Patient Right to Know Drug Prices Act (Sec. 2) This bill amends the Public Health Service Act to prohibit a health insurance plan or pharmacy benefits manager from restricting a pharmacy from informing an enrollee of any difference between the out-of-pocket cost of a drug under the plan and the cost of the drug without health insurance coverage. (Such restrictions are commonly referred to as gag clauses.) (Sec. 3) The bill also amends the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 to apply certain antitrust filing requirements for generic drug applicants to biosimilar biological product applicants. (Biosimilar biological products, commonly referred to as biosimilars, are biological products approved by the Food and Drug Administration based on their similarity to an already-approved biological product.) Under current law, generic drug applicants that make agreements with brand name drug companies or other generic drug applicants regarding the manufacture, marketing, or sale of their drugs must file such agreements with the Federal Trade Commission and the Department of Justice. The bill subjects biosimilar biological product applicants to the same filing requirements.