Artiva halts AlloNK development and cuts workforce by 94% after two deaths
Key Facts
Artiva Biotherapeutics announced on October 27, 2026, that it was halting development of its AlloNK cell therapy, including not proceeding with the pivotal Phase 3 trial it had planned. The decision followed two deaths among participants in a Phase 2a basket study and the U.S. Food and Drug Administration's request to pause enrollment and dosing in that study. In a filing with the Securities and Exchange Commission, the company said the agency requested the pause after being notified of the fatal neurological event. Artiva also halted enrollment and dosing in the planned Phase 3 trial. It also announced a workforce reduction of about 94%, a move it said was intended to preserve capital while it evaluates strategic alternatives.
The first death occurred after the participant received the study treatment, which included protocol-based lymphodepletion using cyclophosphamide and fludarabine. The company disclosed the event as a fatal neurological condition, leukoencephalopathy. The investigator and an independent safety reviewer assessed the event as likely related to neurotoxicity caused by fludarabine. After the company notified the FDA, the agency requested a pause in enrollment and dosing in the Phase 2a study. The filing distinguishes this regulatory request from the halt to the Phase 3 trial, which Artiva said it initiated.
The second death was sudden and occurred about two months after treatment began, according to the company's filing. The investigator assessed the case as unrelated to AlloNK or any other component of the treatment regimen used in the study. The cause of death had not been determined when the company announced it. Artiva thus described two cases with different assessments: a possible link between the first death and fludarabine toxicity, versus no link between the second death and treatment, according to the investigator's assessment. The company did not say that the agency's request to pause the study was in response to the second death; it said the request followed the FDA being notified of the fatal neurological event.
Alongside the medical events, Artiva said longer follow-up had not shown durability of clinical response at the level it considers necessary to continue developing the therapy. The company wrote that "longer follow-up did not reflect the level of clinical response durability that the company believes is necessary to support continued development." In its second-quarter financial update, the company had reported that 5 of 7 patients, or 71%, in the Phase 2a study of refractory rheumatoid arthritis achieved an ACR50 response after six months, based on data through April 3, 2026. In an August update, it said none of the responding patients had lost their response, required high-dose steroids or started a new b/tsDMARD class treatment as of the data cutoff. But the company said its assessment of the longer follow-up, together with the events it announced in October, did not support continuing the program.
In August, Artiva had planned to launch a randomized, registrational Phase 3 trial in the second half of 2026, comparing AlloNK with rituximab alone in about 150 patients. The primary efficacy endpoint was to be an ACR50 response after six months. The company also said at the time that the FDA had granted the combination of AlloNK and rituximab Regenerative Medicine Advanced Therapy designation for refractory rheumatoid arthritis, and that the designation offered accelerated development and review mechanisms and greater opportunities for engagement with the agency. Financially, Artiva reported that cash, cash equivalents and investments totaled about $319.1 million on September 30, 2026, based on preliminary, unaudited figures. Its balance on June 30, 2026, was $349.4 million, which the company said in August was expected to fund operations through 2029.
After halting the program and cutting staff, the company said it was evaluating strategic alternatives that could include a merger, business combination, asset sale or licensing, or dissolution and liquidation. It appointed Leerink Partners as financial adviser to assist with the evaluation. Artiva did not announce an outcome of the review or an agreement with another party in the filing. It also canceled its investor webinar scheduled for November 9, 2026, and said it would not present the clinical data it had previously announced plans to present at ACR Convergence 2026. In trading, Reuters reported that the stock fell 30% in premarket trading on October 27 following the announcement that development of the therapy had been halted.