Several companies want to stretch IBD antibodies from a shot every few weeks to one every three months, or even six. Keeping the drug in the blood that long is the easy part. Whether the disease stays controlled right up to the next dose is the hard part, and the bet the newest programs are making.
“Long-acting” hides three claims: the drug stays in the blood (PK), keeps blocking its target (PD), and keeps the disease controlled (durability). Only the last proves a long interval works. Across 1,147 IBD trials, TL1A is the most crowded emerging target, with 7 antibodies, 6 sponsors and 36 trials, and 3 already in Phase 3. The leading long-acting candidates report 56–85 day half-lives, a 3–5× leap. But the trough, how much drug is left at the next dose, tells the real story: at the proposed quarterly and six-month intervals it sits at roughly 19–47% of peak, inside the range today’s biologics already tolerate. The PK was never the wall; durability is, and only XmAb942 is yet testing a long interval in patients.
Prometheus gave IBD its best shot at oncology-style patient selection: a companion diagnostic for its anti-TL1A drug, tulisokibart. Merck paid $10.8 billion, then built its Phase 3 trials to enroll everyone. The more crowded the anti-TL1A field gets, the stronger the case for a precision-medicine approach, even as the science has yet to deliver one.
Prometheus built a companion diagnostic to pick the ulcerative colitis patients its anti-TL1A antibody tulisokibart would help, and Merck bought the company for $10.8B. But when Merck launched the Phase 3 program in 2023 (soon after the acquisition), it chose to enroll everyone and demote the test to a secondary endpoint, a design choice fixed years before the trials read out. The now-positive Phase 3 confirms it, and the rest of the anti-TL1A class (Roche, Sanofi/Teva, Spyre, the newly-launched Bionyra) competes on potency and half-life, not patient selection. Yet the more crowded the field gets, the stronger the case for a precision-medicine approach, even as the science has yet to deliver it.
Of 214 industry IBD trials terminated or withdrawn over two decades, only ~23% stopped for efficacy or safety. The rest ran out of patients, money, or corporate priority — the trial failed, not the biology.
We read the sponsor’s stated reason — the ClinicalTrials.gov whyStopped note — on all 214 terminated or withdrawn industry IBD trials. Business and portfolio decisions are the single largest cause (36%); inability to enroll is next (22%). Lack of efficacy (20%) and safety (4%) together are only ~23% — so when an IBD trial is pulled early, ~77% of the time the reason says nothing about whether the drug worked.
Eleven years after approval, Entyvio remains the only IBD drug that acts only in the gut — and two large pharma programs have failed trying to replicate it.
Tysabri (natalizumab) blocks α4 integrin broadly — and 541 patients developed fatal brain infections. Entyvio (vedolizumab) blocks only α4β7, which binds MAdCAM-1 on gut endothelium. One Greek letter difference. Over a million patient-years, no REMS, no MRI surveillance. Takeda's $6 billion franchise is built on that subtraction — and on a head-to-head trial where vedolizumab beat Humira directly in ulcerative colitis.
