PF-06801591 is an immunotherapy that Pfizer is developing for several types of cancer. It is called an anti-PD-1 treatment because it blocks the PD-1 protein on the surface of immune T-cells that can sometimes attack healthy cells.

How PF-06801591 works

PD-1 is an immune checkpoint protein that prevents T-cells from attacking healthy cells. Healthy cells produce a protein called PD-L1 that binds to PD-1, inactivating T-cells.

But some tumors have adapted to T-cell checkpoints by producing PD-L1 to prevent the immune system from identifying and destroying them.

When PF-06801591 binds to PD-1 on T-cells, it prevents PD-L1 found on cancer cells from binding to PD-1. This allows T-cells to do their job: find and destroy cancer cells.

PF-06801591 in clinical trials

The first clinical trial of PF-06801591 started in December 2015. The Phase 1 trial (NCT02616185) is investigating a PF-06801591 vaccine to treat prostate cancer. It continues to recruit participants in the United States.

Another Phase 1 trial of PF-06801591 started in February 2016. The trial (NCT02573259) is evaluating the therapy in patients with several types of cancer who have already received some treatment for their disease. The cancers include melanoma, ovarian cancer, head and neck cancer, sarcoma, non-small cell lung cancer, urinary system cancer, and other solid tumors.

The study has two parts. In part 1, researchers are evaluating PF-06801591 safety and participants’ ability to tolerate increasing doses of it. The objective is to establish a maximum tolerated dose for a Phase 2 trial later on.

Part 2 of the second Phase 1 trial continues to recruit participants. Its goals are to confirm the recommended dose determined in part 1 and to evaluate the safety and effectiveness of PF-06801591 in patients with non-small cell lung cancer or urinary system cancer. The study is occurring at several U.S. sites.


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