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Phase 3 study of ZL-1310 versus topotecan hydrochloride in patients with relapsed small cell lung cancer

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on adults with Small Cell Lung Cancer that has returned after previous therapy. One group will receive an experimental medicine called ZL-1310, which is designed to target a protein called DLL3 on cancer cells and deliver a cell‑killing payload. The other group will receive a standard chemotherapy drug known as topotecan hydrochloride, which can be taken as a pill or given through a vein (intravenous). “Relapsed” means the cancer has come back, and “antibody drug conjugate” refers to a lab‑made antibody that carries a drug directly to cancer cells.

The purpose of the trial is to compare how well the new medicine works against the standard treatment in shrinking tumors and helping patients live longer. Participants will be randomly assigned to one of the two treatment arms and will receive the assigned therapy in repeated cycles every few weeks. Throughout the study, doctors will perform regular safety checks, blood tests, and imaging scans to see how the disease responds, and they will record any side effects that occur.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessments

    After joining the study, you undergo a series of baseline assessments that include a physical examination, blood tests, and imaging studies to document the current status of small cell lung cancer.

    The results are used to determine eligibility for the study and to provide a reference point for future comparisons.

  2. Step 2

    Randomization to treatment group

    Based on the study protocol, you are randomly assigned to receive either the investigational drug zl-1310 or a comparator therapy known as topotecan hydrochloride.

    The assignment is made by the study team and you are not involved in the decision.

  3. Step 3

    Initiation of study medication

    If assigned to zl-1310, the drug is given by intravenous infusion at a dose of 1.60 mg/kg (milligrams per kilogram of body weight). the infusion is administered on day 1 of each treatment cycle, and cycles are repeated every three weeks unless the study doctor decides otherwise.

    If assigned to the comparator, you receive topotecan hydrochloride either orally or by intravenous injection, depending on the investigator’s choice:

    – oral formulation: 2.30 mg/m2 (milligrams per square meter of body‑surface area) taken each day for five consecutive days in a cycle.

    – intravenous formulation: 1.50 mg/m2 given on each of five consecutive days in a cycle.

    The chosen regimen is repeated every three weeks, matching the schedule of the investigational arm.

  4. Step 4

    Regular monitoring during treatment

    Before each new cycle, you undergo blood tests and a physical check to assess safety and organ function.

    Imaging studies (such as CT scans) are performed approximately every six weeks to evaluate tumor size and determine if the disease is responding to treatment.

    Any side effects are recorded and graded according to standard criteria.

  5. Step 5

    Assessment of tumor response

    The imaging results are reviewed by an independent central reviewer using the recist v1.1 criteria, which classify the change in tumor size as complete response, partial response, stable disease, or progressive disease.

    The same criteria are also applied by the treating investigator for additional reference.

  6. Step 6

    Continuation or discontinuation of therapy

    Treatment cycles continue as long as the disease does not progress and side effects remain manageable.

    The study protocol allows discontinuation of the medication if there is documented disease progression, unacceptable toxicity, or if the study doctor determines that further treatment is not beneficial.

  7. Step 7

    Post‑treatment follow‑up

    After the last dose of study medication, you enter a follow‑up phase during which survival and long‑term safety are monitored.

    Follow‑up visits occur every three months and include a physical exam, blood tests, and imaging to track overall survival and any late side effects.

Who can join the trial?

