In short
ONA-255 is an investigational protein-based substance being studied in people with advanced cancer. It is given by intravenous infusion and has no marketing authorisation, meaning it is not yet approved as a medicine. One registered Phase 1/2 trial is testing its safety and early anti-tumour activity in 117 participants with advanced breast cancer and metastatic gastric or gastroesophageal junction cancer.
Key points
- ONA-255 is an investigational protein-based substance with no marketing authorisation.
- It is being studied in a Phase 1/2 trial for advanced cancer, including breast cancer and metastatic gastric / gastroesophageal junction cancer.
- The trial plans to enrol 117 participants and is currently authorised.
- ONA-255 is given as a solution for intravenous infusion.
- The trial aims to find the minimum biologically active dose and the maximum tolerated dose, and to assess the overall response rate.
What is ONA-255?
ONA-255 is a protein-based substance that is still investigational, meaning it has not received marketing authorisation and is not yet approved as a medicine. The substance is developed by ONA Therapeutics S.L. It is classified in the therapeutic area of neoplasms, which covers cancers. In the registered trial, ONA-255 is given as a single agent, which means it is being tested on its own rather than in combination with other cancer treatments.
How does ONA-255 work?
The registered trial does not describe the molecular target of ONA-255. What is known from the trial record is that the researchers use two types of biological response to judge whether the drug is active: a decline in circulating tumour DNA (ctDNA) or a shrinkage of tumours measured by imaging according to RECIST criteria. The trial aims to find the minimum dose at which one of these biological responses occurs, called the minimum biological active dose (MBAD).
Which conditions is ONA-255 studied for?
The registered trial studies ONA-255 in people with advanced cancer. The trial lists three groups of conditions:
- Advanced cancer – cancer that has spread or is no longer curable by local treatments alone.
- Breast cancer – specifically hormone receptor-positive, HER2-negative advanced breast cancer in the dose-optimisation part of the trial.
- Metastatic gastric / gastroesophageal junction cancer – cancer of the stomach or the area where the stomach meets the oesophagus that has spread to other parts of the body.
How is ONA-255 given?
ONA-255 is prepared as a solution for infusion and is given by intravenous infusion, which means it is delivered directly into a vein over a period of time. The trial record does not report the dose or the length of each infusion.
What do the clinical trials show?
There is one registered clinical trial of ONA-255. It is a Phase 1/2 study with a planned enrolment of 117 participants, and its status is authorised, meaning it has received the necessary approvals and may proceed. The trial is divided into three parts:
- Phase 1a – determines the minimum biological active dose (MBAD) and the maximum tolerated dose (MTD) of ONA-255 as a single agent.
- Phase 1b – determines the optimal dose and the recommended Phase 2 dose (RP2D) in hormone receptor-positive, HER2-negative advanced breast cancer, and, if applicable, in metastatic gastric or gastroesophageal junction cancer.
- Phase 2a – assesses the preliminary overall response rate of ONA-255 at the recommended Phase 2 dose.
The main measures in the trial include the number of participants who experience dose-limiting toxicities during the first 21-day cycle, safety and tolerability assessed through treatment-related adverse events, drug interruptions, dose reductions and treatment discontinuations, and the investigator-assessed overall response rate defined as the proportion of participants with a complete or partial tumour response according to RECIST version 1.1.
What side effects are known?
No side effects of ONA-255 are reported in the available sources. The registered trial is designed to measure side effects, including dose-limiting toxicities, treatment-related adverse events and serious adverse events, but no results are yet available.