Comparing rituximab to newer anti-CD20 monoclonal antibodies for induction therapy of CD20+ B-cell non-Hodgkin lymphomas

This study aimed to compare standard therapy Rituximab (Rituxan) to newer anti-CD20 monoclonal antibodies (mAbs) such as obinutuzumab (Gazyva), ofatumumab (Arzerra), ¹³¹I-tositumomab (Bexxar), and ⁹⁰Y-ibritumomab tiuxetan (Zevalin) for the treatment of patients with B-cell non-Hodgkin lymphomas (B-NHL).

The authors concluded that patients responded well to obinutuzumab and ⁹⁰Y-ibritumomab tiuxetan.

B-NHL is a type of blood cancer. CD20 is a protein found on cells of the immune system called B cells (CD20 positive B cells; CD20⁺). Targeted therapies against CD20 such as rituximab have greatly improved survival outcomes of patients with B-NHL. Despite this, there are still patients that do not respond to rituximab therapy or relapse (cancer returns) sooner.

Many new therapies targeting CD20, called mAbs, are emerging. They are expected to be more effective than rituximab. However, the safety and effectiveness of these mAbs compared to rituximab in the treatment of CD20⁺ B-NHL remain under investigation.

This study analyzed the results of 11 other studies with a total of 5,261 patients with CD20⁺ B-NHL. Rituximab treatment was compared to other mAbs including obinutuzumab, ofatumumab, ¹³¹I-tositumomab, and ⁹⁰Y-ibritumomab tiuxetan.

4 studies with 3,465 patients compared rituximab with obinutuzumab. Patients who received obinutuzumab were 16% more likely to have better survival without cancer worsening compared to rituximab. Response to treatment and overall survival were similar between the 2 drugs. However, obinutuzumab-treated patients were 29% more likely to experience serious side effects.

2 studies with 854 patients compared rituximab with ofatumumab. Patients who received ofatumumab were 27% less likely to respond well to treatment compared to those treated with rituximab. Ofatumumab was also 2.25 times more likely to cause side effects that lead to patients stopping treatment. There were no significant differences in survival between rituximab and ofatumumab.

3 studies with 769 patients compared rituximab to ¹³¹I-tositumomab. No significant differences were found in response to treatment and survival between the 2 drugs. However, ¹³¹I-tositumomab was associated with a 2.47 times higher risk of severe to life-threatening side effects compared to rituximab.

2 studies with 173 patients compared rituximab to ⁹⁰Y-ibritumomab tiuxetan. Patients treated with ⁹⁰Y-ibritumomab tiuxetan were 3.07 times more likely to respond to treatment compared to those treated with rituximab. However, there were no significant differences in survival or side effects between groups. 

The authors outlined that among newer mAbs, obinutuzumab improved survival rates without cancer progression but with an increased risk of side effects, and ⁹⁰Y-ibritumomab provided better responses compared to rituximab.

The data is based on patients with different subtypes of CD20⁺ B-NHL. These results need to be verified in clinical trials that focus on each particular type of B-NHL.