9 criteria

  • You must have a laboratory test (such as a tissue sample examined under a microscope) that confirms you have Small Cell Lung Cancer (SCLC); other types of lung cancer are not allowed.
  • You need to have already received a first‑line platinum‑based therapy (a type of chemotherapy that contains a platinum drug) – with or without an immune checkpoint inhibitor (anti‑PD‑(L)1) – and your cancer must have gotten worse during or after that treatment. No later lines of treatment are allowed except for a specific drug called tarlatamab.
  • Your tumor must be measurable on scans, meaning doctors can track its size using standard criteria called RECIST v1.1.
  • If you have had cancer spread to the brain or spinal cord (central nervous system (CNS) metastases), those spots must have been treated and currently be stable.
  • If you have untreated brain or spinal cord metastases, they must not be causing symptoms and you must not need steroids, anti‑seizure medicines, or local treatments for them.
  • Your overall health and ability to carry out daily activities must be rated as 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) performance status scale (0 = fully active, 1 = restricted but able to care for yourself).
  • You should have a life expectancy of at least three months.
  • Your blood tests and organ checks must show that your organ and marrow function are adequate (within normal limits).
  • You must be willing to have a new tumor biopsy taken or to give a previously stored tumor tissue sample for testing before the study starts.

Who cannot join the trial?

5 criteria

  • Had more than one previous course of systemic therapy (treatment that goes through the bloodstream) for small cell lung cancer, except for the drug tarlatamab.
  • Previously received an antibody‑drug conjugate (ADC) that contains a topoisomerase I inhibitor (a drug that blocks DNA replication).
  • Has a past or current history of non‑infectious interstitial lung disease (ILD) or pneumonitis that needed corticosteroids (steroid medicines), or any suspected ILD/pneumonitis that cannot be ruled out by imaging.
  • Has severe lung problems, such as a resting oxygen saturation below 90% on room air, or a history of lung disease, autoimmune or inflammatory disorders affecting the lungs, removal of a lung (pneumonectomy), or needs continuous supplemental oxygen.
  • Received radiation treatment (radiotherapy) to the chest within the last 4 weeks, to other parts of the body within the last 2 weeks, or received more than 30 Gy (gray) of chest radiation before the first study dose.
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Investigated drugs

  • Topotecan

    is a chemotherapy medicine that is used as a standard treatment option chosen by doctors for people whose small cell lung cancer has come back after previous therapy. In this study it may be taken by mouth or given through a vein, depending on the doctor's decision. The drug works by stopping cancer cells from growing and dividing, helping to shrink or control the tumor. It is used as the comparison (or “comparator”) to see how well the new drug works.

  • ZL-1310

    is an experimental medicine that targets a protein called DLL3 on the surface of small cell lung cancer cells. It is an antibody‑drug conjugate, which means it combines an antibody that seeks out the cancer cells with a chemotherapy payload that is released directly onto those cells. In the trial it is given as an infusion into a vein. Researchers are testing ZL‑1310 to see if it can shrink tumors and help patients live longer compared with the standard treatments.

What is already known about the treatment

  • Topotecan Hydrochloride

    This drug can be taken by mouth or given through an IV infusion, and the dose is calculated based on body surface area. It is an approved chemotherapy medicine that has been used for many years to treat small cell lung cancer and other cancers. It works by blocking an enzyme called topoisomerase‑I, which cancer cells need to copy their DNA, so the cells cannot grow or divide. It belongs to the class of topoisomerase inhibitors, a type of anticancer chemotherapy.

  • ZL‑1310

    ZL‑1310 is given as an IV infusion, with the amount adjusted to the patient’s weight. It is an experimental drug that is currently being studied in clinical trials for relapsed small cell lung cancer. The medicine is an antibody‑drug conjugate that seeks out the DLL3 protein on cancer cells, attaches to it, and then releases a cell‑killing payload directly inside the tumor. It is classified as a targeted therapy and an antibody‑drug conjugate.

Investigated diseases

Small Cell Lung Cancer - Small Cell Lung Cancer is a fast‑growing type of lung cancer that starts in the cells lining the airways. It usually begins in the central part of the lungs and can spread quickly to nearby lymph nodes and other organs. The disease often starts with symptoms such as coughing, shortness of breath, or chest pain. As it progresses, cancer cells may invade blood vessels and travel to distant sites like the brain, liver, or bones. The tumor may increase in size, causing worsening breathing problems and other discomfort.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522818-23-00Protocol codeZL-1310-003Estimated enrolment480 patientsSponsorZai Lab (US) LLC

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