Obinutuzumab-related adverse events: A systematic review and meta-analysis

Rituximab, the first anti-CD20 monoclonal antibody, has dramatically improved outcomes for patients with B-cell lymphoproliferative disorders. Obinutuzumab was developed to potentiate activity and overcome resistance to rituximab. Clinical data suggest that obinutuzumab is superior to rituximab in follicular lymphoma (FL) and chronic lymphocytic leukemia (CLL). Yet, it has increased toxicity. This systematic review and meta-analysis compiled all randomized controlled trials (RCTs) comparing obinutuzumab-based regimens with rituximab-based regimens to better assess their toxicity profile. Primary outcome was grade 3-4 infections; secondary outcomes included any adverse events (AE), grade 3-4 AE, drug discontinuation rate, and 3-years mortality. Relative risks (RRs) were estimated and pooled using a fixed-effect model, unless there was significant heterogeneity, in which case a random-effects model was used. Our comprehensive search yielded five RCTs conducted between 2009 and 2014, including 4247 patients. The trials included FL patients, CLL and diffuse large B cell lymphoma. Monoclonal antibodies were given with different chemotherapy regimens (in four trials) or as monotherapy (in one trial). The point estimate favored increase in both grade 3-4 infections rate (RR 1.17 [95% CI, 1.0-1.36]) and any AE rate (RR 1.05 [95% 1-1.1]) with obinutuzumab, although this was not statistically significant. There was a significantly increased rate of grade 3-4 AE (RR 1.15 [95% CI, 1.09-1.2]), as well as grade 3-4 toxicities including thrombocytopenia (RR 2.8 [95% CI, 1.92-4.06]), infusion related reactions (RR 2.8 [95% CI, 2.16-3.64]) and cardiac events (RR 1.65 [95% CI, 1.11-2.46]). There was no significant difference in grade 3-4 anemia and neutropenia nor in the 3-year mortality rate. The point estimate favored increase in discontinuation rate due to AE with obinutuzumab, although without statistical significance (RR 1.24 [95% CI, 1.0-1.54]). In conclusion, physicians need to weigh the clinical benefits of this agent against higher toxicity.