Restoring Immune Mediated Disease Control by Ipilimumab Re-exposition in a Heavily pretreated Patient With MSI-H mCRC.

Background: Immune-Checkpoint-inhibitors (ICIs) are approved in first line therapy of microsatellite-instable, deficient miss-match-repair (MSI-H-dMMR) metastatic colorectal cancer (mCRC), and in second line after standard chemotherapy. Evidence supporting immunotherapy after immunotherapy is scarce. Case report: This case report highlights the course of a heavily pretreated patient with MSI-H mCRC with progression after multiple local therapies, standard chemotherapies and pembrolizumab. After 4 cycles of ipilimumab and nivolumab followed by nivolumab-maintenance he achieved a long-lasting disease control of 22 months. After further subsequent progression he regained immune mediated disease control by a second "boost" of ipilimumab.

Conclusion: Re-exposition with ipilimumab is a potential option to restore immune-mediated-disease-control in patients with preceding long-lasting response to ipilimumab/nivolumab and with dMMR-tumors. The clinical situation of progress after long-lasting disease control on ICIs becomes more common and is an opportunity to investigate potential strategies for restoring immune mediated disease control.