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• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides

Definitions

• sequence listing is submitted with the present application.
• the sequence listing is submitted as a .txt file entitled 7120102_SEQ_ST25.txt and is 12kb in size. The entire contents of the sequence listing are hereby incorporated by reference.
• Current treatment methods are limited and are typically related to invasive surgical procedures and post-injury rehabilitative treatments rather than limiting or reversing the damage caused by the initial injury to the brain.
• NMDA receptors two functionally distinct pools of NMDA receptors (NMDAR) defined by the presence of NR2A (NR2A-NMDAR) or NR2B (NR2B-NMDAR) containing subunits (Luo et al. 1997; Tovar and Westbrook 1999; Kohr 2006).
• NR2B-NMDARs are generally thought to be involved in triggering cell death and subsequent brain damage following an excitotoxic insult (Liu et al. 2007; Tu et al. 2010).
• pharmaceutical application of NR2B-NMDAR antagonists have been unsuccessful in clinical trials, since they interfere with physiological functions of these receptors, in addition to blocking excitotoxic cascades (Rodrigues et al. 2001; Zhao et al. 2005; Walker and Davis 2008).
• targeting components of the intracellular signaling cascades downstream of NMDAR signaling may provide novel compounds for therapeutic approaches to interventions in excitotoxicity.
• the brain-enriched tyrosine phosphatase STEP (also known as STriatal Enriched Phosphatase or PTPN5) may be one such target molecule that is activated following stimulation of NMDARs and is emerging as an important regulator of neuronal survival and death.
• STEP is expressed specifically in neurons of the striatum, neo-cortex and hippocampus (Boulanger et al. 1995).
• STEP 61 and STEP 46 the two STEP isoforms (Bult et al. 1997) contain a highly conserved substrate -binding domain termed as the kinase interacting motif or KIM domain (Pulido et al. 1998).
• Phosphorylation of a critical serine residue within the KIM domain is mediated through dopamine/Dl receptor dependent activation of the Protein Kinase A (PKA) pathway (Paul et al. 2000). Dephosphorylation of this residue by Ca2+ dependent phosphatase calcineurin, following glutamate/NMDA receptor stimulation, renders STEP active in terms of its ability to bind to its substrates (Paul et al. 2003). Active STEP, in turn can bind to and modulate the activity of its substrate through tyrosine dephosphorylation of a regulatory tyrosine residue.
• Known substrates of STEP include ERK (extracellular regulated kinase 1/2) and p38 MAPKs (Paul et al.
• Fig. 1 is a schematic diagram of STEP 6 i.
• Fig. 2 is a schematic diagram of STEP 46 .
• FIG. 3 is a schematic diagram of a STEP-derived peptide according to an embodiment of the present disclosure, wherein the PKA phosphorylation site * has been modified.
• Fig. 4 is a schematic diagram of a STEP-derived peptide according to another embodiment of the present disclosure, wherein both the PKA phosphorylation site * and the KIS-domain phosphorylation sites have been modified.
• Fig. 5 is a schematic diagram of a STEP-derived peptide according to still another embodiment of the present disclosure, wherein the PKA phosphorylation site * has been modified and further including a TAT sequence at the N-terminal of the peptide.
• FIG. 6 is a schematic diagram of a STEP-derived peptide according to another embodiment of the present disclosure, wherein both the PKA phosphorylation site * and the KIS-domain phosphorylation sites have been modified and further including a TAT sequence at the N-terminal of the peptide.
• FIG. 7 is a schematic diagram of a STEP-derived peptide according to yet another embodiment of the present disclosure, wherein the PKA phosphorylation site * has been modified and further including a TAT sequence at the N-terminal of the peptide and a myc- tag at the C-terminal of the KIM domain.
• FIG. 8 is a schematic diagram of a STEP-derived peptide according to another embodiment of the present disclosure, wherein both the PKA phosphorylation site * and the KIS-domain phosphorylation sites have been modified and further including a TAT sequence at the N-terminal of the peptide and a myc-tag at the C-terminal of the KIM domain.
