Pfizer faces surge in Depo-Provera brain tumor lawsuits ahead of pivotal hearing

Federal litigation linking Pfizer's (PFE) Depo-Provera birth control injection to brain tumors has swelled to more than 5,500 cases after roughly 1,700 new lawsuits were filed in a single month, with a critical court hearing this week set to determine whether the claims can proceed to trial.

The multidistrict litigation, already among the faster-growing pharmaceutical mass torts in recent memory, added the new cases at a pace significantly faster than earlier in the proceedings, when a comparable number accumulated over three and a half months. Plaintiffs allege that Pfizer failed to adequately warn patients and physicians that prolonged use of the injectable contraceptive could raise the risk of developing meningiomas — tumors that form in the membranes surrounding the brain and spinal cord.

Although most meningiomas are benign, plaintiffs report suffering vision problems, seizures, cognitive impairment, hearing loss and the need for invasive brain surgery.

The pivotal moment in the litigation arrives this week, with a Daubert hearing scheduled for June 24 to 26. The proceeding will determine whether expert witnesses can present scientific testimony linking Depo-Provera to meningiomas before future juries. If the presiding judge allows the testimony, it is expected to increase settlement pressure on Pfizer and advance cases toward bellwether trials, the first of which is scheduled for December. A ruling against plaintiffs' experts, however, could significantly undermine thousands of claims.

The lawsuits gained momentum following a 2024 study published in the British Medical Journal, which found that prolonged use of medroxyprogesterone acetate — the active compound in Depo-Provera — was associated with a substantially elevated risk of meningiomas requiring surgery. The research drew on national health data from more than 18,000 women who underwent such procedures. Subsequent studies have reinforced that finding, with plaintiffs arguing that because meningiomas frequently carry progesterone receptors, extended exposure to the synthetic progestin in the injection may stimulate tumor growth.

A secondary strand of the litigation focuses on delayed diagnosis. Meningiomas typically grow slowly, and their symptoms — including chronic headaches, dizziness, memory problems, visual disturbances and personality changes — can be mistaken for stress, migraines or hormonal fluctuations. Attorneys argue that clearer warnings could have prompted earlier detection and potentially spared some plaintiffs from complex neurosurgical procedures.

The volume of filings accelerated after the FDA approved updated Depo-Provera labeling in December 2025, warning of meningioma risks associated with prolonged use. Pfizer has maintained that the contraceptive remains safe and effective when used appropriately, but plaintiffs contend the company should have acted sooner.