Plus Therapeutics has completed subject enrolment in the second cohort of the ReSPECT-LM Phase I/IIa dose escalation clinical trial evaluating rhenium (186Re) obisbemeda to treat leptomeningeal metastases (LM).

The sequential cohort, multicentre, open-label, single dose, dose escalation ReSPECT-LM trial uses a modified Fibonacci 3+3 study design.

It has been designed for assessing the maximum tolerated and feasible dose, and the safety and efficacy of a single rhenium (186Re) obisbemeda administration through an intraventricular catheter for LM after standard surgical, radiation, and/or chemotherapy treatment.

The incidence and severity of adverse events/serious adverse events and dose limiting toxicities are the study’s primary endpoints.

Secondary endpoints of the trial include duration of response, overall response rate, progression free survival, and overall survival.

Plus Therapeutics chief medical officer and SVP Norman LaFrance said: “Based on the significant clinical need in LM and promising early data, we continue to see increasing interest from top US cancer centres in the ReSPECT-LM Phase I/IIa trial.

“Next steps, following the Data and Safety Monitoring Board (DSMB) review anticipated next month, will be completing enrolment in the Phase I/Part A, followed by a meeting with the US FDA to consider dose expansion in the Phase I/Part B trial.”

Additionally, preliminary results from Phase I/Part A are expected in the second half of this year.

Phase I data from the ReSPECT-LM trial demonstrated that a single administered rhenium (186Re) obisbemeda dose was safe, feasible, and well-tolerated across two dosages in four patients from the first and second cohorts.

The Cancer Prevention & Research Institute of Texas (CPRIT) provided a three-year $17.6m grant for ReSPECT-LM.

Rhenium (186Re) obisbemeda received Fast Track designation from the US Food and Drug Administration for the treatment of LM, a rare cancer complication in which the disease spreads to the cerebrospinal fluid (CSF) and central nervous system.

The new, injectable radiotherapy has been specifically formulated for delivering highly targeted, high dose radiation to CNS tumours.