Plus Therapeutics Completes Dosing in Cohort 5 of ReSPECT-LM Phase 1 Trial of Rhenium (186Re) Obisbemeda in Leptomeningeal Metastases

Rhea-AI Summary

Plus Therapeutics, Inc. completes dosing in Cohort 5 of ReSPECT-LM Phase 1 trial for treating leptomeningeal metastases. The Company plans to move into Cohort 6 in Q2 2024. Fast Track designation and Orphan Drug Designation granted for rhenium obisbemeda.

Insights

Medical Research Analyst

The progression to Cohort 6 in the ReSPECT-LM Phase 1 trial by Plus Therapeutics represents a significant milestone in the development of rhenium (186Re) obisbemeda for leptomeningeal metastases (LM). The absence of dose limiting toxicities at this stage is a positive indicator of the treatment's safety profile, which is crucial for patients with CNS cancers. The increase in radiation dose up to 66.14 millicuries without observed toxicities is noteworthy, suggesting a potentially favorable therapeutic window.

Furthermore, the expansion of clinical trial sites from two to seven could enhance patient enrollment rates, thereby accelerating the trial's timeline and potentially leading to quicker FDA approval processes. The Fast Track designation by the FDA is indicative of the treatment's potential to address an unmet medical need and the Orphan Drug Designation for breast cancer with LM could provide certain benefits, including market exclusivity upon approval. The financial support from CPRIT underscores the therapy's promise and the importance of continued research in this area.

The implications for stakeholders include the potential for Plus Therapeutics to secure a strong position in the CNS cancer treatment market, should the therapy prove to be effective and safe in later-stage trials. Investors may view these developments as indicators of the company's research and development capabilities and its ability to progress through regulatory milestones.

Oncology Doctor

Leptomeningeal metastases are a severe complication of solid tumors where cancer cells spread to the membranes surrounding the brain and spinal cord. Current treatment options are limited and often have poor prognoses, highlighting the need for new therapies. Rhenium (186Re) obisbemeda's targeted radiotherapeutic approach could offer a more localized and potentially less toxic alternative to systemic chemotherapy.

The ten-fold increase in the administered radiation dose from Cohort 1 to Cohort 5 without reaching dose limiting toxicity is a promising development. It suggests that the therapy might be effective at higher doses, which could be crucial in treating aggressive CNS cancers. The addition of five new clinical trial sites may also contribute to a more diverse patient population, which is essential for understanding the treatment's efficacy across different demographics and genetic backgrounds.

For patients and healthcare providers, these developments represent a beacon of hope for more effective treatments. The Fast Track and Orphan Drug Designations not only expedite the development process but also reflect the therapy's potential to significantly improve patient outcomes for a condition where treatment options are currently very limited.

Financial Analyst

The financial backing from the Cancer Prevention & Research Institute of Texas, totaling $17.6M, provides Plus Therapeutics with a substantial resource to fund ongoing clinical trials. This support mitigates some of the financial risks associated with the development of new therapeutics. The Fast Track and Orphan Drug Designations are critical factors that can streamline the regulatory process and reduce the time to market, potentially enhancing the company's competitive edge.

Investors may interpret the successful completion of Cohort 5 and the planned initiation of Cohort 6 as positive signals for the company's operational execution and regulatory strategy. The absence of dose limiting toxicities to date may also suggest a lower likelihood of encountering significant hurdles in future trial phases, which can be a concern for biotech investments. The expansion of clinical trial sites can lead to increased enrollment rates and diversity in trial participants, which is beneficial for robust data collection and may improve the chances of successful trial outcomes.

Overall, these developments could have a favorable impact on Plus Therapeutics' stock valuation, as they reflect progress in a critical drug development program with significant market potential. However, it is essential to note that the clinical trial is still in early stages and further data will be required to fully assess the drug's efficacy and safety profile.

