Belviq, also known by its drug name lorcaserin, is a weight loss aid designed to reduce feelings of hunger in overweight and obese individuals. The medication works by activating the serotonin receptors in the brain that affect a person’s appetite. Belviq was available in two formulations: Belviq—taken twice a day—and Belviq XR—taken once a day.

Use of Belviq was intended to accompany a low-calorie diet and doctor-supervised evaluation of weight loss. Patients who did not lose at least 5% of their body weight during the first 12 weeks on Belviq were generally not considered good candidates for continued use of the medication.

Belviq was initially developed by Eisai, Inc., a Japanese pharmaceutical company—making its path to FDA approval atypical. Drugs developed in other countries can receive U.S. approval without additional clinical trials. In these scenarios, FDA officials review the information gathered from the drug’s development in its home country to inform their decision.

Eisai first asked the FDA to approve the medication’s sale in the US in 2009. However, the application was rejected when a majority of review panel participants agreed that its dangerous side effects outweighed its usefulness as a weight loss aid.

Following this rejection, Arena Pharmaceuticals, an American company, stepped in to conduct additional testing and resubmit the application for Belviq’s approval in 2012. The FDA approved this second request but added certain monitoring requirements and restrictions. One such restriction was limiting Belviq candidates to those patients who either met the criteria for obesity or overweight status and had at least one related condition, such as diabetes or hypertension.

Another monitoring requirement for Belviq’s approval was conducting an additional trial into the drug’s impact on cardiovascular health. This ongoing testing ultimately uncovered the drug’s links to cancer and led to its FDA-sanctioned demise.

Initially, the side effects associated with Belviq appeared to be minor. According to the medication’s package insert, only 11 side effects were reported by more than 5% of users who tried Belviq during clinical trials.

Certain other potentially serious side effects were reported, including an increased risk of serotonin syndrome in patients who took Belviq with other serotonin-acting medications, including SSRIs used to treat depression. The package insert listed several such symptoms with the advice to seek immediate medical attention if they occurred. None of the listed symptoms, however, included cancer.

Additional Side Effects for Patients Without Diabetes

For patients without diabetes, the most common reported side effects included, constipation, dizziness, dry mouth, fatigue, headache, and nausea.

Additional Side Effects for Patients With Diabetes

Patients with diabetes were more likely to report hypoglycemia, cough, and back pain.

The FDA’s request that Eisai, Inc. take Belviq off the market was spurred by the results of the five-year study of Belviq patients. The research indicated that these patients were more likely to develop various types of cancer than similarly-situated patients who did not take Belviq.

The study followed 12,000 patients, some of whom took Belviq and some of whom took a placebo. The resulting data revealed that cancer developed in 7.7% of patients taking Belviq and in 7.1% of patients taking the placebo. Three specific types of cancer—pancreatic, colorectal, and lung cancer—were more likely to occur in the group of patients taking Belviq than in the group taking the placebo.

The FDA recommended that patients stop taking Belviq immediately and talk to their doctors about alternative options for weight management. The FDA also provided guidelines for disposing of unused medication in a safe manner.

Assessing both compensatory and punitive damages for Belviq patients will require careful evaluation of each patient’s individual circumstances. Depending on the patient’s cancer diagnosis and prognosis, damages could include medical expenses incurred from cancer treatment, pain and suffering caused by the patient’s cancer and treatments, loss of income earning capacity, and loss of enjoyment of life secondary to the patient’s cancer.

Since Belviq was removed from the market, product liability lawsuits against the drug’s manufacturer and U.S. sponsor have begun to appear. These lawsuits, which are in their infancy, typically claim that the companies behind Belviq had a duty to create a non-cancer-causing product or to alert consumers about the increased cancer risk. With very serious health implications on the line, lawsuits will surely continue to emerge regarding Belviq and its alleged links to cancer.

As Belviq lawsuits continue to develop, they are likely to require the perspectives of expert witnesses. Since Belviq targets serotonin production, neuroscience experts who can discuss serotonin’s role in the body may be among those consulted. Likewise, oncology experts may discuss how certain types of cancer develop within the body.

Physicians specializing in weight loss management may also be consulted on the benefits and risks of Belviq as a weight-loss drug, as well as on the relationship, if any, between increased weight and cancer risk. Pharmacology experts will be helpful for explaining the process by which Belviq was developed as well as its chemical composition. Experts in FDA approvals will also be essential for explaining how Belviq was approved for use in the United States and the regulatory responsibilities of the FDA.

As this litigation proceeds, expert witnesses will play a vital role in establishing the key technical and medical facts for judges and juries.