On December 9, 2019 MacroGenics, Inc. (NASDAQ: MGNX), a clinical-stage biopharmaceutical company focused on discovering and developing innovative monoclonal antibody-based therapeutics for the treatment of cancer, reported updated results from a Phase 1/2 dose expansion study of flotetuzumab, an investigational, bispecific CD123 x CD3 DART molecule in patients with primary induction failure and early relapsed acute myeloid leukemia (AML) (Press release, MacroGenics, DEC 9, 2019, View Source [SID1234553172]). The data were presented in an oral session at the 61st Annual Meeting of the American Society of Hematology (ASH) (Free ASH Whitepaper) in Orlando, FL, taking place December 7-10, 2019.

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"Patients with AML who have failed primary induction therapy or relapsed early after an initial response represent a significant unmet medical need. A remission rate of 32% observed in the ongoing study of flotetuzumab in this extremely challenging patient population is noteworthy," said Geoffrey Uy, M.D., Associate Professor, Department of Medicine, Division of Oncology at the Washington University School of Medicine in St. Louis. "Importantly, by implementing a lead-in dosing schedule for flotetuzumab, as well as early intervention with tocilizumab in this study, we were able to mitigate cytokine release syndrome, known to be associated with T-cell engagers."

In the Phase 1/2 (NCT02152956) open-label, dose expansion study, 30 patients classified as primary induction failure or early relapsed AML who had received a median of four prior therapies were treated with flotetuzumab at the recommended phase 2 dose (RP2D) of 500 ng/kg/day by continuous infusion. Data were reported as of the cut-off date of November 1, 2019. The study is currently ongoing, with additional patients being enrolled.

Responses, including complete remission (CR), CRh (CR with partial hematological recovery) and CRi (CR with incomplete hematological improvement) per a modified International Working Group (IWG) Response Criteria for AML, are summarized in the table below. Four responders received allogeneic hematopoietic stem cell transplantation as consolidation therapy and remain in remission after 6 to 21 months.

The most common treatment-related adverse event (TRAE) was infusion-related reaction/cytokine release syndrome (IRR/CRS) that occurred in all (30/30) patients. However, most CRS events observed were of short duration and mild to moderate (grade 1 or 2) in severity, with only one grade 3 event reported in one patient.

"Based on the encouraging data from this study, and pending anticipated discussions with the FDA in the first half of 2020, we are planning for a potential registration-enabling study of flotetuzumab in this high unmet need population of patients with refractory AML, who have limited treatment options," said Scott Koenig, M.D., Ph.D., President and CEO of MacroGenics.

A separate oral presentation described translational research that showed an inflammatory (IFN-γ-related) gene expression signature in a subset of patients with AML that correlated with a lack of response to induction chemotherapy. Furthermore, the same gene signature was associated with patients more likely to respond to flotetuzumab, supporting the mechanism being exploited by this molecule. In addition, AML patients with an immune-infiltrated tumor micro-environment show high expression of immune checkpoint molecules, including PD-L1, which provides a scientific rationale for combining flotetuzumab with checkpoint blockade as a potential mechanism for enhanced anti-leukemic activity. MacroGenics has initiated a study combining flotetuzumab with MGA012, an anti-PD-1 antibody, given the strong preclinical and translational data that indicate the combination may enhance CD123-directed T cell killing.

Flotetuzumab Presentations at ASH (Free ASH Whitepaper)

Oral Presentations

Abstract #733: Uy, et al. "Flotetuzumab, an Investigational CD123 x CD3 Bispecific DART Protein, in Salvage Therapy for Primary Refractory and Early Relapsed Acute Myeloid Leukemia (AML) Patients"
Abstract #460: Vadakekolathu, et al. "Immune Landscapes Predict Chemotherapy Resistance and Anti-Leukemic Activity of Flotetuzumab, an Investigational CD123 × CD3 Bispecific DART Molecule, in Patients with Relapsed/Refractory Acute Myeloid Leukemia"
Poster Presentations

Abstract #1410: Goodwin, et al. "Flotetuzumab (FLZ), an Investigational CD123 x CD3 Bispecific DART Protein-Induced Clustering of CD3+ T Cells and CD123+ AML Cells in Bone Marrow Biopsies Is Associated with Response to Treatment in Primary Refractory AML Patients"
Abstract #1387: Gopalakrishnapillai, et al. "Effect of Ara-C on T-Cell Function and Flotetuzumab Activity in Pediatric Acute Myeloid Leukemia"
Abstract #2662: Wei, et al: "A Phase 1 Study of Flotetuzumab, a CD123 x CD3 DART Protein, Combined with MGA012, an Anti-PD-1 Antibody, in Patients with Relapsed or Refractory Acute Myeloid Leukemia"
These slide and poster presentations are available on the Events & Presentations page on MacroGenics’ website at View Source

Conference Call & Webcast

MacroGenics management and external guest speakers will host a conference call and audio webcast today at 8:00 p.m. ET to review the flotetuzumab data presented at the ASH (Free ASH Whitepaper) Annual Meeting and discuss ongoing clinical development plans.

To participate in the MacroGenics ASH (Free ASH Whitepaper) 2019 Conference Call, please dial (877) 303-6253 (domestic) or (973) 409-9610 (international) five minutes prior to the start of the call and provide the Conference ID: 3625435. A listen-only slide and audio webcast of the conference call can be accessed under "Events & Presentations" in the Investor Relations section of the Company’s website at View Source A replay of the webcast will be available shortly after the conclusion of the call and archived on the Company’s website for 30 days.

About Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a hematopoietic stem cell malignancy characterized by differentiation arrest and uncontrolled clonal proliferation of neoplastic precursors that prevent normal bone marrow hematopoiesis. Nearly 20,000 new cases of AML are diagnosed in the U.S. each year, with a median age of 69 years at diagnosis. Approximately 40-50% of newly diagnosed patients fail to achieve a complete remission with intensive induction therapy (primary induction failure) or experience disease recurrence after a short remission duration (<6 months; early relapsed). A very small number of these patients are expected to respond to salvage therapy. In addition, although new targeted agents have been approved for the treatment of frontline or relapsed/refractory AML in recent years, approximately 50% of patients have no known targetable mutations.

About Flotetuzumab

Flotetuzumab (also known as MGD006) is a clinical-stage molecule that recognizes both CD123 and CD3. CD123, the interleukin-3 receptor alpha chain, has been reported to be over-expressed on cancer cells in AML and other hematologic malignancies. The primary mechanism of action of flotetuzumab is believed to be its ability to redirect T lymphocytes to kill CD123-expressing cells. To achieve this, the DART molecule combines a portion of an antibody recognizing CD3, an activating molecule expressed by T cells, with an arm that recognizes CD123 on the target cancer cells.

Flotetuzumab is currently being evaluated in the U.S. and Europe in a Phase 1/2 dose expansion study designed to assess the safety, tolerability, and initial anti-leukemic activity of the molecule in patients with relapsed/refractory AML. The U.S. Food and Drug Administration has granted orphan drug designation to flotetuzumab for the treatment of AML. A Phase 1/2 study in combination with MGA012, a proprietary anti-PD-1 monoclonal antibody, in patients with relapsed/refractory AML is being conducted ex-U.S. MGA012 (also known as INCMGA00012) was exclusively licensed to Incyte Corporation in 2017 under a global collaboration and license agreement; MacroGenics retains the right to develop its pipeline molecules with MGA012. MacroGenics retains global development and commercialization rights to flotetuzumab.