A Study to Assess the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, Immunogenicity and Anti-tumour Activity of IPN01203 in Adults With Locally Advanced or Metastatic Solid Tumours Exposed to Immune Checkpoint Inhibitor Therapies

The purpose of this study is to determine the appropriate dosage, safety and effectiveness of a new drug, IPN01203, in adults with advanced solid tumours. Advanced solid tumours are cancers that can occur in various organs or tissues and have spread from their original site to nearby tissues or other parts of the body. There will be two parts to this study: * Phase Ia: This part (called dose escalation) will find the dose range that shows activity against the tumour and can be tolerated by participants by testing different increasing doses of IPN01203. * Phase Ib: This part (called dose optimisation) will assess the ability of the drug to prevent, slow down, or stop the growth of tumours and how the body processes and responds to the drug when given in "low dose" or "high dose." It will also further explore the safety and tolerability. An additional part (phase II) may be added to the study based on the results of phase Ia and phase Ib. Each part will consist of the following periods: * A screening period (up to 28 days) to assess whether the participant can take part, requiring at least 1 visit to the study centre. * A treatment period where all eligible participants will receive IPN01203. Requires approximately 15 visits for the first 2 months followed by 3 visits every month from month 3 until unacceptable toxicity, disease progression, death, upon participant's withdrawal of consent, investigator decision, or study termination by the sponsor, whichever occurs first. There will also be one visit at the end of treatment (EoT), 30 days after the last administration of the study intervention or prior to the start of new anticancer treatment, whichever is earlier. Additionally, there will be one visit (the safety follow-up visit) 90 days after the last administration of study intervention or prior to the start of new anticancer treatment, whichever is earlier. In both parts of the study, participants will undergo blood sampling, urine collection, physical examinations and clinical evaluations. They may continue some other medications, but the details need to be recorded. Each participant will be in this study until death or withdrawal from the study. IPN01203 will be provided to participants who tolerate it for as long as their disease does not progress. Participants may withdraw consent to participate at any time.