In its many embodiments, the present invention provides certain 2-imino-3-methyl pyrrolo pyrimidone compounds, including compounds Formula (II): and include tautomers, steroisomers, or pharmaceutically acceptable salts or solvates of said compounds, stereoisomers, or said tautomers, wherein R2, R3, R4, R5, R6, R7, R8, and R9 are each selected independently and as defined herein. Pharmaceutical compositions comprising one or more such compounds, and methods for their preparation and use in treating pathologies associated with amyloid beta (Aβ) protein, including Alzheimer's Disease, are also disclosed.