On April 21, 2017 Atara Biotherapeutics, Inc. (Nasdaq:ATRA), a biopharmaceutical company focused on developing meaningful therapies for patients with severe and life-threatening diseases, reported that it has entered into a clinical trial collaboration agreement with Merck (known as MSD outside the United States and Canada), to evaluate Atara Bio’s allogeneic Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTL), or ATA129, in combination with Merck’s anti-PD-1 (programmed death receptor-1) therapy, KEYTRUDA (pembrolizumab), in patients with platinum resistant or recurrent EBV-associated NPC (Press release, Atara Biotherapeutics, APR 21, 2017, View Source [SID1234518658]). The Phase 1/2 trial will evaluate the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of the combination and is planned for initiation in 2018.

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Atara Bio’s ATA129 is an investigational therapy in which a healthy donor’s T-cells are stimulated to recognize EBV antigens, or viral proteins, expressed in the cells of certain liquid and solid tumors. ATA129 has previously been evaluated as a single agent in Phase 1 and 2 trials that enrolled patients with a variety of EBV-positive malignancies including 14 patients with chemotherapy refractory, metastatic NPC. In these trials, evidence of radiographic response was observed and EBV-CTLs were also shown to expand after administration without concomitant lymphodepleting chemotherapy. Recent studies suggest that EBV upregulates the transcription of PD-L1 in EBV-associated solid tumors such as NPC and gastric cancer, suggesting the potential for synergy in combination with anti-PD-1 therapies, such as KEYTRUDA.

KEYTRUDA is a humanized monoclonal antibody that works by increasing the ability of the body’s immune system to help detect and fight tumor cells. KEYTRUDA blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.

"Both ATA129 and KEYTRUDA have shown evidence of objective radiographic responses in NPC, and there is a strong biologic rationale to combine these therapies as their complementary mechanisms of action may enhance the anti-tumor activity," said Chris Haqq, M.D., Ph.D., Executive Vice President of Research and Development and Chief Scientific Officer of Atara Bio.

The collaboration agreement is between Atara Biotherapeutics, Inc. and Merck Sharp & Dohme B.V. Under the agreement, the trial will be sponsored by Atara Bio. Additional details of the collaboration were not disclosed.

About ATA129

EBV is associated with a wide range of hematologic malignancies and solid tumors, as well as certain autoimmune conditions such as multiple sclerosis. T-cells are a critical component of the body’s immune system and can be harnessed to counteract viral infections and some cancers. By focusing the T-cells on specific proteins involved in the cancers and infections, the power of the immune system can be employed to combat these diseases. Atara Bio’s ATA129 utilizes a technology in which T-cells are collected from the blood of third-party donors and then exposed to EBV antigens. The resulting activated T-cells are then expanded, characterized, and stored for future therapeutic use in an appropriate partially human leukocyte antigen, or HLA, matched patient, providing an allogeneic, cellular therapeutic option for patients. In the context of EBV infection, ATA129 finds the cells expressing EBV and kills them. ATA129 is currently being studied in ongoing Phase 2 clinical trials in patients with EBV-associated cancers, including EBV-associated post-transplant lymphoproliferative disorders (EBV-PTLD) and NPC. ATA129 is also available to eligible patients with EBV-positive tumors through an ongoing multicenter expanded access protocol trial. Atara Bio is planning to initiate two Phase 3 trials of ATA129 in patients with rituximab-refractory EBV-PTLD following either hematopoietic cell transplant (HCT) or solid organ transplant (SOT).