Plus Therapeutics (PSTV) 2026 AANS Annual Scientific Meeting presentation summary

Mechanism of action and preclinical data

• 186RNL is a nanoliposome-encapsulated radiotherapeutic delivering localized beta radiation, causing DNA damage over ~2mm and sparing healthy tissue.

• BMEDA chelation traps the isotope inside the liposome, ensuring superior retention and enhanced tissue distribution.

• Preclinical studies in animal models showed significant survival benefit and tumor reduction compared to controls.

Clinical need and disease background

• Leptomeningeal metastases are a fatal complication of advanced cancers, with ~110,000 US cases annually and no FDA-approved therapies.

• Standard treatments are palliative, with median survival of 3–8.7 months and 2-year survival of only 3%.

• 186RNL’s beta path length matches the cortical ribbon, enabling precise CSF irradiation with minimal deep-tissue exposure.

Phase 1 RESPECT-LM trial design and safety

• Single administration dose escalation via Ommaya reservoir, with primary objectives of safety and tolerability.

• 29 patients dosed over 6 cohorts; study completed with feasibility, safety, and efficacy signals.

• Recommended Phase 2 Dose (RP2D) determined at 44.1 mCi; most adverse events were mild or moderate, with few serious events.

• Excellent target/off-target absorbed dose ratio (>100:1), with low radiation exposure to critical organs.