GT Biopharma Oral Presentation at the SITC 2026 Annual Meeting

The combination cleared tumors in several animals; a human combination study remains under consideration.

Rhea-AI Summary

GT Biopharma (GTBP) presented preclinical pancreatic cancer data showing enhanced tumor control from combining GTB-5550 with a KRAS inhibitor.

The results, presented at SITC 2026, came from mouse models bearing pancreatic tumors. The combination produced complete tumor clearance in several animals, reduced local invasion and prevented metastasis. Compared with the KRAS inhibitor alone, it was associated with a two-fold increase in tumor infiltration by transferred natural killer cells, immune cells that kill cancer cells.

A Phase 1a/1b trial of GTB-5550 alone is underway and includes pancreatic cancer patients. The company is considering options for a future Phase 1b combination study.

Positive

• Minor pointGTB-5550 plus a KRAS inhibitor achieved complete tumor clearance in several animals in pancreatic cancer models.
• Minor pointCombination treatment reduced local invasion and prevented metastasis in pancreatic cancer models.
• Minor pointCombination treatment showed two-fold greater tumor infiltration by transferred natural killer cells versus KRAS inhibitor alone.
• Minor pointTransferred natural killer cells showed increased persistence and CXCR3 expression with combination treatment versus KRAS inhibitor alone.
• Minor pointEnhanced treatment effects correlated with increased markers of tumor-cell death.
• Minor pointGTB-5550 monotherapy’s Phase 1a/1b trial is underway, including a pancreatic cancer cohort.

Negative

• Minor pointA future Phase 1b combination study remains under consideration rather than underway.

News Explained

The release also says the University of Minnesota is entitled to royalties if commercial sales occur for products using TriKE technology, including GTB-5550, making those sales subject to a contingent royalty obligation.

Key Figures

Tumor infiltration: Two-fold increase

Tumor infiltration

Two-fold increase

GTB-5550 plus KRASi vs. KRASi alone in orthotopic PDAC models

Key Terms

pancreatic ductal adenocarcinoma, kras inhibitor, orthotopic xenograft models, cytotoxicity

4 terms

pancreatic ductal adenocarcinoma medical

"in pancreatic ductal adenocarcinoma (PDAC)"

A fast-growing cancer that starts in the cells lining the pancreas’ small ducts; it is the most common and aggressive form of pancreatic cancer. It matters to investors because its severity and limited treatment options drive high unmet medical need, large potential markets for effective drugs or diagnostics, and strong sensitivity of company valuations to clinical trial results, regulatory approvals, or changes in treatment guidelines—similar to how fixing a main leak can prevent major damage in a building.

kras inhibitor medical

"with a KRAS inhibitor (KRASi)"

A KRAS inhibitor is a drug designed to block the KRAS protein, which in many cancers acts like a stuck “on” switch that tells cells to keep dividing. For investors, these drugs matter because successfully turning that switch off can create high-value treatments for hard-to-treat cancers, but they also carry typical drug-development risks—clinical trial results and regulatory decisions can cause big swings in a company’s value, like fixing a faulty engine part that either restores performance or fails in testing.

orthotopic xenograft models medical

"In orthotopic PDAC xenograft models"

Laboratory animal models in which tissue or cells from a human tumor are implanted into the equivalent organ or anatomical site of a host animal (typically an immunodeficient mouse) so the tumor grows in the same local environment it would in a patient. These models preserve organ-specific interactions, blood supply and patterns of invasion or metastasis better than tumors placed under the skin (subcutaneous xenografts), but they require immunocompromised hosts and still differ from humans in immune response, physiology and drug metabolism.

cytotoxicity medical

"NK cell cytotoxicity"

Cytotoxicity is the ability of a substance to kill or damage living cells. Investors watch cytotoxicity results because they indicate whether a drug or chemical is likely to be effective against targeted cells (for example, cancer cells) and whether it poses safety risks to healthy tissue, which affects clinical success, regulatory approval, and commercial potential—similar to knowing if a powerful weed killer also harms the lawn around the weeds.

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GT Biopharma showcased new preclinical data in an oral presentation at SITC demonstrating an enhanced effect of combining GTB-5550, a B7-H3-targeted tri-specific NK cell engager (TriKE^®), with a KRAS inhibitor (KRASi), which was shown to sensitize pancreatic tumor cells to NK cell cytotoxicity

The new data show that the combination promotes NK cell infiltration to provide superior disease control in orthotopic xenograft models, and provides novel mechanistic insight into KRAS-dependent anti-tumor NK regulation to establish a strong preclinical rationale for combining KRASi with GTB-5550 in pancreatic ductal adenocarcinoma (PDAC)

A Phase 1a/1b basket trial with GTB-5550 monotherapy is currently underway (NCT07541573), which includes a cohort for PDAC patients, and the Company is considering potential options for a future Phase 1b study to evaluate the combination of GTB-5550 and a KRAS inhibitor

SAN FRANCISCO, CALIFORNIA, Nov. 09, 2026 (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 preclinical data presented at the Society for Immunotherapy of Cancer (SITC) 2026 Annual Meeting taking place from November 4-8, 2026 in Phoenix, AZ.

