6 March 2019

New biologics for psoriatic arthritis

Biologics Clinical Medications Psoriatic Athritis

Two new biologics have recently been added to the PBS: one for severe psoriatic arthritis and another for severe chronic plaque psoriasis. 

Ixekizumab (TALTZ) is now available at an affordable price for adult patients with severe psoriatic arthritis who don’t respond well to DMARD therapies. 

Instead of paying up to $3400 per script, Australians with psoriatic arthritis would now only need to pay $40.30. 

“Ixekizumab is part of a group of medicines known as interleukin inhibitors,” Professor Stephen Hall, a rheumatologist based in Victoria, said.

“It works by targeting a specific protein interleukin 17 in the immune system to hinder the development of psoriatic arthritis.”

Ixekizumab can be prescribed as a monotherapy or in combination with cDMARDs. The drug is given as a subcutaneous injection every four weeks by a specialist or a self-administered by the patient. 

In clinical trials, over half of patients taking ixekizumab saw an improvement in psoriatic arthritis symptoms (ACR 20) at week 24.

“In biologic naïve patients, ixekizumab demonstrated significantly improved joint symptoms as early as week one and sustained improvement in joint symptoms over one-year,”  Professor Hall said.

Tildrakizumab (ILUMYA) was also recently PBS-listed for the treatment of severe chronic plaque psoriasis. 

Patients need to have tried at least three other treatments, including non-biologic treatments such as UV exposure or methotrexate, to be considered eligible for the drug. 

The drug targets the immune system slightly differently to other PBS-listed biologics for psoriasis. (The drug works by inhibiting interleukin-23 and controlling the release of the cytokines interleukin-17A and TNF, which cause chronic inflammation.)

 In clinical trials, the majority of patients taking the therapy saw a marked reduction in the severity of their psoriasis, achieving a 75%  reduction in severity from baseline ( PASI 75).

After one year on the medication, many patients who initially had psoriatic plaques over 30-40% of their body only had 3-4% of their body surface area involved. 

The treatment is given by subcutaneous injection every 12 weeks by a specialist, after the first two doses given at weeks zero and four. 

In the future, tildrakizumab might be used to treat severe psoriatic arthritis and clinical trials are under way to test this indication.   

In a randomised, controlled trial of around 400 patients conducted in 2016, tildrakizumab improved both chronic plaque psoriasis and psoriatic arthritis.