Zai Lab’s Zocilurtatug Pelitecan (Zoci, Formerly ZL-1310) Demonstrates High Response Rates, Encouraging Durability and Well-Tolerated Safety Profile in First-Line Extensive-Stage Small Cell Lung Cancer

The platinum-free doublet had fewer severe treatment-emergent adverse events than the carboplatin-containing triplet in this early trial.

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• 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

Investor conference call and webcast to discuss data being presented at ESMO 2026 and zoci clinical trial plans scheduled today, October 23 at 8:00 a.m. ET / 8:00 p.m. HKT

SHANGHAI & CAMBRIDGE, Mass.--(BUSINESS WIRE)-- Zai Lab Limited (NASDAQ: ZLAB; HKEX: 9688), an innovation-driven, global biopharma company, today 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.

ESMO 2026 zoci poster details:

Title: ZL 1310 (DLL3 ADC) plus Atezolizumab ± Carboplatin in extensive-stage small cell lung cancer: Part 1b/1c results from Study ZL 1310-001
Session Title: SCLC
Date/Time: October 26, 2026; 12:00-12:45 CEST
Location: Poster Area – Hall 5
Poster Board Number: 3817P
Abstract Number: 1569

Details regarding the webcast and conference call are as follows:

Date/Time: Friday, October 23, 2026, at 5:00 a.m. PT / 8:00 a.m. ET / 8:00 p.m. HKT

Presenters: Rafael G. Amado, M.D., President, Head of Global Research and Development, Zai Lab; Pedro Rocha, M.D., Ph.D., MSc, Medical Oncology Department, Vall d’Hebron University Hospital

Registration available at:

Webcast presentation (preferred): https://edge.media-server.com/mmc/p/isgbbewu
Dial-in: https://register-conf.media-server.com/register/BI6b181d421fba49dc9171528aeda3974e

A replay will be available shortly after the call on the Company’s website at http://ir.zailaboratory.com.

About Zocilurtatug Pelitecan (zoci, formerly ZL-1310)

Zoci is a novel, potential first-in-class antibody-drug conjugate (ADC), that targets Delta-like ligand 3 (DLL3), a validated therapeutic target that is overexpressed in SCLC, making it a promising target for the treatment of these aggressive, lethal and difficult-to-treat malignancies. The DLL3 antigen is generally associated with poor clinical outcomes.

Zoci remains on track to become Zai Lab’s first global oncology launch. In addition to the Phase 3 combination trial in first-line extensive stage SCLC that Zai Lab is advancing toward initiation, the Company is also conducting the Phase 3 DLLEVATE study evaluating zoci in previously treated ES-SCLC vs. physician’s choice of chemotherapy, and a Phase 1/2 trial in neuroendocrine carcinomas (NECs) and other DLL3-positive solid tumors. Data presented at AACR 2026 from an ongoing Zai Lab Phase 1 trial of adults with previously-treated ES-SCLC demonstrate that zoci achieved meaningful intracranial efficacy, including in patients who have not received radiotherapy to the brain.

Earlier this year, Zai Lab entered into a global clinical trial collaboration with Amgen to evaluate zoci in combination with Amgen’s IMDELLTRA® (tarlatamab-dlle), a DLL3/CD3 bispecific T-cell engager (TCE), for ES-SCLC, and a clinical collaboration with Boehringer Ingelheim to evaluate zoci in combination with obrixtamig, a DLL3/CD3 bispecific TCE, for SCLC and other NECs.

About Zai Lab

Zai Lab Limited (NASDAQ: ZLAB; HKEX: 9688) is an innovative, research-based, commercial-stage biopharmaceutical company based in China and the United States. We are focused on discovering, developing, and commercializing innovative products that address medical conditions with significant unmet needs in the areas of oncology, immunology, neuroscience, and infectious disease. Our goal is to leverage our competencies and resources to positively impact human health.

For additional information about Zai Lab, please visit www.zailaboratory.com or follow us at www.linkedin.com/company/zai-lab or https://x.com/ZaiLab_Global.

