Plus Therapeutics Completes Type B Meeting With FDA Over Next Steps On REYOBIQ Pivotal Study Strategy For Leptomeningeal Metastases

Plus Therapeutics, Inc. (Nasdaq: PSTV) ("Plus" or the "Company"), a healthcare company developing and commercializing precision diagnostics and radiopharmaceuticals for central nervous system (CNS) cancers, announces the completion of a Type B meeting with the U.S. Food and Drug Administration (FDA) on next steps on REYOBIQ pivotal trial strategy for leptomeningeal metastases (LM). The meeting resulted in constructive discussion with the FDA regarding key elements of the potential pivotal study design for REYOBIQ in LM. Plus intends to incorporate the FDA's feedback in the current dose optimization trial and seek alignment with the FDA on a revised protocol, likely later this year. The company's goal is to be ready for a potential pivotal trial following completion of the current dose optimization trial and, ultimately, work towards the potential approval of REYOBIQ for patients affected by LM.

• Accelerated approval – FDA indicated that accelerated approval may be appropriate for the LM indication, but there are insufficient data to support the use of circulating tumor cells (CTCs) as an intermediate clinical endpoint. FDA and Plus discussed that additional steps would be necessary to validate CTCs as a surrogate endpoint to potentially support other future applications.
   
• Primary and key endpoints – FDA recommended that the study evaluate an endpoint with established clinical benefit, such as overall survival, while encouraging further study of patient reported outcomes and neurologic function as endpoints that could potentially support a marketing application. FDA and Plus aligned that CTCs could be considered for use as a secondary endpoint.
   
• Trial design and comparator group - FDA and Plus discussed a randomized controlled trial design approach and that the study may include an intrathecal chemotherapeutic as a comparator, as well as approaches to standardize the comparator and any additional interventions available under the trial protocol.
   
• Treated populations - FDA conveyed it may be reasonable to incorporate multiple histologies (i.e., multiple underlying disease etiologies) in a single trial.