MacroGenics, Inc a clinical-stage biopharmaceutical company focused on discovering and developing innovative monoclonal antibody-based therapeutics for the treatment of cancer, as well as autoimmune disorders and infectious diseases, announced the presentation of clinical data from its ongoing Phase 1 study of flotetuzumab in an oral session at the 59th Annual Meeting of the American Society of Hematology (ASH) in Atlanta, Georgia. John E. Godwin, M.D., Program Leader, Hematologic Malignancies at Earle A. Chiles Research Institute at Providence Cancer Center in Portland, Oregon presented "Preliminary Results of a Phase 1 Study of Flotetuzumab, a CD123 x CD3 Bispecific DART Protein, in Patients with Relapsed/Refractory Acute Myeloid Leukemia and Myelodysplastic Syndrome."
The ongoing Phase 1, first-in-human study of flotetuzumab was designed to determine safety, tolerability, maximum tolerated dose and initial anti-leukemic activity in patients with relapsed or refractory acute myeloid leukemia (AML) or intermediate-2/high risk myelodysplastic syndrome (MDS). To date, a total of 57 patients have been enrolled, including 11 AML patients in the dose expansion cohort.
Consistent with the dose escalation data that was previously presented at ESMO Congress 2017 in September, flotetuzumab has continued to demonstrate acceptable tolerability in patients treated to date in the dose expansion cohort. Infusion-related reaction and cytokine release syndrome (CRS) were the most common adverse events observed, with Grade 3 CRS occurring in 9 of 57 patients (15.8%). Implementation of a two-step, lead-in dose as well as early intervention with anti-cytokine therapy has helped to limit the severity and incidence of CRS.
As of the data cut-off date, of the eight evaluable patients in the dose expansion cohort who received a lead-in dose followed by 500 ng/kg/day of flotetuzumab via continuous IV infusion, six patients (75%) have evidence of anti-leukemic activity, with three of these patients experiencing an objective response. This included two patients who experienced CR/CRi and one patient who achieved MLF (morphologic leukemia-free state).
The duration of response for the eight patients who have achieved a MLF, CRi or CR in the dose escalation and dose expansion cohorts ranged from 1.0 to 5.8 months, with five of these responses still ongoing as of the November 30, 2017 data cut-off.
Further, in a translational data poster presentation, MacroGenics also described studies that support a rationale for using checkpoint blockade as an approach to potentially enhance the anti-leukemic activity of flotetuzumab. Among these findings, modulation of the PD-1/PD-L1 pathway was observed in patients treated with flotetuzumab, and the combination of flotetuzumab and PD-1/PD-L1 inhibitors was shown to synergistically enhance T-cell mediated cytotoxicity against AML cell lines in vitro.
"We continue to be encouraged by the tolerability and anti-leukemic activity of flotetuzumab as well as by the early data regarding the durability of responses observed in patients from our ongoing Phase 1 study of flotetuzumab," said Scott Koenig, M.D., Ph.D., President and CEO of MacroGenics. "In addition, given the data-supported rationale for combining flotetuzumab with anti-PD-1, we intend to initiate a combination study with the anti-PD-1 mAb, MGA012, in the coming months, while we continue to enroll the AML and MDS dose expansion cohorts. We look forward to sharing additional flotetuzumab clinical data in 2018.”
