The ALTB-268 ulcerative colitis trial has produced an early signal in a hard-to-treat group, according to AltruBio. The company reported Phase 2a results from its open-label ASCEND UC2a study in patients with moderately to severely active ulcerative colitis who had not responded adequately to prior advanced therapies: clinical remission at week 12 in 23.1% (3 of 13) on the higher dose and 11.4% (4 of 35) on the lower dose. The company says ALTB-268 was generally well tolerated and plans a placebo-controlled Phase 2b trial in 2027. The treatment remains investigational, the cohorts were small and there was no placebo group.
ALTB-268 ulcerative colitis trial: key takeaways
- Week 12 clinical remission was 23.1% (3 of 13) on the higher dose and 11.4% (4 of 35) on the lower dose, per AltruBio’s announcement of 20 October 2026.
- ASCEND UC2a is open-label with no placebo group and enrolled patients sequentially into two cohorts.
- The company calls the drug well tolerated; one serious adverse event and no deaths were reported.
- A placebo-controlled Phase 2b trial, ASCEND UC2b, is expected to start in 2027.
- ALTB-268 is investigational and not approved anywhere.
What ALTB-268 is
ALTB-268 is described by the company as a first-in-class, subcutaneously administered, tetravalent agonist antibody that targets PSGL-1, also known as CD162. According to AltruBio, it preferentially downregulates chronically activated, late-stage T effector cells, which may lead to their exhaustion or cell death, with the aim of restoring immune balance without broadly suppressing the immune system. That description is the company’s. In plain terms, the idea is to quiet the specific immune cells that keep driving inflammation in the gut, and not to dampen the whole immune system. More on the company is on the AltruBio website.
How the ALTB-268 ulcerative colitis trial was run
The trial registry entry for ASCEND UC2a and the company describe ASCEND UC2a as a Phase 2a, open-label, dose-exploration trial in adults with moderately to severely active ulcerative colitis who had an inadequate response to at least one prior advanced therapy, such as a biologic, a JAK inhibitor or an S1P receptor modulator. Cohort 1, the lower dose, had 35 patients, and Cohort 2, the higher dose, had 13, enrolled one after the other. The doses differ by two-fold, though the amounts were not disclosed. The 12-week induction period was followed by a period in which dosing was at the investigator’s discretion.
ALTB-268 ulcerative colitis trial: the week 12 results
- Clinical remission: 23.1% (3 of 13) on the higher dose and 11.4% (4 of 35) on the lower dose.
- Endoscopic improvement: 23.1% (3 of 13) and 17.1% (6 of 35).
- Clinical response: 53.8% (7 of 13) and 34.3% (12 of 35).
- Quality-of-life (IBDQ) response: 53.8% (7 of 13) and 51.4% (18 of 35).
By our simple subtraction, remission was about 11.7 percentage points higher in the higher-dose cohort. Because the cohorts were enrolled sequentially and are very small, that difference cannot be read as a reliable dose effect.
The exploratory exposure analysis in the ALTB-268 ulcerative colitis trial
The company also reports an exploratory pooled analysis of 18 patients whose Day 29 trough drug level was at or above a target, in whom clinical remission was 38.9% (7 of 18), endoscopic improvement 38.9% and clinical response 55.6%. Preliminary modelling showed a positive relationship between drug level and week 12 remission. This section is our caution: grouping patients by how much drug they had in the blood after the fact is an exploratory approach that can overstate benefit, and it needs confirmation in the planned randomised trial.
Safety in the ALTB-268 ulcerative colitis trial
AltruBio describes ALTB-268 as well tolerated, with a similar overall rate of treatment-emergent adverse events in both cohorts despite the two-fold dose difference. The most common event was injection-site reaction, which decreased with repeat dosing and was not seen in either cohort by the end of induction. There was one serious adverse event, in Cohort 1, and no deaths. With only 48 patients and a short observation period, rarer or longer-term effects cannot be assessed.
What comes next: ASCEND UC2b
The company plans a global, placebo-controlled Phase 2b trial, expected to start in 2027, that will evaluate two active dose levels in patients who have tried advanced therapies and in those who have not. Its endpoints include induction of clinical remission and durability of response during maintenance. David T. Rubin, M.D., of the University of Chicago, who presented the data at United European Gastroenterology Week 2026, described the early signals in this long-standing, advanced-therapy-refractory population as important initial signals, and chief executive Judy Chou called the remission rates highly encouraging.
Why placebo comparison matters
This section is general background. In ulcerative colitis trials, a meaningful share of patients on placebo often reach remission, so a result without a placebo group is hard to interpret. An open-label design also lets patients and doctors know the treatment, which can raise reported improvement. For these reasons, the planned Phase 2b trial is the real test, and we make no comparison with other drugs, whose trials differ in design and patients.
What the ALTB-268 ulcerative colitis trial does not disclose
- The actual dose amounts.
- Results beyond week 12 and maintenance outcomes.
- Any comparison with placebo or existing therapies.
- The size and timing of the Phase 2b trial.
Risks and caveats on the ALTB-268 ulcerative colitis trial
- Cohorts were small and the study had no placebo group.
- Observed remission rates are not proof of efficacy.
- They should not be read as a direct comparison against existing treatments.
- This is news reporting, not medical advice.
In our assessment, the ALTB-268 ulcerative colitis trial gives a modest, early signal in patients who have run out of options, and the credible next step is the randomised Phase 2b study planned for 2027. See also Emvistegrast Phase 2 Success: Bold Oral Colitis Data. More in our pharmaceutical coverage.
What to watch next on the ALTB-268 ulcerative colitis trial
- Start and design of ASCEND UC2b in 2027.
- Longer follow-up from the Phase 2a cohorts.
- Disclosure of dose levels.
Frequently asked questions
What is ALTB-268?
An investigational, subcutaneous antibody targeting PSGL-1 on activated T cells, developed by AltruBio.
What were the Phase 2a results?
Week 12 clinical remission was 23.1% on the higher dose and 11.4% on the lower dose, in an open-label study.
Does this prove ALTB-268 works?
No. The study was small and had no placebo group.
How we reported this: we relied on AltruBio’s announcement of 20 October 2026 and the trial registry. Our calculations and general background are labelled. Last updated: 20 October 2026. This article is news reporting and not medical advice.