Zai Lab presents data from ZL-1310 study

Zai Lab (ZLAB) presented data from the ongoing global Phase 1a/1b study of ZL-1310, a next-generation antibody-drug conjugate, or ADC, at the EORTC-NCI-AACR, or ENA, Symposium 2024 in Barcelona, Spain, as an oral presentation during the plenary session. ZL-1310 is being tested in patients with previously treated extensive-stage Small Cell Lung Cancer, or ES-SCLC, after at least one prior platinum-based chemotherapy regimen. Data shared in the ENA presentation from the ongoing Part 1a monotherapy dose-escalation portion of the study included results from 25 patients across four dose cohorts. Nineteen patients had evaluable tumor assessments. Key efficacy results include: The ORR in patients with at least one post-treatment evaluation was 74%. ZL-1310 anti-tumor activity was demonstrated across all dose levels. Responses were seen in patients with DLL3 H-scores from 5. No response was observed in a patient whose tumor did not express DLL3. Across all cohorts, median length of follow up is 2.4 months making duration of response not estimable. Of the 14 responders, 13 remain on treatment with the longest patient ongoing at 6.5+ months. Of the six response-evaluable patients with baseline brain metastases, all achieved a partial response, or PR. One patient who progressed after prior DLL3 bi-specific therapy achieved PR at the first tumor assessment. Key safety findings include: ZL-1310 was well tolerated across all dose levels with the majority of treatment emergent adverse events, or TEAE, being Grade 1 or 2. One dose-limiting toxicity, or DLT, was observed at 2.4mg/kg. Grade 3 treatment-related adverse events occurred in five of the 25 patients; neutropenia was the most common grade 3 event, occurring in three of the 25 patients. Serious treatment-related adverse events occurred in two patients; three patients required dose reductions, and no patients discontinued treatment due to TEAE. All patients had progressed following standard platinum-based chemotherapy, and 92% of patients progressed after immune checkpoint inhibitors. Fifty-six percent had failed at least two prior lines of therapy. Twenty-eight percent of patients had brain metastases at baseline. At the time of the data cutoff, Oct. 10, 19 patients had at least one post-baseline tumor assessment per RECIST v1.1. DLL3 expression H-scores were assessed in 16 out of 19 patients.