Plus Therapeutics announces positive REYOBIQ Phase 1 trial results.

Plus Therapeutics announces positive data from the ReSPECT-LM Phase 1 trial of REYOBIQ for leptomeningeal metastases (LM) treatment. The trial demonstrated a clinical benefit rate of over 75% in 3 clinically relevant outcome measures, with RNA sequencing and circulating tumor cell reduction consistent with tumor cell death. No dose-limiting toxicities were observed, and the overall safety profile was favorable.

Plus Therapeutics, Inc. (NASDAQ: PSTV) has announced positive data from the ReSPECT-LM Phase 1 trial for its REYOBIQ™, a novel injectable radiotherapy, in treating leptomeningeal metastases (LM). The trial, presented at the SNO/ASCO CNS Metastases Conference in Baltimore, MD, demonstrated significant efficacy and a manageable safety profile.

The trial involved 29 subjects across six cohorts, receiving doses ranging from 6.6 mCi to 75 mCi of REYOBIQ. Key outcomes included a 76% radiographic response rate and an 87% clinical response rate through day 112. Notably, 100% of subjects showed a reduction in CSF tumor cells at day 28, with five of seven patients achieving 80% tumor cell reduction and surviving at least one year. The median overall survival reached 9 months, substantially better than the typical 4-month survival rate in LM patients [1].

The trial also established a recommended Phase 2 single dose of 44.1 mCi, with no dose-limiting toxicities observed in cohorts 1-4. The overall safety profile was favorable, with only grade 4 cytopenia observed in higher dose cohorts [1].

RNA sequencing data provided mechanistic insights, showing early induction of apoptosis followed by immune response activation, suggesting a multi-modal effect. This indicates that REYOBIQ may not only directly kill tumor cells but potentially sensitize them to immune surveillance [1].

Dr. Andrew Brenner, M.D., Ph.D., Professor of Medicine in the Division of Hematology and Oncology at The University of Texas Health Science Center at San Antonio, commented, "The trial gave us exactly what we needed to move into the ongoing dosing optimization trial and then to a potential approval trial" [1].

Leptomeningeal metastases (LM) are a rare but severe complication of advanced cancer, affecting the fluid-lined structures of the central nervous system. LM occurs in approximately 5% of patients with metastatic cancer, with breast cancer, lung cancer, and melanoma being the most common sources. Median survival is typically 2-6 months, and effective treatment options are limited, highlighting the urgent need for novel therapies [1].

REYOBIQ™ (rhenium Re186 obisbemeda) is a novel injectable radiotherapy specifically formulated to deliver direct targeted high dose radiation in CNS tumors in a safe, effective, and convenient manner to optimize patient outcomes. It has the potential to reduce off-target risks and improve outcomes for CNS cancer patients compared to currently approved therapies [1].

The Company’s ReSPECT-LM trial is funded by a three-year $17.6M grant by the Cancer Prevention & Research Institute of Texas (CPRIT). The ReSPECT-GBM clinical trial for recurrent glioblastoma is supported by an award from the National Cancer Institute (NCI), part of the U.S. National Institutes of Health (NIH) [1].

For more information, visit [Plus Therapeutics](https://www.plustherapeutics.com).

References:
[1] https://www.stocktitan.net/news/PSTV/plus-therapeutics-presents-positive-re-spect-lm-clinical-trial-qzzo3x3gtdxo.html