Updated results from a Phase II study that showed treatment with blinatumomab (AMG 103/MT103,?Amgen, Inc/Micromet AG,) helped achieve a high-rate of complete response (CR) in 72% of adult patients with relapsed or refractory B-precursor acute lymphoblastic leukemia (ALL) treated in the study.

Acute lymphoblastic leukemia (ALL) is an aggressive cancer of the blood and bone marrow ? the spongy tissue inside bones where blood cells are made. The disease progresses rapidly and affects immature blood cells, rather than mature ones.[1] Worldwide, ALL accounts for more than 12% of leukemia. Of the 42,000 people diagnosed worldwide, 31,000 will die from the disease.[2] Patients with ALL have abnormal white blood cells (lymphocytes) that crowd out healthy white blood cells, red blood cells and platelets, leading to infection, anemia (fatigue), easy bleeding and serious side effects.[3,4].

Blinatumomab is the first of a new class of agents called bi-specific T cell engagers (BiTE?) antibodies, designed to harness the body’s cell-destroying T cells to kill cancer cells.

Blinatumomab targets cells expressing CD19, a protein found on the surface of B-cell derived leukemias and lymphomas, such as ALL. The modified antibodies are designed to engage two different targets simultaneously, thereby juxtaposing T cells to cancer cells.

?Blinatumomab has meaningfully altered the treatment outcome for patients with relapsed B-precursor ALL,? said Professor Max Topp, Department of Internal Medicine II, University of Wuerzburg and the chair of the study. ?The difference in efficacy and improved tolerability that I have seen has been impressive compared to the standard of care.”

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The trial drug is the first of the BiTE antibodies and Amgen has received orphan drug designation from the U.S. Food and Drug Administration for the treatment of ALL, chronic lymphocytic leukemia (CLL), hairy cell leukemia, prolymphocytic leukemia and indolent B cell lymphoma and from the European Medicines Agency for the treatment of indolent B cell lymphoma, ALL, CLL and mantle cell leukemia (MCL).

ASCO 2012
Full results of the study will be presented during an oral abstract session at the 48th Annual Meeting of the American Society of Clinical Oncology (ASCO) on June 4, 2012 (Abstract Number 6500, 8:00 a.m. – 8:15 a.m. CDT, E354a).

In this Phase II single-arm dose-ranging trial, 26 of the 36 patients treated with blinatumomab across all of the tested doses and schedules achieved a CR with partial hematologic recovery (CRh*). All but two patients achieved a molecular response, meaning there was no evidence of leukemic cells by polymerase chain reaction. No treatment related deaths or serious adverse events (AEs) were reported in the study.

Median survival
At the time of the analysis, median survival was 9.0 (8.2, 15.8) months with a median follow-up period of 10.7 months. In the group of patients who received the selected dose, median survival was 8.5 months. The median duration of response in the 26 patients who responded to treatment was 8.9 months.

“For these patients with limited treatment options, the remission rate observed in the trial is a vast improvement over the current standard of care,” said Professor Max Topp, Department of Internal Medicine II,?University of Wuerzburg, Germany. “These results also represent significant progress in our research of immunotherapies; a new approach to fighting cancer that we believe could make a real difference for patients.”

Common adverse events
For patients who received the selected dose and schedule, the most common adverse events were grade one or two and included pyrexia (70%), headache (39%), tremor (30%) and fatigue (30%). These were most frequently seen at the onset of treatment in cycle one. Reversible central nervous system events led to treatment interruptions in six patients with two patients permanently discontinuing treatment. Cytokine release syndrome led to treatment interruption in two patients.

In addition to the results from this study, data from studies of 12 Amgen investigational molecules and marketed products will be presented at the ASCO Annual Meeting. These include results from studies of the immunotherapy talimogene laherparepvec, pipeline molecules such as rilotumumab (AMG 102) and AMG 386, and marketed products.

Phase II Study Design
This Phase II dose-ranging study evaluated the efficacy, safety and tolerability of blinatumomab in adult patients with B-precursor ALL who had relapsed following treatment with standard front-line chemotherapy or allogeneic stem cell transplant. Patients received blinatumomab for 28 days followed by two weeks off therapy over a six week treatment cycle, for up to five treatment cycles. Patients received a continuous intravenous infusion of blinatumomab at an initial dose of five or 15 micrograms per meter squared per day, ranging up to 30 micrograms for the remainder of the treatment. The primary endpoint of the study was the rate of CR/CRh. Secondary endpoints included molecular response rate, duration of response and overall survival. As of April 13, 2012, all 36 patients were evaluable for efficacy and safety.

For more information:
EMEA – Public summary of opinion on orphan designation: Blinatumomab for the treatment of acute lymphoblastic leukaemia.

[1] Definition of Acute lymphocytic leukemia. Mayo Clinic. Last accessed April 16, 2012.
[2] World.?Globocan 2008 website. Last accessed May 4, 2012.
[3]Causes of Acute lymphocytic leukemia. Mayo Clinic. . Last accessed April 16, 2012.
[4]Symptoms of Acute lymphocytic leukemia. Mayo Clinic. Last accessed April 16, 2012.

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