GT Biopharma has provided an update with respect to the further clinical development of GTB-1550.
GTB-1550 (DT2219) is a novel multi-target directed therapy for the treatment of chemotherapy-refractory B-cell malignancies, including Non Hodgkins Lymphoma and Leukemia. To date, GT Biopharma has completed one dose escalation Phase I-II expansion clinical trial, and one fixed dose Phase I-II expansion clinical trial which collectively enrolled a combined 43 patients.
Top-line Consolidated Results:
- Two patients exhibited a Complete Remission (CR) with one patient currently disease-free at 50 months post treatment.
- Five patients exhibited Stable Disease (SD), cancers that are neither increasing nor decreasing in severity, with the longest response lasting 12 months post treatment.
- Two patients with transformed lymphoma showed transient tumor shrinkage, however, therapy was discontinued due to dose-limiting toxicities after the 1st cycle.
- Greater than 50% of evaluable patients, (patients where response to treatment can be measured because enough data has been collected), receiving 60 mg/kg dose had positive clinical response defined as stable disease, partial remission, or complete remission.
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"We are pleased the patient who experienced a complete remission following treatment with GTB-1550 is doing well, and we are excited about moving forward with a GTB-1550 Phase II clinical trial for the treatment of chemotherapy-refractive B-cell malignancies," 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 said.
"GTB-1550 has shown positive results in its two Phase I-II clinical trials in advanced cancer patients who have failed all other therapies, and we are now planning to proceed with a Phase II clinical trial," Anthony Cataldo, the Chairman and Chief Executive Officer of GT Biopharma said.
The initial Phase I-II expansion clinical trial demonstrated decreased tumor mass in one patient, and a complete response in a second patient that remains on-going at 50 months post treatment. After a single course of GTB-1550 (DT2219) at dose level 40 mg/kg/day x 4, a 77-year-old patient with chemotherapy-refractory CD19+/CD22- chronic lymphocytic leukemia (CLL) experienced a 40% reduction in cervical and axillary adenopathy with decrease of an abdominal tumor mass at day 28 after treatment, which was sustained for 2 months. The second clinical response occurred in a 53-year-old patient with relapsed CD19+/CD22+ diffuse large B cell lymphoma (dose level 60 mg/kg) who experienced a 75% reduction in size of lymphoma lesion after a single course complicated by a grade 3 capillary leak syndrome. Eight weeks later after FDA approval, this patient received a second DT2219 course at a reduced dose of 40 mg/kg/dose for 4 days, which resulted in a complete resolution of a subcutaneous mass and pelvic lymphadenopathy. The patient is alive and in complete remission with no neutralizing antibodies, currently at 50 months after therapy.
The results of the second GTB-1550 Phase I-II expansion trial targeting CD22 and CD19 for treatment of refractory B-cell malignancies showed treatment was well tolerated at 60 mg/kg x 8 doses. 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.