Determining toxicity risk in CAR T-cell therapy

A method of ameliorating the development of a toxicity in a subject, the method comprising administering to the subject an agent capable of treating the development of a toxicity that is severe cytokine release syndrome (CRS) or severe neurotoxicity, wherein the subject has been administered a dose of about 1.0×107 to about 1×108 total CAR-expressing T cells expressing a recombinant receptor that is a chimeric antigen receptor (CAR), wherein the subject is treated, following assessment of the number of recombinant receptor-expressing cells in a blood sample of the subject, when:

• (a) no more than four days after initiation of the dose of the recombinant receptor-expressing T cells, the number of recombinant receptor-expressing cells in the blood sample of the subject is at least at or about 2 recombinant receptor-expressing cells per microliter;
• (b) no more than five or six days after initiation of the dose of the recombinant receptor-expressing T cells, the number of recombinant receptor-expressing cells in the blood sample of the subject is at least at or about 5 recombinant receptor-expressing cells per microliter;
• or
• (c) no more than seven days after initiation of the administration the number of recombinant receptor-expressing cells in the blood sample of the subject is at least at or about 15 recombinant receptor-expressing cells per microliter;
• and wherein the agent is a steroid or an IL-6 or IL-6 receptor inhibitor, or a combination thereof.