MEET US AT ASIATIDES
AsiaTIDES is the premier event in Asia for accelerating promising oligonucleotide and peptide molecules from research to commercialization. The 2018 edition will take place on February 27th – March 1st at the Westin Miyako Kyoto, Kyoto, Japan.
AsiaTIDES brings 250+ global oligonucleotide and peptide leaders across Asia, Europe and North America together to present case studies, best practices and to discuss current strategies and trends to accelerate promising molecules to market. Do not miss the presentation of Dr. Daniel Samson, Vice President API SPPS, Bachem AG, “Higher Molecular Weight (HMW) Peptide Impurities – Control Strategies and Acceptance Criteria” on Wednesday, February 28th, at 4 pm (Main Conference, Peptide Track).
Bachem‘s pipeline contains more than 150 customer projects in preclinical and clinical phases. Recently, some of our projects in phase III trials received marketing authorization and phase II projects progressed to pivotal phase III clinical trials. Bachem’s services include pegylated peptides, lipidated peptides, various other peptide conjugates, sterile fill and finish (Clinalfa®), and selective chemical glycosylation. The glycosylation technology is applicable to large scale and has the potential to be applied to a variety of peptides, where we can pioneer the concept of improving current and future drugs.
We are excited to meet with our customers and discuss how Bachem can help with their peptide API custom manufacturing needs. We invite you to visit us at our Booth A-6: please contact us to schedule a meeting in advance. We look forward to meeting you at AsiaTIDES 2018!
TAU AND ALZHEIMER’S DISEASE
Aggregation of β-amyloid peptides, which results from processing of amyloid precursor protein, into senile plaques as well as formation of neurofibrillary tangles (NFT) from tau (Microtubule-Associated Protein Tau) protein are associated with the neurodegenerative disease Alzheimer’s disease (AD). Neither plaques nor NFT are a cause of neurodegeneration, but markers of damage and progression of AD. Nevertheless, both proteins play a central role in the development of AD and serve as biomarkers measured in cerebrospinal fluid. It is not clear yet which of them is the real culprit responsible for eventual neuronal death. A number of observations point at tau. For example, neurofibrillary degeneration, and not β-amyloidosis, correlates with the presence of dementia in humans.
Microtubules, tubulin polymers with various cellular tasks, are part of the cytoskeleton. For instance, they play a role in stabilizing cell shape and during mitosis. Furthermore, they act as tracks for intracellular transport by motor proteins. Tau stabilizes the microtubules of the neuronal cytoskeleton und thus is important for their regular function. It is primarily expressed in neuronal cell bodies and axons.
The binding affinity of tau for microtubules is regulated by the phosphorylation state of the protein. In healthy neurons, the protein is phosphorylated by a number of kinases and dephosphorylated by phosphatases. An equilibrium of phosphorylated and non-phosphorylated forms serving as tau pool exists in the cytosol. Phosphorylation is reverted when tau binds to tubulin. Glycogen-synthase kinase-3β (GSK-3β), cyclin-dependent protein kinase 5 (cdk5), and cAMP-dependent protein kinase (PKA) are amongst the most important tau kinases. Protein phosphatase PP2A was found to be the major tau phosphatase.
In Alzheimer’s disease or other pathological conditions known as tauopathies, phosphorylation of the protein is dysregulated leading to a decrease of the tubulin-binding capacity. Whereas the microtubules are destabilized, hyperphosphorylated tau protein aggregates yielding the NFT. There, the extent of tau phosphorylation was found to be 3 to 4 times higher than in cytosolic tau of healthy and AD brains. Neurofibrillary degeneration due to aberrant phosphorylation of tau could be prevented by inhibiting the involved enzymes. Dephosphorylation could be promoted by upregulating PP2A, a phosphatase with broad substrate specificity.
Tau Pathology
The mechanism of tau aggregation is not completely understood. Association with microtubules preserves the disordered structure of the protein. Aberrant post-translational modifications and conformational changes of tau go together with loss of affinity for tubulin and risk of aggregate formation. Phosphorylation of two or three serine or threonine residues is required for the optimal function of tau, for pertaining its unfolded structure in free form, whereas phosphorylation of more than six serines or threonines (hyperphosphorylation) inactivates the protein.
Nε acetylation of lysines may also be involved in the regulation of tau as well as in pathological processes. This modification mediated by histone acetyltransferases (HAT) eliminates positive charges. Aberrant acetylation could interfere with the binding of tau to microtubules.
