Genentech Does it Again, Wins FDA Approval for ‘Son of Rituxan’

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a course of treatment for chronic lymphocytic leukemia, said Genentech spokeswoman Emmy Wang. A course of treatment with the drug consists of four intravenous infusions in the first month, then once-monthly infusions from months 2-6, Wang says.

The new antibody came to Genentech through an unusual path, which I described in a feature back in June. Roche acquired GlycArt Biotechnology in 2005, and then Roche acquired all of Genentech in 2009. Genentech has long worked on various iterations on rituximab, particularly through a long-running partnership with Weston, MA-based Biogen Idec (NASDAQ: BIIB). Under that partnership, Biogen Idec provides 35 percent of the R&D costs of obinutuzumab, and stands to receive 35-39 percent of the U.S. sales of the drug based on hitting certain sales milestones, Wang said.

Although this is just the first approval in a specific patient population for obinutuzumab, the long-term potential of the drug is obviously huge. Rituximab, first approved for non-Hodgkin’s lymphoma by the FDA in 1997, generated $7.29 billion in worldwide sales last year, making it the world’s fifth-biggest selling drug, according to Genetic Engineering and Biotechnology News. The new product will need to prove its worth in multiple other patient populations to achieve what the original antibody has over time, but it’s not inconceivable.

The new drug is not just a simple knock-off, although it is designed to hit the same molecular marker—CD20. The key difference is that the new drug was designed through “glycoengineering” to remove a sugar group that would otherwise be attached to the backbone of the Y-shaped protein drug. That way, Genentech’s antibody engineers were hoping to improve upon a phenomenon they observed with rituximab known as “antibody-dependent cell-mediated cytotoxicity,” or ADCC. While rituximab was made to bind specifically with the CD20 target commonly found on the surface of tumor cells, its effectiveness couldn’t be completely explained by the antibody’s direct tumor-killing ability. The binding of the antibody to the target would also send a signal that alerted the immune system to start attacking those tumor cells. For the next-generation antibody, the goal was to hit the same CD20 target, but do a better job at triggering the critical immune response.

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