Zai Lab’s Zoci Shows 82% Response Rate in Early Lung Cancer Study

Key Points

• Zai Lab’s zoci-plus-atezolizumab doublet produced an 81.8% confirmed response rate in 33 first-line extensive-stage small cell lung cancer patients, with an 81.9% six-month progression-free survival rate at the 1.6 mg/kg dose.
• Adding carboplatin increased the response rate to 92.3% but also led to more serious and Grade 3 or 4 toxicities, particularly neutropenia and thrombocytopenia.
• Zai Lab plans to launch a global Phase III trial by the end of 2026 comparing zoci plus a checkpoint inhibitor with chemotherapy plus immunotherapy, aiming to develop a chemotherapy-free frontline treatment.

Zai Lab NASDAQ: ZLAB presented early-stage data at the 2026 European Society for Medical Oncology meeting for zoci, its DLL3-targeted antibody-drug conjugate, in combination with atezolizumab, with or without carboplatin, for first-line extensive-stage small cell lung cancer.

Rafael Amado, Zai Lab’s president and head of global research and development, said the results support the company’s plans to advance zoci in frontline treatment. The company expects three potentially registrational trials for the program to be underway by the end of the year, including studies in second-line small cell lung cancer, second-line extrapulmonary neuroendocrine carcinoma and first-line small cell lung cancer.

Doublet Shows Early Response Activity

Pedro Rocha, a medical oncologist and clinical researcher at Vall d’Hebron University Hospital in Barcelona, reviewed findings from the Phase I study’s zoci-plus-atezolizumab doublet cohort. The study enrolled patients with extensive-stage disease, including patients with untreated brain metastases.

Among 33 patients who received zoci at 1.6 mg/kg with atezolizumab, 27 achieved a confirmed response, representing an objective response rate of 81.8%. Across the broader doublet population, the confirmed objective response rate was 81.4%, according to Rocha.

Responses generally emerged early. Of 35 responders, 34 had a response at their first post-baseline tumor assessment. For the initial 15 patients treated at the 1.6 mg/kg dose, who had at least 10 months of follow-up, median duration of response and median progression-free survival had not been reached. Two-thirds of those patients remained progression-free at the data cutoff.

For the full 33-patient 1.6 mg/kg cohort, six-month progression-free survival was 81.9%. Rocha contrasted that figure with a roughly 30% six-month progression-free survival rate reported for chemoimmunotherapy in the IMpower133 study, while noting that the zoci data remain early.

Triplet Produced Higher Response Rate, More Toxicity

Zoci also was evaluated alongside atezolizumab and carboplatin. The triplet cohort produced a confirmed objective response rate of 92.3%, with rapid and deep tumor reductions reported in the small patient group.

However, adding carboplatin increased toxicity. Rocha said serious drug-related adverse events, Grade 3 or 4 toxicities and treatment interruptions were more common with the triplet than with the doublet. The additional toxicity was primarily hematologic, including greater neutropenia and thrombocytopenia, which he said was consistent with expectations for platinum-based chemotherapy.

In the doublet cohort, no dose-limiting toxicities were observed during dose escalation. At the 1.6 mg/kg dose, 9.1% of patients experienced Grade 3 or higher adverse events attributed to zoci. The most common treatment-related events were anemia, nausea and leukopenia, mainly Grade 1 or 2. The company reported one case of Grade 1 interstitial lung disease, with no zoci-related treatment discontinuations or treatment-related deaths in that cohort.

Company Plans Chemotherapy-Free Phase III Study

Amado said Zai Lab plans to initiate a global Phase III study by the end of 2026 evaluating zoci plus a checkpoint inhibitor against chemotherapy plus immunotherapy. The company said the study could allow lurbinectedin maintenance treatment.

The company’s stated goal is to assess whether zoci can replace chemotherapy as part of a frontline treatment backbone. Amado said Zai Lab is also working with Boehringer Ingelheim and Amgen on potential combinations involving T-cell engagers, though those studies remain early.

Rocha said a chemotherapy-free frontline regimen could be attractive if an antibody-drug conjugate provides rapid tumor reduction while allowing patients to remain on treatment longer with manageable toxicity. He added that chemotherapy could remain available for later lines of treatment.

Zai Lab said its ongoing global second-line-plus small cell lung cancer study remains on track for enrollment, data analysis and a potential filing next year. Its potentially registrational extrapulmonary neuroendocrine carcinoma study is fully enrolled. The company also said it expects multiple program readouts over the next 12 to 18 months and anticipates its first potential U.S. biologics license application submission next year.

About Zai Lab (NASDAQ:ZLAB)

Zai Lab Ltd. NASDAQ: ZLAB is a biopharmaceutical company focused on discovering, developing and commercializing medicines for cancer and other serious diseases. Its research and development activities have included oncology, autoimmune and inflammatory disorders, neuroscience, infectious diseases and other areas of significant unmet medical need.

Founded in 2014, Zai Lab has built its business through a combination of internally developed programs and licensing or collaboration agreements with international pharmaceutical and biotechnology companies.

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