The "Stop the Importation and Manufacturing of Synthetic Analogues Act of 2025" (SIMSA Act of 2025) introduces a new regulatory framework for synthetic controlled substance analogues. It amends the Controlled Substances Act by creating a sixth category, Schedule A , specifically for drugs or substances that are imported or offered for import. To qualify for Schedule A, a substance must have a chemical structure substantially similar to an existing controlled substance (Schedules I-V) and exhibit similar or greater stimulant, depressant, or hallucinogenic effects on the central nervous system. The bill empowers the Attorney General (AG) to issue temporary orders adding substances to Schedule A for up to five years, with potential extensions, if they meet the specified criteria and help prevent abuse. These temporary orders are not subject to judicial review. For permanent scheduling, the AG can act after three years, unless the Secretary of Health and Human Services determines the substance lacks sufficient potential for abuse, in which case the temporary order must be terminated. Violations involving Schedule A substances carry severe penalties, including imprisonment for up to 20 years, or life if death or serious bodily injury results, along with substantial fines. Repeat offenders face even harsher sentences. Furthermore, the bill makes it unlawful to import or export Schedule A substances without clear labeling using International Union of Pure and Applied Chemistry (IUPAC) nomenclature, though FDA-approved drugs or those in investigational trials are exempt. The legislation also establishes registration requirements for importers and exporters of Schedule A substances, primarily for research, analytical, or industrial purposes, with the AG considering public interest factors like diversion control and technical advancements. It includes provisions to allow ongoing research on substances newly added to Schedule A, facilitating continued scientific study under specific conditions. Finally, the bill provides a mechanism for sentencing review, allowing individuals convicted of Schedule A offenses to petition for a reduced sentence if the substance is later descheduled or moved to a schedule with lower penalties. It clarifies that the Act does not limit existing authority to prosecute controlled substance analogues or the AG's power to schedule or decontrol substances under current law.