A therapeutic protein for use in a method of treatment of a CD20+ B-cell malignancy, wherein the method comprises administering the therapeutic protein to a subject in a dosing regimen to reduce the incidence or severity of cytokine release syndrome or infusion-related reaction, the method comprising: administering fractions of a primary dose of the therapeutic protein in week 1 of the dosing regimen, wherein the primary dose comprises 1 mg of the therapeutic protein, a first dose fraction (F1D1) comprises 50% of the total primary dose and is administered to the subject on day 1 of week 1, and a second dose fraction (F2D1) comprises the remaining 50% of the total primary dose and is administered to the subject from 12 to 96 hours following administration of the F1D1; administering fractions of a secondary dose of the therapeutic protein in week 2 of the dosing regimen, wherein the secondary dose comprises 20 mg of the therapeutic protein, a first dose fraction (F1D2) comprises 50% of the total secondary dose, a second dose fraction (F2D2) comprises the remaining 50% of the total secondary dose, and the F2D2 is administered to the subject from 12 to 96 hours following administration of the F1D2 during week 2 of the dosing regimen; and administering the maximum weekly dose of the therapeutic protein to the subject as a single dose in a subsequent week of the dosing regimen, wherein the maximum weekly dose comprises 80 mg, 160 mg or 320 mg of the therapeutic protein, wherein the therapeutic protein is a bispecific anti-CD20 x anti-CD3 antibody comprising an anti-CD20 binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 10 and a light chain comprising the amino acid sequence of SEQ ID NO: 12, and an anti-CD3 binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 11 and a light chain comprising the amino acid sequence of SEQ ID NO: 12. administering fractions of a primary dose of the therapeutic protein in week 1 of the dosing regimen, wherein the primary dose comprises 1 mg of the therapeutic protein, a first dose fraction (F1D1) comprises 50% of the total primary dose and is administered to the subject on day 1 of week 1, and a second dose fraction (F2D1) comprises the remaining 50% of the total primary dose and is administered to the subject from 12 to 96 hours following administration of the F1D1; administering fractions of a secondary dose of the therapeutic protein in week 2 of the dosing regimen, wherein the secondary dose comprises 20 mg of the therapeutic protein, a first dose fraction (F1D2) comprises 50% of the total secondary dose, a second dose fraction (F2D2) comprises the remaining 50% of the total secondary dose, and the F2D2 is administered to the subject from 12 to 96 hours following administration of the F1D2 during week 2 of the dosing regimen; and administering the maximum weekly dose of the therapeutic protein to the subject as a single dose in a subsequent week of the dosing regimen, wherein the maximum weekly dose comprises 80 mg, 160 mg or 320 mg of the therapeutic protein, wherein the therapeutic protein is a bispecific anti-CD20 x anti-CD3 antibody comprising an anti-CD20 binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 10 and a light chain comprising the amino acid sequence of SEQ ID NO: 12, and an anti-CD3 binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 11 and a light chain comprising the amino acid sequence of SEQ ID NO: 12.