What happened

bluebird bio (NASDAQ:BLUE) is up 10.1% at 3:40 p.m. EDT after Novartis (NYSE:NVS) got its chimeric antigen receptor T-cell (CAR-T) therapy Kymriah approved by the Food and Drug Administration (FDA) today. Bluebird is developing CAR-T therapies of its own, including bb2121, its lead candidate using CAR-T technology, which reprograms immune cells to attack cancer cells.

So what

Usually, an approval of a drug using the same technology sends a rival stock down, not up, but bb2121 and Kymriah train the immune system to target different proteins, BCMA and CD19, respectively. These are expressed on different types of cancerous cells, and therefore won't really compete with each other.

Kymriah was approved for children and young adults with B-cell precursor acute lymphoblastic leukemia, and Novartis has data for the therapy in non-Hodgkin lymphoma, where it likely will eventually be approved, as well. Bluebird and partner Celgene (NASDAQ:CELG), on the other hand, are studying bb2121 in another blood cancer called multiple myeloma.

Drawing of a cell

Image source: Getty Images.

Novartis' approval certainly shows the FDA is willing to approve CAR-T therapies, but after the FDA advisory committee unanimously recommended the approval of Kymriah, an approval seemed highly likely. Shares of Novartis are trading basically flat today, suggesting its investors widely expected an approval.

Now what

The approval of bb2121 will ultimately be determined by the clinical data -- it's only in phase 1, after all -- not whether the FDA is willing to approve Kymriah, so long-term investors can ignore today's move as a blip, albeit a positive one, on the stock chart.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends bluebird bio and Celgene. The Motley Fool has a disclosure policy.