Social Security and Medicare Lock-Box Act This bill establishes: (1) in the Federal Old-Age and Survivors Insurance Trust Fund, a Social Security Surplus Protection Account; and (2) in the Federal Hospital Insurance Trust Fund, a Medicare Surplus Protection Account. The Managing Trustee of each trust fund (in both cases, the Secretary of the Treasury): (1) must transfer the annual surplus of the trust fund to its respective account; and (2) may not invest the balance in the account until a law takes effect that authorizes, for amounts in the trust fund, an investment vehicle other than U.S. obligations. The bill establishes in the executive branch a commission to study the most effective vehicles for investment of the trust funds, other than investments in the form of U.S. obligations.