FDA Clears Investigational New Drug Application for Potential Leukemia Treatment, GTB-3650


Phase I dose escalation study expected to begin in the second half of 2024; initial data expected in the first half of 2025.

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The FDA has cleared GT Biopharma’s Investigational New Drug (IND) application for GTB-3650. GT Biopharma will proceed with a Phase I clinical trial of GTB-3650, expected to begin later this year. The potential leukemia treatment is based on the company's proprietary natural killer (NK) cell engager, TriKE platform.1

“FDA clearance for GTB-3650 is a tremendous accomplishment and we look forward to submitting our next IND in the first quarter of 2025 for GTB-5550, which will target multiple solid tumors,” Michael Breen, executive chairman and interim chief executive officer of GT Biopharma said in a press release. “As we ramp up our clinical activities, we plan to start the Phase I trial with GTB-3650 in the coming months followed by multiple data readouts in 2025. We also expect to start a basket trial with GTB-5550 for multiple solid tumors in 2025 and remain very enthusiastic in our pursuit of additional opportunities for various autoimmune indications where our TriKE’s may have therapeutic utility.”

According to GT Biopharma, the planned Phase I dose escalation study will evaluate GTB-3650 in up to six cohorts of adult patients with relapsed or refractory (r/r) CD33 expressing hematologic malignancies, including acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS). GTB-3650 will be dosed in two-week blocks, two weeks on and two weeks off 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.

“GTB-3650 is designed to target NK cells within the immune system to potentially overcome many of the limitations of current AML chemotherapies,” Breen added. “Our trial design should give us an early read on safety and potential therapeutic activity and also provide valuable learnings that we can translate into our clinical development plans for follow-on TriKE molecules, including GTB-5550.”

GTB-5550, another product in GT Biopharma’s pipeline, is a novel tri-specific killer engager (TriKE) molecule. In November 2023, GT Biopharma shared preclinical data that demonstrated normal donor and prostate cancer patient natural killer (NK) cells displayed better, specific, degranulation against prostate cancer cell lines in the presence of PSMA or B7H3 TriKEs. NK cell cytotoxicity was also improved. The TriKE molecules displayed improved tumor control, compared to IL-15 control or no treatment, in xenogeneic models of prostate cancer.2

GT Biopharma expects initial data from the GTB-3650 trial to be available in the first half of 2025.


1. GT BIOPHARMA ANNOUNCES FDA CLEARANCE OF INVESTIGATIONAL NEW DRUG (IND) APPLICATION FOR GTB-3650, AN NK CELL ENGAGER FOR TREATMENT OF CD33+ LEUKEMIA. News release. GT Biopharma. June 27, 2024. Accessed July 5, 2024. https://www.gtbiopharma.com/news-media/press-releases/detail/283/gt-biopharma-announces-fda-clearance-of-investigational-new

2. GT BIOPHARMA PRESENTED POSITIVE PRECLINICAL DATA FOR GTB-5550, A NOVEL TRIKE® MOLECULE FOR TARGETED PROSTATE CANCER TREATMENT DURING THE SOCIETY FOR IMMUNOTHERAPY OF CANCER (SITC) 2023 ANNUAL MEETING. News release. GT Biopharma. November 6, 2023. Accessed July 5, 2024. https://www.gtbiopharma.com/news-media/press-releases/detail/276/gt-biopharma-presented-positive-preclinical-data-for

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