• FIG. 9 is a schematic illustration showing the injection site of the TAT-STEP peptide.
• Fig. 10 shows the immunohistochemistry of coronal section of striatum with anti-myc antibody to detect exogenous TAT-STEP.
• Fig. 11 shows the immunohistochemistry of cortex with anti-myc antibody to detect exogenous TAT-STEP.
• Fig. 12 shows representative TTC (triphenyltetrazolium choloride) stained sections from saline and TAT-STEP-myc treatment groups where treatment was administered immediately before an ischemic event.
• Fig. 13 is a quantitative analysis of the infarct volume. Infarct volumes are expressed as a percentage of the contralateral (control) hemisphere and the data are mean +/- SEM (p ⁇ 0.01).
• Fig. 13 shows representative TTC (triphenyltetrazolium choloride) stained sections from saline and TAT-STEP-myc treatment groups where treatment was administered 1.5 hours after an ischemic event.
• Fig. 14 is a quantitative analysis of the infarct volume. Infarct volumes are expressed as a percentage of the contralateral (control) hemisphere and the data are mean +/- SEM (p ⁇ 0.01). Detailed Description
• the present disclosure provides a plurality of novel peptide sequences that are modified derivatives of a neuron-specific tyrosine phosphatase.
• the novel peptide sequences are modified derivatives of striatal- enriched tyrosine phosphatase (STEP).
• STEP has been modified so as to be able to ameliorate and treat brain injury resulting from glutamate toxicity, hypoxia and/or transient ischemic insult.
• Examples of the types of brain injury which the presently disclosed peptide sequences are useful for treating includes acute brain injury resulting from stroke and traumatic brain injury, and chronic disorders such as Huntington's chorea and schizophrenia.
• the presently described peptide sequences may further be useful in the treatment and amelioration of disorders associated with fear memory such as post-traumatic stress disorder.
• Glutamate the most common excitatory neurotransmitter in the brain, is a major target for clinical intervention in ischemic stroke. Sustained elevation of glutamate has been observed for at least 24 hours in patients with acute ischemic stroke (Bullock et al., 1995; Davalos et al., 1997). This maintained glutamate excitotoxicity is presumably related to the progression of ischemic brain damage over a period of hours to days after the primary event.
• NMDA N- methyl-D-aspartate
• Activation of p38 MAPK signaling pathway in particular has been implicated in enhancing ischemic brain injury and has been linked to the production of cyclooxygenase-2, a key enzyme involved in inflammatory response and generation of reactive oxygen species (Nito et al., 2008; Iadecola et al., 2001, Barone et al., 2001a and b).
• NMDA receptor antagonists a significant concern in the pharmaceutical application of NMDA receptor antagonists is that they not only block its pathological effects but also interferes with physiological functions of NMDAR (Chazot et al., 2004; Dirnagl et al., 1999; Kemp et al., 2002; Lipton et al., 2004) that includes excitatory synaptic transmission and plasticity.
• STEP is an intracellular protein tyrosine phosphatase (PTP) that is exclusively expressed in the central nervous system. STEP is preferentially expressed in neurons of the basal ganglia, hippocampus, cortex and related structures (Lombroso et al. 1993, Boulanger et al. 1995).
• the STEP-family of PTPases includes both membrane associated (STEP 6 i) and cytosolic (STEP 4 6) variants that are formed by alternative splicing of a single gene (Bult et al. 1997).
• STEP 6 i differs from STEP46 by the presence of an additional 172 amino acids at its N- terminus (Bult et al. 1996).
• specific amino acids residues within the STEP protein are frequently referred to using the numbering from the STEP46 variant.
• the 107 amino acid sequence of the STEP protein discussed herein is highly conserved between animal species with 95% sequence homology between rat and human. (Compare SEQ IDs 1 and 2.)
