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Roche’s cancer immunotherapy Tecentriq (atezolizumab), a PD-L1 inhibitor, scored its fifth Food and Drug Administration approval on Friday, for advanced triple-negative breast cancer, but the fifth was a first: Before this decision, no immunotherapies had been approved for any form of breast cancer.

The approval, as is typical, was narrow: for locally advanced or metastatic triple-negative breast cancer expressing PD-L1, the molecule that locks onto PD-1 receptors on the surface of T cells. (Triple-negative means the tumor cells do not have estrogen receptors, progesterone receptors, or HER2, all of which fuel uncontrolled cell proliferation but can be blocked with drugs such as Herceptin.)


The PD-L1/PD-1 handshake blocks T cells from attacking the tumor. The first drugs that prevent the handshake, such as Bristol-Myers Squibb’s nivolumab and Merck’s pembrolizumab, target PD-1. Tecentriq binds with PD-L1, preventing the T-cell-sidelining handshake.

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