The Government Accountability Office (GAO) has issued a report entitled "Medicare Part D: Spending, Beneficiary Cost Sharing, and Cost-Containment Efforts for High-Cost Drugs Eligible for a Specialty Tier." The report provides a variety of information regarding high-cost drugs eligible for a specialty tier in 2007 (such as immunosuppressant drugs, those used to treat cancer, and antiviral drugs). The GAO reports that specialty tier-eligible drugs accounted for 10%, or $5.6 billion, of the $54.4 billion in total Medicare Part D drug spending in 2007. Medicare beneficiaries who received a low-income subsidy accounted for 70% of this specialty tier-eligible drug spending. Among all beneficiaries who used at least one specialty tier-eligible drug in 2007, 55% reached the catastrophic coverage threshold, compared to 8% of those who did not use a specialty tier-eligible drug. Plan sponsors reported having little leverage to negotiate price concessions from manufacturers for most specialty-tier drugs, in part because of CMS's limitation on sponsors’ ability to exclude drugs from their formularies in favor of competing drugs, although price concessions were more likely for drugs with more competitors on the market. Plan sponsors also used practices such as prior authorization to manage beneficiaries’ utilization of specialty tier drugs somewhat more frequently than for lower-cost Part D drugs.