The purpose of this clinical trial is to investigate the treatment for adult patients suffering from advanced or metastatic solid tumours and has 2 parts to the study: the Phase 1 where ascending doses of the experimental study drug, TAX2, will be tested and the Phase 2a where all the participants will receive the study drug at the same dose considered as the recommended Phase 2 dose from Phase 1 part. The participation in the Phase 1 or in the Phase 2a part depends on when the participant is proposed to join the study.
The study purpose is to assess:
* How safe and tolerable TAX2 is. This assessment will be based on the adverse effects collected during the study.
* How well TAX2 enters the body, circulates in the body, and leaves the body (known as pharmacokinetics, PK) by measuring the level of the drug in the blood
* What the drug does with the body and the tumour (known as pharmacodynamics, PD)
* The effect TAX2 has on the tumours (anti-tumour activity)
* Also define the Dose Limiting Toxicity (DLT) and the recommended Phase 2 Dose (RP2D)