I think it´s because their patent for rituximab is on the end and they will not do much money from it anymore.
That's my understanding of the situation as well.
If a patent is at the end of its life, then the drug company cannot invest any more money into the drug, because it will not see a return on its investment.
However, quite often, drug companies create very similar drugs, that have exactly the same effect, but are slightly chemically different, and so they get a new patent, for almost the same drug. (Is there a word to describe this process?) So perhaps this might happen at some point in the future, and then the drug company can carry on investing.
Also, I'm pretty sure that I've read that various other, similar, drugs are in the pipeline, and are in various stages of development.
In the mean time, we have to get our funding from elsewhere.
It was thought that the Norwegian government might still fund the research, in their next funding-round, but we haven't heard any more about that recently.