Second-Line Biologic in Crohn's Disease: Choosing Between Two Interleukin-Targeted Antibodies
A single Crohn's disease patient who has failed anti-TNF therapy, testing whether ustekinumab's longer track record or risankizumab's narrower, more selective mechanism is the better second-line biologic for her specific disease pattern.
Simone K., a 36-year-old woman who works as a freelance graphic designer, was diagnosed with ileocolonic Crohn's disease three years ago and has been through adalimumab, her first biologic, for the past fourteen months — a genuine trial at an optimized, dose-intensified regimen with a confirmed therapeutic drug level, not an underdosed attempt, that nonetheless failed to control her disease. She's still having four to five loose stools a day, a calprotectin holding stubbornly at 290, and endoscopic evidence of persistent moderate inflammation on her most recent colonoscopy despite everything the team has tried to optimize about her current regimen. Adalimumab is being discontinued, and the group is now facing a genuinely different kind of decision than her first biologic choice was — not whether to start a biologic, but which of two interleukin-targeted mechanisms gives her the best shot after a real, confirmed anti-TNF failure.
Ustekinumab and risankizumab both work by blocking interleukin-23, a cytokine central to the inflammatory pathway driving her disease, but through meaningfully different mechanisms: ustekinumab targets the shared p40 subunit common to both IL-12 and IL-23, while risankizumab selectively targets IL-23's own p19 subunit, sparing IL-12 signaling entirely. Ustekinumab has the considerably longer track record as a second-line option specifically in anti-TNF-experienced Crohn's disease patients — the population Simone herself now belongs to — with years of accumulated real-world effectiveness and safety data behind it. That track record is the older kind of evidence, though, and it now has a randomized counterweight aimed at precisely her situation. SEQUENCE (Peyrin-Biroulet et al., NEJM 2024) randomized 520 patients with moderate-to-severe Crohn's disease after anti-TNF failure — Simone's exact entry criteria — to risankizumab or ustekinumab, and split its two endpoints: risankizumab was merely noninferior for symptomatic clinical remission at week 24 (58.6% vs 39.5%), but superior for endoscopic remission at week 48 (31.8% vs 16.2%). That split is the part that reads directly onto her chart. Her stools have not changed and her calprotectin has not moved, but what her last colonoscopy actually documented was persistent moderate mucosal inflammation — she is a patient defined by the endpoint the trial separated on, not the one it tied on.
Clinic, choosing a second-line biologic after anti-TNF failure
I'd start ustekinumab. It has by far the longer track record specifically in anti-TNF-experienced patients, exactly the population Simone is now in, with years of accumulated real-world effectiveness and safety data behind it. I know SEQUENCE went the other way, and I'm not pretending it didn't — but it was open-label, it stopped at 48 weeks, and a single trial reading out at one year is a different kind of evidence from a decade of watching a drug behave in practice.
I'd start risankizumab, and I want to be precise about why, because "a track record" and "a randomized comparison" aren't two grades of the same evidence. SEQUENCE is the counterfactual a track record structurally cannot give you: 520 anti-TNF-failure patients, randomly assigned, risankizumab superior for endoscopic remission at week 48 — 31.8% against 16.2%, roughly double — and superior on every ranked secondary endpoint. Open-label is a real limitation, but the endoscopies were centrally read and blinded, which is exactly the endpoint in question here.
The methodological caution I'd actually raise is narrower than "one trial isn't enough," and it cuts the other way once you apply it to her. SEQUENCE separated the two drugs on endoscopy and not on symptoms — so if Simone's problem were her stool frequency, I'd say the trial genuinely doesn't distinguish them and the track record should break the tie. But her stool frequency is the part that hasn't changed on anything; what her colonoscopy documented is the part risankizumab actually won on. The honest residual uncertainty is durability past 48 weeks, and that argues for scheduled endoscopic reassessment rather than for choosing the drug the trial beat.
Agreed: risankizumab started at SEQUENCE's regimen — 600mg IV at weeks 0, 4 and 8, then 360mg subcutaneously every 8 weeks — with a repeat colonoscopy scheduled rather than left to symptoms, since endoscopy is both the endpoint the choice was made on and the only place her disease has been showing itself. NOT agreed: how much the gastroenterologist's durability concern should count. He accepts SEQUENCE's week-48 result and still holds that a decade of practice experience tells you something a one-year trial cannot, and would have wanted ustekinumab if Simone's disease had been symptomatic rather than endoscopic. That disagreement was left standing; it simply did not describe this patient.