A drug developed at The University of Texas Health Science Center at San Antonio (UT Health San Antonio) has shown significant promise in extending survival for patients with glioblastoma, the most common and aggressive type of primary brain tumor in adults. The results of a trial led by the university revealed that a unique investigational drug formulation called Rhenium Obisbemeda (186RNL) more than doubled median survival and progression-free survival times compared to traditional treatments. Notably, this was achieved without the dose-limiting toxic effects commonly associated with many cancer therapies.
Glioblastoma remains one of the most challenging cancers to treat, with patients typically having a very poor prognosis once standard therapies like surgery, radiation, and chemotherapy fail. The median survival time for patients with recurrent glioblastoma is only around eight months, and over 90% of cases see a recurrence at the original tumor site. As a result, the need for effective, durable treatments that can target the tumor directly while minimizing damage to healthy tissue has never been more urgent. Rhenium Obisbemeda offers a potential breakthrough in this area, and the clinical trial findings offer renewed hope for those battling this devastating disease.
The Phase I clinical trial, led by Dr. Andrew J. Brenner, professor and chair of neuro-oncology research at the Mays Cancer Center at UT Health San Antonio, tested the drug on 21 patients who had failed one to three previous therapies. These patients were treated with Rhenium Obisbemeda delivered directly to their tumors using a technique known as convection-enhanced delivery. This method involves using specialized neuronavigation tools and catheters to ensure that the drug is delivered precisely to the tumor site, minimizing exposure to surrounding healthy brain tissue.
The trial revealed that the patients who received higher doses of the drug (greater than 100 gray units of radiation) experienced remarkable results. The median overall survival for these patients was 17 months, significantly longer than the typical survival time of eight months seen in historical controls. Moreover, their progression-free survival was six months, far exceeding the typical duration seen with traditional therapies. These encouraging results demonstrate that Rhenium Obisbemeda could provide a more effective option for patients with recurrent glioblastoma, extending both survival and quality of life.
Rhenium Obisbemeda works by utilizing rhenium-186, a beta-emitting radioisotope, which is delivered to the tumor within liposomes—tiny, artificial vesicles made from lipid bilayers. The rhenium-186 is chelated to a custom molecule called BMEDA, which allows it to be transported into the liposome. Once inside the liposome, the rhenium-186 is irreversibly trapped, allowing for targeted radiation to be delivered directly to the tumor. This delivery method allows for very high doses of radiation to be administered directly to the tumor while sparing healthy surrounding tissue, minimizing toxic side effects.
The combination of nanoliposome radiotherapy, convection-enhanced delivery, and neuronavigation tools provides a novel approach to treating glioblastoma. This targeted therapy helps ensure that the tumor receives a high dose of radiation, which could potentially lead to improved patient outcomes without the common side effects associated with traditional radiation therapies. Importantly, the trial did not observe any dose-limiting toxic effects, with most adverse events being unrelated to the study drug itself. This makes Rhenium Obisbemeda a promising new treatment for a disease that has been notoriously difficult to manage.
The study, titled “Convection Enhanced Delivery of Rhenium (186Re) Obisbemeda (186RNL) in Recurrent Glioma: A Multicenter, Single Arm, Phase 1 Clinical Trial,” was published in Nature Communications. The trial was a collaborative effort involving researchers from several esteemed institutions, including UT Southwestern Medical Center, Case Western Reserve University, and the University of Texas MD Anderson Cancer Center, as well as Plus Therapeutics Inc., the clinical-stage pharmaceutical company sponsoring the trial.
The researchers focused on determining the drug’s maximum tolerated dose, as well as evaluating its safety, overall response rate, disease progression-free survival, and overall survival. The positive findings from the trial suggest that Rhenium Obisbemeda could play a key role in extending survival for glioblastoma patients who have exhausted other treatment options.
Dr. Brenner, also a clinical investigator at the Institute for Drug Development at UT Health San Antonio, emphasized that glioblastoma has long been known for its pattern of recurrence, resistance to therapies, and difficulty to treat. He noted that Rhenium Obisbemeda offers a new hope for patients with this disease. With a second phase of the trial already underway, the team hopes to continue building on these positive results and potentially offer an effective new treatment for patients by the end of the year.
The success of this Phase I trial has sparked significant excitement in the field of neuro-oncology, as it represents a potentially transformative treatment for glioblastoma. The ability to deliver targeted radiation directly to the tumor with minimal side effects could change the treatment landscape for this devastating disease. If the ongoing Phase II trial continues to show similar benefits, Rhenium Obisbemeda could become an essential treatment for glioblastoma patients, offering a better chance at survival and a better quality of life.
The technology used in this trial could have broader applications for treating other cancers of the central nervous system. Convection-enhanced delivery and liposomal radiotherapy could be adapted for other hard-to-treat brain tumors, opening up new possibilities for targeted therapies that are both effective and safer for patients.
This trial is an example of how innovation in drug delivery systems can lead to breakthroughs in cancer treatment. The findings underscore the importance of continuing to invest in research and development for better cancer therapies. With cancer rates continuing to rise globally, the need for novel treatments is critical. The development of Rhenium Obisbemeda and its promising results provide a glimpse into the future of cancer treatment, where precision therapies may become the standard of care.
More information: Andrew J. Brenner, et al. Convection Enhanced Delivery of Rhenium (186Re) Obisbemeda (186RNL) in Recurrent Glioma: a multicenter, single arm, phase 1 clinical trial, Nature Communications (2025). DOI: 10.1038/s41467-025-57263-1