Zai Lab Forward-Looking Statements

This press release contains forward-looking statements relating to our future expectations, plans, and prospects, for Zai Lab, including, without limitation, statements relating to our prospects and plans for developing and commercializing zoci, and the potential treatment of extensive-stage small cell lung cancer (ES-SCLC). All statements, other than statements of historical fact, included in this press release are forward-looking statements, and can be identified by words such as “aim,” “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “goal,” “intend,” “may,” “plan,” “possible,” “potential,” “will,” “would,” and other similar expressions. Such statements constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are not guarantees or assurances of future performance. Forward-looking statements are based on our expectations and assumptions as of the date of this press release and are subject to inherent uncertainties, risks and changes in circumstances that may differ materially from those contemplated by the forward-looking statements. We may not actually achieve the plans, carry out the intentions or meet the expectations or projections disclosed in our forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results may differ materially from those indicated by forward-looking statements as a result of various important factors, including but not limited to (1) our ability to successfully commercialize and generate revenue from our approved products, (2) our ability to obtain funding for our operations and business initiatives, (3) the results of our clinical and pre-clinical development of our product candidates, (4) the content and timing of decisions made by the relevant regulatory authorities regarding regulatory approvals of our product candidates, (5) risks related to doing business in China, and (6) other factors identified in our most recent annual and quarterly reports and in other reports we have filed with the U.S. Securities and Exchange Commission (SEC). We anticipate that subsequent events and developments will cause our expectations and assumptions to change, and we undertake no obligation to update or revise any forward-looking statements, whether as a result of new information, future events, or otherwise, except as may be required by law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release.

Our SEC filings can be found on our website at www.zailaboratory.com and on the SEC’s website at www.SEC.gov.

View source version on businesswire.com: https://www.businesswire.com/news/home/20261022534590/en/

For more information, please contact:

Investor Relations:
Christine Chiou / Cyan Liu
+1 (917) 886-6929 / +86 195 3130 8895
christine.chiou1@zailaboratory.com / cyan.liu@zailaboratory.com

Media:
Shaun Maccoun / Xiaoyu Chen
+1 (857) 270-8854 / +86 185 0015 5011
shaun.maccoun@zailaboratory.com / xiaoyu.chen@zailaboratory.com

Source: Zai Lab Limited

Key Terms

objective response rate medical

The objective response rate (ORR) is the percentage of patients in a clinical trial whose tumors measurably shrink or disappear according to preset rules. Investors use it as a quick, objective signal of a drug’s ability to produce a clear treatment effect—like counting how many plants visibly respond after applying a new fertilizer—and higher ORR can improve odds of regulatory approval, commercial success, and company valuation.

progression-free survival medical

Progression-free survival is the length of time during and after a treatment that a patient's disease does not get worse, measured from the start of treatment until the disease shows measurable signs of progression or the patient dies. Investors care because longer progression-free survival in clinical trials often signals that a drug is effective, improving chances of regulatory approval, market adoption, and revenue potential—think of it as a stopwatch showing how long a therapy can keep the illness at bay.

dose-limiting toxicities medical

Dose-limiting toxicities are the harmful side effects seen in early clinical trials that are severe enough to stop researchers from raising a drug’s dose. Like a car’s speed limiter marking the safe top speed, DLTs define the maximum tolerable dose, and they matter to investors because they determine whether a medicine can reach effective levels, influence development timelines, costs, and regulatory chances, and thus affect a drug’s commercial prospects.

antibody-drug conjugate medical

An antibody-drug conjugate is a targeted medicine that combines an antibody, which can identify specific cells, with a powerful drug designed to destroy those cells. This approach allows for precise treatment, minimizing damage to healthy tissue. For investors, developments in this area can signal advances in cancer therapies and potential growth opportunities in the biotech sector.

interstitial lung disease medical

A group of lung conditions that cause inflammation and scarring of the thin tissue between the air sacs, which makes it harder for oxygen to pass into the blood; imagine the lungs’ fine filters becoming stiff and less effective. Investors care because reports of interstitial lung disease can affect a drug’s safety profile, trigger regulatory warnings or label changes, and shift demand for treatments or create liability risks that influence a company’s valuation.