Y-mAbs Therapeutics (YMAB) Status Update summary

Strategic Vision and Platform Development

• Focus on pioneering next-generation immunotherapy and radiopharmaceutical platforms, aiming to transform patient care in oncology and beyond, with minimal off-target effects and a fully operational theranostic platform leveraging proprietary radiohaptens for isotope modularity.

• Business realigned into two units: DANYELZA and Radiopharmaceuticals, with increased organizational focus, new executive leadership, and a mission to maximize Danyelza's potential and accelerate the SOTTA-PRIT platform.

• Five strategic enablers guide growth: pre-targeting to reduce off-target toxicity, a theranostic platform, multi-isotope modularity, strategic R&D investment, and enhanced physician participation throughout the treatment journey.

• SOTTA platform enables in-patient assembly of protein and radioisotope, reducing manufacturing costs and leveraging existing physician infrastructure.

• Investment strategy prioritizes development over capital expenditures, emphasizing physician participation.

Clinical Trial Progress and Safety Findings

• Part A of Phase 1 Trial 1001 for GD2 SOTTA/GD2-SADA-177Lu-DOTA met its primary safety endpoint, demonstrating safety and tolerability across all dosing cohorts, with no dose-limiting toxicities or treatment-related serious adverse events; most adverse events were mild to moderate.

• Pharmacokinetics of GD2 SOTTA protein and Luzoda radiohaptin were predictable, dose-dependent, and matched preclinical expectations, supporting tailored clearance intervals.

• 22 patients enrolled; expanded tumor uptake analysis revealed 16 with uptake, more than initially identified, supporting broader patient selection.

• Protocol limitations excluded some tumors with uptake from evaluation; future trials will use central review and advanced imaging to assess all lesions.

• No pain historically associated with anti-GD2 therapies was observed.

Dosimetry, Molecule Optimization, and Platform Enhancements

• Dosimetry indicated the optimal therapeutic index was not reached, informing future study design and molecule optimization.

• Preclinical studies led to selection of Proteus, a universal radiohapten enabling modular use of multiple isotopes, including alphas and PET tracers, and is in GMP manufacturing for clinical trials.

• Improved GD2-SADA molecules with higher tumor uptake identified in preclinical models; to be incorporated into a bridge study in 1H 2026.

• IND amendment planned to incorporate Proteus into Trial 1001; Bridge study to assess safety and therapeutic index in 1H 2026, with data in 2H 2026.

• Dose escalation portion (Part B) of Trial 1001 expected to launch in 1H 2027, with data in 2H 2027.