FDA Grants Fast Track Designation to MT-125 in Glioblastoma

MT-125, an investigational myosin IIA and IIB inhibitor, received fast track designation from the FDA as a treatment for patients with glioblastoma, according to a press release from the developer, Myson Therapeutics, Inc.¹

According to the developer, the FDA previously granted orphan drug designation to MT-125 as a therapy for those with malignant gliomas, including glioblastoma.

Developers engineered MT-125 as a first-in-class dual inhibitor of non-muscle myosin IIA and IIB, a mechanism that may facilitate simultaneous targeting of proliferative and invasive phenotypes of glioblastoma while boosting the efficacy of radiation. MT-125 is also being developed for other oncology indications beyond glioblastoma.

“Receiving fast track designation validates our conviction that MT-125 has the potential to offer an entirely novel treatment approach to patients with even the most aggressive forms of glioblastoma,” Courtney Miller, PhD, chief executive officer at Myosin Therapeutics, stated in the press release.¹ “We are energized by the open communication with the FDA that the fast track [designation] offers because it will ensure we advance MT-125 as quickly as possible with our patient-centered approach.”

Investigators are currently assessing the preliminary activity, safety, and pharmacokinetics of MT-125 for patients with glioblastoma in a phase 1/2 trial (NCT07185880). Patients with newly diagnosed disease will be assigned to receive different doses of MT-125 in combination with radiation to determine the highest tolerated dose of the novel agent.²

The study is planned to include a maximum of 36 patients across several different cohorts. Patients will receive MT-125 at 25 mg, 50 mg, 83.5 mg, or 100 mg for 5 days, then off 2 days plus radiotherapy.

The trial’s primary end points will be dose-limiting toxicities and incidence and severity of adverse effects. Secondary end points include the maximum tolerated dose, the recommended phase 2 dose, and several pharmacokinetic parameters. Pharmacokinetic outcomes include the maximum or peak serum concentration at certain periods, the time it takes for MT-125 to reach maximum concentration following administration, the area under the plasma concentration time curve, time required for plasma concentrations of the agent to decrease by 50%, and the steady state volume of distribution describing how MT-125 distributes throughout the body at the time of reaching equilibrium.

Patients 18 years and older with newly diagnosed, histologically or molecularly confirmed IDH wild-type and MGMT unmethylated glioblastoma are eligible for enrollment on the trial. Other eligibility criteria include having an ECOG performance status of 0 to 2, adequate laboratory values, a left ventricular ejection fraction of at least 55%, the ability to complete questionnaires independently or with assistance, and a stable steroid dose for at least 2 weeks prior to study entry.

Because the investigational agent may have unknown genotoxic, mutagenic, or teratogenic effects on a developing fetus, patients who are pregnant, nursing, or of childbearing potential are ineligible for enrollment on the trial. Patients are also ineligible for enrollment if they have comorbid systemic illnesses or other severe concurrent diseases that may interfere with safety assessments.

In June 2025, developers announced that the FDA accepted an investigational new drug application for MT-125.³ Acceptance of the application permitted investigators to pursue a phase 1 study of the agent plus radiotherapy for patients with newly diagnosed glioblastoma.

“Glioblastoma remains one of the most aggressive and treatment-resistant cancers, with limited advances over the past 2 decades. In collaboration with the Mayo Clinic, we have rapidly advanced our MT-125 program in glioblastoma, and we’re driven and encouraged by the FDA's clearance to proceed with our first-in-human trial. Preclinical studies suggest targeting non-muscle myosin II represents a uniquely holistic approach to tackling this complex and devastating disease,” Miller stated regarding the acceptance of the investigational new drug application.³

References

1. Myosin Therapeutics receives FDA fast track designation for MT-125 in glioblastoma. News release. Myosin Therapeutics, Inc. October 22, 2025. Accessed October 23, 2025. https://tinyurl.com/2p9jkf99
2. A phase 1 study of the safety and tolerability of MT-125 in GBM patients (STAR-GBM). ClinicalTrials.gov. Updated September 22, 2025. Accessed October 23, 2025. https://tinyurl.com/dkraupe6
3. Myosin Therapeutics receives FDA clearance to initiate first-in-human trial of MT-125 in glioblastoma. News release. Myosin Therapeutics, Inc. June 9, 2025. Accessed October 23, 2025. https://tinyurl.com/y2tzf5y8