Lamassu Biotech Presents Initial Safety and Pharmacokinetic Data for MDM2 Inhibitor SA53 from First-in-Human Phase 1/2a Study at ESMO Congress 2026

No dose-limiting toxicities and no Grade ≥2 treatment-emergent adverse events through four dose levels; Plasma exposures exceed those predicted by nonclinical PK/PD modeling to be pharmacologically active

MADRID, Oct. 26, 2026 /PRNewswire/ -- Lamassu Biotech today announced initial safety and pharmacokinetic data from the ongoing first-in-human Phase 1/2a clinical trial (LB-SA53-101) of SA53, an oral MDM2 inhibitor, at the European Society for Medical Oncology (ESMO) Congress 2026.

Across four single-patient dose-escalation cohorts (0.054 to 0.44 mg/kg/day on a 3-day dosing schedule), SA53 has produced no dose-limiting toxicities (DLTs) and no Grade ≥2 treatment-emergent adverse events. MDM2 inhibition has shown antitumor activity by restoring the body's natural p53 tumor-suppression pathway. Earlier MDM2 inhibitors have been limited by severe, dose-dependent hematologic toxicities, most notably thrombocytopenia. In this initial dose escalation, SA53 has reached plasma exposures predicted by nonclinical modeling to be pharmacologically active without dose-limiting toxicity.

The findings were presented in Madrid by Peter Anderson, MD, PhD, an investigator on the trial at Cleveland Clinic.

Study Highlights:

• No Dose-Limiting Toxicities: No DLTs, no Grade ≥2 treatment-emergent adverse events, and no serious adverse events (SAEs) through 0.44 mg/kg/day.
• Hematologic Profile: Platelet nadirs were Grade 1 or lower, and neutrophil counts remained within normal limits in all patients.
• Pharmacokinetics: Cmax increased approximately dose-proportionally across cohorts, and plasma exposures at the current dose level exceed those predicted by nonclinical PK/PD modeling to be pharmacologically active.

"Targeting the MDM2-p53 interaction has long held therapeutic promise, but drug development across this class has historically been limited by severe systemic toxicities," said Greg Palmer, PhD, Co-founder and Chief Scientific Officer of Lamassu Biotech. "Our initial data shows that SA53 has reached exposures predicted to be pharmacologically active without dose-limiting toxicities. These early results support continued dose escalation toward defining the recommended Phase 2 dose."

SA53 is an investigational oral small molecule designed to selectively inhibit MDM2, thereby reactivating the wild-type p53 tumor suppressor protein, often termed the "Guardian of the Genome." Functional, wild-type p53 is preserved in roughly half of human cancers. An MDM2 inhibitor that avoids the historical serious class toxicities could therefore offer therapeutic utility across a broad cancer patient population.

The Phase 1 dose-escalation portion of the multicenter Phase 1/2a study remains ongoing. It aims to establish the maximum tolerated dose and recommended Phase 2 dose (RP2D) and to further characterize preliminary single-agent antitumor activity. Patient screening and enrollment are active.

About Lamassu Biotech
Lamassu Biotech is a clinical-stage biopharmaceutical company focused on developing targeted small-molecule therapeutics for high-unmet-need oncology and metabolic indications. The company's lead pipeline programs include SA53, a targeted MDM2 inhibitor in Phase 1/2a development for p53 wild-type cancers, and RABI-767, a lipase inhibitor advancing in clinical trials and animal health. Working in close collaboration with premier medical research institutions, Lamassu accelerates bedside delivery of precision medicines. For more information, visit LamassuBiotech.com.

Contact:
Bob Driscoll
[email protected]
1-716-307-7406

SOURCE Lamassu Biotech