Abstract
BACKGROUND AND AIMS: Vedolizumab was shown to be safe and effective for the treatment of Crohn's disease [CD] and ulcerative colitis [UC] in the GEMINI Long-Term Safety [LTS] study. The vedolizumab Extended Access Program [XAP] provides patients with continued treatment. This XAP pharmacokinetics [PK] sub-study investigated vedolizumab efficacy, safety, and PK. METHODS: Vedolizumab dosing frequency was reduced from every 4 weeks [Q4W] to every 8 weeks [Q8W] at XAP enrolment, and patients were followed for 56 weeks. Outcomes included: efficacy, loss of clinical benefit, and re-escalation to Q4W dosing; and vedolizumab PK, immunogenicity, and adverse events. RESULTS: Among 167 enrolled patients [CD = 88, UC = 79], 80 [91%] with CD and 73 [92%] with UC completed 56 weeks; 76 [86%] and 71 [90%] with CD and UC, respectively, remained on Q8W dosing for 56 weeks. Clinical remission, corticosteroid-free clinical remission, and C-reactive protein levels were stable among patients remaining on Q8W through Week 56. Four patients with CD and two with UC resumed Q4W dosing [three with CD regained clinical response]. Patients with CD who completed Week 56 on Q8W dosing had median trough vedolizumab concentrations of 43.6 µg/mL at enrolment and 10.4 µg/mL at Week 56; concentrations were 42.4 µg/mL and 13.3 µg/mL, respectively, in patients with UC. Treatment-related adverse events were infrequent; no new or serious adverse events related to vedolizumab were reported. CONCLUSIONS: In the XAP-PK sub-study, adherence to Q8W dosing was high, with no loss of efficacy; very few patients required re-escalation to Q4W. There were no new safety signals.