No, amyloid buildup is no more than a symptom, scarring that's occurred from underlying disease. It does contribute to neuronal dysfunction, so there is some temporary improvement when it's reduced or eliminated. But it is a marker of the disease, not its core biology.
To mistake symptom markers for core disease markers is a significant mistake. The mabs can get their credit for their symptomatic relief, but it's wrong to say that Anavex's upstream, disease modifying treatment is impeached by its delayed effect on a downstream symptom.