Enzymatic degradation is a major modification of tau protein in AD. Caspase-3-mediated cleavage at Asp421 and further C-terminal truncation promotes maturation of NFTs. The truncated proteins could serve as biomarkers for AD.
Glycation, deamidation, oxidation, and nitration of tau are further modifications of the protein associated with tauopathies, whereas O-glycosylation of serine or threonine with N-acetylglucosamine reduces aberrant phosphorylation.
Conformation strongly affects the enzymatic (de)phosphorylation of serines and threonines in the vicinity of a proline residue. The peptidyl-prolyl cis/trans isomerase Pin1 isomerizes phosphoserine/threonine-proline motifs. A trans-cis conversion of the pThr231-Pro232 bond has been observed during early stages of AD. Pin1 prevents the accumulation of the resulting pathogenic cis form of tau by reverting the isomerization allowing dephosphorylation by PP2A. Trans-tau promotes microtubule assembly. In AD brains, activities of both Pin1 and PP2A are decreased.
VQIINK (tau 275-280) and VQIVYK (tau 306-311, PHF6), two hexapeptide motifs from the N-termini of repeats R2 and R3 with a marked tendency for β-sheet formation are involved in the aggregation of hyperphosphorylated tau yielding neurotoxic polymers. PHF formation can be abolished by incorporating proline in one of the segments. The chaperone Hsp90 binds to the VQIVYK motif and, together with cochaperones, assists in tau clearance via autophagy or proteasome-mediated degradation.
Tau Protein
Tau is a rather disordered highly flexible protein. It consists of four domains characterized by their amino acid composition and function: the N-terminal domain, a proline-rich region, the microtubule-binding part, and the C-terminal sequence. The N-terminal part is called projection domain as it projects from the surface of the microtubule. It interacts with other cytoskeletal elements and the neuronal plasma membrane, and is involved in signal transduction. A central domain of tau, residues 198 to 369 for the longest isoform, aggregates with tubulin and promotes formation of microtubules. It is characterized by 3 to 4 repeat domains, all involved in binding (Fig. 1).
Fig. 1: Structure and normal function of tau. The protein contains 2-3 phosphoserine or threonine residues.
Tau protein is a dipolar molecule. Its N-terminal region contains a large proportion of acidic amino acid residues, whereas the proline-rich middle part and the C-terminus are dominated by basic amino acids. The distribution of charges can be changed under pathological conditions. Tau exists in six major isoforms differing in number of tubulin-binding domains and varying in size from 352 to 441 amino acid residues. The short isoforms allow plasticity of the cytoskeleton whereas the longer ones may preferentially play a role in its stabilization. In adult human brains, the six isoforms can be found whereas in fetal brains, only the shortest isoform is expressed.
Conclusion
Knowledge auf tau and its functions could lead to promising therapeutic approaches tackling the neuropathological effects of either aberrant tau modification or β-amyloid aggregate formation. This gives rise to hope that an effective cure for AD will be developed in the foreseeable future.
TAU-TARGETING DRUGS IN CLINICAL DEVELOPMENT
In Alzheimer’s disease (AD) and related neurodegenerative diseases known as tauopathies, the protein tau is abnormally hyperphosphorylated and aggregated, leading to neurofibrillary degeneration (1). Tau pathology coincides with the start of AD symptoms making it an interesting target. Treatment strategies targeting tau may offer an advantage over those targeting amyloid because tau hyperphosphorylation occurs later in the disease progression compared to amyloid-beta deposition, which begins before the onset of AD symptoms. This raises the possibility that tau-targeted drugs could be administered after the onset of AD symptoms and still have efficacy. In recent years, commercial interest in tau as a drug target has been growing with several companies entering candidates into clinical trials (2). Several tau-based drug candidates are shown in Table 1.
