Kyverna's cell therapy improves mobility in mid-stage study

By Kamal Choudhury

Dec 15 (Reuters) - Kyverna Therapeutics KYTX.O said its experimental cell therapy met the main goal of "significantly" improving patients' ability to walk and reducing muscle stiffness in a mid-stage study for a rare disorder with no approved treatments.

Shares of the company, which plans to seek a U.S. approval in the first half of 2026, surged 45% to a more-than-one-year high of $12.73 in early trading on Monday.

The therapy, miv-cel, was tested in patients with stiff person syndrome, a rare autoimmune disorder that makes muscles rigid and causes painful spasms, often affecting the back and legs.

The trial data is a "best-case scenario for Kyverna," with compelling efficacy, Leerink Partners analyst Thomas Smith said.

The registrational trial, designed to generate data for regulatory approval, enrolled 26 patients who failed to show improvement on other treatments. They were given a single dose of the therapy and tracked for 16 weeks.

Walking speed improved by a median of 46% at 16 weeks, with 81% of the patients achieving clinically meaningful gains, and two-thirds on walking aids no longer requiring them. All patients were able to stop other immune-suppressing drugs.

The therapy was generally well-tolerated, the company said.

The CAR T-cell therapy works by using a patient's immune cells, which are modified to find and remove the cells causing the disorder.

Standard care usually involves muscle relaxants such as diazepam or baclofen and may use immune therapies like intravenous immunoglobulin, steroids or rituximab, if symptoms persist.

The company said it would initially target 2,000 to 2,500 patients, or roughly 30% to 40% of those diagnosed, who have failed to respond adequately to off-label immunotherapies.