Tocilizumab, but not dexamethasone, prevents CRS without affecting antitumor activity of bispecific antibodies

Abstract

Bispecific antibodies (bsAb) and chimeric antigen receptor (CAR) T cells allow for antibody guided recruitment of T cells against tumors. Both are successfully used for treatment of CD19 expressing leukemias, but may cause cytokine release syndrome (CRS) as a major dose-limiting side effect. For CRS prevention, steroids are recommended prior to bsAb treatment, despite their well-known lymphotoxic activity. The IL-6 receptor antibody tocilizumab is established for treatment of CRS induced by CAR T cells, but was not considered for CRS prevention in bsAb therapy. We here compared the influence of dexamethasone and tocilizumab on bsAb-mediated T cell proliferation and tumor lysis in vitro and in vivo and found that dexamethasone profoundly inhibited T cell proliferation and antitumor activity as induced by two different bsAb, particularly at low effector:target ratios, whereas tocilizumab did not affect efficacy. When we applied tocilizumab early during treatment of three patients with a newly developed PSMAxCD3 bsAb, significant CRS attenuation despite high IL-6 serum levels was observed. Thus, early IL-6 blockade may reduce the undesired sequelae of CRS upon bsAb therapy without affecting therapeutic activity, allowing in turn for safe application of effective doses.

Keywords: antibodies, neoplasm; immunotherapy; lymphocyte activation.

Figure 1

T cell proliferation and tumor cell lysis in the presence of dexamethasone or tocilizumab in vitro and in vivo. (A) PBMC of healthy donors (n=3) were incubated with the PSMAxCD3 bispecific antibody (bsAb) CC-1 (1 µg/mL) in the presence of PSMA⁺ LNCaP cells for 72 hours (effector:target (E:T) ratio 2:1) and additionally treated with tocilizumab (TOCI) or dexamethasone (DEXA) at the indicated concentrations. T cell proliferation was assessed by thymidine uptake assays. (B) LNCaP cells were used in xCELLigence assays. After 24 hours, cell indices were normalized and tumor cell lysis was measured after addition of PBMC of healthy donors (E:T = 3.3:1) as well as CC-1 (bsAb, 1 µg/mL) and TOCI (10 µg/mL) or DEXA (0.1 µg/mL). Cell indices were measured every 15 min and represent the amount of viable tumor cells. Representative data from three independent experiments are shown. (C) Tumor cell lysis was assessed in a flow cytometry-based assay with PBMC of healthy donors (n=4) and LNCaP cells at different E:T ratios for 72 hours in combination with CC-1 (1 µg/mL) and TOCI (10 µg/mL) or DEXA (0.1 µg/mL). (D) NSG mice (n=5 per group) with established LnCaP flank tumors were repeatedly treated with PBMC in combination with CC-1 (2 µg/mouse) (d1, d8, d15) and TOCI (200 µg/mouse) or DEXA (5 µg/mouse) (d1). Statistical analysis was done using Mann-Whitney U test. *p<0.05; **p<0.01; n.s. not significant.

Figure 2

Temperature and cytokine release of three patients treated with a bispecific antibody (bsAb) and tocilizumab (TOCI). The PSMAxCD3 bsAb CC-1 was applied to three patients on compassionate use basis in an individual dose escalation regime as indicated. The bsAb was applied as continuous infusion over 22 hours. TOCI was applied as soon as body temperature reached 38.5°C (dotted line). Serum IL-6 levels and soluble IL-2 receptor (sIL-2R) levels were determined by ELISA at the central laboratory of the University Hospital Tübingen. Temperature was measured at least every 2 hours. Each panel (A–C) represents one individual.