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A study to evaluate the safety and effectiveness of PTT-4256 and nivolumab in patients with solid tumors.

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What is this trial about?

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

This study focuses on individuals with solid tumours, which are types of cancer that form lumps or masses in the body. The purpose of the study is to evaluate the safety and effectiveness of the experimental drug PTT-4256. This medication may be used alone or in combination with nivolumab, a type of treatment known as a PD-1 inhibitor that helps the immune system recognize and attack cancer cells.

During the study, participants may receive PTT-4256 as an oral tablet. If the combination treatment is used, nivolumab will be administered through an infusion, which is a method of delivering medication directly into a vein. The research involves observing how the body processes these drugs and monitoring for any side effects to determine the best possible dose for patients.

The research process

The trial runs in 3 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Participation in the study

    The study begins with the administration of ptt-4256, which is taken as a tablet by mouth.

    The ptt-4256 may be administered alone or in combination with opdivo (nivolumab), which is a solution for infusion delivered into a vein.

  2. Step 2

    Monitoring and assessment

    Health status is monitored by tracking adverse events, which are any unwanted or harmful medical occurrences during the trial.

    The response of the solid tumours is evaluated using imaging, such as scans, to check for changes in the size or activity of the tumours.

  3. Step 3

    Follow-up

    After the active treatment period, overall survival is monitored through telephone follow-ups conducted every 3 months.

Who can join the trial?

18 criteria

  • You must be 18 years of age or older.
  • You must provide a tumor tissue sample, which is a piece of the tumor used for testing. This sample must be a biopsy (a procedure where a small piece of tissue is removed) rather than a cytological sample (a sample of individual cells, such as from a needle aspiration).
  • The tissue sample must be preserved in a way that allows for testing, specifically as a formalin-fixed, paraffin-embedded (FFPE) block or on unstained slides.
  • For those with clear cell renal cell carcinoma (ccRCC) or papillary renal cell carcinoma (pRCC), the cancer must be unresectable (cannot be removed by surgery), locally advanced (has spread to nearby areas), or metastatic (has spread to other parts of the body).
  • For those with head and neck squamous cell carcinoma (HNSCC), the cancer must be located in the oral cavity, pharynx, or larynx and cannot be treated with the intent to cure through surgery or radiation.
  • Patients with HNSCC must have documentation regarding p16 status, which is a test used to determine if the tumor is related to the human papillomavirus (HPV).
  • You must have measurable disease, meaning the tumors can be clearly seen and measured on medical imaging like scans.
  • You must have an ECOG performance status of 0 or 1, which is a scale used by doctors to measure how well you can perform daily activities and your overall physical health.
  • The doctor must estimate that you have a life expectancy of at least 3 months.
  • You must have adequate blood counts, including enough hemoglobin (the protein in red blood cells that carries oxygen), neutrophils (a type of white blood cell that helps fight infection), and platelets (cells that help blood clot).
  • You must have healthy liver function, as measured by levels of bilirubin and liver enzymes known as AST and ALT.
  • You must have healthy kidney function, measured by the estimated glomerular filtration rate (eGFR), which shows how well your kidneys filter waste from your blood.
  • You must not have had a blood or platelet transfusion within 7 days before being screened for the study.
  • If you are a woman of childbearing potential, you must have a negative pregnancy test and agree to use highly effective contraception (methods to prevent pregnancy) during the study and for a set period after the last dose of the study drug.
  • Women who are not of childbearing potential must be confirmed as postmenopausal (no periods for at least 12 months) or have undergone specific surgeries to prevent pregnancy.
  • Men must either be surgically sterile (such as having had a vasectomy) or agree to use barrier contraceptive methods (like condoms) along with another highly effective method if they have sexual contact with a woman who can become pregnant.
  • You must provide written informed consent, which means you have read the study information and officially agreed to participate.
  • Your cancer must have progressed (continued to grow or spread) despite receiving standard treatments, such as PD-1/PD-L1 inhibitors (a type of immunotherapy) or VEGF TKIs (a type of targeted therapy).

Who cannot join the trial?

