A fatality has been reported in a patient participating in a clinical trial by Allogene Therapeutics for its investigational CAR-T cell therapy, which is being developed to treat large B-cell lymphoma (LBCL). The death was associated with the company’s anti-CD52 monoclonal antibody, which is used for lymphodepletion.
According to a press release, the male patient was a participant in the ALPHA3 study. This significant trial is evaluating cemacabtagene ansegedleucel (cema-cel), an allogeneic anti-CD19 CAR-T, as a first-line consolidation treatment for patients with LBCL. Allogene Therapeutics stated that the death was not caused by cema-cel.
The grade 5 adverse event took place 54 days after the patient was infused with cema-cel, ALLO-647, and the standard lymphodepletion regimen of fludarabine and cyclophosphamide (FC). The patient’s death has been linked to the antibody, ALLO-647.
The patient’s death was attributed to liver failure, which is believed to have stemmed from a widespread adenovirus infection. This serious complication, where a pervasive virus affects multiple organs outside of the usual respiratory or gastrointestinal tracts, developed while the patient was in an immunosuppressed state because of the antibody.
According to Allogene Therapeutics CEO David Chang, the purpose of ALLO-647 is to intensify the lymphodepletion process. Following the patient’s fatality, the company is now completely abandoning the drug. Chang confirmed that this decision will have no effect on any other clinical studies.
He stated that ALPHA3 had been the sole remaining trial still utilizing ALLO-647. He went on to note that Allogene Therapeutics had gradually been shifting its focus away from that asset in favor of the company’s next-generation platform, known as Dagger.
Allogene has now converted its trial from a three-arm study into a two-arm study that uses only the standard FC approach. The original ALPHA3 trial was structured differently; it had a cohort which received ALLO-647 and FC as the lymphodepletion regimen before their cema-cel treatment, a second group that received only FC and cema-cel, and a third group for observation.
Chang confirmed that the trial’s statistical design and specified conduct remain unchanged. The next key event for the trial is an analysis to assess futility, which is anticipated for the first half of 2026. Originally, the biotech company had planned to use this event to determine which lymphodepletion method it would advance. Instead, the patient’s death initiated an unscheduled review, which hastened that decision.
Chang indicated that the latest update had been driven by an unfortunate situation but represented a clear and assured move ahead. He also mentioned that phasing out ALLO-647 would streamline the trial.
Chang added that administering cema-cel in an outpatient setting after FC lymphodepletion will expedite enrollment while making any potential regulatory review more efficient. The two-arm study continues to recruit participants.
Allogene made the decision to halt the use of ALLO-647 after consulting with a panel that oversees data and safety, a guiding committee, and the FDA. Chang mentioned that the federal agency was extremely prompt in its discussions with Allogene Therapeutics.
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The shift by Allogene Therapeutics away from ALLO-647 underscores the risks of combining strong lymphodepletion regimens with novel immunosuppressive antibodies. Experts in oncology have noted that while deep lymphodepletion can improve CAR-T cell expansion and persistence, it also increases vulnerability to opportunistic infections. In this case, disseminated adenovirus infection in the setting of immune suppression proved fatal.
This change also has implications for patient safety monitoring. Allogene Therapeutics will likely increase surveillance of viral reactivation and infections in future trials, particularly when using agents that produce deeper or longer-lasting immunosuppression. Prophylactic measures, earlier detection, and possible antiviral therapy may become more standard in protocols.
On the regulatory front, the discontinuation of ALLO-647 may affect how FDA and other agencies evaluate safety margins for lymphodepleting agents used with CAR-T products. It may lead to more conservative approaches or demands for clearer risk mitigation strategies.
Finally, the company’s Dagger platform—which aims to reduce or eliminate the need for intense lymphodepletion—might now carry greater importance. If Allogene Therapeutics can demonstrate that its next-generation CAR-T products maintain efficacy with less immunosuppression, it could represent a safer model for CAR-T cell therapy in settings beyond heavily pretreated disease, including first-line consolidation.
