Background – What is Neurodegeneration?
A normal nerve cell receives signals, processes them in the cell body and transports them through the axon, a long-arm nerve fiber that extends out from the cell body and connects to the synapses, or fingers. These fingers then touch the successive nerve cell(s), where the signals are relayed further.
When brain cells become injured or stressed their first response is reduction and impairment of axonal transport. All neurodegenerative diseases show impairment in axonal transport, which means that information is not moving through the nerve cell and not transferring to other nerve cells. If the insult persists, axonal vesicle transport remains impaired resulting in decreased levels of neurotransmitters and leading to depression (serotonin), anxiety and insomnia (GABA), cognitive impairment, such as AD (acetylcholine), and movement disorders, such as PD (dopamine). It also results in lower levels of neurotrophic factors and in nerve cells getting sick. When the immune system sees a sick cell, it proceeds to remove it, which leads to inflammation in the brain. Eventually the sick cell is killed by the immune system.
ANVS-401 – Our Solution to Reverse Neurodegeneration
ANVS-401 is a small lipophilic molecule that is orally available and readily enters the brain as demonstrated by pharmacokinetic analyses showing brain concentrations approximately 6 to 8 times higher than plasma concentrations. ANVS-401 has a unique mechanism of action in that it inhibited the translation and, therefore, the levels of several key neurotoxic proteins both in vitro and in vivo including APP, tau and αSYN.
Brain injuries and stresses lead to increases in neurotoxic proteins, impaired axonal transport and nerve cell death – neurodegenerative diseases.
To date, all approaches have targeted one or the other neurotoxic protein with negative outcomes. We believe ANVS-401 is the only drug in development that targets multiple neurotoxic proteins.
Attacking one neurotoxic protein alone results in minimal effect. ANVS-401 is the only drug we know to attack multiple neurotoxic proteins and to normalize axonal transport in DS, AD and PD.
By targeting multiple neurotoxic proteins, ANVS-401 resembles a combination therapy approach, with the added convenience of being a single drug with a single drug target. Therefore, we have worked to understand how ANVS-401 is able to inhibit the translation of more than one neurotoxic protein.
Novel Mechanism of Action and Target Engagement
The brain responds to a number of insults by increasing the levels of neurotoxic proteins (APP/Aβ, tau/phospho-tau and α-synuclein) and neurotoxic proteins slow or stop axonal transport.
We undertook an extensive exploration of the mechanism of action of ANVS-401 on APP and αSYN synthesis and determined that ANVS-401 specifically inhibits translation of mRNAs coding for neurotoxic proteins only. Using 5 different methods we came up with overlapping results. mRNAs of neurotoxic proteins have a conserved stem loop in the 5′ untranslated region (5’UTR) called an iron-response element (IRE) type II stem loop. These IREs bind to an RNA binding protein, specifically to iron regulatory protein 1 (IRP1). When the mRNAs are bound, they are not translated, when the iron levels in the cytoplasm go up, IRP1 releases its mRNAs and they are translated.
ANVS-401 specifically binds to the IRE/IRP1 complex of mRNAs coding for neurotoxic proteins and stops the release of the mRNAs when iron levels are high. At the same time, it does not bind to IRE/IRP1 complexes of mRNAs coding for iron carrying or shuttling proteins, such as ferritin, transferring or ferroportin.
APP/IRE/IRP1/ ANVS-401 Kd 3.2 nM
Ferritin IRE/IRP1/ANVS-401 no Kd
ANVS-401 binds to the APP IRE/IRP1 complex but not the Ferritin IRE/IRP1 complex.
Since the 5’ UTR IRE is highly conserved among the mRNAs of neurotoxic proteins, ANVS-401 can inhibit the translation of several neurotoxic aggregating proteins by having just one binding site and by increasing the binding of that conserved IRE to IRP1 under high iron conditions (see graph below). This has been shown for APP and αSYN. We now understand that ANVS-401 only increases the binding of IREs of neurotoxic aggregating proteins to IRP1 under stress conditions, so it does not affect healthy tissue and does not affect other proteins whose mRNAs form a different kind of IRE stem loop (e.g. ferritin, ferroportin).
ANVS-401 inhibits over-expression of neurotoxic proteins by binding to the IRE-IRP1 complex and preventing the opening of IRP1 and concomitant release of the mRNA when iron levels are high, thereby lowering their levels and normalizing axonal transport.
Interestingly, the translation of APP, tau, and αSYN displays several similar features and is regulated in a homologous way with over expression leading to neurodegeneration: by damaging axonal transport and synaptic transmission, causing inflammation, forming aggregates, and, finally, leading to nerve cell death. Through several studies, we have found that by reducing APP, tau and αSYN levels, ANVS-401 treatment restores normal axonal transport and prevents or inhibits the toxic cascade leading to neurodegeneration.
Top: Normal nerve cells show a linear and smooth movement of vesicles carrying the neurotrophic factor BDNF
Middle: Down syndrome nerve cells show a disturbed, erratic and slowed transport of the vesicles carrying BDNF
Bottom: When the Down syndrome nerve cells are treated with ANVS-401, their transport is fully restored and the vesicles carrying BDNF again move smoothly and expeditiously along the axon.
ANVS-401 normalizes anterograde and retrograde vesicle transport in fully differentiated Down syndrome nerve cells.