GTB-5550 in Advanced Solid Tumors

NCT07541573 | Recruiting Phase 1 DMC FDA Drug

• 4 other identifiers: 2025LS049W81XWH-20-1-0659HT9425-25-1-0438W81XWH-22-1-0242
• Study Type: interventional
• Target: 175
• Locations: 1 country
• Sites: 1

Brief Summary

This is a first-in-human Phase 1a/1b trial of a B7-H3-targeted natural killer (NK) cell engager, referred to as a TriSpecific Killer Engager (TriKE), for the treatment of select solid tumor cancers. To be considered for the study, a patient must be 18 years or older, have histologically or cytologically confirmed advanced/metastatic cancer that, based on literature reports, expresses B7-H3 at a high frequency, measurable disease by RECIST 1.1 (exception: mCRPC limited to bone metastasis are exempt from this requirement), meets the disease specific criteria for prior failed therapy, and refractory to, intolerant of, or ineligible for therapy options that are known to provide clinical benefit for their diagnosis.

Conditions

Tri-specific Killer Engager; Solid Tumor; Advanced Solid Tumor

Keywords

TriKE; GTB-5550

Outcome Measures

Primary Outcomes (1)

• Maximum tolerated dose (MTD)

  The primary objective is to identify one of the six dose-level strategies of GTB-5550 (cam anti-CD16/WT IL 15/cam anti-B7-H3 TriKE) that corresponds to the desired maximum toxicity rate of less of equal to 20%, defining the MTD.

  1 year

Study Arms (6)

Dose Level Cohort -1

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 90 µg (or 20 µL) of GTB-5550.

Drug: GTB-5550

Dose Level Cohort 1

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 270 µg (or 60 µL) of GTB-5550.

Drug: GTB-5550

Dose Level Cohort 2

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 900 µg (or 200 µL) of GTB-5550.

Drug: GTB-5550

Dose Level Cohort 3

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 2700 µg (or 600 µL) of GTB-5550.

Drug: GTB-5550

Dose Level Cohort 4

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 5400 µg (or 1200 µL) of GTB-5550.

Drug: GTB-5550

Dose Level Cohort 5

EXPERIMENTAL

Patients with histologically or cytologically confirmed advanced/metastatic cancer. Patients will receive 9000 µg (or 2000 µL) of GTB-5550.

Drug: GTB-5550

Interventions

GTB-5550 DRUG

GTB-5550 is given as a subcutaneous (SQ) injection in the abdominal area at the patient-assigned dose once a day for 5 consecutive days for 2 weeks in a row (i.e. Day 1-5 and Day 8-12) followed by 2 weeks of no treatment. This 4-week period equals 1 treatment cycle, or 28 days. Starting with Cycle 2 and beyond, this will be repeated with three times per week dosing for weeks 1 and 2 of the cycle (but not on 3 consecutive days) followed by 2 weeks of no treatment.

Also known as: Camelid Nanobody B7-H3 Tri-Specific Killer Engager (camB7-H3 TriKE®)

Dose Level Cohort -1; Dose Level Cohort 1; Dose Level Cohort 2; Dose Level Cohort 3; Dose Level Cohort 4; Dose Level Cohort 5

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Measurable disease per RECIST 1.1. (Exception: mCRPC limited to bone metastasis is exempt from this requirement).
• Age 18 years or older at the time of consent, ECOG Performance Status 0 to 2
• Acute effects of any prior therapy must have resolved to baseline or Grade ≤ 1 NCI CTCAE v5 except for AEs not constituting a safety risk in the opinion of the enrolling Investigator.
• Adequate organ function within 14 days (30 days for cardiac) of Cycle 1 Day 1 defined as:
• Hematologic: hemoglobin ≥ 9 g/dL (may be transfused not more than 2 units of pRBCs within 7 days prior to Cycle 1 Day 1 to meet this requirement); absolute neutrophil count (ANC) ≥ 1500/ul (granulocyte colonystimulating factor (s) is not allowed to achieve ANC threshold or within 7 days of Cycle 1 Day 1); platelets ≥ 100 x 10\^9/L (may be transfused not more than 2 units of platelets within 7 days prior to Cycle 1 Day 1 to meet this requirement); absolute lymphocyte count (ALC) ≥ 300/ul.
• Albumin ≥ 3.0 g/dL.
• Renal: a patient BSA corrected glomerular filtration rate ≥ 45 mL/min as calculated using the Modified Cockroft-Gault equation (Rostoker et al. 2007).
• Hepatic: AST and ALT ≤1.5 x upper limit of normal (ULN) and total bilirubin ≤1.5 x ULN.
• Cardiac: New York Heart Association (NYHA) Class I or II ; left ventricular ejection fraction (LVEF) ≥ 45% by echocardiogram, MUGA, or cardiac MRI.
• Adequate pulmonary function with PFTs \> 50% FEV1 if symptomatic or known impairment.
• Sexually active couples of childbearing-potential must agree to use effective contraception or abstinence during treatment and for at least 4 months after the final dose of GTB-5550.
• Agrees to stay within a 60-minute drive of the study center through the Cycle 1 Day 15 visit for the Phase 1a study only.
• Provides voluntary written consent prior to the performance of any research related activity

You may not qualify if:

• Anti-cancer treatment including surgery, radiotherapy, chemotherapy, other immunotherapy, or investigational therapy within 14 days prior to the 1st dose of GTB-5550. Radioligand therapy requires at least 1 cycle washout (6 weeks for Pluvicto, 4 weeks for Xofigo).
• Prior organ allograft or allogeneic transplantation. An exception is made for FA patients with prior history of allogeneic hematopoietic stem cell transplant off immune suppressive therapy for \> 1 year.
• Pregnant or breastfeeding or planning pregnancy within 4 months after the last dose of GTB-5550.
• Prior malignancy other than the one under treatment except for the following: adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, adequately treated Stage I or II cancer which is currently in complete remission, or any other cancer from which the patient has been disease-free for 1 year after surgical or other definitive treatment.
• Active autoimmune disease that has required systemic treatment (except replacement therapy) within the past 1 year or any other diseases requiring immunosuppressive therapy while on study. Inhaled or topical steroids, and adrenal replacement steroid doses ≤10 mg daily prednisone equivalent, are permitted in the absence of active autoimmune disease.
• Active systemic infection requiring parenteral antibiotic therapy. Any prior systemic infections must have resolved to Grade 1 or lower following optimal therapy.
• Psychiatric illness/social situations that in the judgement of the enrolling investigator would limit compliance with study requirements.
• Other illness or a medical issue that, in the judgement of the enrolling Investigator, would exclude the patient's participation.

Sponsors & Collaborators

• Masonic Cancer Center, University of Minnesota: lead
• GT Biopharma, Inc.: collaborator

Study Sites (1)

Masonic Cancer Center at University of Minnesota

Minneapolis, Minnesota, 55455, United States

RECRUITING

Central Study Contacts

Nicholas Zorko, MD

CONTACT

612-625-3051; zorko004@umn.edu

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: April 14, 2026
• First Posted: April 21, 2026
• Study Start: April 8, 2026
• Primary Completion (Estimated): January 1, 2031
• Study Completion (Estimated): January 1, 2032
• Last Updated: April 23, 2026

Record last verified: 2026-04

Locations

US (1)