In previous studies the authors validated the inhibition of calpains as a therapeutic target against their overactivation in AD toward the recovery of synaptic dysfunctions induced by Aβ. These findings led to an effort aimed to discovering novel calpain inhibitors that might be utilized against AD. Here the authors report findings from a phenotypic screening of three generations of peptidomimetic epoxide warhead containing molecules that have been previously proved to be unreactive toward reaction with free thiols while displaying irreversible active site calpain 1 inhibition with sub-micromolar potency. The investigators designed their drug screening for calpain inhibitors using a phenotypical modality combined with medicinal chemistry refined through target-based computational approach, focusing on the capability of our candidate molecules to protect from the detrimental effect of oligomerized Aβ42 on hippocampal long-term potentiation (LTP), a type of synaptic plasticity thought to underlie learning and memory. Following this screening, the last generation of leads was further tested for pharmacokinetic and toxicological features, and then for the recovery of cognitive impairments in a mouse model of amyloid deposition, the AβPP/PS1 mouse. Data from both functional and preliminary toxicological investigations proved the efficacy, potency, and safety of the novel and selective calpain inhibitors NYC438 and NYC488 as possible therapeutics against Alzheimer's disease.