Severe pyrexia from nivolumab-resistant advanced melanoma after successful combined therapy with encorafenib plus binimetinib.

Various serious adverse events (AE) have been reported to occur at a high rate in patients treated with BRAF plus mitogen-activated protein kinase kinase (MEK) inhibitor combination therapy, but their subtypes differ among the BRAF/MEK inhibitors. Pyrexia or a spike of fever are well-known AE of BRAF inhibitors, with or without MEK inhibitors, and have been reported to have a high incidence after dabrafenib/trametinib, but not after encorafenib/binimetinib. In this report, we describe three cases of severe pyrexia in nivolumab-resistant advanced melanoma after successful combined therapy with encorafenib plus binimetinib. Interestingly, in all cases, the serum levels of soluble CD163 C-X-C motif chemokine (CXCL)9, CXCL10 and CXCL11, which are known biomarkers for adult-onset Still's disease (AOSD), increased in parallel with the development of pyrexia. Our present cases suggest that pyrexia caused by BRAF/MEK inhibitors may possess a similar pathophysiology as that of AOSD.