David Oberlin, MD, is a board-certified dermatologist practicing in Grand Rapids and Hastings, Michigan.

David Oberlin, MD

 approved a label update for guselkumab (Tremfya) in May 2026, crediting the phase 3b APEX trial (NCT04882098) with inhibiting radiographic joint damage in psoriatic arthritis.¹ David Oberlin, MD, dermatologist at Forefront Dermatology in Grand Rapids, Michigan, and Jesse Veenstra, MD, PhD, of Henry Ford Health, co-authored a commentary on the findings in the Journal of the American Academy of Dermatology.² The pair questioned whether APEX's enriched population reflects general dermatology patients.

"The most informative trial is not necessarily the one with the largest effect, but the one whose participants most closely resemble the patient being treated," said Oberlin. APEX enrolled biologic-naive patients with erosive disease, elevated CRP, and PsA duration beyond 6 months, criteria far more restrictive than those used in comparator trials such as DISCOVER-2 and KEEPsAKE 1.

Baseline joint damage closely tracked placebo-arm progression on radiographic Sharp scores across trials, with a near-linear correlation of 0.97.² This made a statistically significant treatment effect easier to reach in a more enriched population, regardless of drug mechanism. DISCOVER-2 carried some baseline enrichment of its own, Oberlin noted, but APEX pushed enrichment further to widen the placebo-progression gap.

This relationship helps explain why APEX reached significance on its radiographic endpoint while DISCOVER-2, also testing guselkumab, and KEEPsAKE 1, testing risankizumab (Skyrizi), did not, despite both drugs working through interleukin-23 inhibition.³ No head-to-head trial has directly compared the two drugs on joint damage outcomes, Oberlin noted. In the following interview, Oberlin discusses how trial design, rather than drug mechanism, shaped APEX's radiographic results.

: Can you walk me through the core takeaway you and your co-author wanted dermatologists to take from this commentary?

 I think the big thing Dr. Veenstra and I were looking at is, with this label update for guselkumab following the APEX trial demonstrating radiographic inhibition of joint disease in patients with PsO and PsA, what we really wanted to analyze is whether this applies to general dermatology patients. After we looked at the data and the enrichment of the baseline characteristics of these patients, we wanted to make sure we were better educating providers regarding these enrichment strategies and asking whether this particular study applies to our patients in general dermatology.

: Why does APEX's baseline erosive-disease requirement matter when comparing radiographic results across trials?

 Because of what we've seen in a regression plot with a correlation of almost 1, at 0.97, it's almost a straight line: the more baseline disease these patients have, the more placebo progression they will have over that 24-week period, with BE OPTIMAL only being a 16-week period. The higher the baseline joint disease, the more likely the placebo group is to progress in terms of Sharp scores. This allows for a statistically significant difference between baseline characteristics and the treatment arm, so by enriching for placebo progression, you're able to show statistical significance for the treatment arm.

: What does the correlation between baseline joint damage and placebo progression tell us about differing treatment effects across trials?

Not all IL-23 agents are created equally, and we know that with the IL-17 inhibitors as well; there are different nuances and different binding capacities. We don't necessarily have head-to-head data, and that's really the key for us to be able to tell these drugs apart. But what we can say is that in this specifically enriched population with APEX, they show statistical significance, whereas the other interleukin-23 agents, specifically guselkumab in DISCOVER-2 and risankizumab in KEEPsAKE, are not showing statistical significance, simply because the lack of placebo progression did not allow for that delta from the treatment arm.

Editor’s note: Oberlin disclosed having received honoraria for serving as a key opinion leader for Amgen, AbbVie, UCB, and Arcutis, and for participating on advisory boards for AbbVie, Sensus, UCB, Sanofi, Incyte, and Apogee. This transcript has been edited for grammar and clarity using artificial intelligence tools.

Johnson & Johnson. FDA approves label expansion, cementing TREMFYA as the only IL-23 inhibitor proven to help stop further joint damage. Published May 28, 2026. Accessed September 14, 2026. 

https://www.jnj.com/media-center/press-releases/fda-approves-label-expansion-cementing-tremfya-as-the-only-il-23-inhibitor-proven-to-help-stop-further-joint-damage

Oberlin D, Veenstra J. Interpreting radiographic outcomes across IL-23 inhibitor trials in psoriatic arthritis: the role of trial design. J Am Acad Dermatol. Published online July 3, 2026. doi:10.1016/j.jaad.2026.06.135.

