A patient treated with standard Allogene Therapeutics experimental cell therapy was diagnosed with a chromosomal problem, prompting the FDA to halt all of the company’s clinical trials while investigating the cause and severity of the problem.
Allogene said Thursday that clinical precautions were in place after informing the FDA of what the company called a “chromosomal abnormality”. A total of seven allogeneic programs have reached human testing, all in early clinical development. On a conference call, Allogene CEO David Chang said it was too early to know what needs to happen for the studies to resume, but added that it was “a bit of a surprise” that the FDA all has put clinical trials on hold.
South San Francisco-based allogeneic stocks fell more than 32% in after-hours trading.
The problem was identified in a patient who was being treated for follicular lymphoma and who had not responded to previous chemotherapy or radiation therapy. According to the company, the patient was unable to receive autologous CAR-T cell therapy made from the patient’s own cells because the expansion step of the manufacturing process did not produce enough cells.
Allogene cell therapies are well suited for such cases. Instead of making the therapy from the patient’s own cells, these allogeneic or commercial treatments are made from the immune cells of healthy donors; these constructed cells are ready for use when needed. Allogene said that after being infused with the experimental therapy ALLO-501A, the patient experienced an immune response called cytokine release syndrome as well as neurotoxicity – both known side effects of CAR-T therapy. These side effects were treated with steroids.
The patient also developed lower levels of platelets and red and white blood cells in the blood, which is another known CAR-T complication. A bone marrow biopsy done to assess the low blood count was what discovered the allogeneic CAR T cells with the chromosomal abnormality. Rafael Amado, executive vice president of research and development and chief medical officer of Allogene, said a fraction of the cells were detected with the abnormality. Chang said the abnormality was seen on chromosome 14, but more details are still being investigated.
“This is a case-by-case report from more than 100 patients that we tried,” said Chang. “This is not something we normally look for because most patients recover and CAR-T cells disappear from the patient’s body.”
The patient’s response to treatment with allogeneic cell therapy was partial, requiring an allogeneic stem cell transplant. This rescue treatment has already been carried out in some cases by autologous CAR T.
The study that identified the chromosomal problem is the phase 1 part of a phase 1/2 test to evaluate ALLO-501A, the company’s most advanced cell therapy candidate. Allogene worked with the FDA to design the pivotal Phase 2 part of the trial, which is expected to begin later this year.
Photo from FDA