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.

Inclusion Criteria:

• Participant must be ≥18 years of age, at the time of signing the informed consent.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.
• Measurable disease per RECIST version 1.1 (at least one lesion that is measurable by RECIST 1.1. Tumour lesions in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions after radiation) and documented locally advanced or metastatic disease with CT and/or MRI.
• All acute, clinically significant (CS) treatment-related AEs from a prior therapy resolved to Grade 1 or lower prior to study entry. Participants with chronic toxicities such as Grade ≤2 neuropathy or alopecia can be included.
• Have a life expectancy for disease-related mortality, as evaluated by the investigator.
• Male and female participants: Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
• Adequate haematologic and end organ function
• Participant is capable of giving signed informed consent as described in the protocol.

Exclusion Criteria:

• Have untreated or active primary brain tumour, Central Nervous System (CNS) metastases, leptomeningeal disease, or spinal cord compression.

• Experienced severe, life-threatening immune-mediated AEs, or infusion-related reactions such as those that lead to permanent discontinuation while on treatment with prior anticancer therapy such as immune checkpoint inhibitor therapy.

• History of known autoimmune disease

• History of stroke or significant cerebrovascular disease, encephalitis, meningitis, organic brain disease (e,g., Parkinson's disease) or uncontrolled seizures in the year prior to first dose of study drug.

• History of CS cardiac disease within 6 months prior to the initiation of study intervention, including but not limited to unstable angina, acute myocardial infarction, endoscopic or open-heart cardiac surgery, or heart failure classified as New York Heart Association Grade 2 or higher. Additional exclusion criteria include:

  1. Left ventricular ejection fraction <45%
  2. QT interval corrected by Fridericia (QTcF) >470 ms (for women) and >450 ms (for men) or CS arrhythmias.

• History of CS respiratory disease within 6 months prior to the initiation of study intervention, including severe chronic obstructive pulmonary disease or asthma.

• Prior organ transplantation.

• Chronic or ongoing active infections within 4 weeks prior to Cycle1 Day1 (C1D1).

• Presence of hepatitis B surface antigen (HBsAg) [or hepatitis B core antibody (HBcAb)] at screening or within 3 months prior to the first dose of study intervention.

• Positive hepatitis C antibody test result at screening or within 3 months prior to the first dose of study intervention.

• Participants with known history of HIV infection are excluded from the study unless they meet the following criteria:

  1. Stable Antiretroviral Therapy: Participants must be on a stable antiretroviral therapy regimen for at least 4 weeks prior to enrolment.
  2. CD4+ T cell Count: Participants must have a CD4+ T cell count of at least 200 cells/µL.
  3. Viral Load: Participants must have an undetectable viral load (HIV RNA <50 copies/mL)
  4. No Opportunistic Infections: Participants must not have had any opportunistic infections or other human immunodeficiency virus (HIV)-related illness within the past 6 months Note: HIV testing will be performed in any countries where it is mandatory per local requirements.

• History of other malignancy within the last years.

• Significant concurrent, uncontrolled medical condition that would put participants at unacceptable risk from study participation or preclude them from complying with study procedures per investigator including, but not limited to renal, hepatic, haematologic, gastrointestinal, endocrine, pulmonary, neurological, cerebral, or psychiatric disease.

• Treatment with >10 mg per day of prednisone (or equivalent) or other immune suppressive drugs within 7 days prior to the initiation of study drug. Exceptions may be made for participants who have had allergic reaction to iodinated contrast media. Steroids for topical, ophthalmic, inhaled, or nasal administration are allowed.

• Concurrent participation in another therapeutic treatment study.

• Participants accommodated in an institution because of regulatory or legal order; prisoners or participants who are legally institutionalised.

• For French participants only: participants are under court protection, not affiliated to a social security system or protected adults.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, annotated case report form, statistical analysis plan, and dataset specifications.

Patient level data will be anonymized and study documents will be redacted to protect the privacy of study participants.

Where applicable, data from eligible studies are available 6 months after the studied medicine and indication have been approved in the US and/or EU.

Further details on Ipsen's sharing criteria and process for sharing are available here (https://www.ipsen.com/science/clinical-trials/clinical-data-transparency/).