Zai Lab expands ZL-1310 trial to 166 patients after 38.2% ORR in NEC data
The enrollment increase follows preliminary Phase 1b data showing a 38.2% response rate in extrapulmonary neuroendocrine carcinoma, but the trial has changed primary completion dates twice and grown enrollment three times since March 2025.
Executive Summary
- Zai Lab (Hong Kong), Ltd. raised the anticipated enrollment for its ZL-1310 (zocilurtatug pelitecan) trial in neuroendocrine carcinoma from 112 to 166 patients, the second target increase since the study opened in 2025 Press ReleasePress ReleaseJul 7, 2026.
- The increase follows preliminary Phase 1b results the company presented at AACR 2026 showing a 38.2% objective response rate and 55.9% disease control rate in 34 evaluable, heavily pretreated extrapulmonary NEC patients.
- FDA granted zoci Fast Track designation on May 11, 2026 for extrapulmonary neuroendocrine carcinoma progressing after first-line therapy, adding a formal regulatory signal beside the clinical one.
- AppliedXL's protocol stability tool labels the trial 'Unstable,' citing two primary completion date changes and a cumulative 304-day delay, alongside a critical risk score tied to the repeated enrollment target changes.
- No results have posted to ClinicalTrials.gov, the AACR data is company-flagged as immature, and the Phase 2 primary ORR endpoint that will decide the drug's fate has not yet been read out.
The enrollment move
Zai Lab lifted the anticipated enrollment for NCT06885281 to 166 patients on July 7, 2026, up from 112 patients set five months earlier and 86 patients at the trial's original filing Press ReleasePress ReleaseJul 7, 2026. The trial, a Phase 1b/2 open-label study of ZL-1310 (zocilurtatug pelitecan, known as zoci) in tumors including neuroendocrine carcinoma, has now logged two separate enrollment increases and two primary completion date changes since it launched in March 2025. The primary completion date has moved from October 2026 to December 2026 to August 2027, a cumulative slip AppliedXL's registry-based risk tool puts at 304 days.
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
The data prompting it
The expansion follows preliminary Phase 1b results Zai Lab presented at the AACR Annual Meeting 2026, with a data cutoff of February 18, 2026. In 34 evaluable, pretreated patients with extrapulmonary neuroendocrine carcinoma, the confirmed objective response rate reached 38.2% (13/34) and the disease control rate reached 55.9% (19/34). Across the broader safety population of 58 patients, the only Grade 3 or higher treatment-related adverse event occurring in more than one patient was a decrease in neutrophil count, at 5.2% (3/58). AppliedXL's own event classification flags the underlying data as immature, and the company's results-confidence field for this disclosure is marked false, meaning the numbers come from an early, non-registrational readout rather than the trial's registered primary endpoint.
Regulatory context
The FDA granted zoci Fast Track designation on May 11, 2026, specifically for extrapulmonary neuroendocrine carcinomas following progression on standard first-line therapy. Fast Track allows rolling review submissions and more frequent FDA meetings; AppliedXL's designation interpretation notes it carries an approval rate of roughly 80% historically, a weaker signal than Breakthrough Therapy designation but still constructive. Zai Lab has said it is engaging with health authorities on a registrational path for this indication and plans three registration-enabling studies across second-line SCLC, first-line SCLC, and extrapulmonary NEC by the end of 2026, though the current trial itself remains classified as non-registrational on ClinicalTrials.gov.
The operational tension
AppliedXL's risk assessment for this trial lands at a critical risk score of 100 out of 100, driven by the repeated primary completion date changes, the cumulative delay, and two rounds of enrollment target increases of 30.2% and 48.2% respectively. The trial's protocol stability label reads 'Unstable,' with 3.31 registry change events per year against 4 total change events logged since inception. Growing a trial's enrollment target after a favorable early readout is a common sponsor response, expanding the dataset behind a promising signal, but the frequency of completion-date and enrollment changes here also fits a pattern AppliedXL's landscape tool separately labels 'Struggling in easy territory': a favorable competitive landscape paired with operational execution difficulty.
Competitive standing
No trial in AppliedXL's competitive landscape qualifies as a direct comparator to ZL-1310 in neuroendocrine carcinoma; the dossier's comparator set marks every named peer, including Suzhou Zelgen's Phase 3 ZG006 and Phanes Therapeutics' Peluntamig, as mechanistically distinct DLL3-directed assets rather than same-target rivals. ZL-1310's own target remains undisclosed in the registry, which is why the first-in-class question cannot be resolved either way; the dossier attributes this to an unknown lead target rather than to a validated absence of competition. The broader indication landscape carries 22 trials and 8 active studies totaling 1,260 enrolled patients, concentrated in small cell lung cancer and neuroendocrine carcinoma across DLL3, SEZ6, VEGFR, and mTORC1 mechanisms.
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.