Publications by authors named "Chester E Markwalter"

Peptide and protein therapeutics generally exhibit high potency and specificity and are increasingly important segments of the pharmaceutical market. However, their clinical applications are limited by rapid clearance and poor membrane permeability. Encapsulation of the peptide or protein into a nano-scale carrier can modify its pharmacokinetics and biodistribution.

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The dosing of peptide and protein therapeutics is complicated by rapid clearance from the blood pool and poor cellular membrane permeability. Encapsulation into nanocarriers such as liposomes or polymersomes has long been explored to overcome these limitations, but manufacturing challenges have limited clinical translation by these approaches. Recently, inverse Flash NanoPrecipitation (iFNP) has been developed to produce highly loaded polymeric nanocarriers with the peptide or protein contained within a hydrophilic core, stabilized by a hydrophobic polymer shell.

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The tachykinin 2 receptor (NK2R) plays critical roles in gastrointestinal, respiratory and mental disorders and is a well-recognized target for therapeutic intervention. To date, therapeutics targeting NK2R have failed to meet regulatory agency approval due in large part to the limited characterization of the receptor-ligand interaction and downstream signaling. Herein, we report a protein engineering strategy to improve ligand-binding- and signaling-competent human NK2R that enables a yeast-based NK2R signaling platform by creating chimeras utilizing sequences from rat NK2R.

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The encapsulation of water-soluble therapeutics and biologics into nanocarriers to produce novel therapeutics has been envisioned for decades, but clinical translation has been hampered by complex synthesis strategies. The methods that have been developed are often limited by poor encapsulation efficiency/loading or complex processing to achieve therapeutic loadings high enough to be medically relevant. To address this unmet need, we introduce a solubility-driven self-assembly process to form polymeric nanocarriers comprising a biologic in a hydrophilic core, encapsulated by a poly(lactic acid) shell, and stabilized by a poly(ethylene glycol) brush.

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Background: "Nanomedicine" is the application of purposely designed nano-scale materials for improved therapeutic and diagnostic outcomes, which cannot be otherwise achieved using conventional delivery approaches. While "translation" in drug development commonly encompasses the steps from discovery to human clinical trials, a different set of translational steps is required in nanomedicine. Although significant development effort has been focused on nanomedicine, the translation from laboratory formulations up to large scale production has been one of the major challenges to the success of such nano-therapeutics.

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Article Synopsis
  • The use of nanoparticles (NPs) for therapeutic compounds can enhance drug bioavailability and provide protection for hydrophilic drugs against clearance in the body.
  • Flash NanoPrecipitation (FNP) is an efficient method for creating polymeric NPs, allowing for precise control over size and distribution (30-400 nm).
  • This protocol facilitates laboratory-scale production and offers a seamless transition to larger scales while maintaining consistency and high drug loading.
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The development of an improved short and efficient commercial synthesis of the JAK2 inhibitor, a complex pyrrolopyridine, BMS-911543, is described. During the discovery and development of this synthesis, a Pd-catalyzed C-H functionalization was invented which enabled the rapid union of the key pyrrole and imidazole fragments. The synthesis of this complex, nitrogen-rich heterocycle was accomplished in only six steps (longest linear sequence) from readily available materials.

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Unusual Pd deactivation and inhibition pathways were observed in a C-N coupling system. Irreversible catalyst deactivation involved C-H insertion of Pd into BippyPhos leading to an off-cycle palladaphosphacyclobutene. Product inhibition led to deactivated Pd but released ligand in the process, allowing it to react with additional Pd precursor to re-enter the catalytic cycle.

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Flash NanoPrecipitation is a scalable approach to generate polymeric nanoparticles using rapid micromixing in specially designed geometries such as a confined impinging jets mixer or a Multi-Inlet Vortex Mixer (MIVM). A major limitation of formulation screening using the MIVM is that a single run requires tens of milligrams of the therapeutic. To overcome this, we have developed a scaled-down version of the MIVM, requiring as little as 0.

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Fundamental understanding of protein stability away from physiological conditions is important due to its evolutionary implications and relevance to industrial processing and storage of biological materials. The molecular mechanisms of stabilization/destabilization by environmental perturbations are incompletely understood. We use replica-exchange molecular dynamics simulations and thermodynamic analysis to investigate the effects of ionic liquid-induced perturbations on the folding/unfolding thermodynamics of the Trp-cage miniprotein.

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