Merck Healthcare KGaA has initiated NCT07311603, a first-in-human interventional study evaluating M7437, an anti-Ly6E exatecan antibody-drug conjugate (ADC), in patients with advanced or metastatic solid tumors expressing Ly6E.

M7437 is designed to deliver a cytotoxic exatecan payload selectively to tumor cells via targeting Ly6E, an antigen overexpressed in several difficult-to-treat cancers. The Phase I/II trial aims to assess safety, tolerability, pharmacokinetics (PK), and preliminary clinical activity of M7437 in adults with unresectable disease refractory to standard therapies.

Study design and scope

• Status: Not yet recruiting (as of late December 2025)
• Phase: First-in-human, dose escalation and expansion
• Target enrollment: ~138 participants
• Tumor types eligible: Non-small cell lung cancer (NSCLC), triple-negative breast cancer (TNBC), epithelial ovarian cancer (EOC), squamous cell carcinoma of the head and neck (SCCHN), pancreatic ductal adenocarcinoma (PDAC), and gastric cancer (GC) with documented Ly6E expression
• Primary measures: Dose-limiting toxicities and treatment-emergent adverse events during dose escalation
• Secondary endpoints: Plasma drug levels, overall response per RECIST 1.1, and cardiac QTc changes

The study commenced January 2, 2026, at a site in Darmstadt, Germany, with primary completion anticipated by September 20, 2028, and overall completion by March 28, 2029.

Key takeaways

Ly6E (lymphocyte antigen 6 complex, locus E) is a member of the Ly6 family of cell-surface proteins involved in immune signaling and increasingly implicated in tumor biology. Recent reviews highlight the role of Ly6 family members, including Ly6E, in driving tumorigenesis and shaping clinical outcomes.

Drug development efforts targeting Ly6E are now concentrated on antibody-drug conjugates. The antigen is considered an attractive target because it is overexpressed in multiple solid tumors, including breast, lung, and pancreatic cancers, while showing limited expression in healthy tissues, raising the prospect of a favorable therapeutic index.

Merck’s M7437 is entering a still nascent field. At present the key rival is ZW327, being developed by Canada-based Zymeworks, which—like M7437—carries a topoisomerase I (TOP1) inhibitor payload. Preclinical and IND-enabling data presented at the 2025 AACR meeting suggested ZW327 demonstrates improved binding and internalization versus earlier benchmarks and has been engineered to be Fc-silent to reduce off-target toxicity.

The first clinical proof-of-concept for Ly6E targeting came from DLYE5953A (RG7841), an ADC developed by Roche/Genentech that used an MMAE (tubulin inhibitor) payload. Phase I studies published between 2020 and 2022 showed a manageable safety profile and a 12% partial response rate in patients with refractory solid tumors. While these results validated Ly6E as a viable target, the modest efficacy has driven the field toward second-generation Ly6E ADCs incorporating more potent TOP1 payloads, including M7437 and ZW327.