A study to test the safety and effectiveness of ONA-255 in patients with advanced cancer including breast cancer and gastric cancer

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What is this study about?

This study involves people with advanced cancer, specifically breast cancer that is hormone receptor-positive and HER2-negative, or metastatic gastric cancer or gastroesophageal junction cancer. The treatment being tested is ONA-255, which is given as a solution for infusion directly into the vein. The study will examine how safe and effective this new medicine is in treating these types of cancer. The purpose of the study is to find the best dose of ONA-255 to use, to understand how well it works, and to learn about any side effects it may cause.

The study is divided into different phases. In the first phase, the study will test different doses of ONA-255 to find the lowest dose that has a biological effect and the highest dose that people can tolerate without serious side effects. In the next phase, the study will focus on finding the best dose to use for future studies in people with hormone receptor-positive, HER2-negative breast cancer and possibly in people with metastatic gastric or gastroesophageal junction cancer. In the final phase, the study will look at how many people respond to treatment with ONA-255 at the recommended dose. Throughout the study, doctors will monitor participants closely with physical examinations, blood tests, and imaging scans to check how the cancer is responding and to watch for any side effects.

The study will also collect blood samples to measure how the body processes ONA-255 and how long it stays in the body. Tissue samples from the cancer may be collected to study markers like FGFR4, HER2, and genetic changes such as ESR1, PIK3CA, TP53, and RB1 mutations to better understand how the treatment works. Some participants may also have their response measured using RECIST criteria, which is a standard way of measuring tumor size changes. The study may use placebo in some cases. Doctors will track how long the treatment works, how long people live without their cancer getting worse, and overall survival.

1 Initial treatment period

Treatment will begin with ONA-255, which is given through intravenous infusion (a drip into a vein).

The medication will be administered in cycles, with each cycle lasting 21 days.

The exact dose will be determined based on the phase of the study and individual assessment.

2 First cycle monitoring

During the first 21-day cycle, close monitoring will occur to assess how the body responds to the treatment.

Blood samples will be collected to measure the levels of the medication in the body at specific times during Cycle 1.

Physical examinations, vital signs measurements (such as blood pressure, breathing rate, and temperature), and laboratory tests will be performed regularly.

Heart function will be monitored using 12-lead electrocardiograms (ECG), which record the electrical activity of the heart.

3 Ongoing treatment cycles

Treatment with ONA-255 will continue in 21-day cycles as long as the treatment is beneficial and tolerated.

Additional blood samples for medication level measurements may be collected during Cycle 3.

Regular assessments will include physical examinations, blood tests to check organ function and blood cell counts, and monitoring of overall health status.

Performance status will be evaluated using the ECOG scale, which measures how the disease affects daily living abilities.

4 Tumor response assessment

Imaging scans will be performed at regular intervals to measure changes in tumor size.

Response to treatment will be assessed using RECIST 1.1 criteria, which are standardized methods for evaluating whether tumors are shrinking, staying the same, or growing.

These assessments will help determine if the treatment is working.

5 Laboratory and safety monitoring

Regular blood tests will monitor levels of blood cells, including neutrophils (a type of white blood cell), platelets (cells that help blood clot), and hemoglobin (the protein in red blood cells that carries oxygen).

Kidney function will be checked by measuring creatinine levels in the blood.

Liver function will be monitored through tests measuring ALT and AST (enzymes that indicate liver health) and bilirubin (a substance processed by the liver).

Electrolyte levels, including potassium, sodium, and calcium, will be checked to ensure they remain within normal ranges.

Any side effects or adverse events will be recorded and graded according to severity.

6 Additional biological samples

Blood samples may be collected to analyze circulating tumor DNA (ctDNA), which are small fragments of cancer DNA in the bloodstream.

Tests may be performed to check for anti-drug antibodies (ADA), which are immune responses the body might develop against the treatment medication.

If antibodies are detected, additional tests will measure their levels and whether they affect the medication’s activity.

7 Contraception requirements during treatment

If female and of childbearing potential, highly effective contraception must be used throughout the study period and for 6 months and 20 days after the last dose of ONA-255.

If male and sexually active with a partner of childbearing potential, highly effective contraception must be used during the study and for 3 months and 20 days after the last dose of ONA-255.

8 Treatment continuation or completion

Treatment will continue for as long as it provides benefit and is tolerated without unacceptable side effects.

The treatment may be interrupted, the dose may be reduced, or treatment may be stopped based on how the body responds or if significant side effects occur.

Follow-up assessments will track disease status and any effects from subsequent treatments received after completing this study treatment.

Who Can Join the Study?

