Plus Therapeutics (NASDAQ:PSTV) reported updated data from two ongoing trials of its radiotherapy rhenium (186Re) obisbemeda in patients with recurrent glioblastoma (GBM), and leptomeningeal metastases (LM).
GBM is a type of cancer that affects the brain or spinal cord, while LM occurs when the cancer spreads to membranes surrounding the brain and spinal cord.
A phase phase 1/2a trial, dubbed ReSPECT-GBM is evaluating a single dose of Rhenium-186 NanoLiposome (186RNL) in 24 patients with recurrent glioma (GBM).
The company said that the data showed a statistically significant improvement in overall survival correlated with both the average absorbed dose of radiation to the tumor and the percent volume of tumor treated. A 100 Gy increase in the absorbed dose correlated with a 35.7% decrease in the risk of death.
The company noted that a 1% increase in tumor volume treated is linked with a 4.5% decrease in the risk of death.
A recommended phase 2 dose of 22.3 mCi in 8.8 mL is being studied for tumor volumes of 20 mL or less and is expected to enroll up to an additional 31 patients, the company added.
In addition, the company reported data from the first two groups of the phase 1/2a trial, dubbed ReSPECT-LM, in patients with LM.
herein obisbemeda dose administered through an intraventricular catheter (Ommaya reservoir)
The company said data showed that as single rhenium 186RNL obisbemeda dose administered via an intraventricular catheter (Ommaya reservoir) at 6.6 mCi in 5.0 mL in group 1 achieved absorbed doses of 18.7 to 29.0 Gy to the ventricles and cranial subarachnoid space. The dose was well tolerated with no treatment-related adverse events of greater than grade 1.
All four patients treated to date in groups 1 and 2 were seen to have prompt and complete rhenium (186Re) obisbemeda distribution throughout the cerebrospinal fluid (CSF) subarachnoid space that was durable to 28 days, according to the company.
Plus Therapeutics noted that all patients showed a decreased CSF tumor cell count after therapy, ranging from 46% to 92%.
Plus, in collaboration with Lurie Children’s Hospital investigators, expects to file an investigational new drug (IND) seeking FDA clearance to start a trial phase 1/2a trial in children of rhenium (186Re) obisbemeda in supratentorial recurrent or progressive pediatric ependymoma and high-grade glioma.
“Targeted radiotherapy using rhenium (186Re) obisbemeda in patients with GBM and LM has, thus far, been shown to be both feasible and safe across a range of dosages and a variety of delivery parameters. Furthermore, it is unusual to see such a tight correlation between overall survival and absorbed dose at this point of clinical development,” said Andrew Brenner, and principal investigator of the ReSPECT-GBM and ReSPECT-LM trials.
In August too, Plus had reported initial data from the trials.
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