Zai Lab's Zoci Shows Promising Results in Treating Small Cell Lung Cancer

Zai Lab, an innovation-driven, global biopharma company (NASDAQ: ZLAB; HKEX: 9688), has announced promising results from its Phase 1b clinical trial evaluating zocilurtatug pelitecan (zoci, formerly ZL-1310) in combination with atezolizumab for first-line treatment of extensive-stage small cell lung cancer (ES-SCLC). The trial, which used a recommended Phase 3 dose (RP3D) of 1.6 mg/kg, showed that zoci plus atezolizumab achieved a confirmed objective response rate (ORR) of 81.8% (27/33) and an estimated 6-month progression-free survival rate of 81.9% (n=33) in patients with 1L ES-SCLC.

Among patients with at least six-months follow-up (n=15) treated at 1.6 mg/kg zoci plus atezolizumab, median progression-free survival and median duration of response were not yet reached after a median follow-up of 10 months. Ten of these 15 patients (66.7%) remained free from disease progression or death at the data cut-off. The most common treatment-emergent adverse events (TEAEs) related to zoci at 1.6 mg/kg and of all grades (≥20%) were anemia (48.5%), nausea (36.4%), leukopenia (30.3%), decreased appetite, ALT increase, neutropenia (27.3% each), and lymphopenia (21.2%). The majority of AEs were Grade 1 or 2 and non-serious. At the 1.6 mg/kg dose, Grade ≥3 AEs related to zoci occurred in 3/33 (9.1%) patients, there were no treatment-related discontinuations, and only one Grade 1 interstitial lung disease (ILD) / pneumonitis.

In a separate arm of the trial, patients who received the triplet regimen of zoci in combination with atezolizumab and carboplatin as first-line therapy (n=13) demonstrated a high ORR (92.3%), with a median progression-free survival (mPFS) of 8.4 months (95% CI: 3.7-NA) and a median duration of response (mDOR) of 7.7 months (2.6, NA) across all dose levels. Compared with the doublet regimen, the triplet therapy was associated with more frequent Grade ≥3 TEAEs, including study-drug related hematological AEs, and a higher rate of dose interruptions. Grade ≥3 TEAEs for the doublet 1.6 mg/kg dose was 21.2%; Grade ≥3 TEAEs for the triplet across all doses was 76.9%.

The results of this trial are particularly encouraging given that today's standard of care for first-line SCLC is a checkpoint inhibitor plus chemotherapy, which delivers a 60-70% response rate, an mPFS of about 5 months, and is associated with Grade >3 treatment-related AEs around 60%. A regimen such as zoci, combined with an immune-oncology (IO) or other novel agents that are free of platinum chemotherapy, could offer better tolerability, allow longer treatment duration compared to the typical four to six cycles of platinum-based induction chemotherapy, and improve control of brain metastases.

Zai Lab is preparing to initiate a global Phase 3 randomized study evaluating a zoci and IO regimen in first-line treatment of ES-SCLC by year-end 2026. The company will discuss the data being presented at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain, and zoci clinical trial plans during an investor conference call and webcast scheduled today, October 23, at 8:00 a.m. ET / 8:00 p.m. HKT.