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SummaryAutophagy activation has the potential to ameliorate neurodegenerative disease phenotypes, including protein aggregation, lipid level perturbations and axonal trafficking defects. We performed a high content imaging-based screen assessing 940,000 small molecules to identify those that accelerate lipid droplet clearance. Hits were validated in diverse cell lines and by counter-screening. Of the 77 validated structurally diverse hits, 24 increase autophagy flux. Herein, we highlight CCT020312 as a mammalian target of rapamycin (mTOR) inhibitor-independent autophagy activator, which should function without suppressing the immune response. CCT020312 dose-dependently reduces cytotoxic axonal mutant prion protein aggregate levels within endosomes of primary murine hippocampal neurons and normalizes axonal trafficking deficiencies. Moreover, CCT020312 robustly clears phosphorylated insoluble tau, while reducing tau-mediated neuronal stress vulnerability in patient-derived neuronal models. CCT020312 also restores lysosomal function in neurons differentiated from sporadic Alzheimer’s patients fibroblasts bearing epigenetic marks of aging. Taken together, we describe a promising strategy to uncover novel pharmacological agents that normalize cellular neurodegenerative disease pathology.

BackgroundHigh-grade meningioma is an aggressive type of brain cancer that is often recalcitrant to surgery and radiotherapy, leading to poor overall survival. Currently, there are no FDA-approved drugs for meningioma, highlighting the need for new therapeutic options, but development is challenging due to the lack of predictive preclinical models.MethodsTo leverage the known overexpression of procaspase-3 in meningioma, PAC-1, a blood-brain barrier penetrant procaspase-3 activator, was evaluated for its ability to induce apoptosis in meningioma cells. To enhance the effects of PAC-1, combinations with either hydroxyurea or temozolomide were explored in cell culture. Both combinations were further investigated in small groups of canine meningioma patients and assessed by MRI, and the novel apoptosis tracer, [18F]C-SNAT4, was evaluated in patients treated with PAC-1 + HU.ResultsIn meningioma cell lines in culture, PAC-1 + HU are synergistic while PAC-1 + TMZ show additive-to-synergistic effects. In canine meningioma patients, PAC-1 + HU led to stabilization of disease and no change in apoptosis within the tumor, whereas PAC-1 + TMZ reduced tumor burden in all three canine patients treated.ConclusionsOur results suggest PAC-1 + TMZ as a potentially efficacious combination for the treatment of human meningioma, and also demonstrate the utility of including pet dogs with meningioma as a means to assess anticancer strategies for this common brain tumor.

Therapeutic proteins alleviate disease pathology by supplementing missing or defective native proteins, sequestering superfluous proteins, or by acting through designed non-natural mechanisms. Although therapeutic proteins often have the same amino acid sequence as their native counterpart, their maturation paths from expression to the site of physiological activity are inherently different, and optimizing protein sequences for properties that 100s of millions of years of evolution did not need to address presents an opportunity to develop better biological treatments. Because therapeutic proteins are inherently non-natural entities, optimization for their desired function should be considered analogous to that of small molecule drug candidates, which are optimized through expansive combinatorial variation by the medicinal chemist. Here, we review recent successes and challenges of protein engineering for optimized therapeutic efficacy.