A total of 18 patients have been dosed in the trial to date

Company anticipates moving into Cohort 6 in Q2 2024 following standard safety review

AUSTIN, Texas, March 11, 2024 (GLOBE NEWSWIRE) -- Plus Therapeutics, Inc. (Nasdaq: PSTV) (the “Company”), a clinical-stage pharmaceutical company developing targeted radiotherapeutics with advanced platform technologies for central nervous system (CNS) cancers, today announced it has completed dosing in Cohort 5 of the ReSPECT-LM Phase 1 dose escalation clinical trial of rhenium (¹⁸⁶Re) obisbemeda for the treatment of leptomeningeal metastases (LM) from solid tumors.

Three patients were dosed as part of Cohort 5, bringing the total to 18 patients dosed in the ReSPECT-LM trial to date. There have been no dose limiting toxicities observed to date with administered radiation doses up to 66.14 millicuries in Cohort 5, a ten-fold increase over Cohort 1. The Company plans to initiate dosing in Cohort 6 in the second quarter of 2024, pending Data Safety Monitoring Board (DSMB) approval. In addition, five new clinical trial sites were added to this trial over the last year, bringing the total number of sites to seven. The Company anticipates that this will allow for continued maximal enrollment allowed under the protocol.

The FDA has granted Fast Track designation to rhenium (¹⁸⁶Re) obisbemeda for LM and Orphan Drug Designation for the treatment of breast cancer with LM, and the ReSPECT-LM program continues to be funded in part by a 3-year $17.6M grant from the Cancer Prevention & Research Institute of Texas (CPRIT). Patients interested in learning more about the ReSPECT-LM trial can visit ClinicalTrials.gov (NCT05034497).

About Leptomeningeal Metastases (LM)
LM is a rare complication of cancer in which the primary cancer spreads to the cerebrospinal fluid (CSF) and leptomeninges surrounding the brain and spinal cord. All malignancies originating from solid tumors, primary brain tumors, or hematological malignancies have this LM complication potential with breast cancer as the most common cancer linked to LM, with 3-5% of breast cancer patients developing LM. Additionally, lung cancer, GI cancers and melanoma can also spread to the CSF and result in LM. LM occurs in approximately 5% of people with cancer and is usually terminal with 1-year and 2-year survival of just 7% and 3%, respectively. The incidence of LM is on the rise, partly because cancer patients are living longer and partly because many standard chemotherapies cannot reach sufficient concentrations in the spinal fluid to kill the tumor cells, yet there are no FDA-approved therapies specifically for LM patients, who often succumb to this complication within weeks to several months, if untreated.

About Rhenium (¹⁸⁶Re) obisbemeda 
Rhenium (¹⁸⁶Re) 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. Rhenium (¹⁸⁶Re) obisbemeda has the potential to reduce off target risks and improve outcomes for CNS cancer patients, versus currently approved therapies, with a more targeted and potent radiation dose. Rhenium-186 is an ideal radioisotope for CNS therapeutic applications due to its short half-life, beta energy for destroying cancerous tissue, and gamma energy for real-time imaging. Rhenium (¹⁸⁶Re) obisbemeda is being evaluated for the treatment of recurrent glioblastoma and leptomeningeal metastases in the ReSPECT-GBM and ReSPECT-LM clinical trials. ReSPECT-GBM is supported by an award from the National Cancer Institute (NCI), part of the U.S. National Institutes of Health (NIH), and ReSPECT-LM is funded by a three-year $17.6M grant by the Cancer Prevention & Research Institute of Texas (CPRIT).

About Plus Therapeutics
Plus Therapeutics, Inc. is a clinical-stage pharmaceutical company developing targeted radiotherapeutics for difficult-to-treat cancers of the central nervous system with the potential to enhance clinical outcomes for patients. Combining image-guided local beta radiation and targeted drug delivery approaches, the Company is advancing a pipeline of product candidates with lead programs in recurrent glioblastoma (GBM) and leptomeningeal metastases (LM). The Company has built a supply chain through strategic partnerships that enable the development, manufacturing, and future potential commercialization of its products. Plus Therapeutics is led by an experienced and dedicated leadership team and has operations in key cancer clinical development hubs including Austin and San Antonio, Texas. For more information, visit https://plustherapeutics.com/.

