FDA Approves Pimjetmi for Rare Joint Tumors

The approval is narrow, and the narrowness is the point. On November 10, 2026, the Food and Drug Administration approved pimicotinib, brand name Pimjetmi, from EMD Serono, for adults with symptomatic tenosynovial giant cell tumor, or TGCT, whose surgical removal might cause worsening functional limitation or severe morbidity. TGCT is a rare, noncancerous but locally aggressive tumor that grows in or around the lining of a joint. It doesn't metastasize. It takes the joint apart in place, causing pain, swelling, stiffness and, over time, joint damage.

The evidence comes from one well-built trial. MANEUVER, registered as NCT05804045, was a randomized, double-blind, placebo-controlled international study that assigned patients two-to-one to pimicotinib 50 milligrams once daily or placebo; the primary analysis covered 94 patients, 63 on the drug and 31 on placebo. The main measure was overall response rate at week 25, read by blinded independent reviewers using standard tumor criteria. The result was 56 percent on pimicotinib, with a 95 percent confidence interval of 42 to 68, against 3.2 percent on placebo. That's an absolute difference of about 53 percentage points, not a relative framing.

Durability is the second question every response rate owes, and here the data hold up so far. The median duration of response hadn't been reached at the FDA's analysis. Of the patients who responded, 91 percent kept their response for at least six months and 77 percent for at least twelve months. The response also started early: 41.3 percent of patients on the drug, 26 of 63, had responded by week 13. The trial's results were published in The Lancet in March 2026, and pimicotinib arrived at approval carrying both Fast Track and Breakthrough Therapy designations, with the review run under the FDA's Project Orbis program for concurrent international oncology review.

For this disease, the patient-reported outcomes aren't decoration; they're half the disease. At week 25, patients on pimicotinib improved significantly against placebo on three prespecified measures: active range of motion of the affected joint, measured with a goniometer; worst pain, on the Brief Pain Inventory scale; and physical functioning, on the PROMIS Physical Function score. A tumor that shrinks on a scan but leaves a knee just as stiff hasn't solved the patient's problem. MANEUVER measured the joint as well as the mass, and both moved the right way.

The drug's mechanism explains both its effect and its place in the class. Pimicotinib blocks the colony-stimulating factor-1 receptor, CSF-1R, a signal TGCT tumors exploit to recruit the cells that make up most of the tumor mass. It isn't the first CSF-1R inhibitor approved for TGCT, and the FDA label's specifics on warnings and liver monitoring are in the full prescribing information posted at Drugs@FDA. Merck, EMD Serono's parent, notes the drug has also been approved in China, Canada and Switzerland, and that only one patient in the trial stopped treatment because of a drug-related adverse event, with 7.9 percent needing a dose reduction.

Who should skip it is written into the approval itself. Patients whose tumors can be removed surgically without risking the joint aren't the population this was tested in, and the trial excluded people who'd already had anti-CSF-1 or CSF-1R therapy. For the patients it does cover — symptomatic, and facing a surgery that could leave them worse off than the tumor does — the choice is no longer between a damaging operation and watchful decline. It's a daily pill with a measured response rate, a durability record past a year for most responders, and joint function data to argue with.