Using the immune system to fight cancer just took a big step forward. We already have Dendreon's (Nasdaq: DNDN ) Provenge, which trains the immune system to attack prostate cancer, and Bristol-Myers Squibb's (NYSE: BMY ) Yervoy, which treats melanoma by blocking an immune cell protein that dampens the immune response called CTLA-4.
Like Yervoy, Bristol's newest drug, BMS-936558, acts on another break on the immune system called PD-1. Some tumors express PD-L1, which binds to PD-1 on the immune cell, signaling that the tumor shouldn't be attacked.
The impressive thing about BMS-936558 is that it seems to be working in multiple tumor types. Like Yervoy, the drug works in melanoma, shrinking tumors in 28% of patients. But the drug also seems to work well in kidney cancer, with 27% of patients seeing tumor shrinkage, and 18% of patients with lung cancer seeing their tumors shrink as well. The lung cancer result is the weakest of the three, but it's also the most telling. I don't know of any immunotherapy that has worked well on lung cancer, a notoriously hard type of tumor to treat.
Shrinking the tumors is important, but keeping them from growing back is equally necessary for extended survival. The data on BMS-936558 is still pretty immature, but 20 patients in the trial had tumor responses that lasted a year or longer. Bristol plans to move straight into pivotal trials in lung and kidney cancer this year, with testing in melanoma to start in late 2012 or early 2013.
The speed is partially due to the strong data, but it's also because Bristol has a lot of competition in the space. Merck (NYSE: MRK ) , Roche, Teva Pharmaceuticals (Nasdaq: TEVA ) , and GlaxoSmithKline (NYSE: GSK ) are all developing drugs in the same pathway.
Bristol is also developing a drug that works on the other half of the tumor-immune cell interaction, blocking the PD-L1 on the tumor cells. Sensitizing the tumor to killing by the immune system could work better because it shouldn't cause the side effects seen when patients' immune systems are over-activated and start attacking other non-cancerous tissue. One of BMS-936558's side effects was lung inflammation, although it seems to be controllable with steroids.
Perhaps an anti-PD-L1 will be the next-next big thing in immunotherapy.
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