JCO publishes Micromet's blinatumomab Phase 2 trial data in acute lymphoblastic leukemia

Micromet, Inc. (Nasdaq: MITI) today announced that data from a Phase 2 clinical trial of the Company's lead product candidate blinatumomab in patients with minimal residual disease positive (MRD) acute lymphoblastic leukemia (ALL) were published in the May 16^th on-line edition of the Journal of Clinical Oncology (JCO). Results of the study demonstrated that blinatumomab produced durable remissions in front-line adult ALL patients at high risk of relapse. Blinatumomab is the most advanced of a new class of agents called BiTE® antibodies, designed to harness the body's T cells to kill cancer cells.

"ALL patients with residual leukemic cells in the bone marrow following treatment with front-line chemotherapy have a 90% risk of relapse and a resulting poor long-term prognosis," said Professor Max Topp, Department of Internal Medicine II, University of Wuerzburg, and lead author of the publication. "Results from this study show that blinatumomab has the potential to fundamentally change the long-term outcome for this difficult-to-treat disease."

Phase 2 Study Design

The multi-center Phase 2 study evaluated the efficacy and safety of blinatumomab in adult patients with B precursor ALL. Enrolled patients had evidence of leukemic cells in the bone marrow following treatment with front-line chemotherapy, otherwise known as minimal residual disease (MRD). The primary endpoint of the study was molecular complete response, or elimination of MRD below detectable levels. Key secondary endpoints included time to hematological relapse, time to molecular relapse and overall incidence and severity of adverse events. Patients received 15 micrograms per meter squared per day of blinatumomab for 28 days followed by two weeks off therapy over a six week treatment cycle. Patients received up to seven treatment cycles.

Phase 2 Results

21 patients were treated in the study. Of 20 evaluable patients, 80% (16 out of 20) achieved a complete molecular response, all within the first cycle of treatment. A priori a 22% molecular response rate was expected. A subset of the patients in the study received an allogeneic hematopoetic stem cell transplant (HSCT), a procedure that typically carries a high risk of mortality. Notably, all transplanted patients were alive 100-days following the transplant.

"Historically stem cell transplantation is associated with a high mortality rate, approximately 25% in adult patients," said Professor Topp. "Data from this study highlights the potential for blinatumomab to improve the outcome of the transplant by improving the physical status of the patient and safely reducing the burden of disease before the transplant."

Overall, blinatumomab was well-tolerated. Most adverse events occurred early, were transient and reversible. The most common clinical adverse events (any grade) were fever, headache and chills. Two patients discontinued treatment due to fully reversible adverse events; a seizure and a syncope (temporary loss of consciousness), respectively.

"These data continue to validate our confidence in blinatumomab's potential as a promising new treatment option for patients with ALL and heighten our excitement in the broad-based development program now on-going in this disease setting," said Jan Fagerberg, M.D., Ph.D., Micromet's Chief Medical Officer.