Development of Novel Small molecule modulators of synaptic plasticity for the treatment of AD-induced cognitive decline

PROJECT SUMMARY Pharmacological treatment to slow or stop the progression or prevent Alzheimer’s Disease (AD) represents an unmet medical need. Clinical evidence shows that the core pathology of AD is the relentless destruction of memory as the disease progresses. A large body of research literature has demonstrated that synaptic plasticity is the pivotal underpinning mechanism of learning and memory. Notably, amyloid-β and tau have been shown to produce deleterious effects by suppressing synaptic plasticity. Disruption of mechanisms of neuronal plasticity, eventually resulting in a net loss of synapses, is implicated as an early pathological event in AD. Synaptic dysfunction is likely a final common biological mechanism linking protein pathologies to disease symptoms. Therefore, this evidence together motivated our company, ENCUE, LLC, to initiate a drug discovery program that focuses on restoring synaptic health at the earliest stages of AD-induced dementia. The lead molecule in our platform, JB2, induces structural and functional synaptic plasticity in the brain via activation of the insulin-like growth factor 2 receptor (IGF2R). Our mechanisms of action studies have described a feed-forward/amplification mechanism of JB2 for inducing synaptic plasticity. We discovered that JB2 showed specific binding to IGF2R- containing spines in cortical neurons, IGF2R-containing complexes in synaptoneurosomes, and recombinant IGF2R. JB2 can enhance intracellular calcium in HEK cells expressing IGF2R, at concentrations that are present in the CSF following therapeutic dosing (1 mg/kg). In addition, JB2 facilitates synaptic strength in primary cultures in a manner that is transcription and translation dependent, involves MEK/ERK signaling, and is dependent on IGF2R (blocked by an IGF2R-specific antibody) but not IGF1R activation. We have also confirmed that JB2 induced long-term potentiation in a growth factor-like manner that is independent of the IGF1R and led to an increase in N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor (AMPAR) activity as well as in IGF2R cell surface expression, suggesting a growth-factor-like autocrine mechanism. Preliminary data also show that a single dose of JB2 reverses cognitive deficits in the 5XFAD mouse model of Alzheimer’s. Building on these achievements, we proposed in this Phase I SBIR project to further develop JB2 as a novel therapeutic to reverse or at least significantly delay the onset of cognitive dysfunction in AD by returning the normal expression and function of AMPAR-dependent synaptic plasticity with our novel platform of glutamatergic modulators. We will evaluate the pharmacokinetics profile, determine the maximum tolerated dose of JB2 in mice, and examine the efficacy of JB2 in mouse AD models. The success of our Phase I study will prepare the company for further pre-clinical evaluation of the dosing regimen (e.g., reduced dose frequency) of JB2 in animal models of AD in Phase II. In addition, our Phase II project would consist of IND- enabling toxicology studies and Chemistry, Manufacturing, and Controls (CMC) studies of JB2.