--- title: "EXCLUSIVE: GT Biopharma Begins Testing Of Lead Solid Tumor Drug Candidate Across Multiple Cancer Types" type: "News" locale: "en" url: "https://longbridge.com/en/news/286415809.md" description: "GT Biopharma has initiated a Phase 1 trial for its drug candidate GTB-5550, targeting B7-H3-positive solid tumors. The trial will initially focus on prostate cancer patients, with plans to expand to seven tumor types. The treatment involves subcutaneous injections over a four-week cycle, with patient monitoring for up to 12 months. The company reported a cash balance of approximately $9 million, expected to last through Q4 2026. GT Biopharma shares rose 13.94% to $0.35 during premarket trading." datetime: "2026-05-14T12:16:07.000Z" locales: - [zh-CN](https://longbridge.com/zh-CN/news/286415809.md) - [en](https://longbridge.com/en/news/286415809.md) - [zh-HK](https://longbridge.com/zh-HK/news/286415809.md) --- # EXCLUSIVE: GT Biopharma Begins Testing Of Lead Solid Tumor Drug Candidate Across Multiple Cancer Types **GT Biopharma Inc.** (NASDAQ:GTBP) on Thursday dosed the first patient on a Phase 1 dose-escalation basket trial evaluating GTB-5550, its B7-H3-targeted NK cell engager for solid tumors expressing B7-H3. ## GT Biopharma Advances TriKE Platform Into Solid Tumors "The ongoing Phase 1 progress with GTB-3650 in hematologic malignancies now gives us the confidence to advance the platform with GTB-5550 to target B7-H3, which is broadly expressed across many of the most common and difficult-to-treat solid tumor cancers. We look forward to providing updates on the trial's progress throughout the second half of 2026", said **Michael Breen**, Executive Chairman and CEO of GT Biopharma. **Read Also: EXCLUSIVE: GT Biopharma Reports Progresses Phase 1 Trial Of Lead Drug Candidate For Blood Cancers** ## Phase 1 Trial To Focus Initially On Prostate Cancer Patients The Phase 1 trial of GTB-5550 will be the first nanobody TriKE tested using subcutaneous dosing. The Phase 1a dose-escalation portion will primarily enroll prostate cancer patients and evaluate up to six dose levels to identify the maximum tolerated dose (MTD). Following dose escalation, the Phase 1b expansion phase will enroll patients across up to seven tumor types, including castration-resistant prostate cancer, ovarian cancer, breast cancer, head and neck cancer, non-small cell lung cancer, pancreatic cancer, and bladder cancer, while further evaluating safety, tolerability, and preliminary anti-tumor activity. ## GTB-5550 Dosing Schedule And Patient Monitoring Details GTB-5550 will be administered through subcutaneous injection in the abdominal area for five consecutive days during Week 1 and Week 2, followed by two weeks without treatment. Each treatment cycle lasts four weeks. Subsequent cycles will include treatment three times weekly for two weeks, followed by two weeks off treatment. A minimum of two cycles is planned, with disease reassessment scheduled after two cycles and every 8-12 weeks thereafter. Treatment may continue until disease progression, unacceptable toxicity, patient refusal, or when treatment is no longer considered in the patient's best interest. Patients will be followed for 12 months to evaluate progression-free survival (PFS) and overall survival (OS). The immuno-oncology company had cash and cash equivalents of approximately $7 million as of December 31, 2025, and an unaudited pro-forma cash balance as of January 31, 2026, of approximately $9 million, which is anticipated to provide cash runway through the fourth quarter of 2026. **GTBP Price Action:** GT Biopharma shares were up 13.94% at $0.35 during premarket trading on Thursday. The stock is trading near its 52-week low of $0.26, according to Benzinga Pro data. _Photo via Shutterstock_ ### Related Stocks - [GTBP.US](https://longbridge.com/en/quote/GTBP.US.md) - [SBIO.US](https://longbridge.com/en/quote/SBIO.US.md) - [IBBQ.US](https://longbridge.com/en/quote/IBBQ.US.md) - [XBI.US](https://longbridge.com/en/quote/XBI.US.md) - [BIB.US](https://longbridge.com/en/quote/BIB.US.md) - [FBT.US](https://longbridge.com/en/quote/FBT.US.md) - [LABU.US](https://longbridge.com/en/quote/LABU.US.md) - [IBB.US](https://longbridge.com/en/quote/IBB.US.md) - [PBE.US](https://longbridge.com/en/quote/PBE.US.md) - [BBH.US](https://longbridge.com/en/quote/BBH.US.md) ## Related News & Research - [Candel Therapeutics Reports Positive Phase 3 Prostate Cancer Trial Data](https://longbridge.com/en/news/286652611.md) - [US cancer clinics scramble to get experimental Revolution Medicines pancreatic cancer drug](https://longbridge.com/en/news/286394551.md) - [Korro Bio To Advance KRRO-111 As Potential Treatment For AATD](https://longbridge.com/en/news/287089978.md) - [Eton Pharmaceuticals Adds Another 2026 Launch As It Secures U.S. Rights To IMPAVIDO](https://longbridge.com/en/news/287025596.md) - [GT Biopharma reports Q1 results](https://longbridge.com/en/news/286567387.md)