Cautionary Statement Regarding Forward-Looking Statements
This press release contains statements that may be deemed “forward-looking statements” within the meaning of U.S. securities laws, including statements regarding clinical trials, expected operations and upcoming developments. All statements in this press release other than statements of historical fact are forward-looking statements. These forward-looking statements may be identified by future verbs, as well as terms such as “potential,” “anticipating,” “planning” and similar expressions or the negatives thereof. Such statements are based upon certain assumptions and assessments made by management in light of their experience and their perception of historical trends, current conditions, expected future developments and other factors they believe to be appropriate. These statements include, without limitation, statements regarding the following: the potential promise of rhenium (¹⁸⁶Re) obisbemeda including the ability of rhenium (¹⁸⁶Re) obisbemeda to safely and effectively deliver radiation directly to the tumor at high doses; expectations as to the Company’s future performance including the next steps in developing the Company’s current assets; the Company’s clinical trials including statements regarding the timing and characteristics of the ReSPECT-GBM, ReSPECT-LM and ReSPECT-PBC and increase of ten o, clinical trials; possible negative effects of rhenium (¹⁸⁶Re) obisbemeda; the continued evaluation of rhenium (¹⁸⁶Re) obisbemeda including through evaluations in additional patient cohorts; and the intended functions of the Company’s platform and expected benefits from such functions.

The forward-looking statements included in this press release could differ materially from those expressed or implied by these forward-looking statements because of risks, uncertainties, and other factors that include, but are not limited to, the following: the early stage of the Company’s product candidates and therapies, the results of the Company’s research and development activities, including uncertainties relating to the clinical trials of its product candidates and therapies; the Company’s liquidity and capital resources and its ability to raise additional cash, the outcome of the Company’s partnering/licensing efforts, risks associated with laws or regulatory requirements applicable to it, market conditions, product performance, litigation or potential litigation, and competition within the cancer diagnostics and therapeutics field, ability to develop and protect proprietary intellectual property or obtain licenses to intellectual property developed by others on commercially reasonable and competitive terms, and material security breach or cybersecurity attack affecting the Company’s operations or property. This list of risks, uncertainties, and other factors is not complete. Plus Therapeutics discusses some of these matters more fully, as well as certain risk factors that could affect Plus Therapeutics’ business, financial condition, results of operations, and prospects, in its reports filed with the SEC, including Plus Therapeutics’ annual report on Form 10-K for the fiscal year ended December 31, 2023, quarterly reports on Form 10-Q, and current reports on Form 8-K. These filings are available for review through the SEC’s website at www.sec.gov. Any or all forward-looking statements Plus Therapeutics makes may turn out to be wrong and can be affected by inaccurate assumptions Plus Therapeutics might make or by known or unknown risks, uncertainties, and other factors, including those identified in this press release. Accordingly, you should not place undue reliance on the forward-looking statements made in this press release, which speak only as of its date. The Company assumes no responsibility to update or revise any forward-looking statements to reflect events, trends or circumstances after the date they are made unless the Company has an obligation under U.S. federal securities laws to do so.

Investor Contact
Corey Davis, Ph.D.
LifeSci Advisors
(212) 215-2577
cdavis@lifesciadvisors.com 

FAQ

How many patients have been dosed in the ReSPECT-LM Phase 1 trial for leptomeningeal metastases by Plus Therapeutics, Inc.?

A total of 18 patients have been dosed in the trial to date.

When does the Company anticipate moving into Cohort 6 in the ReSPECT-LM Phase 1 trial?

The Company anticipates moving into Cohort 6 in Q2 2024 following a standard safety review.

What designations has the FDA granted for rhenium obisbemeda in the treatment of leptomeningeal metastases?

The FDA has granted Fast Track designation and Orphan Drug Designation for rhenium obisbemeda for the treatment of leptomeningeal metastases.

How many clinical trial sites were added to the ReSPECT-LM trial over the last year?

Five new clinical trial sites were added to the trial over the last year, bringing the total number of sites to seven.

What is the source of funding for the ReSPECT-LM program by Plus Therapeutics, Inc.?

The ReSPECT-LM program is funded in part by a 3-year $17.6M grant from the Cancer Prevention & Research Institute of Texas (CPRIT).