• the present disclosure provides for a number of possible mutations of the STEP protein in order to achieve the useful peptides of the disclosed herein.
• the various STEP-based peptides described herein may be based on or derived from the STEP proteins from a variety of species and that such peptides may or may not be derived from proteins that are endogenous to the specific species being treated and/or studied. Accordingly, the peptides disclosed herein should not be construed as being limited to the specific peptides sequences included in the sequence listing.
• STEP along with two other PTPs, PTPRR and HePTP belongs to a family of PTPs that contains a highly conserved 16-amino acid substrate-binding domain termed the kinase interacting motif (KIM domain) (Pulido et al. 1998).
• KIM domain kinase interacting motif
• a regulatory serine residue, ser 49 lies in the middle of the KIM domain and dephosphorylation of this residue renders STEP active in terms of its ability to bind to its substrates.
• Phosphorylation of ser 49 is mediated by dopamine/Dl receptor dependent activation of the cAMP/PKA pathway (Paul et al. 2000) while dephosphorylation is mediated by glutamate/NMDA receptor induced activation of the Ca2+ dependent phosphatase, calcineurin (Paul et al. 2003).
• a second conserved domain carboxy-terminal to the KIM domain is present in STEP, PTP-SL and HePTP.
• this domain termed the kinase specificity sequence (KIS domain) includes two phosphorylation sites, Thr 59 (Thr 231 in STEP 6 i) and Ser 72 (Ser 244 in STEP 6 i), which are important in regulating the stability of the STEP protein.
• FIGs. 1 and 2 are schematic diagrams of STEP 6 i and STEP46, respectively, indicating the positions of the phosphatase domain, putative proteolytic sites (PEST), transmembrane domain (TM), polyproline rich domain (PP), kinase interacting motif (KIM), kinase specificity sequence (KIS) and the above-mentioned phosphorylation sites involved in the activation and subsequent degradation of STEP.
• PEST putative proteolytic sites
• TM transmembrane domain
• PP polyproline rich domain
• KIM kinase interacting motif
• KIS kinase specificity sequence
• STEP can modulate synaptic plasticity by regulating the activity of extracellular regulated kinase 1/2 (ERK 1/2), a key protein involved in memory formation (Paul et al. 2007 and Thomas and Huganir 2004). Active STEP can also modulate NMD A receptor-dependent long term potentiation by interfering with NMDA receptor trafficking to synaptic membrane, possibly through regulation of the upstream kinase Fyn (Nguyen et al. 2002) and tyrosine dephosphorylation of NR2B-NMDA receptor subunits (Snyder et al. 2005). Several studies also indicate a role of active STEP in neuroprotection through its regulation of p38 MAPK (Poddar et al., 2010, Xu et al., 2009).
• FIG. 3 is a diagram of a constitutively active STEP- derived peptide according to an embodiment of the present disclosure.
• the peptide contains the first 107 amino acids of STEP 46 including the KIM and KIS domains.
• the serine residue (Ser 49) which acts as a PKA phosphorylation site * has been modified. (See SEQ. ID. No.
• Ser 49 has been converted, using standard point mutation techniques, to alanine, which is non-phosphorylatable, resulting in a constitutively active peptide. Modification of the PKA phosphorylation site addresses the problem of inactivation of the STEP-derived peptide due to phosphorylation.
• FIG. 4 is a schematic illustration of a STEP-derived peptide according to an embodiment of the present disclosure, wherein Ser49 has been converted to alanine, which is non-phosphorylatable and Thr 59 and Ser 72 are converted, to glutamic acid to mimic the phosphorylatable form. (See SEQ. ID. No. 4.) However, it will be appreciated that other phopho-mimics may be used including, for example, Aspartic acid.
• the present disclosure further provides a STEP peptide including a mutated Cys 23 residue (cysteine to alanine) (SEQ. ID. No. 5).
• SEQ ID. No. 8 provides the amino acid sequence of the human STEP Peptide including all the mutations points discussed above.
