FDA Grants Fast Track Designation to Zai Lab’s DLL3-Targeting ADC for epNECs

Zai Lab has received Fast Track designation from the FDA for zocilurtatug pelitecan (zoci; formerly ZL-1310), an investigational DLL3-targeting antibody-drug conjugate (ADC) being developed for patients with extrapulmonary neuroendocrine carcinomas (epNECs) following progression after first-line therapy.¹

The designation highlights growing regulatory interest in novel targeted therapies for aggressive neuroendocrine malignancies, an area where treatment options remain limited and prognosis is often poor. epNECs are rare, fast-growing tumors that originate outside the lungs and frequently demonstrate resistance to standard chemotherapy regimens.²

According to Zai Lab, the FDA’s Fast Track designation is intended to facilitate the development and expedite review of investigational therapies that address serious conditions and unmet medical needs.¹ Benefits of the program may include more frequent FDA interactions, eligibility for rolling review, and potential consideration for accelerated approval pathways.²

Expanding the Role of DLL3-Targeted Therapies

Zoci targets delta-like ligand 3 (DLL3), a protein highly expressed across multiple neuroendocrine tumors and associated with poor clinical outcomes.¹ The investigational ADC combines a humanized anti-DLL3 monoclonal antibody with a camptothecin-based topoisomerase 1 inhibitor payload designed to selectively deliver cytotoxic therapy to tumor cells.¹

The candidate was developed using Zai Lab’s TMALIN technology platform, which aims to improve payload delivery within the tumor microenvironment while potentially reducing off-target toxicity observed with earlier-generation ADCs.¹

“This is the second FDA Fast Track Designation for zoci, underscoring the significant potential of this investigational medication to provide an important new treatment option for patients with difficult-to-treat cancers that have few available therapies,” said Rafael G. Amado, MD, president and head of global research and development at Zai Lab, in the company announcement.¹

The latest designation follows a previous Fast Track designation granted in 2025 for extensive-stage small cell lung cancer (ES-SCLC), another DLL3-expressing malignancy.³

Clinical Data Support Continued Development

The FDA decision follows encouraging early-stage clinical findings presented at the 2026 American Association for Cancer Research (AACR) Annual Meeting. In a Phase 1b/2 study evaluating zoci in patients with previously treated epNECs and other selected solid tumors, investigators reported an objective response rate of 38.2%.⁴ Responses were observed across multiple tumor types, including gastroenteropancreatic neuroendocrine carcinomas, with investigators noting antitumor activity in a heavily pretreated patient population.⁴ The safety profile was reported to be generally consistent with prior studies in small cell lung cancer, with common adverse events including nausea, anemia, leukopenia, and vomiting.⁴

Zai Lab is currently advancing a broader global clinical development program for zoci, including studies in relapsed ES-SCLC and combination strategies involving immunotherapies and T-cell engagers.² Recent collaborations with companies including Amgen and Boehringer Ingelheim reflect increasing industry interest in DLL3-directed therapeutic approaches.²

ADC Momentum Continues in Oncology

The Fast Track designation adds to continued momentum surrounding ADC development in oncology, particularly for difficult-to-treat solid tumors. ADCs have become a major focus of cancer drug development as companies seek to improve therapeutic precision while minimizing systemic toxicity.

DLL3 has emerged as a particularly attractive target in neuroendocrine cancers because of its high tumor specificity and limited expression in healthy tissue.² As competition intensifies in the ADC space, regulatory designations such as Fast Track may help accelerate development timelines and strengthen investor confidence in emerging oncology programs.

For patients with epNECs, the designation may represent an important step toward expanding treatment options in a disease setting where survival outcomes remain poor and innovation has historically lagged behind more common tumor types.

References

1. Zai Lab Limited. (2026, May 11). Zai Lab receives U.S. FDA Fast Track designation for zocilurtatug pelitecan (Zoci), a DLL3-targeting ADC, for treatment of extrapulmonary neuroendocrine carcinomas (epNECs). Business Wire. https://www.businesswire.com/news/home/20260511041273/en/Zai-Lab-Receives-U.S.-FDA-Fast-Track-Designation-for-Zocilurtatug-Pelitecan-Zoci-a-DLL3-Targeting-ADC-for-Treatment-of-Extrapulmonary-Neuroendocrine-Carcinomas-epNECs
2. Zai Lab Limited. (2026, April 1). Zai Lab announces global clinical trial collaboration and supply agreement to evaluate novel DLL3 ADC, zocilurtatug pelitecan, in combination with a bispecific T-cell engager therapy. Zai Lab Investor Relations. https://ir.zailaboratory.com/news-releases/news-release-details/zai-lab-announces-global-clinical-trial-collaboration-and-supply/
3. Zai Lab receives U.S. FDA Fast Track designation for ZL-1310, a DLL3-targeted antibody-drug conjugate, for treatment of extensive-stage small cell lung cancer. (2025, May 19). Zai Lab Limited. https://ir.zailaboratory.com/news-releases/news-release-details/zai-lab-receives-us-fda-fast-track-designation-zl-1310-dll3
4. Fabbricatore, R. (2026, April 25). Zocilurtatug pelitecan displays meaningful responses in pretreated epNECs. Cancer Network. https://www.cancernetwork.com/view/zocilurtatug-pelitecan-displays-meaningful-responses-in-pretreated-epnecs