- Scarcity of AD markers in preclinical stage
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- Scarcity of markers of AD phenotypes
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- Difficulty to obtain molecules with selective action on diseased cells
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- Most drugs will have weak effects since they act only on a part of the etiopathogenic chain
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- It is necessary to distinguish between symptomatic action and changes in the course of the disease
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- Need of a prolonged period of observation to prove delay in progression
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- Need to work with very wide human samples to achieve clinical evidence and statistical signification
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- High economic cost of trials designed to ascertain modifications in AD evolution
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