Tremfya is a brand-name prescription medication for the biologic drug guselkumab. Generic versions of biologic drugs are called biosimilars. Currently, there’s no biosimilar version available for Tremfya.

Medicare Part D drug plans may cover either version if a doctor or healthcare professional prescribes it.

Private insurance companies administer Part D prescription drug plans on Medicare’s behalf. So drug costs and drug availability can vary by plan type and plan provider.

If you have psoriatic arthritis (PsA), a doctor or healthcare professional may prescribe Tremfya (guselkumab). And when medically necessary, Medicare may cover some or all of the costs.

It’s important to check with Medicare or your plan provider before going ahead with this medication. This is because it’s typically high cost and may be on a higher formulary tier than other medications.

Part D drug plans have three coverage stages, including the:

  • deductible stage
  • initial coverage stage
  • catastrophic coverage stage

If you receive approval for the medication, the coverage should be as follows:

The deductible stage

Not all Part D prescription drug plans have a deductible, but if yours does, you’ll join at this stage.

Once you’ve paid the plan deductible in full, the plan will begin paying its share of eligible costs.

Initial coverage stage

During this stage, you’ll pay a 25% coinsurance toward the cost of Tremfya (guselkumab).

In 2025, you’ll continue paying the 25% coinsurance until you’ve paid a total of $2,000. In 2026, this is expected to increase to $2,100.

Catastrophic coverage stage

During this stage, you’ll pay no further costs toward your prescription medications for the remaining calendar year.

You’ll receive an explanation of benefits (EOB) the month after your pharmacy bills your plan provider. The EOB will detail:

  • the prescriptions you’ve filled.
  • the total amount the plan has paid
  • the total amount you’ve paid
  • the amount others have paid, such as another insurer (if applicable)
  • which coverage stage you’re at
  • what the plan has counted toward your total out-of-pocket expenses
  • the total amount the pharmacy has charged for your medications

Tremfya is a brand-name drug containing the active ingredient guselkumab. It’s an interleukin-23 antagonist and doctors prescribe it to help treat adults with:

  • moderate to severe plaque psoriasis who are eligible for systemic therapy or phototherapy
  • active PsA
  • moderate to severe active ulcerative colitis
  • moderate to severe active Crohn’s disease

Interleukin-23 antagonisits work by blocking the action of the cytokine IL-23, which is a protein involved with the immune system and inflammation.