| Product Name | Active Ingredient | Condition Treated | Highest Phase | Companies |
|---|---|---|---|---|
| LMTX | methylene blue | Alzheimer's Disease(III) Frontotemporal Dementia(III) Progressive Supranuclear Palsy(II) Parkinson's Disease(I) | Phase III | TauRx Pharmaceuticals Ltd |
| AADvac1 | -- | Alzheimer's Disease(II) Frontotemporal Dementia(I) | Phase II | Axon Neuroscience SE |
| ABBV-8E12 | -- | Alzheimer's Disease(II) Progressive Supranuclear Palsy(II) Neurological Disorders(PC) | Phase II | AbbVie Inc C2N Diagnostics |
| BMS986168 | microtubule-associated protein tau monoclonal antibody | Progressive Supranuclear Palsy(II) Neurodegenerative Disorders(I) | Phase II | Bristol-Myers Squibb Company, Biogen, iPierian Inc |
| Posiphen | phenserine tartrate | Alzheimer's Disease(II) Down Syndrome(II) Parkinson's Disease(II) Huntington's Disease(PC) Traumatic Brain Injury(PC) | Phase II | QR Pharma Inc, The Rockefeller University, Axonyx Inc, TorreyPines Therapeutics, Inc |
| RG6100 | -- | Alzheimer's Disease(I) | Phase II | AC Immune SA, Genentech Inc, Roche |
| T3D959 | -- | Alzheimer's Disease(II) Metabolic Disorders(I) | Phase II | Bayer AG, T3D Therapeutics, Midatech Pharma US Inc |
| TPI287 | -- | Glioblastoma Multiforme(II) Metastatic Breast Cancer(II) Metastatic Melanoma(II) Neuroblastoma(II) Alzheimer's Disease(I) Neurodegenerative Disorders(I) Oncology(I) | Phase II | Tapestry Pharmaceuticals Inc, Cortice Biosciences Inc |
| ACI35 | -- | Alzheimer's Disease(I) | Phase I | AC Immune SA, Janssen Pharmaceuticals Inc |
| SGC1061 | -- | Alzheimer's Disease(I) | Phase I | Queen's University, sGC Pharma Inc, University of Illinois at Chicago |
| Taupro | -- | Progressive Supranuclear Palsy(I) | Phase I | ProteoTech Inc |
Phase III Candidates
The most advanced candidate is LMTX® (methylene blue), an orally delivered small molecule under development by TauRx Therapeutics. LMTX acts as a neuroprotectant and inhibits tau hyperphosphorylation, dissolves tau aggregates and prevents tau aggregation. In 2016, TauRx completed two Phase III clinical trials in AD and another trial in behavioral variant frontotemporal dementia. The primary endpoints for the trials were not met but TauRx saw encouraging data from subjects taking LMTX as a monotherapy. The results also suggested that LMTX administered at a dose as low as 8 mg/day may be useful. The company plans to initiate further clinical studies in order to build on these study results (4).
Phase II Candidates
Axon Neuroscience SE is developing AADvac1, a vaccine containing a peptide fragment, amino acids 294 to 305 of the tau sequence, coupled to KLH. The vaccine is designed to stimulate patients’ immune systems to attack dysfunctional tau proteins and thereby stop the progression of AD (5). In 2017, Axon Neuroscience completed enrollment for a Phase II trial of AADvac1 in AD. The main objective of the study is to evaluate the safety and tolerability of AADvac1 in patients with mild AD. The company also announced that it initiated a Phase I study with the vaccine in patients with non-fluent variant of primary progressive aphasia, a subgroup of frontotemporal dementia (2).
ABBV-8E12 is an anti-tau antibody under development by AbbVie for the treatment of tauopathies such as AD, progressive supranuclear palsy and mild cognitive impairment. Both the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) have granted Orphan Drug Designation to ABBV-8E12 for supranuclear palsy. Furthermore, the FDA has granted Fast Track Designation to ABBV-8E12 for supranuclear palsy. In 2017, AbbVie initiated Phase II clinical trials with ABBV-8E12 in early AD and progressive supranuclear palsy. (2).
In 2017, Biogen licensed BMS986168, also known as BIIB092, from Bristol-Myers Squibb. BMS986168, an antibody and tau protein inhibitor, is under development for the treatment of progressive supranuclear palsy and neurodegenerative disorders. Biogen has already started a Phase II study of BMS986168 in patients with progressive supranuclear palsy. The company is also planning a Phase II study that will start enrolling patients with AD in 2018 (3).
Posiphen® (phenserine tartrate) is a small molecule under development by QR Pharma. It acts by reducing tau hyperphosphorylation as well as inhibiting the synthesis of amyloid precursor protein, reducing β-amyloid peptide and inhibiting α-synuclein. Posiphen is in Phase II clinical studies for the treatment of AD. In 2017, QR Pharma initiated a Phase I/II study to evaluate safety, tolerability, pharmacokinetics and pharmacodynamic effects of Posiphen in patients with early AD (3).
RG6100 is an anti-tau monoclonal antibody under development for the treatment of AD by AC Immune and Genentech, part of the Roche group. In 2017, Genentech started a Phase II clinical trial in AD with RG6100 to assess safety, tolerability and efficacy of this monoclonal antibody in patients with prodromal to mild AD (3).
T3D Therapeutics is developing a tau hyperphosphorylation inhibitor known as T3D959. T3D959 is currently in a phase IIa study for the treatment of mild to moderate AD. In 2016, the company reported preliminary data showing that more than half the subjects treated with T3D959 had cognitive score improvements (3).
