Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that causes the progressive loss of motoneurons and, unfortunately, there is no effective treatment for this disease. Interconnecting multiple pathological mechanisms are involved in the neuropathology of this disease, including abnormal aggregation of proteins, neuroinflammation and dysregulation of the ubiquitin proteasome system. Such complex mechanisms, together with the lack of reliable animal models of the disease have hampered the development of drugs for this disease. Protein kinases, a key pharmacological target in several diseases, have been linked to ALS as they play a central role in the pathology of many diseases. Therefore several inhibitors are being currently trailed for clinical proof of concept in ALS patients. In this review, we examine the recent literature on protein kinase inhibitors currently in pharmaceutical development for this diseaseas future therapy for AS together with their involvement in the pathobiology of ALS.
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This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.6/issuetoc
TDP‐43 has been identified as the major component of protein aggregates found in affected neurons in FTLD‐TDP and amyotrophic lateral sclerosis (ALS) patients. TDP‐43 is hyperphosphorylated, ubiquitinated, and cleaved in the C‐terminus. CDC‐7 was reported to phosphorylate TDP‐43. There are no effective treatments for either FTLD‐TDP or ALS, being a pressing need for the search of new therapies. We hypothesized that modulating CDC‐7 activity with small molecules that are able to interfere with TDP‐43 phosphorylation could be a good therapeutic strategy for these diseases. Here, we have studied the effects of novel brain penetrant, thiopurine‐based, CDC‐7 inhibitors in TDP‐43 homeostasis in immortalized lymphocytes from FTLD‐TDP patients, carriers of a loss‐of‐function GRN mutation, as well as in cells derived from sporadic ALS patients. We found that selective CDC‐7 inhibitors, ERP1.14a and ERP1.28a, are able to decrease the enhanced TDP‐43 phosphorylation in cells derived from FTLD‐TDP and ALS patients and to prevent cytosolic accumulation of TDP‐43. Moreover, treatment of FTLD‐TDP lymphoblasts with CDC‐7 inhibitors leads to recovering the nuclear function of TDP‐43‐inducing CDK6 repression. We suggest that CDC‐7 inhibitors, mainly the heterocyclic compounds here shown, may be considered as promising drug candidates for the ALS/FTD spectrum.
A potent cell division cycle 7 (CDC7) kinase inhibitor, known as PHA-767491, has been described to reduce the transactive response DNA binding protein of 43 KDa (TDP-43) phosphorylation in vitro and in vivo, which is one of the main proteins found to aggregate and accumulate in the cytoplasm of motoneurons in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) patients. However, the main drawback of this compound is its low permeability to the central nervous system (CNS), limiting its use for the treatment of neurological conditions. In this context, the use of drug delivery systems like nanocarriers has become an interesting approach to improve drug release to the CNS. In this study, we prepared and characterized biodegradable nanoparticles in order to encapsulate PHA-767491 and improve its permeability to the CNS. Our results demonstrate that poly (lactic-co-glycolic acid) (PLGA) nanoparticles with an average radius between 145 and 155 nm could be used to entrap PHA-767491 and enhance the permeability of this compound through the blood–brain barrier (BBB), becoming a promising candidate for the treatment of TDP-43 proteinopathies such as ALS.
Phosphodiesterase 7 (PDE7) is an enzyme responsible for the degradation of cyclic adenosine monophosphate (cAMP), an important cellular messenger. PDE7’s role in neurotransmission, expression profile in the brain and the druggability of other phosphodiesterases have motivated the search for potent inhibitors to treat neurodegenerative and inflammatory diseases. Different heterocyclic compounds have been described over the years; among them, phenyl-2-thioxo-(1H)-quinazolin-4-one, called S14, has shown very promising results in different in vitro and in vivo studies. Recently, polymeric nanoparticles have been used as new formulations to target specific organs and produce controlled release of certain drugs. In this work, we describe poly(lactic-co-glycolic acid) (PLGA)-based polymeric nanoparticles loaded with S14. Their preparation, optimization, characterization and in vivo drug release profile are here presented as an effort to improve pharmacokinetic properties of this interesting PDE7 inhibitor.
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