GT Biopharma has successfully completed dosing of the first patient participating in its Phase 1/2 clinical trial of GTB-3550 (OXS-3550), the company’s experimental treatment for relapsed or refractory acute myeloid leukemia (AML).
GTB-3550 is a tri-specific recombinant (man-made) fusion protein conjugate made up of parts of two antibodies, one targeting CD-16 and another CD33, and a modified form of interleukin-15 (IL-15). CD16 is a strong receptor activator of natural killer (NK) immune cells, while CD33 is a protein normally found in malignant AML cells. IL-15 is a cytokine — a molecule that mediates and regulates immune and inflammatory responses — that stimulates the activity of NK cells.
“When the NK stimulating cytokine human IL-15 is used [to link the two antibodies], it provides a self-sustaining signal that activates NK cells and enhances their ability to kill [cancer cells containing the CD33 protein],” the company states on its website.
The safety, efficacy, and pharmacological properties of GTB-3550, which is part of the company’s tri-specific NK cell engagers, or TriKE, are currently being evaluated in a Phase 1/2 trial (NCT03214666). The trial, which is still recruiting participants, is expected to enroll approximately 60 patients with relapsed or refractory AML, high risk myelodysplastic syndromes, or advanced systemic mastocytosis.
All patients enrolled in the open-label trial will receive a single course of GTB-3550, which will be administered in four 24-hour continuous infusions, for three consecutive weeks. Each patient will receive one of six different doses of the therapy.
According to the company, the first patient with relapsed or refractory AML enrolled in the trial is receiving GTB-3550 at a daily dose of 5 micrograms (mcg)/kg has completed treatment.
The patient did not experience any adverse side effects over the course of treatment, and achieved a status of stable disease, based on the numbers of AML blasts (immature white blood cells that are usually associated with leukemia).
In addition, trial investigators found the total numbers of NK cells in the patient’s blood increased after treatment with GTB-3550, which may be due to the presence of IL-15 in the therapy’s composition. No other significant increments in other immune cell populations were observed.
“We are pleased to see these results in our first patient who is being administered GTB-3550. We remain optimistic that GTB-3550 will demonstrate therapeutic benefit in patients who have relapsed/refractory AML and other hematologic malignancies that are at an advanced stage,” Anthony Cataldo, chairman and CEO of GT Biopharma, said in a press release.
“We believe the robustness of the TriKE platform will enable the development of therapeutics for the treatment of other cancers and certain infectious diseases, such as HIV and coronavirus infections,” Cataldo said.