- Design
- Cross-sectional observational study
- Population
- 59 patients with ankylosing spondylitis on golimumab
- Primary outcome
- Trough concentration, antidrug antibodies and disease activity
- Effect
- Median trough 0.41 mg/L; ADAs 13.6%; trough the only predictor of ASDAS and ADAs
A Therapeutic Drug Monitoring study measured golimumab trough concentrations and antidrug antibodies in 59 Iraqi patients with ankylosing spondylitis, after a median of seven doses, and related them to disease activity (ASDAS).
Median trough was 0.41 mg/L (range 0.21–1.38). Antidrug antibodies were found in 13.6%. Troughs were higher in antibody-negative patients and fell as disease activity rose. In regression, trough concentration was the only predictor of both disease activity and antibody formation. Only about 35% had low disease activity.
Proactive and reactive drug monitoring is established for infliximab and adalimumab in inflammatory bowel disease. These data suggest the same exposure–response relationship holds for golimumab in spondylitis, so a patient who is not responding may simply be under-exposed.
The study was small, cross-sectional and from one country, and no therapeutic range was established. Reactive monitoring when response is poor is reasonable where the assay is available; routine proactive monitoring is not yet supported.
- Consider a golimumab trough and antidrug antibody level when a spondylitis patient is not responding
- Distinguish low drug levels without antibodies, which may respond to dose optimisation, from antibody-mediated loss
- Check adherence and injection technique before attributing poor response to the drug
- Note that no validated target trough exists yet for golimumab in spondylitis
Why it matters
Some apparent non-response to golimumab may be under-exposure rather than drug failure.
Don't overread it
Small and cross-sectional: it shows association, not that trough-guided dosing improves outcomes.
The statistics, in plain English
A negative correlation between trough and ASDAS means higher drug levels went with lower disease activity; it does not show that raising the dose would lower activity.
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