// Avadhut D. Joshi 1,* , Rachel C. Botham 2,* , Lisa J. Schlein 3 , Howard S. Roth 2 , Antonella Mangraviti 1 , Alexandra Borodovsky 1 , Betty Tyler 1 , Steve Joslyn 4 , Jayme S. Looper 5 , Michael Podell 6 , Timothy M. Fan 7 , Paul J. Hergenrother 2 and Gregory J. Riggins 1 1 Department of Neurosurgery, School of Medicine, Johns Hopkins University, Baltimore, MD, USA 2 Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL, USA 3 Department of Pathobiology, University of Illinois Urbana-Champaign, Urbana, IL, USA 4 VetCT Australia, Fremantle WA, Australia 5 Department of Veterinary Clinical Sciences, Louisiana State University, Baton Rouge, LA, USA 6 Department of Neurology, MedVet Chicago, Chicago, IL, USA 7 Department of Veterinary Clinical Medicine, University of Illinois Urbana-Champaign, Urbana, IL, USA * These authors have contributed equally to this work Correspondence to: Gregory J. Riggins, email: // Paul J. Hergenrother, email: // Timothy M. Fan, email: // Keywords : PAC-1, procaspase-3 activator, glioblastoma, small molecule therapy Received : March 29, 2017 Accepted : June 09, 2017 Published : July 07, 2017 Abstract Purpose: Glioblastoma is a deadly brain cancer with a median survival time of ~15 months. Ionizing radiation plus the DNA alkylator temozolomide (TMZ) is the current standard therapy. PAC-1, a procaspase-3 activating small molecule, is blood-brain barrier penetrant and has previously demonstrated ability to synergize with diverse pro-apoptotic chemotherapeutics. We studied if PAC-1 could enhance the activity of TMZ, and whether addition of PAC-1 to standard treatment would be feasible in spontaneous canine malignant gliomas. Experimental Design: Using cell lines and online gene expression data, we identified procaspase-3 as a potential molecular target for most glioblastomas. We investigated PAC-1 as a single agent and in combination with TMZ against glioma cells in culture and in orthotopic rodent models of glioma. Three dogs with spontaneous gliomas were treated with an analogous human glioblastoma treatment protocol, with concurrent PAC-1. Results: Procaspase-3 is expressed in gliomas, with higher gene expression correlating with increased tumor grade and decreased prognosis. PAC-1 is cytotoxic to glioma cells in culture and active in orthotopic rodent glioma models. PAC-1 added to TMZ treatments in cell culture increases apoptotic death, and the combination significantly increases survival in orthotopic glioma models. Addition of PAC-1 to TMZ and radiation was well-tolerated in 3 out of 3 pet dogs with spontaneous glioma, and partial to complete tumor reductions were observed. Conclusions: Procaspase-3 is a clinically relevant target for treatment of glioblastoma. Synergistic activity of PAC-1/TMZ in rodent models and the demonstration of feasibility of the combined regime in canine patients suggest potential for PAC-1 in the treatment of glioblastoma.

Drug candidates that form covalent linkages with their target proteins have been underexplored compared with the conventional counterparts that modulate biological function by reversibly binding to proteins, in part due to concerns about off-target reactivity. However, toxicity linked to off-target reactivity can be minimized by using latent electrophiles that only become activated towards covalent bond formation on binding a specific protein. Here we study sulfuramidimidoyl fluorides, a class of weak electrophiles that undergo sulfur(VI) fluoride exchange chemistry. We show that equilibrium binding of a sulfuramidimidoyl fluoride to a protein can allow nucleophilic attack by a specific amino acid side chain, which leads to conjugate formation. We incubated small molecules, each bearing a sulfuramidimidoyl fluoride electrophile, with human cell lysate, and the protein conjugates formed were identified by affinity chromatography-mass spectrometry. This inverse drug discovery approach identified a compound that covalently binds to and irreversibly inhibits the activity of poly(ADP-ribose) polymerase 1, an important anticancer target in living cells.

Procaspase-Activating Compound 1 (PAC-1) is an ortho-hydroxy N-acyl hydrazone that enhances the enzymatic activity of procaspase-3 in vitro and induces apoptosis in cancer cells. An analogue of PAC-1, called S-PAC-1, was evaluated in a veterinary clinical trial in pet dogs with lymphoma and found to have considerable potential as an anticancer agent. With the goal of identifying more potent compounds in this promising class of experimental therapeutics, a combinatorial library based on PAC-1 was created, and the compounds were evaluated for their ability to induce death of cancer cells in culture. For library construction, 31 hydrazides were condensed in parallel with 27 aldehydes to create 837 PAC-1 analogues, with an average purity of 91%. The compounds were evaluated for their ability to induce apoptosis in cancer cells, and through this work, six compounds were discovered to be substantially more potent than PAC-1 and S-PAC-1. These six hits were further evaluated for their ability to relieve zinc-mediated inhibition of procaspase-3 in vitro. In general, the newly identified hit compounds are two- to four-fold more potent than PAC-1 and S-PAC-1 in cell culture, and thus have promise as experimental therapeutics for treatment of the many cancers that have elevated expression levels of procaspase-3.

This protocol describes the gram-scale solution-phase synthesis of the colorimetric caspase-3/7 substrate Ac-DEVD-pNA. The caspase enzymes are integral to cellular inflammation and apoptotic cascades, and are commonly studied by cell biologists, medicinal chemists and chemical biologists. In particular, the assessment of caspase enzymatic activity is a standard method to evaluate cell death pathways and new apoptosis-modulating agents. Caspase enzymatic activity can be conveniently monitored with peptidic chromogenic or fluorogenic substrates, with certain peptide sequences imparting selectivity for certain caspases. The synthesis of these peptide substrates is typically carried out by solid-phase synthesis, a method that is not ideal for production of the gram quantities needed for high-throughput screening. Described herein is a facile method for the synthesis of the Ac-DEVD-pNA caspase-3/7 substrate using solution-phase peptide synthesis. This protocol, involving iterative PyBOP-mediated couplings and Fmoc deprotections, is rapid (about 5 d), operationally simple and can be used to generate over 1 g of product at a fraction of the cost of the commercial substrate.