Mease PJ, Ritchlin CT, Coates LC, et al. Inhibition of structural damage progression with the selective interleukin-23 inhibitor guselkumab in participants with active PsA: results through week 24 of the phase 3b, randomized, double-blind, placebo-controlled APEX study. Ann Rheum Dis. 2025:S0003-4967(25)04305-5. doi:10.1016/j.ard.2025.08.006.

Articles

FDA’s May 2026 label update for guselkumab in psoriatic arthritis cites APEX phase 3b evidence for inhibiting radiographic joint damage, but generalizability is debated. APEX selectively enrolled biologic-naive patients with erosive disease, elevated CRP, and longer disease duration, enriching for rapid placebo-arm progression on Sharp scores. Across trials, baseline structural damage strongly correlated with placebo progression (r=0.97), making statistical separation easier in enriched cohorts. This design effect may explain discordant radiographic outcomes versus DISCOVER-2 and KEEPsAKE 1 despite shared IL‑23 targeting.

David Oberlin, MD, explains why APEX's enriched trial population, not drug mechanism, likely drove its unique radiographic success in psoriatic arthritis.

Q&A: How Trial Enrichment Shaped APEX's Radiographic Findings in Psoriatic Disease

David Oberlin, MD, a board-certified dermatologist at Forefront Dermatology in Grand Rapids, Michigan, spoke with 

 about a commentary he co-authored with Jesse Veenstra, MD, PhD, of Henry Ford Health, in the 

Journal of the American Academy of Dermatology (JAAD)

 label update crediting guselkumab (Tremfya) with inhibiting radiographic joint damage in psoriatic arthritis (PsA), based on the phase 3b APEX trial (NCT04882098), and asks whether its enriched population reflects general dermatology patients.

What Baseline Disease Severity Hides in PsA Trial Data, With David Oberlin, MD

Oberlin said APEX enrolled biologic-naive patients with erosive disease, elevated CRP, and PsA duration beyond 6 months, criteria he called far more restrictive than those used in comparator trials such as DISCOVER-2 and KEEPsAKE 1. He and Veenstra found baseline joint damage closely tracked how much a trial's placebo arm progressed on radiographic Sharp scores, making a statistically significant treatment effect easier to reach in a more enriched population regardless of the drug's mechanism.

Oberlin said this relationship helps explain why APEX reached significance on its radiographic endpoint while DISCOVER-2, also testing guselkumab, and KEEPsAKE 1, testing risankizumab (Skyrizi), did not, despite guselkumab and risankizumab both working through interleukin (IL)-23 inhibition. He noted no head-to-head trial exists comparing the 2 drugs directly on joint damage outcomes.

"The biggest message we want to get across to providers is make sure the baseline characteristics of the trial represent the patient in front of you. If the patient in front of you fits the APEX trial, then you may be able to inhibit radiographic progression, but otherwise you cannot look at that study and say it has mechanistic superiority compared to other IL-23 agents," Oberlin said.

Oberlin said APEX alone would not change how he selects a biologic for psoriatic disease. He weighs oral versus injectable preference, disease severity, comorbidities, how quickly a patient needs to clear, dosing frequency, and formulary coverage, and said dermatologists now have enough effective IL-23 and IL-17 options, so no single trial should dictate the choice.

Oberlin D, Veenstra J. Interpreting radiographic outcomes across IL-23 inhibitor trials in psoriatic arthritis: the role of trial design. J Am Acad Dermatol. Published online 2026. doi:10.1016/j.jaad.2026.06.135.

Smith T. Trial Design Drives Radiographic Outcomes Across IL-23 Inhibitors in PsA. HCPLive. August 26, 2026. Accessed September 9, 2026. 

https://www.hcplive.com/view/trial-drives-radiographic-outcomes-il-23-inhibitors-psa

FDA approves label expansion cementing Tremfya as the only IL-23 inhibitor proven to help stop further joint damage. Johnson & Johnson. Published May 28, 2026. Accessed September 9, 2026.

Videos

David Oberlin, MD, on why trial enrichment, not mechanistic superiority, likely explains differing radiographic results in PsA drug trials.