Cortice Biosciences is developing TPI287, a novel taxoid derivative that acts by stabilizing neuronal microtubules and decreasing toxic tau aggregation (3). During the Clinical Trials on Alzheimer’s Disease conference in 2017, Cortice announced results from Phase I clinical trials evaluating TPI287 for the treatment of AD, progressive supranuclear palsy and corticobasal syndrome. The results with TPI287 in mild-to-moderate AD patients were encouraging with no change in cognitive assessment scores after a period of 12 weeks (2).
Phase I Candidates
There are a few tau-targeting drug candidates in the pipeline in Phase I development. Among these candidates is an immunotherapy known as ACI-35, a liposomal vaccine containing a phosphorylated human tau protein fragment (3). AC Immune is collaborating with Janssen Pharmaceuticals to develop ACI-35 and the product is currently in a Phase Ib clinical study in patients with mild to moderate AD (6). Additional Phase I candidates are in development at other companies including sGC Pharma and Proteotech.
Conclusion
Tau-centric therapies have been the subject of increased interest and debate in recent years. To support researchers and organizations in their quests to develop a treatment for AD and related tauopathies, Bachem offers a selection of tau fragments, custom peptide synthesis and the production of peptide-based new chemical entities.
References
(1) Cerapedics Receives FDA Approval for i-FACTOR™ Peptide Enhanced Bone Graft in Cervical Spine Surgery, PR Newswire (2015)
(2) Medtrack (2017)
(3) GlobalData (2017)
(4) ReGenTree Announces Results of ARISE-2 Dry Eye Trial (2017)
(5) Araim Pharmaceuticals’ Cibinetide (ARA 290) Regenerates Small Nerve Fibers and Improves Neuropathic Clinical Symptoms in the Orphan Disease of Sarcoidosis, PR Newswire (2017)
(6) RGN-137, RegeneRx (2016)
MEET BACHEM: REBEKKA RANFT
What is your official job title at Bachem?
Marketing Communications Associate
How long have you been with Bachem? Where did you work before Bachem?
I started working at Bachem in October 2017. Before joining Bachem, I completed my studies in Business Administration with specialization in tourism at the Cooperative State University of Baden-Wuerttemberg in Loerrach. In these studies, you switch regularly from your academic studies at the university to practical training by your partner company. My partner company was a tourism marketing organization.
Briefly, what do you do at Bachem?
I am responsible for the organization of tradeshows, especially in Asia, internal events and for all matters relating our Corporate Gifts and Giveaways.
What do you like to do outside of work (interests, hobbies)?
I like going hiking, playing volleyball and meeting my friends and family.
What do you like most about your job?
I like most about my job that it is very varied, no day is like the day before. I really like the team I am working with and I like being in contact with colleagues from other departments of Bachem and also with various suppliers and service providers around the world.
What is your business motto?
Great things in business are never done by one person. They’re done by a team of people.
Thank you very much Rebekka.
Peptide highlights
Interesting news about peptides in basic research and pharmaceutical development:
Triple-acting diabetes drug reverses memory loss in Alzheimer’s disease mouse models-GEN
Simple one-pot synthesis of druggable tricyclic peptides-University of Amsterdam
Computational strategies overcome obstacles in peptide drug development-University of Washington
Synthetic peptide might be potential treatment for bacterial infection often seen in CF patients-Cystic Fibrosis News Today
LITERATURE CITATIONS
Bachem peptides and biochemicals are widely cited in research publications. Congratulations to all our customers with recent publications!
H. Choi et al.
Increased acetylation of Peroxiredoxin1 by HDAC6 inhibition leads to recovery of Abeta-induced impaired axonal transport.
Mol. Neurodegener. 12, 23 (2017)
T.A. Enache and A.M. Oliveira-Brett
Alzheimer’s disease amyloid beta peptides in vitro electrochemical oxidation.
Bioelectrochemistry 114, 13-23 (2017)
A. Ferreira and S. Afreen
Chapter 13 – Methods related to studying tau fragmentation.
Methods in Cell Biology 141, 245-258 (2017)
P. Sandhu et al.
Ser(422) phosphorylation blocks human Tau cleavage by caspase-3: Biochemical implications to Alzheimer’s Disease.
Bioorg. Med. Chem. Lett. 27, 642-652 (2017)
D.M. Vadukul et al.
Amyloidogenicity and toxicity of the reverse and scrambled variants of amyloid-β 1-42.