DETERMINE Trial Treatment Arm 03: Entrectinib in Adult, Teenage/Young Adults and Paediatric Patients With ROS1 Gene Fusion-positive Cancers. (DETERMINE)

THE PARTICIPANT MUST FULFIL THE ELIGIBILITY CRITERIA WITHIN THE DETERMINE MASTER PROTOCOL (NCT05722886) AND WITHIN THE TREATMENT ARM 03 (ENTRECTINIB) OUTLINED BELOW* *When entrectinib-specific inclusion/exclusion criteria or precautions below differ from those specified in the Master Protocol, the entrectinib-specific criteria will take precedence. Inclusion Criteria: A. Confirmed diagnosis of a ROS1 gene fusion-positive malignancy, other than NSCLC, that has been identified using an analytically validated sequencing technique. B. Patients must be able and willing to undergo a fresh biopsy. C. Patients with a BSA of 0.43m^2 and over. D. ADULT PATIENTS: Adequate organ function as per haematological and biochemical indices within the ranges shown below. These measurements should be performed to confirm the patient's eligibility. Haemoglobin (Hb): ≥90 g/L (transfusion allowed) Absolute neutrophil count (ANC): ≥1.5×10^9/L (no granulocyte colony-stimulating factor [GCSF] support in preceding 72 hours) Platelet count: ≥100×10^9/L (unsupported for 72 hours) Bilirubin: <2.5 x upper limit of normal (ULN). Patients with known Gilbert's syndrome who have a serum bilirubin: ≤3 x ULN may be enrolled. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST): ≤2.5 x ULN or ≤5 x ULN if raised due to metastases. estimated glomerular filtration rate (eGFR): eGFR: ≥30 mL/min (uncorrected value) Coagulation - prothrombin (PT) (or international normalized ratio [INR]), and activated partial thromboplastin clotting time (aPTT): ≤1.5 x limit of normal (unless patient is on anticoagulants e.g. warfarin [INR should be stable and within indicated therapeutic range], or direct oral anticoagulants [DOAC]. E. PAEDIATRIC PATIENTS: Adequate organ function as per haematological and biochemical indices within the ranges shown below. These measurements should be performed to confirm the patient's eligibility. Haemoglobin (Hb): ≥80 g/L (transfusion allowed) ANC: ≥1.0×10^9/L (no GCSF support in preceding 72 hours) Platelet count: ≥75×10^9/L (unsupported for 72 hours) Bilirubin: ≤1.5 x ULN for age ALT and AST: ≤2.5 x ULN for age or < 5xULN if raised due to metastases. estimated glomerular filtration rate (eGFR): eGFR >70 ml/min/1.73m^2 International Normalised Ratio (INR) or Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT): ≤1.5 x ULN for age (unless patient is on anticoagulants e.g. warfarin [INR should be stable and within indicated therapeutic range], or DOAC). F. Women of childbearing potential are eligible provided that they meet the following criteria: - Have a negative serum or urine pregnancy test before enrolment and either: • Agree to use one form of highly effective birth control method such as: I. Oral, intravaginal or transdermal combined (oestrogen and progestogen containing) hormonal contraception II. Oral, injectable or implantable progestogen-only hormonal contraception associated with inhibition of ovulation III. Intrauterine device (IUD) IV. Intrauterine hormone-releasing system (IUS) V. Bilateral tubal occlusion VI. Vasectomised partner Plus a barrier method: male or female condom with or without spermicide; cap, diaphragm or sponge with spermicide. • Sexual abstinence; Effective from the first administration of entrectinib, throughout the trial and for five weeks after the last administration of entrectinib. G. Male patients with partners who are women of childbearing potential are eligible provided that they agree to the following, from the first administration of entrectinib, throughout the trial and for three months after the last administration of entrectinib: Agree to take measures not to father children by using a barrier method of contraception (condom plus spermicide) or to sexual abstinence. Non-vasectomised male patients with partners who are women of childbearing potential must also be willing to ensure that their partner uses a highly effective method of contraception as in F above. Male patients with pregnant or lactating partners must be advised to use barrier method contraception (for example, condom plus spermicidal gel) to prevent drug exposure of the foetus or neonate. Exclusion Criteria: A. Female patients who are pregnant, breastfeeding or planning to become pregnant during the trial or within five weeks following their last dose of entrectinib. B. Diagnosis of ROS1 fusion-positive Non-Small Cell Lung Cancer (NSCLC). C. Prior treatment with the same class of drug unless genetic profile demonstrates a mechanism of resistance known to be potentially sensitive to entrectinib. D. Patients with significant cardiovascular disease are excluded as defined by: i. Current congestive heart failure requiring therapy (New York Heart Association III or IV) or known left ventricular ejection fraction (LVEF) <50% (moderate to severe) ii. History of unstable angina pectoris or myocardial infarction (MI) up to three months prior to trial entry, or current poorly controlled angina (symptoms weekly or more) iii. Presence of symptomatic or severe valvular heart disease (severe by local echo graphic criteria or American Heart Association/American Cardiac College Stage C or D) iv. History of a clinically significant cardiac arrhythmia up to three months prior to trial entry (asymptomatic atrial fibrillation or asymptomatic first-degree heart block are permitted. v. History of stroke (ischaemic or haemorrhagic) within the last three months. E. Patients with a baseline QTcF (Corrected QT interval by Fridericia formula) interval longer than 450 millisecond (ms) for male patients and 470 ms for female patients, patients with congenital long QTcF syndrome, and patients taking medicinal products that are known to prolong the QTc interval. F. History of additional risk factors for Torsades de Pointes (e.g., family history of long QT syndrome). G. Grade ≥2 peripheral neuropathy. H. Known active infections that would interfere with the assessment of safety or efficacy of entrectinib (bacterial, fungal, or viral, including HIV positive). I. Known hypersensitivity to entrectinib or any of the excipients. J. Patient unable to swallow entrectinib intact, without chewing, crushing or opening the capsules (as per the dosing schedule and suitable dosing strengths available). Any active gastrointestinal disease (e.g., Crohn's disease, ulcerative colitis, or short gut syndrome) or other malabsorption syndromes that would reasonably affect drug absorption. K. Patients with rapidly progressing or symptomatically deteriorating brain metastases. Patients with previously treated brain metastases are eligible, provided the patient has not experienced a seizure or had a clinically significant change in neurological status within the 14 days prior to the start of IMP administration. Such patients must be non-dependent on steroids or on a stable or reducing dose of steroid treatment for at least 14 days (or 7 days for paediatric patients) prior to the start of IMP administration. Primary brain or CNS malignancies are allowed providing the patient is clinically stable (if requiring corticosteroids must be at stable or decreasing doses for at least 14 days for adults and 7 days for paediatric patients prior to the start of IMP administration). Patients who have received brain irradiation must have completed whole-brain radiotherapy and/or stereotactic radiosurgery at least 14 days prior to the start of IMP administration. L. Patients with personal history of significant osteopenia (screening for osteopenia not required). M. Any clinically significant concomitant disease or condition (or its treatment) that could interfere with the conduct of the trial or absorption of oral medications that would, in the opinion of the Investigator, pose an unacceptable risk to the patient in this trial.