Preclinical screening of compounds modulating alpha-synuclein/Synapsin III pathological interplay for the treatment of Parkinson’s disease

Synapsin III (Syn II), a component of alpha-synuclein (AS) fibrils in Parkinson’s disease (PD) brains, participates in and stabilizes AS aggregation and toxicity.
The monoamine reuptake inhibitor threo-methylphenidate (MPH) stimulates AS/Syn III-aggregation-dependent, but DA transporter (DAT)-independent, locomotor activity, by promoting the functional (vs dysfunctional or aggregation promoting) interaction between AS and Syn III. In silico analysis of Syn III crystal structure resolved five putative pockets for threo-MPH binding. We thus designed and synthesized threo-MPH derivatives with modifications intending to enhance the ability to interact with Syn III. The threo-isomer PK1 stimulated functional AS/Syn III interaction and release of Syn III-positive DA vesicles, while inhibiting the toxic aggregation of AS and Syn III more efficiently than threo-MPH.
Therapeutic hypothesis: by promoting Syn III/AS functional interaction, threo-MPH analogs structurally similar to PK1 could improve DA release and reduce Syn III/AS aggregate formation thereby reducing PD motor deficits and progression.
Specific aims:
1) Synthesize and compare the potency of threo-PK1 and threo-MPH analogs derived from our structural analysis of the Syn III binding pockets to improve threo-MPH-Syn III binding. Compounds that, in addition to threo-PK1, exhibit at least a 10-fold superior potency vs threo-MPH will progress.
2) Test threo-PK1 and up to 3 additional potent compounds for preventing AS aggregation, DA release failure and degeneration in iPSC-derived organoids from familial PD patients (SNCA multiplications, GBA mutations) that we have previously found to exhibit AS/Syn IIII co-aggregates.
3) Test the two most potent compounds from Step 2 for in vivo PK/ADME properties to determine plasma half-life and brain penetration as well as in vitro ADME properties such as non-specific protein binding.
4) Determine if the most promising compound from Step 3 reduces AS/Syn III aggregation, motor deficits and nigrostriatal DA release in a human AS transgenic mouse model of PD (interventional design).