e19026 Background: Ipilimumab (IPI) is a CTLA-4 blocking mAb with established activity in patients (pts) with advanced melanoma. Methods: Observational study on the outcome of advanced melanoma pts treated with IPI in an expanded access program (EAP) at a single-center. Results: Fifty pts initiated IPI (3 mg/kg q3wks x4, allowing for reinduction after a PFS of >24 wks). Baseline characteristics: 28M/22F, m50y, Stage: 1x IV-M1a, 2x -M1b, 47x -M1c; 44 pts skin-, 2x mucosal-, and 4x unknown primary melanoma; WHO-PS 0/1/2: 17-, 25-, 8 pts; LDH >ULN 33 pts; CRP >ULN 29 pts; ALC<1000/mm³ 15 pts; all pts were pretreated with dacarbazine and 16 pts for brain metastases. Thirty-one pts completed IPI-induction; 8/11 pts offered reinduction completed the planned 4 administrations (treatment ongoing in 1pt). Most immune-related adverse events (irAE) were generally mild/reversible; CTCAE gr3 irAE: diarrhea/colitis (3), hepatitis (1), hypophysitis (1), pancreatitis (1) and Guillain-Barré syndrome (1); no grade 4/5 irAE. BORR by mWHO-criteria: 1 CR, 3 PR and 4 SD (disease control rate [DCR]: 16%). BORR by immune-related response criteria (irRC): additional 2 PR and 3 SD (DCR: 26%). In 5/10 evaluable pts a similar or lower total tumor burden was obtained following reinduction. Two pts who experienced gr3 irAE during induction did not experience the same irAE at reinduction. After a median follow-up of 18 mths (range 7.5-19.3), 32 pts have died. Six- and 12-mths OS were 53% (95% CI 40-67) and 45% (95%CI 31-59) respectively. Disease control with IPI has been maintained in 8 pts (of which 4 received reinduction) after a median follow-up of 17 mths (range 12-17). Elevated CRP (>5x the upper limit of normal [ULN]) was the only independent baseline co-variable (HR 0,10; 95% CI 0,04-0,25; p 0.001). An ALC of <800/mm³ at week 7 and disease-control by irRC post-induction significantly correlated with OS. Conclusions: This single-center experience with IPI in an EAP for pts with advanced pretreated melanoma is comparable with that of prospective studies. Reinduction therapy seems important for long-term disease control in responding pts. Baseline CRP and ALC at week 7 deserve further evaluation as a prognostic and/or predictive (surrogate) markers.