MacroGenics Announces Publication of Flotetuzumab Interim Phase 1/2 Clinical Trial Results in Blood

ROCKVILLE, MD, Sept. 22, 2020 (GLOBE NEWSWIRE) --  

MacroGenics, Inc. (NASDAQ: MGNX), a clinical-stage biopharmaceutical company focused on discovering and developing innovative monoclonal antibody-based therapeutics for the treatment of cancer, today announced the publication of a manuscript in Blood, a journal of the American Society of Hematology, which highlights interim results of an ongoing Phase 1/2 clinical trial of flotetuzumab in patients with acute myeloid leukemia (AML). Flotetuzumab (also known as MGD006) is an investigational, clinical-stage bispecific DART molecule that recognizes both CD123 on leukemic cells and CD3 on T cells, with the intended result of T cell mediated killing of leukemic blasts.

As described in the article titled “Flotetuzumab as Salvage Immunotherapy for Refractory Acute Myeloid Leukemia,” 88 AML patients were enrolled in the Phase 1/2 trial as of November 1, 2019, including 42 in dose escalation and 46 treated with flotetuzumab at the recommended Phase 2 dose (RP2D) of 500ng/kg/day. The majority (56%) had adverse risk by ELN 2017 criteria and 36% had secondary AML. Patients were heavily pretreated, with a median of three lines of prior therapy (range 1-9). Collectively, this group of patients represents a poor-prognosis population having few effective therapies and an otherwise limited life expectancy.

The most common treatment-related adverse event (TRAE) was infusion-related reaction/cytokine release syndrome (IRR/CRS), the majority reported as grade 1-2. Stepwise dosing during week 1, pre-treatment with dexamethasone, prompt use of tocilizumab and temporary dose reductions/interruptions successfully prevented severe IRR/CRS, resulting in acceptable tolerability.

As described in the publication, of 50 evaluable patients with relapsed or refractory AML, 30 patients entered the study with no prior response to induction therapy (primary induction failure AML or PIF AML) or having relapsed within six months of achieving an initial remission (early relapsed AML or ER AML), a combined population with poor prognosis and high unmet medical needs. This PIF/ER AML subset of patients showed a 16.7% (5/30) complete remission (CR) rate and a combined CR and complete remission with partial hematological recovery (CRh) rate of 26.7% (8/30) following flotetuzumab treatment. In contrast, only one of 20 patients with late relapsed AML achieved a CR following flotetuzumab treatment. PIF/ER patients who achieved CR/CRh showed median overall survival (OS) of 10.2 months (range 1.87-27.27), with 6- and 12-month survival rates of 75% (95% CI, 0.450-1.05) and 50% (95% CI, 0.154-0.846).