25 criteria

  • You cannot participate if you are unable or unwilling to follow the study rules, including the study procedures or taking the study drug (the medicine being tested) by mouth.
  • You are excluded if you have a history of primary immunodeficiency (a condition where your immune system cannot protect your body), have had a bone marrow transplant, or have received a solid organ transplant.
  • You cannot take part if you have used systemic immunosuppressive medication (medicines that lower your body's ability to fight infection) at a high dose within 14 days before the first dose of the study drug.
  • People with an active Hepatitis B or Hepatitis C infection are not eligible.
  • You are excluded if you have an active HIV infection, unless your CD4+ T-cell count (a type of white blood cell that helps fight infection) is at a certain level, your viral load (the amount of virus in your blood) is undetectable, and you are on stable antiretroviral therapy (medicine to treat HIV).
  • You cannot participate if you have an active infection that requires antibacterial (medicine for bacteria), antiviral (medicine for viruses), or anti-fungal (medicine for fungi) treatment.
  • People with significant cardiovascular disease (heart or blood vessel problems) are excluded, such as heart failure, unstable angina (chest pain), myocardial infarction (heart attack), serious arrhythmia (irregular heartbeat), stroke, or pulmonary embolism (a blood clot in the lung) within the last 4 months.
  • You are excluded if your ECG (a test that records the electrical activity of your heart) shows a specific abnormal rhythm called prolonged QT interval, or if you have a history of torsades de pointes (a specific type of dangerous irregular heartbeat).
  • You cannot participate if you have interstitial lung disease (scarring or inflammation in the lungs) or pneumonitis (inflammation of lung tissue) that could make it hard to tell if the study drug is affecting your lungs.
  • You are excluded if you have had or are scheduled for major surgery within 28 days before the first dose of the study drug.
  • You cannot join if you have any other severe or uncontrolled medical, surgical, psychiatric, or social conditions that might make participation unsafe.
  • People with leptomeningeal disease (cancer that has spread to the lining of the brain or spinal cord) or untreated cancer in the central nervous system (the brain and spinal cord) are excluded.
  • You cannot participate if you have used other investigational medicinal products (experimental medicines) within 2 weeks before the study drug.
  • You are excluded if you have received a live vaccine within 28 days of the first dose.
  • People with active or suspected alcohol or drug abuse that might interfere with the study are not eligible.
  • You are excluded if you have gastrointestinal conditions (stomach or bowel issues) that might affect how your body absorbs medicine, such as gastroparesis (slow stomach emptying).
  • You cannot participate if you have a known hypersensitivity (allergic reaction) to the medicine nivolumab or any of its ingredients.
  • You are excluded if you previously had side effects from immunotherapy (treatment that uses the immune system to fight cancer) that caused you to stop treatment or required high doses of steroids (anti-inflammatory medicines).
  • People with active or past autoimmune or inflammatory disorders (conditions where the immune system attacks the body) that make the study drug unsafe are excluded.
  • You are excluded if you have unresolved or severe toxic side effects from previous cancer treatments or radiation therapy.
  • People with another type of malignancy (cancer) within the last 2 years are generally excluded, unless it was a specific type of skin cancer or early-stage cancer that was fully treated.
  • You cannot participate if you received other anti-cancer therapy (such as chemotherapy or radiation) within 28 days before the study drug.
  • You are excluded if you have uncontrolled malignant effusion (unhealthy buildup of fluid caused by cancer) that requires regular drainage.
  • People with active autoimmune hepatitis (an immune system attack on the liver) caused by immunotherapy are excluded.
  • You are excluded if you have colitis (inflammation of the colon/large intestine) that is active, or a history of inflammatory bowel disease, unless the condition has been resolved for more than 2 years.
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Investigated drugs

  • PTT-4256

    is an experimental medication taken as a pill that is being studied to see how safe and effective it is for treating certain types of solid tumors.

  • Nivolumab

    is an approved immunotherapy drug given through an infusion into a vein that helps the body's immune system recognize and attack cancer cells.

What is already known about the treatment

  • PTT-4256

    This medication is taken as a tablet by mouth and is currently being studied in clinical trials to see how well it works against various solid tumors. It belongs to a class of drugs designed to change the environment around cancer cells, specifically by reducing the acidity that helps tumors grow and hide from the immune system. By targeting these acidic conditions at a molecular level, the drug aims to make the tumor more vulnerable to the body's natural defenses.

  • Nivolumab

    This medication is administered as a liquid solution through an infusion into a vein and is already an approved treatment used in various cancer therapies. It is classified as an immune checkpoint inhibitor that works by blocking a specific protein on immune cells called PD-1. By doing this, it prevents cancer cells from "turning off" the immune system, allowing the body's own white blood cells to recognize and attack the tumor more effectively.

Investigated diseases

Solid Tumours - These are masses of tissue formed by the uncontrolled growth of abnormal cells that do not spread easily to other parts of the body like liquid cancers. They can develop in various organs and tissues throughout the body. As these growths increase in size, they can press against or invade nearby structures. The progression involves the continuous division of cells that should normally stop growing. Over time, these masses can alter the function of the organ in which they originated.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2025-522944-41-00Protocol codePTT-4256-01Estimated enrolment150 patientsSponsorPathios Therapeutics Limited

sourced from the EU Clinical Trials Register and site verification

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