On May 29, 2019 GT Biopharma, Inc. (OTCQB: GTBP) (OTC: GTBP.PA) an immuno-oncology company focused on innovative treatments based on the Company’s proprietary NK cell engager (TriKE) platform and Multi-Target Directed Bispecific Drug Conjugate (MTBDC) platform, reported that the results of its second Phase I-II trial (NCT02370160) for GTB-1550 (DT2219), an MTBDC targeting CD22 and CD19 for treatment of refractory B-cell malignancies, will be published (J Clin Oncology 37, 2019 suppl; abstract e19066) on-line in conjunction with the 55th Annual Meeting of the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) in Chicago from May 31 – June 4 (Press release, GT Biopharma , MAY 29, 2019, View Source [SID1234539514]).
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Top Line Results Summary:
Treatment was well tolerated at 60 mcg/kg x 8 doses and the most common adverse events included capillary leak syndrome, elevated AST/ALT, low albumin, weight gain and leukopenia. All were Grade 1-2 and resolved after 3-5 days allowing day 15 GTB-1550 administration.
There were no neutropenic fever or immune mediated adverse events. Four patients experienced dose limiting toxicity (DLT) at dose 80 μg/kg/day: Grade 4 capillary leak syndrome (n=1), Grade 3 liver function test (LFT) abnormalities (n=2) and Grade 4 thrombocytopenia >7 days duration (n=1).
Thirteen patients were evaluable for response, and 3 experienced objective clinical benefit. One patient with primary refractory pre-B acute lymphoblastic leukemia achieved complete remission after 1st cycle. Two patients with transformed lymphoma demonstrated transient tumor shrinkage, however, GTB-1550 therapy was discontinued due to DLT and increased neutralizing antibody titer after 1st cycle (pre C1 28%, pre C2 108%).
Correlative studies showed a low incidence of neutralizing antibody in Non-Hodgkin Lymphoma (NHL) patients recently exposed to Rituximab.
Mr. Anthony Cataldo, the Chairman and Chief Executive Officer of GT Biopharma commented, "We are pleased with the results GTB-1550 has shown in the current Phase I-II clinical trial and in our earlier Phase I-II clinical trial. This now positions us to move forward with the FDA phase II clinical trial."
Dr. Veronika Bachanova, Associate Professor of Medicine, Division of Hematology, Oncology and Transplantation at the University of Minnesota and the Principal Investigator for both clinical trials commented, "We are excited about the progress GTB-1550 is making in the clinic, and look forward to the possibility of exploring additional monotherapy and synergistic combination studies against various B-cell malignancies." Both clinical studies were conducted at the University of Minnesota’s Masonic Cancer Center in Minneapolis.
About GTB-1550 Multi-Target Directed Bispecific Therapy
GTB-1550 targets cancer cells expressing the CD19 receptor or CD22 receptor or both receptors thereby maximizing cancer cell recognition by binding to CD19+, CD22+ and CD19+/CD22+ cancer cells. When GTB-1550 binds to cancer cells, the cancer cells internalize GTB-1550, and are killed due to the action of drug’s cytotoxic diphtheria toxin payload. GTB-1550 has previously demonstrated success in a Phase I-II human clinical trial in patients with relapsed/refractory B-cell lymphoma or leukemia. At the time of the interim review, 13 patients met the evaluation criteria, including nine NHL and four ALL patients. More than 50% of patients (seven of 13) exhibited a clinical benefit, defined as stable disease, partial remission or complete remission at Day 29. Of the seven patients, one demonstrated a complete remission (CR), one demonstrated a partial remission (PR) and five demonstrated stable disease (SD).
About the TriKE Platform
The Company’s TriKE product candidates are single-chain, tri-specific scFv recombinant fusion proteins composed of the variable regions of the heavy and light chains (or heavy chain only) of anti-CD16 antibodies, wild-type or a modified form of IL-15 and the variable regions of the heavy and light chains of an antibody designed to precisely target a specific tumor antigen. GT Biopharma utilizes the NK stimulating cytokine human IL-15 as a cross linker between the two scFvs which is designed to provide a self-sustaining signal leading to the proliferation and activation of NK cells thus enhancing their ability to kill cancer cells mediated by antibody-dependent cell-mediated cytotoxicity (ADCC). GT Biopharma has an exclusive worldwide license agreement with the University of Minnesota to further develop and commercialize cancer therapies using proprietary TriKE technology developed by researchers at the university to target NK cells to cancer.