You must be 18 years of age or older at the time you sign the consent form
You must have advanced breast cancer that is hormone receptor positive and HER2 negative, or metastatic gastric or gastroesophageal junction cancer (cancer of the stomach or where the stomach meets the esophagus that has spread to other parts of the body)
Your cancer diagnosis must be confirmed by examining tissue under a microscope. For breast cancer, tissue must show hormone receptor positive (meaning the cancer cells have receptors for estrogen or progesterone hormones) and HER2 negative (meaning the cancer cells do not have too much of a protein called HER2). The tissue sample must be from cancer that has spread, either taken recently during screening or within 12 months before screening
You must have already received previous cancer treatments. The specific treatments required depend on which phase of the study you join and may include hormone therapy, a type of drug called a CDK4/6 inhibitor (a medicine that blocks proteins that help cancer cells grow), chemotherapy (strong medicines that kill cancer cells), or antibody-drug conjugates (medicines that combine antibodies with cancer-killing drugs)
Your ECOG performance status must be 0 or 1, which means you are able to carry out normal activities or have only slight restrictions in physically demanding activities
Your blood tests and organ function tests must show adequate levels, including enough blood cells, normal kidney function, and acceptable liver function
You must have at least one tumor that can be measured using imaging scans according to a standard system called RECIST 1.1
If you are a woman able to become pregnant, you must agree to use highly effective birth control methods during the study and for 6 months and 20 days after your last treatment. Highly effective methods include tubal ligation, hormonal birth control, intrauterine device, having a partner who has had a vasectomy, or complete abstinence from sexual intercourse
If you are a man who is fertile and sexually active with a partner who can become pregnant, you must agree to use highly effective birth control methods during the study and for 3 months and 20 days after your last treatment
Your life expectancy (how long doctors expect you to live) must be 6 months or longer
You must provide written informed consent before any study activities begin
You must be willing and able to follow all the requirements of the study protocol

Who Cannot Join the Study?

The source data does not provide specific exclusion criteria (reasons why patients cannot participate) for this clinical trial
Without detailed exclusion criteria information, it is not possible to list specific medical conditions, treatments, or situations that would prevent participation in this study
Exclusion criteria typically include things like certain other medical conditions, previous treatments, laboratory test results outside normal ranges, or use of specific medications, but these details are not available in the provided information

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Hospital Universitario Hm Sanchinarro	Madrid	Spain

Other Sites

Site Name	City	Country
Hospital Clinic De Barcelona	Barcelona	Spain
Hospital Universitario Quironsalud Madrid	Pozuelo De Alarcon	Spain
Isqaeugz Chznwq Dqamoayxdwyfzsuwa	L'hospitalet De Llobregat	Spain
Hdgjdaep Vkwc dtjskgsv	Barcelona	Spain

Trial status

Country	Status	Recruitment Start
Spain	Recruiting	01.12.2025

Trial locations

ONA-255 is an investigational medication being studied for the treatment of advanced cancer. This is an experimental drug that is being tested to see if it can help shrink tumors or slow down cancer growth in patients with certain types of advanced cancers, including hormone receptor-positive, HER2-negative advanced breast cancer and metastatic gastric or gastroesophageal junction cancer. The study will look at how safe the medication is, how well it works, and how the body processes it.

Investigated diseases:

Advanced Cancer – Advanced cancer refers to cancer that has grown beyond its original site and cannot be completely removed by surgery. The disease occurs when cancer cells continue to multiply and spread despite the body’s natural defenses. As the cancer progresses, it may affect multiple organs and tissues throughout the body. Patients with advanced cancer often experience symptoms related to the specific organs involved and the overall burden of disease. The condition represents a later stage in cancer development where the disease has become more widespread. Advanced cancer requires ongoing medical management to control its growth and manage symptoms.

Breast Cancer – Breast cancer is a disease in which cells in the breast tissue grow abnormally and form a mass or tumor. The disease begins when cells in the breast start to divide and multiply without normal control mechanisms. It can develop in different parts of the breast, including the milk ducts or the lobules that produce milk. As breast cancer progresses, it may spread to nearby lymph nodes under the arm or to other parts of the body. The disease can occur in both women and men, though it is much more common in women. Different types of breast cancer grow at different rates and respond differently to various medical approaches.

Metastatic Gastric Cancer – Metastatic gastric cancer is stomach cancer that has spread from the stomach to distant parts of the body. The disease starts in the cells lining the stomach and grows through the stomach wall layers. As it advances, cancer cells break away from the original tumor and travel through the bloodstream or lymphatic system to other organs. Common sites where gastric cancer spreads include the liver, lungs, bones, and the lining of the abdominal cavity. Patients may experience symptoms such as abdominal pain, weight loss, difficulty swallowing, and digestive problems. The metastatic stage represents an advanced form of the disease where cancer has established itself in multiple body locations.

Gastroesophageal Junction Cancer – Gastroesophageal junction cancer develops at the area where the esophagus connects to the stomach. This type of cancer arises from cells in this transitional zone and can have characteristics of both esophageal and gastric cancers. The tumor grows in the tissue at this junction and may extend into either the lower esophagus or upper stomach. As the disease progresses, it can block the passage of food, cause difficulty swallowing, and spread to nearby lymph nodes. The cancer may eventually metastasize to distant organs such as the liver, lungs, or bones. This location makes the cancer particularly challenging as it affects a critical area of the digestive system.

Trial ID:

2025-522233-62-00

Protocol code:

ONA-255-101

Trial Phase:

Phase I and Phase II (Integrated) – First administration to humans

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A study to test the safety and effectiveness of ONA-255 in patients with advanced cancer including breast cancer and gastric cancer

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?