The influence of biotic interactions on the expression of inbreeding depression has received only modest investigation; however, these interactions may be important in determining the magnitude and/or variation of inbreeding depression seen in the wild and invoked in models of mating and sexual system evolution. We present the first experimental test of the effects of plant–mycorrhizal fungus interactions on the expression of inbreeding depression. We inoculated selfed and outcrossed seedlings from eight hermaphrodite genotypes of wild strawberry (Fragaria virginiana) with mycorrhizal fungal spores and determined the effect on vegetative growth and sexual and asexual reproduction. We found that inoculated plants grew at rates similar to those of control plants but produced fewer flowers and more plantlets than controls. However, some of these effects varied with maternal genotype and cross type. As a consequence, mycorrhizal fungal inoculation had variable and trait‐dependent effects on the expression of ...

Procaspase-activating compound 1 (PAC-1) is an o-hydroxy-N-acylhydrazone that induces apoptosis in cancer cells by chelation of labile inhibitory zinc from procaspase-3. PAC-1 has been assessed in a wide variety of cell culture experiments and in vivo models of cancer, with promising results, and a phase 1 clinical trial in cancer patients has been initiated (NCT02355535). For certain applications, however, the in vivo half-life of PAC-1 could be limiting. Thus, with the goal of developing a compound with enhanced metabolic stability, a series of PAC-1 analogues were designed containing modifications that systematically block sites of metabolic vulnerability. Evaluation of the library of compounds identified four potentially superior candidates with comparable anticancer activity in cell culture, enhanced metabolic stability in liver microsomes, and improved tolerability in mice. In head-to-head experiments with PAC-1, pharmacokinetic evaluation in mice demonstrated extended elimination half-lives and greater area under the curve values for each of the four compounds, suggesting them as promising candidates for further development.

Combination anticancer therapy typically consists of drugs that target different biochemical pathways or those that act on different targets in the same pathway. Here we demonstrate a new concept in combination therapy, that of enzyme activation with two compounds that hit the same biological target, but through different mechanisms. Combinations of procaspase-3 activators PAC-1 and 1541B show considerable synergy in activating procaspase-3 in vitro, stimulate rapid and dramatic maturation of procaspase-3 in multiple cancer cell lines, and powerfully induce caspase-dependent apoptotic death to a degree well exceeding the additive effect. In addition, the combination of PAC-1 and 1541B effectively reduces tumor burden in a murine lymphoma model at dosages for which the compounds alone have minimal or no effect. These data suggest the potential of PAC-1/1541B combinations for the treatment of cancer and, more broadly, demonstrate that differentially acting enzyme activators can potently synergize to give a significantly heightened biological effect.

PAC-1 is an oral administered procaspase-3 activating drug developed to overcome the malignant cell's barrier to apoptosis. The promising preclinical safety and efficacy of PAC-1 has led to its consideration for a first in human phase 1 clinical trial for recurrent and advanced malignancies. We have found that because PAC-1 is able to reach intracranial brain tumors in effective concentrations, that it is particularly useful for glioblastoma (GBM), an aggressive and invasive malignancy responsible for the most deaths due to brain cancer. In glioblastoma patients a worse prognosis was correlated with high expression of procaspase-3 mRNA, indicating that procaspase-3 activation may be involved in the pathology of the tumor progression. In preclinical testing of PAC-1, it showed significant survival benefit and low systemic toxicity, in orthotopic animal models of glioblastoma. An aqueous suspension of PAC-1 delivered orally to rats with intracranial 9L glioblastoma improved survival compared to untreated controls. Additionally, when PAC-1 was administered as an oral capsule to rats with 9L glioblastoma, median survival increased over three fold. Oral PAC-1 improved survival significantly also in a human xenograft model (p = 0.04) compared to controls. PAC-1 combined effectively with standard of care, and in some animals, either alone or in combination resulted in long term survival. PAC-1 has the ability to penetrate sufficiently within intracranial tumors and its ability to overcome resistance to apoptosis and activate widespread cell death specifically in the malignant cells makes it a promising small molecule for further preclinical and clinical development. Citation Format: Avadhut D. Joshi, Rachel C. Botham, Howard S. Roth, Timothy M. Fan, Theodore M. Tarasow, Paul J. Hergenrother, Gregory J. Riggins. An oral procaspase activating drug, PAC-1, shows preclinical promise for glioblastoma therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3620. doi:10.1158/1538-7445.AM2015-3620