>C</b>) Western blotting for EGFR, Egr-1 or beta-actin of total extracts of SMCs transfected overnight with EGFR siRNA (0.1 µM) and treated with IL-1beta for 30 min. (<b>D</b>) Western blotting for ErbB4, EGFR, Egr-1 or beta-actin of total extracts of SMCs transfected overnight with ErbB4 siRNA (0.1 µM) and treated with IL-1beta for 30 min. (<b>E</b>) Egr-1 mRNA levels in AG825 (10 µM for 30 min)-treated SMCs incubated with IL-1beta for 30 min by qPCR. Data were normalized to beta-actin. (<b>F</b>) Western blotting for Egr-1 or beta-actin in total extracts of SMCs pretreated with AG825 (10 µM for 30 min) then stimulated with IL-1beta for another 30 min.</p