Legend Biotech LB1908 Expands Dosing in Phase 1 for CLDN18.2 Solid Tumors
Clinical Design and Development Status
Legend Biotech Corporation (LEGN)'s LB1908, also known as LCAR-C18S, is an autologous CAR-T therapy targeting Claudin 18.2 (CLDN18.2) on tumor cells. NCT05539430 is a U.S. multi-center, single-arm, open-label Phase 1 dose-escalation and expansion study with a target enrollment of 56 patients. The study is currently Active, Not Recruiting, started in April 2023, and is expected to complete primary outcomes and conclude in December 2027. The current phase's key objective is to establish the recommended expansion dose (RDE) and recommended Phase 2 dose (RP2D).
Early Efficacy and Safety Signals
As of May 14, 2025, nine patients received 0.5 or 1.5 million CAR-positive T cells/kg. Among the eight evaluable patients, one achieved partial response (PR) and three had stable disease (SD). Cytokine Release Syndrome (CRS) occurred in 77.8% (7 patients), all Grade 1–2, and Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) was not observed. However, Grade 3 gastritis and gastric mucosal injury occurred in five patients, with one case classified as a Dose-Limiting Toxicity (DLT). On-target/off-tumor toxicity, where the therapy attacks CLDN18.2 in normal gastric mucosa, has emerged as a key constraint in development.
Patient Selection and Regulatory Status
Eligible patients must have CLDN18.2 expression of at least 1+ in ≥50% of tumor cells and have received at least one prior systemic therapy for advanced gastric cancer, gastroesophageal junction cancer, esophageal adenocarcinoma, or pancreatic adenocarcinoma. LB1908 received U.S. IND approval on June 1, 2022, and FDA Orphan Drug Designation on November 22, 2022. However, it is currently in Phase 1 and not yet an approved therapy. The evaluation separates myelosuppression from prior chemotherapy from CAR-T-specific toxicities, with steroid-based gastrointestinal toxicity mitigation being a key factor in preserving cell expansion and efficacy for subsequent dose decisions.
Market Potential and Competitive Landscape
The benchmark comparator is Astellas Pharma (4503.T)'s Vyloy (zolbetuximab-clzb), a CLDN18.2-targeting cytotoxic antibody approved by the FDA on October 18, 2024, as a first-line combination therapy for HER2-negative, CLDN18.2-positive advanced gastric and gastroesophageal junction cancers. In the post-treatment CAR-T space, CARsgen Therapeutics (2171.HK)'s satri-cel (satricabtagene autoleucel) has advanced to randomized Phase 2, placing it ahead of LB1908 clinically. The 2024 gastric cancer treatment market in the eight major countries was USD 4.70 billion, and the 2025 pancreatic cancer treatment market in the seven major countries is estimated at USD 2.6948 billion. While the commercial foundation is substantial, LB1908's differentiation will require proof of higher response rates and duration at higher doses, along with effective management of gastric mucosal toxicity.
LB1908 is Legend Biotech Corporation (LEGN)'s key solid tumor validation asset, aiming to expand CAR-T therapy beyond hematological malignancies to gastric, gastroesophageal junction, esophageal, and pancreatic cancers in a Phase 1 trial of 56 patients. While 77.8% of the initial nine patients experienced CRS, all were Grade 1–2 and no ICANS was observed, five patients experienced Grade 3 gastritis and gastric mucosal injury, with one DLT, which could directly limit dosing and the treatable patient population. In the short term, the 3 million cells/kg dose and expansion cohort will determine RP2D, objective response rate (ORR), and duration of response (DOR), which are key value drivers for the company. In the medium to long term, LB1908 will need to demonstrate superior efficacy over the FDA-approved marketed antibody Vyloy and the Phase 2 satri-cel in the USD 4.70 billion gastric cancer market. If reproducibility is confirmed in the USD 2.6948 billion pancreatic cancer market, Legend's single-target CAR-T platform value could significantly expand.
Source: ClinicalTrials.gov (api_ct)