Yet almost 20 years after the drug's initial approval, plaintiffs like Clark are saying the company withheld critical information on diabetes that, at the very least, could have helped them watch for onset of the disease.
A key issue in “failure-to-warn” litigation like this is whether Pfizer knew, or should have known from clinical trials, about Lipitor's risk of causing blood-sugar changes that trigger diabetes. “The question is whether Pfizer already knew this and concealed it,” said Kay Dickersin, director of the Center for Clinical Trials at Johns Hopkins Bloomberg School of Public Health.
If the clinical trials provided evidence of a heightened risk, Pfizer could be held liable. Plaintiffs in failure-to-warn cases typically try to establish that a “signal” was detected in the drug's clinical trials that the drug manufacturer either ignored or concealed. But experts disagree about how big a spike in the data is considered a signal for increased risk, Dickersin said.
Since the Lipitor cases are new and little evidence has been made public yet, it's difficult to assess the merits of the cases. Even armed with strong evidence from clinical studies, plaintiffs often find it difficult to prove that a drug caused an individual's medical condition.
Attorneys for Pfizer declined to comment on their litigation strategy. But the company has said in written statements and legal filings that diabetes and heart disease share numerous risk factors, and that cholesterol-cutting drugs such as Lipitor are often prescribed to people who are already at risk for developing diabetes. “We intend to vigorously defend the allegations,” Pfizer said in a written statement responding to questions from Modern Healthcare.
But one of the attorneys suing Pfizer said the plaintiffs can overcome the perception of Lipitor's safety.
“Did you believe that Vioxx, one of the largest selling drugs at the time, caused heart attacks and strokes? A lot of people didn't believe that at first, either,” said Chris Coffin, a partner at Pendley Baudin & Coffin in Plaquemine, La., who is representing Lipitor plaintiffs. “When the science says there is a negative outcome—and the science clearly shows that (for Lipitor)—it's hard to refute.”
The lawsuits also challenge the adequacy of Pfizer's current 20-page consumer brochure for Lipitor. In 2011, an analysis of published medical literature and drug-trial data led the FDA to require Pfizer and other statin makers to update their product labels and brochures to reflect the small risk of increased blood-sugar levels. Pfizer responded by disclosing that the drug may affect “HbA1c and fasting serum glucose levels,” which are two measures of sugar in the blood.
Clark and other plaintiffs claim Pfizer's language was intentionally vague to hide the risk of diabetes. Their lawyers point out that the wording in Pfizer's label change was more obscure than the wording in label changes issued by the makers of other statin drugs. AstraZeneca's label for its statin drug Crestor warns explicitly that increases in glucose levels “may exceed the threshold for the diagnosis of diabetes mellitus.”