Zevalin and Rituxan are almost the same drug, except Zevalin has radioactive Yttrium-90 attached to it. In fact, Biogen developed Zevalin before selling it to Cell Therapeutics
After the antibody targets the drug to the cells, the radioactivity kills the cancer cells, requiring a much shorter course of therapy. But doctors haven't been particularly keen on the drug because, well, it's radioactive. Oncologists can deliver Rituxan by themselves, but dosing Zevalin requires a nuclear medicine specialist.
It should be noted that the radioactive part makes Zevalin useless for rheumatoid arthritis, which Rituxan also treats, but that's not the main issue with the gaping sales differential.
Rather than trying to compete for patients, Spectrum is now going after patients where Rituxan has failed. This week, the company announced that it was starting a phase 3 trial testing Zevalin in diffuse large B-cell lymphoma, after they responded to therapy.
This s- called maintenance therapy for blood cancers is an easy way to extend sales. It's part of the reason that Rituxan has done so well. Same with Celgene's
Rituxan is approved for maintenance therapy in low-grade non-Hodgkin’s lymphoma, but not the higher-grade diffuse large B-cell lymphoma that Spectrum is testing Zevalin in. If it's effective there, Spectrum could find a nice niche where it won't have to compete with Rituxan.
And if doctors start using Zevalin as a maintenance therapy because it's their only choice, they'll have experience with the drug, which might help Spectrum compete directly in areas where both Zevalin and Rituxan are both used.
Overall, I like the strategy. I'm not sure there's enough data to be overly confident that the drug will work -- especially since Rituxan failed -- but it certainly seems worth running the trial.
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