On June 11, 2019 GT Biopharma, Inc. (GTBP) and (Euronext Paris: GTBP.PA) (the "Company"), an immuno-oncology biotechnology company focused on innovative treatments based on the Company’s proprietary platforms, reported preliminary clinical data taken from an interim review, or snapshot, of the OXS-1550 Phase 1/2 trial following a Bi-Specific Antibody Drug Conjugate (ADC) Advisory Board meeting and follow up discussions (Press release, GT Biopharma , JUN 11, 2019, View Source [SID1234539529]). OXS-1550 is a bi-specific scFv recombinant fusion protein-drug conjugate composed of the variable regions of the heavy and light chains of anti-CD19 and anti-CD22 antibodies and a modified form of diphtheria toxin, its cytotoxic drug payload. OXS-1550 targets cancer cells expressing the CD19 receptor, the CD22 receptor or both receptors.
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OXS-1550 is being evaluated in an open-label, two-stage, investigator-led, Phase 1/2 trial at the Masonic Cancer Center, University of Minnesota. The trial has two arms including patients diagnosed with relapsed/refractory B-cell lymphomas (NHL) and leukemias (ALL). Eighteen patients have been enrolled to date, including 12 NHL and six ALL patients. At the time of the interim review, 13 patients met the evaluation criteria, including nine NHL and four ALL patients.
At the interim review more than 50% of patients (seven of 13) exhibited a clinical benefit, defined as stable disease plus partial response or complete remission at Day 29. Of the seven patients, one demonstrated a complete remission (CR), one demonstrated a partial response (PR) and five demonstrated stable disease (SD).
The efficacy signal was most prominent in ALL patients with 75% (three of four) exhibiting clinical benefit including one CR, one PR and one SD. In the NHL population, four of nine patients exhibited SD. Adverse events were mostly grade 1 and 2 and reversible. One patient had a grade 4 low platelet count, two patients had a grade 3 increase in liver function tests, or LFTs, and one patient had a grade 3 capillary leak.
GT Biopharma’s President and Chief Medical Officer (CMO) Dr. Raymond Urbanski said: "In light of these data and discussions with the Bi-Specific ADC Advisory Board, I am increasingly encouraged by OXS-1550 and its potential to have a significant role in an oncologist’s armamentarium. I also remain convinced that the bi-specific ADC platform has the potential to generate additional attractive product candidates. I look forward to continuing to work closely with the University of Minnesota team and other members of the Bi-Specific ADC Advisory Board with the goal of optimizing next steps for this program and the broader bi-specific ADC platform."
The Bi-Specific ADC Advisory Board has recommended that additional ALL patients be enrolled in the trial followed by another interim data review. The Company currently expects final data for this trial to be available in the fourth quarter of 2018 or the first quarter of 2019.
The Bi-Specific ADC Advisory Board is composed of distinguish clinicians, academics and researchers from several well-known institutions. Members include Dr. Jeffrey Miller, Deputy Director at the Masonic Cancer Center, University of Minnesota and Chair of GT Biopharma’s Scientific Advisory Board. Dr. Veronika Bachanova, hematologist/oncologist and the principal investigator of the Phase 1/2 study and Dr. Daniel Vallera, lead researcher for the bispecific ADC program, both at the Masonic Cancer Center. Also included are Drs. Mark Litzow and Arthur Frankel. Mark R. Litzow, M.D., is Professor of Medicine in the Division of Hematology at Mayo Clinic. Arthur E. Frankel, M.D., is the inaugural holder of the Arlene and Mayer Mitchell Endowed Chair in Medical Oncology, Chief of Medical Oncology at Mitchell Cancer Institute (USA-MCI), Interim Associate Director for Basic & Translational Sciences and Professor of Oncological Sciences.