Like with samalizumab, rash, pruritis, and urticaria were observed for 23ME-00610; however, samalizumab was primarily evaluated in hematologic malignancies rather than solid tumors, so the increased number of hematologic AEs seen with samalizumab and not with 23ME-00610 are more likely to be due to the underlying disease tested rather than a specific effect of CD200 versus CD200R1 antagonism. The gene discussed is CD200R1; the disease is urticaria.