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Each year, about 14,000 people in the United States are diagnosed with glioblastoma, one of the deadliest primary brain tumors. With standard treatments of surgery, radiation, and chemotherapy offering a median survival of 14–16 months—and approximately half of patients harboring tumors resistant to approved drugs—novel therapeutic approaches are urgently needed.

In a study published in Cell titled “MT-125 inhibits non-muscle myosin IIA and IIB and prolongs survival in glioblastoma,” researchers from the Wertheim UF Scripps Institute, Mayo Clinic, and collaborators report a promising strategy. Their investigational compound, MT-125, directly targets non-muscle myosin II, a molecular “motor” critical for glioblastoma invasion and cytokinesis. Remarkably, MT-125 appears to render previously resistant tumors newly sensitive to both radiation and kinase inhibitors, while blocking the cancer’s ability to invade brain tissue.

“We know glioblastoma patients are awaiting a breakthrough, and we’re moving as fast as humanly possible,” said senior author Courtney Miller, PhD, of the Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology. The team’s approach stands out by targeting non-muscle myosin IIA and IIB (NMIIA/IIB)—key players downstream of many converging cancer signaling pathways. While oncogenic kinase inhibitors have generally failed in glioblastoma, likely due to pathway redundancies, NMII sits at a convergence point that makes it a hopeful target.

MT-125, a blebbistatin derivative, potently inhibits NMIIA/IIB with minimal impact on cardiac myosin. In mouse models, the researchers reported that the drug showed excellent brain penetrance, a strong safety profile, and did not affect cardiac function or cause significant toxicities at doses well above what is predicted to be therapeutic.

Mechanistically, MT-125 disrupts mitochondrial fission, leading to elevated reactive oxygen species (ROS), DNA damage, and ferroptosis, a type of iron-dependent cell death. It also triggers “oncogene addiction,” causing glioblastoma cells to ramp up PDGFR and mTOR signaling to survive the stress. The upside is that this may make tumors exquisitely vulnerable to existing kinase inhibitors like sunitinib or the PI3K/mTOR inhibitor paxalisib.

In preclinical models, combining MT-125 with sunitinib doubled survival compared to either drug alone, and yielded long-term remission in 40% of treated mice. Adding MT-125 also dramatically sensitized tumors to radiotherapy.

“We found in mice that combining MT-125 with a number of kinase inhibitors created long periods of a disease-free state that we haven’t seen in these mouse models before,” said Steven Rosenfeld, MD, PhD, a neuro-oncologist at Mayo Clinic and study co-lead. The FDA has granted permission to advance MT-125 into clinical trials.

Importantly, MT-125’s unique action could extend beyond glioblastoma. By exploiting cancer cells’ dependence on myosin-driven mechanics and ROS buffering, the strategy may hold promise for other difficult-to-treat malignant gliomas and other tumors.

Nonetheless, researchers caution that while MT-125 caused multinucleation and polyploidy—hallmarks of anti-proliferative stress—long-term implications of inducing chromosomal instability require careful follow-up. Still, the prospect of a first-in-class, brain-penetrant therapy that directly targets the biomechanical underpinnings of cancer cell survival marks an exciting frontier.

A related compound, MT-110, designed to curb methamphetamine cravings via similar myosin pathways, is also advancing toward clinical trials, underscoring the broad therapeutic reach of targeting cellular “motors.”

Scientists have detected microplastics — the tiny and pervasive fragments now found in our seas, drinking water, food and, increasingly, living tissue — in human semen and follicular fluid, according to new research.

A small group of 25 women and 18 men participated in the research, published Tuesday in the journal Human Reproduction. Microplastics were detected in 69% of the follicular fluid samples and 55% of the seminal fluid samples. Follicular fluid is the liquid that surrounds an egg in an ovarian follicle.

The research is an abstract — a short summary of completed research — and has not yet been peer reviewed. It was presented Tuesday in Paris at the 41st Annual Meeting of the European Society of Human Reproduction and Embryology.

“Previous studies had already suggested this possibility, so the presence of microplastics in the human reproductive system is not entirely unexpected,” said lead research author Dr. Emilio Gómez-Sánchez, director of the assisted reproduction laboratory at Next Fertility Murcia in Spain, in a statement provided to the press. “What did surprise us, however, is how widespread it is. This is not an isolated finding — it appears to be quite common.”

Microplastics are polymer fragments that range in size from less than 0.2 inches (5 millimeters) to 1/25,000th of an inch (1 micrometer). Polymers are chemical compounds with long chains of large and repetitive molecular units called monomers, and are known for being flexible and durable. Most plastics are synthetic polymers.

Plastics smaller than the measurement criteria for microplastics are considered nanoplastics, which are measured in billionths of a meter.

“Microplastics primarily enter the body through three routes: ingestion, inhalation, and skin contact,” Gómez-Sánchez said. “From there, they can enter the bloodstream, which then distributes them throughout the body, including to the reproductive organs.”

In previous studies, the fragments have also been detected in various body parts or fluids including the lungs, placenta, brain, testicles, nose tissue at the base of the brain, penises and human stool.

“Decades of studies and the (US Food and Drug Administration) agree that microplastics are not a threat because exposure is extremely low and they are non-toxic,” said Dr. Chris DeArmitt, founder of the Plastics Research Council, via email.

However, while there is little to nothing known about the potential effects of microplastics on human health, chemicals used in plastic production — that often leach from plastics — are linked with health risks including hormonal disruptions, certain cancers, respiratory diseases and skin irritation.

