Drug Policy Reform Act of 2021 or the DPR Act of 2021 This bill transfers federal regulatory authority over controlled substances, eliminates federal penalties for some drug-related offenses, and removes some collateral consequences for certain criminal convictions. A collateral consequence is a penalty (e.g., a restriction on access to a program or service) imposed on an individual in addition to the penalty associated with the sentence. Specifically, the bill transfers regulatory authority over controlled substances from the Department of Justice to the Department of Health and Human Services (HHS). Additionally, the bill directs HHS to establish a commission to determine a benchmark amount of a controlled substance for personal use supply. The bill eliminates federal criminal and civil penalties for simple possession of a controlled substance in an amount equal to or less than the benchmark. Finally, the bill removes the collateral consequences of certain convictions. For example, the bill removes some restrictions on eligibility for federal assistance and benefits for individuals who are convicted of certain drug-related offenses, reinstates the right to vote in federal elections for persons convicted of criminal offenses, and repeals the requirement for states to revoke or suspend driver's licenses of individuals who are convicted of drug offenses as a condition of receiving a full allocation of certain federal grant funds.