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20-F
AC IMMUNE SA filed this Form 20-F on 03/21/2019
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·Crenezumab is currently being evaluated in a Phase 2 clinical prevention trial in Colombia in 300 cognitively healthy individuals of whom 200 are genetically predisposed to develop early AD. As of January 2019, two Phase 3 clinical trials, CREAD 1 and CREAD 2, in prodromal to mild AD patients were discontinued after an interim analysis conducted by our collaboration partner Genentech.

 

Figure 8: Crenezumab overview

 

 

Ref: (1) Amyloid related imaging abnormality-edema; (2) Lin et al, CTAD 2017; (3) Budd-Heaberlein, JPAD 2017; (4) Andelkovic, CTAD 2017; (5) Siemers et al, Alzheimer’s & Dementia 2016;
(6) Logovinsky et al, Alzheimer's Research & Therapy 2016; (7) Swanson et al, AAIC 2018 (8) Salloway et al, New Engl J Med 2014

 

Figure 8 above summarizes crenezumab’s multiple neuroprotective mechanisms of action, in particular direct binding and inhibition of toxic Abeta oligomers which may demonstrate crenezumab's clinical benefit.

 

Results from pre-clinical studies

 

Abeta is produced by the breakdown of a larger protein called amyloid precursor protein, or APP. The Abeta fragment containing 42 amino acids, or Abeta 1–42, is believed to be associated with the highest toxicity of the Abeta fragments. Misfolded Abeta subunits combine to form oligomers and fibrils that are found in amyloid plaques. Data resulting from preclinical and clinical studies show that crenezumab binds with high affinity to amino acids 12–24 of Abeta 1–42, as well as multiple forms of Abeta, including monomers, oligomers, and fibrils, which reduces Abeta 1–42 induced cytotoxicity. Furthermore, these data indicate that crenezumab enhances the uptake of neurotoxic Abeta oligomers by microglial cells, the resident immune cells of the brain, which normally respond to neuronal damage and remove the damaged cells for subsequent disposal and clearance from the brain.

 

A challenge with agents acting to remove Abeta is the potential to induce inflammation leading to vasogenic edema, which is accumulation of fluid in the brain that can lead to headaches, loss of coordination and disorientation. The fluid can be seen clearly on MRI scans and is referred to as ARIA-E. Crenezumab is engineered on an IgG4 backbone, which was selected because IgG4 antibodies are associated with a greatly reduced risk of causing inflammation. As a result, crenezumab’s IgG4 structure activates microglial cells to clear Abeta without producing inflammation and associated vasogenic edema, as demonstrated in the Phase 2 clinical studies. In contrast, ARIA-E and other inflammation-related side effects have been observed in other antibodies with an IgG1 backbone.

 

Positioning of crenezumab’s binding characteristics

 

The formation of neurotoxic Abeta pathology in AD is caused by misfolding, oligomerization and aggregation of Abeta. This process leads to the formation of smaller oligomeric species and larger extracellular plaques. To reduce or reverse disease progression, the therapeutic anti-Abeta strategy focuses on targeting all Abeta species that mediate neurotoxicity in the CNS of patients.

 

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