Seattle Children's T-Cell Immunotherapy Clinical Trial for Children With Relapsed Leukemia Shows 93% Complete Remission Rate

Phase 1 findings show 39 out of 42 patients achieved complete remission; Phase 2 of the trial to launch this month

Seattle Children's announced today that 39 of 42 patients treated in a Phase 1 clinical trial using genetically reprogrammed T cells to treat relapsed or refractory acute lymphoblastic leukemia (ALL) have achieved complete remission, showing no detectable leukemia cells in the most sensitive tests. Patients treated in the trial, known as Pediatric Leukemia Adoptive Therapy-02 (PLAT-02), had less than a 20% chance of survival upon enrollment using current treatments. Seattle Children’s will launch Phase 2 of the trial this month, with the aim to enroll 70 patients in the next year.

"Seeing 93% of our patients achieve complete remission is incredibly promising," said Seattle Children's oncologist, Dr. Rebecca Gardner, who is the lead investigator for the trial and will present the Phase 1 results at the American Society of Clinical Oncology (ASCO) Annual Meeting on Sunday, June 5. "We have patients who are still in remission two years after receiving this therapy. While we still have a lot of work to do, our findings give us tremendous hope as this therapy offers children, who are otherwise unlikely to survive, a real chance at achieving remission.”

The PLAT-02 trial includes patients with ALL who have relapsed after a bone marrow transplant, or who are unable to get into remission to proceed with a bone marrow transplant. Using T-cell immunotherapy, the research team led by Dr. Mike Jensen at the Ben Towne Center for Childhood Cancer Research at Seattle Children's Research Institute reprograms a patient’s T cells so they can hunt down and destroy cancer cells wherever they are hiding in the body.

Gardner, who is also an investigator in the Center for Clinical and Translational Research, said they have been successful in reprogramming and growing T cells for all patients who have enrolled in the trial, a promising finding as similar trials have experienced difficultly producing T cells for all patients.

Another key finding from Phase 1 is that of the patients who achieved initial remission, about 50% are still in remission one year after therapy. For the patients that relapsed, researchers have found that their reprogrammed T cells are no longer present or the cancer has evolved to circumvent the T cells.

“Now that we know we can harness the power of the immune system to successfully get patients into remission, we are working to ensure the T cells remain a long-term defense against cancer for all of our patients,” Gardner said. “Our ultimate goal is to fully develop this therapy so we can offer it to newly-diagnosed patients, reducing the need for toxic therapies and minimizing the length of treatment from months or years, to only weeks. We also believe ALL is the tip of the iceberg – work is already underway to apply immunotherapy to other forms of pediatric cancers, like neuroblastoma.”

The first phase of PLAT-02 was integral in establishing the safety of the therapy and the optimal dose of T cells. Phase 2 will demonstrate how this therapy works for a larger group of patients.

The T-cell immunotherapy trials at Seattle Children’s are funded in part by Strong Against Cancer, a national philanthropic initiative with worldwide implications for potentially curing childhood cancers through immunotherapy treatments. If you are interested in supporting the advancement of this medical breakthrough, please visit Strong Against Cancer’s donation page.

To learn about the experience of one of the patients who participated in the trial, please visit Seattle Children’s On the Pulse blog.

For more information on immunotherapy research trials at Seattle Children's, please call (206) 987-2106 or email immunotherapy@seattlechildrens.org.

About Seattle Children’s

Seattle Children’s Hospital, Foundation and Research Institute together deliver superior patient care, advance new discoveries and treatments through pediatric research, and raise funds to create better futures for patients. Consistently ranked as one of the top 10 children’s hospitals in the country by U.S. News & World Report, Seattle Children’s Hospital specializes in meeting the unique physical, emotional and developmental needs of children from infancy through young adulthood. Through the collaboration of physicians in nearly 60 pediatric subspecialties, Seattle Children’s Hospital provides inpatient, outpatient, diagnostic, surgical, rehabilitative, behavioral, and emergency and outreach services to families from around the world.

Located in downtown Seattle’s biotech corridor, Seattle Children’s Research Institute is pushing the boundaries of medical research to find cures for pediatric diseases and improve outcomes for children all over the world. Internationally recognized investigators and staff at the research institute are advancing new discoveries in cancer, genetics, immunology, pathology, infectious disease, injury prevention, bioethics and much more.

Seattle Children’s Hospital and Research Foundation and Seattle Children’s Hospital Guild Association work together to gather community support and raise funds for uncompensated care, clinical care and research. The foundation receives nearly 80,000 gifts each year, from lemonade stand proceeds to corporate sponsorships. Seattle Children’s Hospital Guild Association is the largest all-volunteer fundraising network for any hospital in the country, serving as the umbrella organization for 450 groups of people who turn an activity they love into a fundraiser. Support from the foundation and guild association makes it possible for Seattle Children’s care and research teams to improve the health and well-being of all kids.

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