GT Biopharma Advances into Cohort 3 of GTB-3650 Phase 1 Trial Following Safety Review of Cohort 2

The first patient in Cohort 3, the fifth patient in the trial, has completed the first week of cycle 1 following the successful safety review of Cohort 2 with no safety or tolerability issues observed

The company plans on releasing initial Phase 1 results later in 2025 following completion of additional dose cohorts

SAN FRANCISCO, CALIFORNIA, Aug. 11, 2025 (GLOBE NEWSWIRE) -- GT Biopharma, Inc. (the “Company”) (NASDAQ: GTBP), a clinical stage immuno-oncology company focused on developing innovative therapeutics based on the Company's proprietary TriKE^® natural killer (NK) cell engager platform, today announced initiation of dosing in Cohort 3 of its Phase 1 dose escalation trial evaluating GTB-3650 for the treatment of relapsed or refractory (r/r) CD33 expressing hematologic malignancies.

The Phase 1 dose escalation trial is evaluating GTB-3650, GT Biopharma’s second-generation TriKE, for the treatment of relapsed or refractory (r/r) CD33 expressing hematologic malignancies. Cohorts 1 and 2 have now both been successfully completed and following the formal safety reviews, no safety or tolerability issues have been observed. This has allowed initiation of dosing in Cohort 3, with the first patient now having completed the first week of cycle 1.

Patients from Cohort 1 and Cohort 2 have shown encouraging early results indicative of GTB-3650’s ability to activate endogenous NK cells and induce NK cell expansion. Data from multiple blood biomarker assays from the first four patients show heightened immune activity. GT Biopharma plans on releasing initial Phase 1 results later in 2025 following completion of additional dose cohorts.

The trial plans to evaluate GTB-3650 in up to approximately 14 patients (seven cohorts) and GTB-3650 will be dosed in two-week blocks, two weeks on and two weeks off (defining a treatment cycle), for up to four months based on clinical benefit. The trial will assess safety, pharmacokinetics, pharmacodynamics, in vivo expansion of endogenous patient NK cells and clinical activity. More details can be found on clinicaltrials.gov with the identifier: .

About GT Biopharma, Inc.

GT Biopharma, Inc. is a clinical stage biopharmaceutical company focused on the development and commercialization of immuno-oncology therapeutic products based on our proprietary TriKE^® NK cell engager platform. Our TriKE^® platform is designed to harness and enhance the cancer killing abilities of a patient’s immune system’s natural killer cells. GT Biopharma has an exclusive worldwide license agreement with the University of Minnesota to further develop and commercialize therapies using TriKE^® technology. For more information, please visit .

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TriKE^® is a registered trademark owned by GT Biopharma, Inc.

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