“We continue to make progress enrolling patients into our ongoing Phase 1a/1b dose escalation basket trial with GTB-5550 in multiple tumor types”, said Michael Breen, Executive Chairman and Chief Executive Officer of GT Biopharma. “Given the recent advances in this field with KRAS inhibitors becoming a new standard of care and these extremely compelling preclinical results, we are considering all options to conduct a future Phase 1b study combining GTB-5550 with a KRASi in pancreatic cancer patients”.

Despite significant recent advances in the field, monotherapy with RAS inhibitors can trigger early resistance via bypass pathways, and the industry is moving more towards the opportunity for multi-drug combinations to provide deeper, more durable responses than single agent KRAS inhibition. The new data demonstrate that GTB-5550 has the potential to improve the effectiveness of KRAS inhibition by making pancreatic cancer cells more susceptible to NK cell cytotoxicity. In orthotopic PDAC xenograft models, the combination of GTB-5550 plus KRASi demonstrated superior tumor control, including complete tumor clearance in several animals, while significantly reducing local invasion and preventing metastasis. When compared to KRASi treatment alone, KRASi + GTB-5550 treatment was associated with a two-fold increase in tumor-infiltration, as well as increases in persistence and CXCR3 expression of adoptively transferred NK cells. This enhanced treatment effect also correlated with a corresponding increase in apoptosis markers on tumor cells.

Oral Presentation Details

Title: Inhibition of the KRAS oncoprotein sensitizes pancreatic cancer to NK cell immunotherapy
Abstract No.: 655
Presenter: Paarth Dodhiawala, University of Minnesota Medical School¹
Date: Friday, November 6, 2026
Time: 3:05-3:20 PM MT
Session 106a: Combination Therapies Involving Cell Therapy, 1:45-3:25 PM MST
Session Description: While cell therapy has transformed the treatment of certain hematologic malignancies, its impact in solid tumors remains limited by antigen heterogeneity, immunosuppressive microenvironments, and nutrient deprivation. As efforts to engineer more effective immune cells continue, there is growing interest in combining cell therapies with complementary approaches to enhance their function and engage endogenous immunity. This session will highlight diverse strategies to extend the clinical impact of cell therapies through rational combination approaches.

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 gtbiopharma.com.

Forward-Looking Statements

Certain statements in this press release may constitute "forward-looking statements" regarding future events and our future results. All statements other than statements of historical facts are statements that could be deemed to be forward-looking statements. These statements are based on current expectations, estimates, forecasts, and projections about the markets in which we operate and the beliefs and assumptions of our management. Words such as "expects," "anticipates," "targets," "goals," "projects", "intends," "plans," "believes," "seeks," "estimates," "endeavors," "strives," "may," or variations of such words, and similar expressions are intended to identify such forward-looking statements. Readers are cautioned that these forward-looking statements are subject to a number of risks, uncertainties and assumptions that are difficult to predict, estimate or verify. Therefore, actual results may differ materially and adversely from those expressed in any forward-looking statements. Such risks and uncertainties include those factors described in our most recent annual report on Form 10-K, as such may be amended or supplemented by subsequent quarterly reports on Form 10-Q, or other reports filed with the Securities and Exchange Commission. Readers are cautioned not to place undue reliance on these forward-looking statements. The forward-looking statements are made only as of the date hereof, and we undertake no obligation to publicly release the result of any revisions to these forward-looking statements. For more information, please refer to our filings with the Securities and Exchange Commission.

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

Investor Relations Contact:

LifeSci Advisors
Corey Davis, Ph.D.
cdavis@lifesciadvisors.com
212-915-2577

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¹ The University of Minnesota, pursuant to its license agreement with GT Biopharma, is entitled to receive royalties should commercial sales of product using the TriKE^® technology be realized, including GTB-3650 and GTB-5550. This interest has been reviewed and managed by the University of Minnesota in accordance with its conflict of interest policies.

FAQ

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What did GT Biopharma’s GTB-5550 combination show in pancreatic cancer models?

GTB-5550 combined with a KRAS inhibitor produced enhanced tumor control, including complete tumor clearance in several animals. The combination also reduced local invasion and prevented metastasis in mouse models bearing pancreatic tumors. These were preclinical results.