Pfizer Faces Lawsuits Alleging Viagra Increases Risk of Melanoma

Lawsuits have been filed against Pfizer Inc. alleging that its erectile dysfunction drug Viagra leads to melanoma, a form of skin cancer. A multidistrict litigation (MDL) was established for Viagra melanoma lawsuits in April. The Judicial Panel on Multidistrict Litigation transferred such lawsuits to the U.S. District Court for the Northern District of California.

MDLs are created when there are a number of lawsuits with similar allegations. They are used to make complex litigation more efficient, since legal proceedings are streamlined to one court before one judge in order to eliminate duplicate discovery. In this case, plaintiffs in the MDL similarly allege that Pfizer failed to warn about the risk of melanoma with Viagra. Allegedly, the company knew or should have known that the cellular pathways through which Viagra works could promote the growth of melanoma cells. According to the American Cancer Society, melanoma is “the most serious type of skin cancer.”

The U.S. Food and Drug Administration (FDA) approved Viagra in 1998 to treat men with erectile dysfunction. Viagra blocks the secretion of phosphodiesterase type 5 (PDE5), which degrades cyclic guanosine monophosphate (cGMP). When PDE5 does not break down cGMP as it normally does, smooth muscles in the erectile tissue relax and causes an erection. Plaintiffs in the MDL allege that this mechanism also promotes or worsens the development of melanoma. Some studies have linked Viagra to cell mutations that ultimately lead to melanoma, the plaintiffs allege.
In the master complaint, plaintiffs cite several studies to support allegations that Viagra presents a risk of melanoma to patients. Among them is a 2012 study published in the Journal of Cell Biochemistry finding that PDE inhibitors can stimulate melanin synthesis, which exacerbates melanoma development.

Plaintiffs also cite a study published in the June 2014 edition of the Journal of the American Medical Association (JAMA) of Internal Medicine. Researchers gathered data from 25,848 participants and found that the recent use of Viagra was associated with an 84 percent increased risk of developing or worsening melanoma. The risk was even higher, 92 percent, among men who had ever used Viagra in the past.

Another study, published March 2016 in Cell Reports, suggested that Viagra may stimulate the growth of melanoma tumors. According to the authors, cGMP helps melanoma cells grow and migrate. Normally, PDE5 degrades cGMP but it is inhibited by Viagra.

Allegedly, Pfizer knew or should have known that the mechanism behind Viagra could increase the risk of melanoma. The company is accused of placing profits before patient safety. Plaintiffs allege that the risk of melanoma outweighs the benefits of Viagra. Plaintiffs allege that Pfizer engages in negligent and wrongful conduct, which ultimately led to plaintiffs’ injuries.

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