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Positive Phase III Data for New Leukemia Drug, Obinutuzumab

Disease progression, death significantly reduced versus chlorambucil (May 16)

Positive results have been reported from a phase III trial that compared the combination of either obinutuzumab (GA101; Roche) or MabThera/Rituxan (rituximab; Roche) and chlorambucil, a standard chemotherapy, with chlorambucil alone in patients with chronic lymphocytic leukemia (CLL).

The open-label CLL11 study included 781 previously untreated patients with CLL and comorbidities (589 patients were included in the current analysis, and an additional 192 patients have been enrolled to allow a forthcoming direct comparison of obinutuzumab versus MabThera/Rituxan, both in combination with chlorambucil). The study’s primary endpoint was progession-free survival (PFS).

Key findings include:

  • The addition of obinutuzumab to chlorambucil led to a statistically significant reduction in the risk of disease progression or death of 86% versus chlorambucil alone (P < 0.0001).
  • The median PFS improved by more than 1 year from 10.9 months for chlorambucil alone to 23.0 months for obinutuzumab plus chlorambucil.
  • The complete response (CR) rate was 22% in the obinutuzumab/chlorambucil arm versus 0% in the chlorambucil arm.
  • At this time, no formal comparison between the obinutuzumab and MabThera/Rituxan arms can be made, as the number of PFS events required for that formal analysis has not yet been reached.
  • The most common grade-3 or grade-4 adverse events for obinutuzumab were infusion-related reactions and neutropenia.

According to a report from Reuters, Roche, the developer of obinutuzumab, hopes to use the new drug to fend off cheaper competition for Rituxan, which loses patent protection in Europe later this year.

Based on the results from the CLL11 study, a marketing application for obinutuzumab has been submitted to the FDA.

Sources: Roche; May 16, 2013; and Reuters; May 16, 2013.

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