Atara Biotherapeutics’s investigative therapy Tab-cel (tabelecleucel) is a potentially safe and viable option to treat transplant-derived lymphoma, according to long-term data from two Phase 2 clinical trials.
The new results will be presented in a poster titled, “Long Term Outcomes of Tabelecleucel (Allogeneic Third-Party EBV-Targeted Cytotoxic T Lymphocytes) for Rituximab-Refractory Post-Transplant EBV+ Lymphomas: A Single Center Experience,” at the upcoming Congress of the European Hematology Association (EHA), June 14-17 in Stockholm, Sweden.
Atara developed Tab-cel as a treatment for transplant-derived lymphomas caused by the activation of dormant Epstein-Barr virus (EBV). Although the virus can lie dormant throughout a person’s life, causing no symptoms, it may be activated during situations when the immune system is suppressed.
Such situations include patients undergoing blood stem cell or organ transplants who receive suppressive immunotherapies to prevent cell/organ rejection.
At these times, the virus can become activated and lead to EBV-associated post-transplant lymphoproliferative disorder (EBV+PTLD), which is mainly associated with infected immune B-cells and strongly impairs the survival of patients.
One of the current strategies to prevent or treat virus reactivation is the administration of Rituxan (rituximab), developed by Genentech, an immunotherapy that targets B-cells. But not all patients respond to Rituxan treatment, and alternative therapies are needed.
Tab-cel comes as an immunotherapy that collects T-cells — a type of white blood cell that recognizes and fights infections and cancer cells — from healthy donors and genetically alters them to specifically recognize and eliminate cancer cells, without affecting healthy ones.
Two single-center, open-label, Phase 2 clinical trials — 11-130 (NCT01498484) and 95-024 (NCT00002663) — evaluated the clinical effects of Tab-cel in patients with EBV+ PTLD who failed to respond to Rituxan. Patients received Tab-cel infusions on day one, eight, and 15 of every four-to-six week cycle.
Atara had already reported durable responses, and that 50-67% of patients who developed the condition after blood stem cell transplants were alive after one year.
Now, the company reports updated longer-term results of these studies, involving 49 patients who developed the condition after blood cell transplants (35 patients) or organ transplants (14 patients), who did not respond to Rituxan.
After one year, 68% of treated patients who underwent blood cell transplants and 64% of treated patients who had organ transplants were alive.
The expected median survival of patients with lymphoma after blood cell transplants who fail to respond to Rituxan is 16-56 days. In these clinical trials, more than half of patients treated with Tab-cel are alive after 23.3 months of follow-up.
The median survival of treated patients after organ transplant was 21.3 months, which, according to Atara, is nearly two times longer than commonly expected in these patients (12-13 months).
Tab-cell was generally well-tolerated and its safety profile was consistent with previous studies, with few reports of serious adverse effects associated with treatment.
“Long-term outcomes including survival, durability of treatment responses and safety continue to highlight the potential compelling benefit of tab-cel for patients with EBV-associated lymphomas,” Dietmar Berger, MD, Atara’s global head of research and development, said in a press release.
Based on the positive findings from the studies, Atara is conducting two Phase 3 clinical trials — the MATCH study (NCT03392142) and the ALLELE study (NCT03394365) — to evaluate Tab-cel in these patients.
Atara expects to have initial results from one of these trials, and to submit a European Union conditional marketing authorization application, in the first half of 2019.