Huperzine A exhibits several mechanisms of action that are relevant to Alzheimer’s disease:

• AChE inhibition: Huperzine A is a potent, selective and reversible inhibitor of acetyl cholinesterase (AChE), the enzyme that breaks down or degrades acetylcholine (ACh). ACh is a neurotransmitter (brain signaling molecule) associated with memory and cognitive function. Reductions in levels of ACh have been associated with memory loss or cognitive impairment in Alzheimer’s disease. AChE inhibitor drugs inhibit the breakdown of ACh, making more ACh available. There are four AChE inhibitors currently on the market in the US; these drugs have been reported to produce symptomatic benefits on cognitive and other functions in mild-to-moderate stage Alzheimer’s disease.

• NMDAr antagonism: Huperzine A also has N-methyl-D-aspartate receptor (NMDAr) antagonist activity. Over stimulation of NMDA receptors by the neurotransmitter glutamate) has been implicated in the pathology of neurodegenerative disorders, including Alzheimer’s disease. Accordingly, a drug that blocks excessive NMDAr receptor activity may protect against glutamate mediated excito-toxicity and nerve cell death. There is one NMDAr antagonist currently on the market in the US; this drug has been demonstrated to have therapeutic activity in moderate-to-severe Alzheimer’s disease.

• Anti-oxidant activity: Huperzine A has anti-oxidant properties. Animal and human study data indicate that oxidative stress (damage to cellular structures caused by free radicals or reactive oxygen species) is one of the earliest events in the pathogenesis of AD. Increased oxidation of lipid, protein and DNA molecules has been reported in both Alzheimer’s disease and Mild Cognitive Impairment (MCI, or “pre-Alzheimer’s”). Oxidative stress may induce accumulation of β-amyloid, a key player in the formation of brain plaques and nerve cell death; inhibition of oxidative stress may be neuroprotective. In a clinical study conducted in China, patients taking Huperzine A demonstrated significant reductions in blood markers of oxidative stress; preclinical studies have shown that Huperzine A is protective against hydrogen peroxide-induced cell death.

• Anti-amyloid activity: Huperzine A also exhibits anti-amyloid properties. One of the key events in the pathogenesis of AD is the formation of amyloid plaques (senile plaques) on blood vessels and outside nerve cells within the brain. These plaques are comprised of amyloid β (β-amyloid or Aβ) protein and ultimately lead to nerve cell death through a number of potential mechanisms. Pre-clinical studies demonstrate that Huperzine A is protective against Aβ-induced cell death.