FDA OKs therapy’s testing in myeloma patients – but trial awaits funding
Novel treatment using killer cells already being tested for other cancers
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The U.S. Food and Drug Administration (FDA) has given GT Biopharma a green light to start a Phase 1 clinical trial testing its immunotherapy candidate GTB-5550 — which uses so-called natural killer cells to fight cancer — in people with multiple myeloma.
Still, while the FDA cleared the developer’s investigational new drug application (IND), allowing the trial to proceed, the timing of its launch remains unclear. In a company press release, GT said the study’s actual start is contingent on securing additional funding.
Specifically, GT stated that it’s awaiting non-dilutive grant funding, meaning monies that won’t require the company to give up equity, ownership, or voting control. In other words, the trial won’t start until a grant or other no-payback funding is secured.
The newly-cleared Phase 1 trial would be the first-in-human study of GTB-5550 in myeloma or any other type of blood cancer. The treatment candidate is designed to harness the cancer-killing capabilities of immune cells called natural killer (NK) cells. Developed with GT’s Trike platform, it works by simultaneously sticking to receptors on NK cells and to a protein called B7-H3 that is expressed by many cancer cells.
GT is already running a Phase 1 study (NCT07541573) testing GTB-5550 in people with several different types of advanced solid tumors, with priority being given to those with prostate, ovarian, and pancreatic cancers. The early trial, also enrolling people with lung and breast cancers, is actively recruiting at a site in Minnesota.
Michael Breen, executive chairman and CEO of GT, said that the FDA’s decision to give the go-ahead for a trial in people with multiple myeloma “highlights the diverse utility of our Trike platform.”
According to its developer, GTB-5550 has shown promising effects in preclinical models of myeloma, a cancer characterized by abnormal growth of certain immune cells in the bone marrow, the spongy inside of certain bones. Studies suggest that B7-H3, the protein targeted by GTB-5550, is expressed at high levels on myeloma cells.
“Targeting B7-H3 remains an active area for clinical development of new anti-cancer drugs, yet most competitive efforts are focused on solid tumors”, said Aimee Merino, MD, PhD, a professor at the University of Minnesota.
New trial will test GTB-5550 for hard-to-treat myeloma
Merino said the experimental therapy showed potential in the lab for treating myeloma.
“Based on our findings of high levels of B7-H3 expression within the bone marrow of newly diagnosed multiple myeloma patients, we have begun a dedicated effort for this novel approach in later-line patients, which continues to be an area of unmet need,” Merino said. “We have been encouraged with our preclinical findings in a bone chip model that show high levels of antitumor cell activity mediated by NK cells in the presence of GTB-5550.”
The newly cleared Phase 1 study will enroll myeloma patients whose disease is not adequately controlled after at least three prior lines of treatment. In the first part of the study, as many as six doses of GTB-5550 will be tested to identify the maximum tolerated dose — meaning the highest dose that can be administered without unacceptable safety risks. In the next part of the study, 25 patients will be treated at the maximum tolerated dose to evaluate safety and antitumor activity.
GTB-5550 treatment will be given in four-week cycles. In the first two weeks of each cycle, the therapy will be administered by subcutaneous, or under-the-skin, injections into the abdominal area on three nonconsecutive days per week. In the second two weeks of each cycle, patients receive no treatment.
Each patient is planned to receive a minimum of two cycles, with additional cycles possible for patients who show signs of a treatment response. All participants will be followed for one year to assess cancer progression and survival outcomes.
The company remains focused on its … ongoing Phase 1 [trial] with GTB-5550 … and we look forward to the potential initiation of [another study], pending receipt of … grant funding.
In addition to GTB-5550, GT is also developing GTB-3650, an experimental anticancer therapy that aims to direct NK cells to attack a different cancer protein target: CD33. A Phase 1 study (NCT06594445) is testing GTB-3650 in people with myelodysplastic syndromes (MDS) or acute myelogenous leukemia (AML), which are forms of blood cancer. That study is also recruiting at the Masonic Cancer Center at the University of Minnesota in Minneapolis, the same site as the other trials.
“The company remains focused on its two ongoing Phase 1 trials with GTB-5550 and GTB-3650, both of which are actively enrolling, and we look forward to the potential initiation of a third Phase 1 trial, pending receipt of non-dilutive grant funding,” Breen said.
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