GT Biopharma Inc. (NASDAQ:GTBP) on Thursday said it submitted an investigational new drug (IND) application to the U.S. Food and Drug Administration (FDA) in December 2025 for GTB-5550 TriKE for solid tumors.
GTB-5550 TriKE is a B7-H3-targeted natural killer (NK) cell engager for B7-H3-expressing solid tumor cancers.
"The IND for GTB-5550 represents the third NK cell engager we plan to move into clinical development and a tremendous accomplishment for the company", said Michael Breen, Executive Chairman and CEO of GT Biopharma.
Initiation of a Phase 1 basket trial with GTB-5550 for multiple solid tumors is planned for 2026. The company looks forward to applying the clinical learnings from the GTB-3650 study to help inform the GTB-5550 program, which targets a patient population with B7-H3-expressing solid tumors.
The company is actively enrolling the Phase 1 trial with GTB-3650 in myeloid blood cancer, and expects the next data readout in the first half of 2026 that could provide potential evidence of clinical activity.
“The global market for B7-H3 expressing solid tumor cancers accounts for a portion of the estimated $362 billion global solid tumor cancers market…,” Breen said in a press release on Thursday.
Trial Design
The Phase 1a dose escalation portion of the trial will test up to 7 dose levels to identify the maximum tolerated dose (MTD).
The Phase 1b dose expansion component of the trial will confirm the MTD identified in the Phase 1a trial across 7 distinct metastatic disease cohorts, and further evaluate its tolerability, assuming the toxicity rates are similar across the groups.
GTB-5550 will be administered by subcutaneous (SQ) injection in the abdominal area for 5 consecutive days during Week 1 and Week 2, followed by 2 weeks of no treatment. One treatment cycle is 4 weeks in duration.
A minimum of 2 cycles is planned, and patient-appropriate disease reassessment is performed after 2 cycles and every 8-12 weeks thereafter. Treatment may continue until disease progression, unacceptable toxicity, patient refusal, or treatment is no longer in the best interest of the patient.
Patients are followed for 12 months to determine progression-free survival (PFS) and overall survival (OS).
Price Action: GTBP stock is up 12.92% at $0.75 during the premarket session at the last check on Thursday.
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