Patients' Access to Treatments Act of 2017 This bill amends the Public Health Service Act to establish cost sharing limits for health plans that cover prescription drugs and use a formulary or other tiered cost sharing structure. Such health plans may not impose higher cost sharing requirements, including copayment and coinsurance, for specialty drugs than for other prescription drugs in a nonpreferred brand name drug tier. If a health plan's formulary contains more than one nonpreferred brand name drug tier, the tier with the lowest cost sharing applies.