Introduction: Adalimumab (ADA) treatment has been shown to be effective and safe in Japanese patients (pts) with moderate to severe Crohn's disease (CD).Table 1: Efficacy outcomes in ADA-treated patients ( N =28)Methods: This study evaluated the efficacy and safety after dose escalation to open-label (OL) ADA 80 mg every other week (eow) in Japanese pts with CD who lost response to maintenance ADA 40 mg eow. Interim analyses to wk 24 are reported. 28 Japanese pts ≥15 years (yrs), who received induction treatment with commercially available ADA (160/80 mg at wks 0/2), achieved CD Activity Index (CDAI) decrease from baseline (BL) ≥70 (CR-70) after 4 wks, and subsequently lost response to maintenance ADA 40 mg eow (defined as CDAI increase ≥50 compared to minimum CDAI during maintenance ADA treatment and absolute CDAI ≥200) were evaluated. Pts with loss of response or intolerance to infliximab (IFX) could enroll. Pts with CRP ≥1 mg/dL during screening received OL ADA 80 mg eow from wks 0-50; disease activity was assessed by CDAI at screening, wk 0, and every 4 wks to wk 52. The primary endpoint was proportion of pts achieving CDAI decrease ≥50 from BL (CR-50) at wk 8 after dose escalation. Pts who did not achieve CR-50 at wk 8 OR at two consecutive CDAI evaluations after wk 8 were withdrawn from the study. Other efficacy outcomes assessed in this interim analysis were: CR-50, CR-70, CR-100, clinical remission (CDAI < 150), and median change from BL in CRP. Non-responder imputation was used for missing CDAI data and last observation carried forward was used for missing CRP data. Results: 43% (12/28) were female, mean age was 33.6 yrs, CD duration 8.6 yrs, mean CDAI 308, and median CRP 2.35 mg/dL at BL. Immunomodulator and corticosteroid use at BL was 46% and 7%, respectively, and 68% were IFX-experienced. The proportion of pts who achieved CR-50 at wk 8 was 75% (21/28). CR-50 response was 71% (20/28) at wk 24 (Table), and CR-50 rates were comparable for IFX-naïve and -experienced pts. CR-70 and CR-100 were achieved by 57-68% and 36-50% of pts over time to wk 24, respectively. Remission rates increased from 25% at wk 8 to 43% by wk 24. CRP levels improved from BL over time following dose escalation. Adverse event (AE), serious AE, and serious infection rates were 75%, 21%, and 7%, respectively, at wk 24. Conclusion: Dose escalation to OL ADA 80 mg eow demonstrated clinical benefit in Japanese pts with CD who had lost response to maintenance ADA treatment. No increased safety risk was identified.