Testing bodily fluids for microplastics

The research participants were patients and donors at Next Fertility Murcia. The women were undergoing egg retrieval, formally known as follicular aspiration, for assisted reproduction, while the men were undergoing semen analysis. The authors stored and froze the samples in glass, then incubated them for two days before analyzing them using an imaging technique combining microscopy and infrared laser.

The research team also analyzed the containers used to collect and store samples to ensure they hadn’t been contaminated with microplastics. The abstract doesn’t disclose what materials the collection containers were made of.

Imaging revealed nine types of microplastics in the reproductive fluids. Over 50% of the follicular fluid samples contained polyamide (PA), polyurethane (PU) and polyethylene (PE), while polytetrafluoroethylene (PTFE) and polyethylene terephthalate (PET) were discovered in over 30% of the follicular fluid samples.

Polypropylene (PP), polyvinyl chloride (PVC) and polylactic acid (PLA) appeared in over 20% of the follicular fluid samples.

In the semen samples, 56% contained PTFE.

Synthetic polyamide is commonly known as nylon, often used in textiles, plastics and automotive parts. Polyurethane is commonly used in coatings, foams and adhesives for furniture, construction, automotive parts, footwear and more. Polyethylene and polypropylene are often found in packaging, construction uses and consumer goods, such as toys and kitchenware.

The plastic PTFE is widely used in nonstick cookware, while PET is found in many food and beverage containers. Polyvinyl chloride is often used in the construction, packaging and medical industries, while PLA is primarily found in food packing, medical implants and 3D-printed objects.

In most samples, the researchers found only one or two particles, but they detected up to five in others, Gómez-Sánchez said. Microplastic concentrations were higher in follicular fluid than in semen. However, the overall concentrations of microplastics in both fluids were relatively low when compared with the concentrations of non-plastic particles. The abstract didn’t disclose what those non-plastic particles were.

“Sadly, (the findings) are not surprising,” said Dr. Matthew J. Campen — a researcher who helped lead the discoveries of microplastics in the brain and testicles — via email.

Though the research is preliminary, it does “set the stage for more advanced studies of the relationship between plastics exposure and reproductive fitness,” added Campen, who wasn’t involved in the study and is a regents’ professor of pharmaceutical sciences at the University of New Mexico.

Important questions remain

The research affirmed previous studies that had found microplastics in these reproductive fluids, and yet again raises important questions, including how these microplastics are absorbed in the intestine then transported to the gonads, Campen said.

“This suggests a very natural mechanism is being hijacked,” he added. “It would also be important to assess plastics in the nanoscale range.”

People trying to conceive naturally or via in vitro fertilization may not need to be concerned about the findings, as they are only preliminary for now, Gómez-Sánchez said.

“We don’t know if they have a direct effect on the capacity of a couple to conceive and carry a baby to term,” he added. “Reproduction is a complex equation, and microplastics are a variable in this equation.”

The findings also can’t yet be linked to more general health outcomes, experts said.

“So far, the effects of microplastics on humans have been mainly extrapolated from animal studies, where microplastics were administered at high concentrations,” Gómez-Sánchez said. “We currently lack direct evidence regarding their impact on humans.”

Betsy Bowers, executive director of the EPS Industry Alliance, echoed these disclaimers and noted that the animal research results aren’t indicative of harm at regular exposure levels. The EPS (expanded polystyrene) Industry Alliance is a North American trade association representing the EPS industry.

The finding that follicular fluid contained more microplastics than semen may be circumstantial, Gómez-Sánchez added, because the study group was small. However, when an ovary is stimulated for assisted reproduction, blood flow to the ovary increases, which may deliver more microplastics to the ovary, he explained.

Additional research is needed to identify the types and quantities of microplastics that could cause health problems, said Dr. Ranjith Ramasamy, a consultant urologist at Jumeirah American Clinic in Dubai. Ramasamy, who wasn’t involved in the study, led the research that found microplastics in penises.

“The plan is to increase the number of cases and conduct a survey on lifestyle habits in order to determine if any of these habits are linked to higher concentrations of plastics found in the ovaries and seminal plasma,” Gómez-Sánchez said.

Gómez-Sánchez and the other researchers also plan to explore whether the presence of microplastics in reproductive fluids affects the quality of sperm and oocytes, he said. Oocytes are cells in ovaries that form an ovum, a mature female reproductive cell that can divide to create an embryo upon fertilization by sperm.

How to reduce your exposure to microplastics

The significance of the findings isn’t yet clear, but they should be considered an additional argument in favor of avoiding the use of plastics in our daily lives, said Dr. Carlos Calhaz-Jorge, professor of obstetrics and gynecology at the University of Lisbon in Portugal, in a news release. Calhaz-Jorge wasn’t involved in the research.

Given the ubiquity of plastics, avoidance can be challenging, said Dr. Philip Landrigan, a pediatrician and director of the Program for Global Public Health and the Common Good at Boston College, via email. In addition to reducing obvious uses of plastic, you can also avoid using plastic cutting boards and eating ultraprocessed foods.

Also limit drinking water from plastic bottles, microwaving food in plastic containers and consuming hot food from plastic containers, Ramasamy said.

Food can be stored in glass, stainless steel or bamboo instead of plastic.

But “the conversation needs to shift — immediately — to policymakers,” Campen said. “Hoping that individual choices can make a difference has been clearly a losing strategy. Federal governments around the world need to make major changes to waste management and recycling policies.”

Annual plastic production by weight has increased by 250 times in the past 75 years and is on track to triple again by 2060, Landrigan said.

“To reduce plastic pollution and safeguard human health, it will be essential that the Global Plastics Treaty that is currently in negotiation at the United Nations impose a global cap on plastic production,” Landrigan, who wasn’t involved in the research, added.

“But smart governments can act now,” Campen urged.

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