At the recommended Phase 3 dose (RP3D) of 1.6 mg/kg, zoci plus atezolizumab achieved a confirmed objective response rate of 81.8% (27/33) and an estimated 6-month progression-free survival rate of 81.9% (n=33) in 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

-  Zoci plus atezolizumab therapy was well-tolerated; Grade >3 AEs related to zoci occurred in 9.1% (3/33) of patients treated at 1.6mg/kg

-  Global, randomized Phase 3 study in 1L ES-SCLC expected to initiate by year-end 2026

Zai Lab Limited (NASDAQ: ZLAB; HKEX: 9688), an innovation-driven, global biopharma company, shared the first data from a global Phase 1b clinical trial evaluating zocilurtatug pelitecan (zoci, formerly ZL-1310) in combination with atezolizumab with and without carboplatin as first-line treatment for extensive-stage small cell lung cancer (ES-SCLC). The data will be presented at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain.

"Despite advances in treatment, extensive-stage small-cell lung cancer remains a devastating disease, with many patients experiencing disease progression within approximately five months of initiating standard first-line treatment," said Rafael G. Amado, M.D., President, Head of Global Research and Development at Zai Lab. "The high confirmed response rate, encouraging durability, and well-tolerated safety profile we are seeing with a standard chemotherapy-free regimen are particularly compelling. We believe zoci's combination of efficacy and safety positions it to become an ADC backbone of choice in small-cell lung cancer, including in combination with immunotherapies. We are preparing to initiate a global Phase 3 trial of zoci and an Immuno-Oncology (IO) regimen and continue to evaluate the potential of combinations with T-cell engagers and IO."

Zoci 1.6 mg/kg plus atezolizumab (n=33)

Results, as of the September 2026 data cut-off to be shared at ESMO show that among patients who received the zoci 1.6 mg/kg and atezolizumab doublet every three weeks (n=33):

• Patients achieved a confirmed objective response rate (ORR) of 81.8% (95% CI: 64.5–93.0) by investigator assessment.
• The six-month progression-free survival (PFS) rate was 81.9%.
• Among patients with at least six-months follow-up (n=15) treated at 1.6 mg/kg zoci plus atezolizumab:  
  • Responses were highly durable, with median progression-free survival (mPFS) not yet reached after a median follow-up of 10 months, indicating the majority of patients continue to benefit from treatment.  
  • Ten of these 15 patients (66.7%) remained free from disease progression or death at data cut-off, with median duration of response (mDOR) for these 15 patients also not yet reached.
• Zoci plus atezolizumab demonstrated a favorable safety profile over a chemo plus IO regimen by indirect comparison. The doublet did not have dose-limiting toxicities observed during dose escalation. 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.  

Zoci plus atezolizumab and carboplatin (n=13; three dose levels)

• Patients in the trial who received the triplet regimen of zoci in combination with atezolizumab and carboplatin as first-line therapy (n=13) also demonstrated a high ORR (92.3%), with an mPFS of 8.4 months (95% CI: 3.7-NA) and mDOR of 7.7 months (2.6, NA) across all dose levels, which included two dose levels of zoci and two dose levels of carboplatin.
• 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%.

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 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. 

"The zoci and atezolizumab doublet demonstrated substantial early antitumor activity with high, durable responses and a favorable safety profile, which are very encouraging results for patients with extensive-stage small cell lung cancer," said Pedro Rocha, M.D., Ph.D., study investigator and medical oncologist at Vall d'Hebron University Hospital in Barcelona, Spain. "Importantly, this platinum-free regimen may allow patients to stay on treatment longer with potentially fewer side effects. These results support further exploration of zoci in combination regimens. I look forward to seeing how this profile evolves as the clinical program advances."

Based on the data from this trial, 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.