• the present disclosure provides for the prevention, treatment, or amelioration of brain injury caused by excessive glutamate release and oxidative stress. Accordingly, the present disclosure also provides STEP-derived peptides which can be delivered to the brain of a patient who is or has suffered from an incident, such as a stroke, resulting in this type of injury.
• Figs. 5 and 6 are schematic illustrations of the previously described constitutively active STEP-derived peptides including a TAT sequence at the N-terminal of the peptide. In Fig. 5 only the phosphorylation site in the KIM domain has been altered. (See SEQ. ID No. 9) In Fig. 6, the phosphorylation sites in both the KIM and KIS domains have been altered.
• TAT is an 11 amino acid peptide that renders peptide sequences cell permeable and enables these peptides to cross the blood brain barrier.
• the ability of the STEP-derived peptide to cross the blood brain barrier enables the peptide to be delivered to a patient's brain via the significantly less invasive mechanism of intravenous injection, for example via the femoral vein, rather than previous treatment mechanisms that require direct surgical access to the brain.
• suitable delivery mechanisms that could be employed including, for example, known targeted and viral-based delivery systems.
• Figs. 7 and 8 are schematic illustrations of the previously described constitutively active STEP-peptides including a TAT sequence at the N-terminus and wherein the C-terminus of the peptide has been modified to include a myc tag.
• Fig. 7 only the phosphorylation site in the KIM domain has been altered.
• Fig. 8 the phosphorylation sites in both the KIM and KIS domains have been altered.
• those of skill in the art will be familiar with various observable tags and mechanisms for modifying peptides to include these tags.
• TAT-STEP peptide when injected stereotactically into the striatum prior to glutamate, could attenuate glutamate-induced excitotoxic cell death in vivo.
• OGD oxygen-glucose deprivation
• a host cell includes a plurality (for example, a culture or population) of such host cells, and so forth.
• N-methyl-D-aspartate receptor complexes in adult rat cerebral cortex contain at least three different subunits (NR1/NR2A/NR2B). Molecular pharmacology 51, 79-86.
• Chazot PL The nmda receptor nr2b subunit: A valid therapeutic target for multiple ens pathologies. Curr Med Chem. 2004;11:389-396
• Lipton SA Failures and successes of nmda receptor antagonists: Molecular basis for the use of open-channel blockers like memantine in the treatment of acute and chronic neurologic insults. NeuroRx. 2004;1: 101-110
• FIGs. 9-15 show that following a single intravenous injection of a TAT-STEP peptide through the femoral vein of an adult rat, the peptide was detectable both in the cortex (Fig. 10) and striatum (Fig. 11).
• Male Wistar rats received a single intravenous injection of 1 ml (1 mg/ml) of the TAT-STEP peptide of Fig. 8 through the femoral vein (Fig. 9). Detection took place 1 hour after injection.
• the TAT-STEP peptide of SEQ ID. No. 11 was administered intravenously immediately before or 1.5 hr after the onset of stroke.
• the findings demonstrate that intravenous injection of the cell-permeable STEP peptide either before or after an acute ischemic stroke can provide significant protection against ischemic brain injury.
• male Wistar rats (260-280 gm) were subjected to middle cerebral artery occlusion (MCAO) for 90 minutes using the intraluminal suture method as described in Cadelario-Jalil et al., 2004.
• TAT-STEP peptide or saline was injected in the rats immediately prior to (Figs. 12-13) or 1.5 hours after (Figs. 14-15) MCAO followed by reperfusion for 24 hr.
• the fact that the peptide when injected even 1.5 hr after the onset of stroke can mitigate ischemic brain injury suggests that the secondary activation of p38 MAPK following the degradation of endogenous STEP is possibly responsible for triggering intracellular death pathways.
• the modified STEP-derived peptide may be an alternative therapeutic target, downstream of NMDAR, for intervention in diseases that involve excitotoxicity.

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