The U.S. Food and Drug Administration says AbbVie did not properly investigate deaths linked to its blockbuster biologic Humira.

FDA inspectors investigated AbbVie’s Chicago plant in 2017. AbbVie had received five death complaints linked to Humira and another drug Venclexta, according to FDA inspectors.

The drug company reported these deaths to the FDA. But AbbVie failed to note another eight to 11 deaths also tied to the same drugs.

FDA inspectors included this information in a Form 483 report in December 2017. FDA inspectors issue Form 483s when a company’s manufacturing practices “may constitute violations of the Food Drug and Cosmetic (FD&C) Act and related Acts.”

AbbVie “investigates all complaints where a death has occurred during the use of our products,” a company spokeswoman told FiercePharma. She also said the company responded “satisfactorily” to the FDA.

But, the FDA found AbbVie’s procedures for handling death complaints “inadequate.”

AbbVie did not investigate drug batches manufactured close to a problematic batch. The company also failed to examine batches for evidence of deterioration.

Humira is AbbVie’s top moneymaker. It treats conditions such as arthritis and Crohn’s disease. The drug brought in $18.4 billion in 2017.

The FDA has not said if it intends to take further regulatory action.

AbbVie Spends Millions on Humira Lobbying, Ads

Humira sales made up 65 percent of AbbVie’s 2017 revenue. Its sales have a large impact on the company’s bottom line, according to AbbVie’s 2017 annual report.

“Any significant event that adversely affects Humira revenues could have a material and negative impact on AbbVie’s results of operations and cash flows,” AbbVie said in its report.

AbbVie spends millions in ads and lobbying efforts to ensure Humira remains the world’s bestselling drug.

For example, it spent $341 million on 16 Humira TV commercials in 2017. It also spent millions on lobbying, including donations to the Crohn’s & Colitis Foundation and the Arthritis Foundation.

AbbVie has also jacked up the price of the drug. It went from $19,000 a year in 2012 to more than $38,000 a year in 2018.

Patients Claim Deadly Humira Side Effects

Humira’s safety profile may also be questionable. Since 2003, the FDA received 374,513 adverse event reports for Humira. Of those, 10,884 were deaths.

The company has faced several lawsuits over Humira side effects.

Humira lawsuits claim the drug caused deadly fungal infections, nerve damage and cancer.

In 2013, a Chicago jury awarded $2.2 million to a man whose wife said Humira gave her a life-threatening fungal infection.

The jury found AbbVie and its parent company Abbott guilty of negligence.