Johnson & Johnson is battling giants in the immunology field with its IL-23 inhibitor Tremfya. With other next-gen drugs already crowding the market, J&J now has the FDA's nod to take Tremfya into psoriatic arthritis in what could prove to be a tough challenge. 

The FDA on Tuesday approved J&J's Tremfya as the first IL-23 inhibitor to treat psoriatic arthritis, which affects around 1.5 million Americans each year, the drugmaker said. 

The agency based its review on data from two pivotal phase 3 trials showing Tremfya topped placebo in the number of psoriatic arthritis patients who showed 20% improvement in disease symptoms at the 24-week mark. 

In the two studies from J&J's Discover program, 58% of patients were also treated with immunosuppressant methotrexate. One of the studies only included patients who had not been previously treated with a biologic while the other enrolled 31% of patients who had previously been treated with an anti-TNF drug. 

Tremfya is administered under the skin in eight-week intervals after patients receive starter doses at the initiation of treatment and the four-week mark, J&J said. 

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Tremfya's entry into psoriatic arthritis will put it up against next-gen blockbusters from AbbVie, Novartis and Eli Lilly, but the drug's unique formulation could help it carve out a sales niche to add to its current plaque psoriasis nod. 

But getting into the same field as those challengers will be tough, and not only because one of them has already proven itself more effective than Tremfya in treating psoriatic arthritis. 

In October, Lilly released phase 4 data showing IL-17a inhibitor Taltz beat out J&J's med in a head-to-head test, completely clearing 41.3% of moderate to severe plaque psoriasis patients’ skin at 12 weeks, compared with the 24.9% Tremfya posted.

Not only did Taltz best its rival at the 12-week primary endpoint, but it also topped Tremyfa in completely and partially clearing skin at a range of weekly markers, Lilly said.

RELATED: Novartis takes aim at Eli Lilly with Cosentyx FDA nod in spondyloarthritis

Alongside Taltz, Novartis' Cosentyx also has an approval in psoriatic arthritis and is battling the Lilly med in a growing list of indications. In June, the FDA approved Cosentyx to treat adult patients with non-radiographic axial spondyloarthritis, just weeks after the agency approved Taltz as the first IL-17 inhibitor in that indication. 

Meanwhile, two next-gen launches from AbbVie—psoriasis med Skyrizi and JAK inhibiotr Rinvoq—are both gunning for psoriatic arthritis nods in their quest to pick up the slack for anti-TNF blockbuster Humira, which will see U.S. biosimilars launch in 2023.