As reported on Medical Daily, Artiva Biotherapeutics has discontinued development of its investigational autoimmune cell therapy, AlloNK, after two participant deaths occurred during a mid-stage clinical study. The San Diego-based company also announced plans to eliminate approximately 94% of its workforce as it evaluates strategic alternatives, including a potential merger, asset sale, or company wind-down.
The decision marks another setback for the emerging field of cellular therapies for autoimmune disorders, where developers are attempting to achieve long-term disease control by resetting the immune system.
Trial Termination Follows Two Patient Deaths
AlloNK was being evaluated in combination with the B cell-depleting therapy rituximab for several autoimmune conditions, including rheumatoid arthritis, Sjögren’s disease, systemic sclerosis, and idiopathic inflammatory myopathies.
According to the company, neither death was directly attributed to the NK cell therapy itself. One participant developed severe neurological complications known as leukoencephalopathy after receiving a preparatory chemotherapy regimen that included cyclophosphamide and fludarabine. Investigators and an independent safety review concluded that the fatal event was likely linked to fludarabine-associated neurotoxicity.
Following notification of the case, the U.S. Food and Drug Administration requested a pause on enrollment and dosing activities. Artiva subsequently halted progress toward a planned Phase 3 rheumatoid arthritis study.
A second participant died unexpectedly roughly two months after initiating treatment. Investigators reportedly determined that the event was not related to AlloNK or other trial therapies, although a definitive cause of death has not been identified.
Durability Concerns Also Influenced Decision
In addition to the safety concerns, Artiva reported that longer-term follow-up data suggested treatment responses were not durable enough to justify further development.
Chief Executive Officer Fred Aslan stated that, after reviewing the available evidence, the company chose to discontinue the program. No additional patients will receive treatment through the study, although ongoing safety monitoring of enrolled participants will continue.
Several details remain unavailable, including the total number of patients treated, demographic information about the deceased participants, and the timing of the first fatality. Artiva has indicated it intends to publish additional information regarding the fludarabine-related case. The company also withdrew a planned presentation from the upcoming ACR Convergence 2026 rheumatology meeting.
Why the Chemotherapy Regimen Matters
Unlike autologous CAR-T therapies, which use genetically modified immune cells collected from the patient, AlloNK relied on natural killer cells sourced from healthy donors.
Before receiving cell therapies, patients typically undergo lymphodepletion, a chemotherapy-based conditioning strategy designed to reduce existing immune cells and improve engraftment of the infused product. Fludarabine is commonly used for this purpose across numerous cellular therapy programs.
As a result, the fatal neurological event may attract attention beyond Artiva’s program. Researchers are increasingly examining whether the risks associated with conditioning chemotherapy are acceptable in autoimmune diseases, where patients are often younger and may have different risk tolerances than individuals undergoing treatment for advanced cancers.
While the incident does not establish that fludarabine is broadly unsafe, it highlights ongoing questions about balancing potential benefits with treatment-related toxicity in non-oncology settings.
Autoimmune Cell Therapies Face Increasing Scrutiny
Artiva’s announcement comes amid a series of safety concerns affecting the broader autoimmune cell therapy landscape.
Several programs have recently encountered trial interruptions after serious adverse events, prompting regulators, investigators, and sponsors to take a closer look at safety monitoring and patient selection. Despite these challenges, many experts continue to believe the approach holds promise because some patients have achieved prolonged periods of disease remission without ongoing medication.
Researchers emphasize that recent setbacks should be viewed as signals for caution and refinement rather than definitive evidence that cellular therapies cannot succeed in autoimmune disease.
What Current and Prospective Trial Participants Should Know
Patients currently enrolled in AlloNK studies should remain engaged with their clinical research teams and continue scheduled follow-up evaluations. Individuals who previously received lymphodepleting chemotherapy should seek immediate medical attention if they experience symptoms such as confusion, seizures, speech difficulties, vision changes, severe weakness, or high fever.
For patients considering enrollment in other autoimmune cell therapy trials, important questions include:
- Which conditioning chemotherapy agents will be used before treatment?
- What serious adverse events have been observed to date?
- How are neurologic complications monitored and managed?
- What long-term safety follow-up is required?
Experts also advise patients not to discontinue prescribed treatments for autoimmune conditions without first consulting their rheumatologist or treating specialist.
As Artiva works with regulators to formally close its clinical programs, additional details from the fatal neurological case may provide important insights for the future development of autoimmune cell therapies.
