Positive Phase 1 Results for Plus Therapeutics’ Rhenium (186Re) Obisbemeda in Glioblastoma Peer-Reviewed in Nature Communications
DENVER, Colo., Mar 07, 2025 (247marketnews.com)- Plus Therapeutics (NASDAQ:PSTV) published a peer-reviewed manuscript in Nature Communications. Titled “Treatment of Recurrent Glioma by Rhenium (186Re) Obisbemeda (186RNL): A Phase 1 Clinical Trial,” the study unveils compelling Phase 1 results from the ongoing ReSPECT-GBM trial, showcasing the safety, response, and potential efficacy of this novel radiotherapeutic. For a disease with few answers and fewer lifelines, these findings could signal a turning point.
Glioblastoma, the most common and lethal brain cancer, strikes approximately 15,000 Americans annually, offering a grim prognosis: a median life expectancy of less than 24 months, a one-year survival rate of 40%, and a five-year survival rate hovering around 5%. Recurrent GBM, which afflicts 90% of patients near the original tumor site, is especially dire, with no FDA-approved treatments to meaningfully extend life. The standard of care—typically bevacizumab—yields a median overall survival (OS) of just 8 months, often accompanied by side effects that limit its use. Enter Rhenium (186Re) Obisbemeda, Plus Therapeutics’ targeted radiotherapeutic is attempting to rewrite the script.
The Phase 1 trial tested this injectable radiotherapy in 21 patients with recurrent GBM, delivering doses up to 22.3 mCi via convection-enhanced delivery (CED)—a technique that bypasses the blood-brain barrier to flood tumors with precision radiation. A median OS of 11 months across all patients, handily outpacing the standard of care. But the real headline lies in the dose-response curve: patients receiving >100 Gy of absorbed radiation (n=12) achieved a staggering median OS of 17 months—more than double the benchmark—compared to just 6 months for those below that threshold (n=9, p=0.001). This isn’t marginal improvement; it’s a leap.
Marc H. Hedrick, M.D., President and CEO of Plus Therapeutics, stated, “Peer-reviewed publication of our Phase 1 glioma data in a prestigious, high-impact factor journal is substantial validation for this important clinical program. Based largely on this data, our ReSPECT-GBM Phase 2 trial is currently enrolling patients at leading medical centers, bringing us closer to delivering a much-needed treatment option for this devastating disease.”
Despite delivering absorbed doses as high as 739.5 Gy—far exceeding the 35 Gy typical of external beam radiation therapy (EBRT)—Rhenium (186Re) Obisbemeda showed no dose-limiting toxicities. Most adverse events were mild and unrelated to the treatment, a stark contrast to the toxicity often seen with conventional options. This potency-without-punishment stems from the drug’s design: Rhenium-186, encapsulated in nanoliposomes, emits beta energy with a short 2 mm penetration range, targeting cancer cells while sparing healthy tissue. Its gamma emissions also allow real-time imaging, ensuring precision that EBRT can’t match.
The correlation between survival and radiation dose is striking. Patients hitting the >100 Gy threshold—enabled by CED and the drug’s localized delivery—saw their tumors absorb up to 20 times the radiation of standard methods, driving tumor destruction without systemic fallout. This dose-dependent efficacy, backed by statistical significance (p=0.001), suggests Plus has cracked a key code in GBM therapy: deliver more where it matters, safely.
Recurrent GBM has long been a therapeutic desert. Current treatments offer fleeting benefits, hampered by the blood-brain barrier, tumor heterogeneity, and collateral damage to healthy tissue. Rhenium (186Re) Obisbemeda sidesteps these hurdles. By threading catheters directly into the tumor, Plus Therapeutics achieves what systemic drugs and external radiation cannot: a concentrated, controlled assault. The 11-month median OS across all patients already beats the 8-month standard, but the 17-month mark for high-dose recipients hints at a ceiling far higher than what’s been imagined.
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