A Study of Radspherin® in Patients with Primary Advanced Epithelial Cancer, with Peritoneal Metastasis That Are Homologous Recombination Proficient Scheduled to Undergo Neoadjuvant Chemotherapy and Interval Debulking Surgery

Inclusion Criteria:

1. Able and willing to provide written informed consent and to comply with the clinicalstudy protocol (CSP).

2. Female of age ≥ 18 years.

3. Patients with primary advanced high-grade serous or high-grade endometrioidepithelial ovarian, fallopian tube, or primary peritoneal cancer (FIGO Stage IIIB/Cor IV).

4. Peritoneal and other metastases eligible for IDS to no residual tumour.

5. Adverse events recovered to at least Grade 1 from the effects (excluding alopecia)of any prior medical therapy for malignancy.

6. Confirmed HR proficient by Myriad MyChoice CDx testing.

7. Completed 3 or 4 cycles of NACT with regress or stable disease on diagnostic imagingand assessed to be operable to R0.

8. Eastern Cooperative Oncology Group (ECOG) Performance Status Score of 0 to 2 andpatient fit enough to undergo IDS and further treatment according to standard ofcare.

9. Adequate renal function:

• Calculated creatinine clearance using the Cockcroft-Gault formula ≥ 40 ml/min ormeasured creatinine clearance ≥ 40 ml/min.

10. Adequate hepatic function:

• Serum bilirubin < 1.5 x upper limit of normal (ULN), and

• Aspartate transaminase and alanine transaminase ≤ 3 x ULN.

11. Adequate bone marrow function:

• Absolute neutrophil count ≥ 1.0 x 10^9/l, and

• Platelets ≥ 100 x 10^9/l, and

• Haemoglobin ≥ 9 g/dL.

12. For females of childbearing potential, a negative pregnancy test must be documentedprior to enrolment.

13. For females of childbearing potential agreement to use at least one of the followinghighly effective (failure rate < 1%) methods of contraception during the treatmentperiod and for at least 9 months if they receive Radspherin®, unless hysterectomy oroophorectomy is performed during IDS.

• Total abstinence (when this is in line with the preferred and usual lifestyleof the patient), periodic abstinence (e.g. calendar, ovulation, symptothermal,post ovulation methods) and withdrawal are not acceptable methods ofcontraception.

• Female sterilisation (have had surgical bilateral oophorectomy with or withouthysterectomy), total hysterectomy, or tubal ligation at least 6 weeks beforeenrolment. In case of oophorectomy alone, only when the reproductive status ofthe woman has been confirmed by follow up hormone level assessment.

• Use of oral (oestrogen and progesterone), injected or implanted hormonalmethods of contraception or placement of an intrauterine device or intrauterinesystem, or other forms of hormonal contraception that have comparable efficacy (failure rate < 1%), for example hormone vaginal ring or transdermal hormonecontraception. In case of use of oral contraception women should have beenstable on the same pill for a minimum of 3 months before taking studytreatment.

Note: In addition to the use of one highly effective method of contraception as listed above, a condom is required for all male partners during the treatment period and for at least 9 months after the dose of IMP, unless vasectomised at least 6 months prior to enrolment.

Exclusion Criteria:

1. Known somatic or germline BRCA1 or BRCA2 mutations or confirmed HR deficient.

2. Suspicion of peritoneal leak, shunt, or otherwise suspected atypical targetcompartment pharmacokinetics, based on investigator's judgement, patient history anddiagnostic images.

3. Epithelial borderline tumours, ovarian clear cell carcinoma, mucinous ovariancarcinoma, malignant Brenner tumours, non-epithelial ovarian malignancies,carcinosarcoma and neuroendocrine tumours or recurrent ovarian cancer.

4. Symptomatic central nervous system metastasis.

5. Another primary malignancy within the past 3 years (except for non melanoma skincancer, cutaneous melanoma stage 1, cervical cancer in situ or FIGO 2023 Stage IA1or IA3 prior or synchronous endometrial cancer).

6. Prior abdominal/pelvic radiotherapy.

7. Disease progression during 3 to 4 cycles of NACT.

8. Pregnant or lactating (nursing) women.

9. Active infections requiring antibiotics, and/or physician monitoring, or recurrentfever > 38.0⁰C associated with a clinical diagnosis of active infection.

10. Active liver disease with positive serology for active hepatitis B, hepatitis C orknown human immunodeficiency virus (HIV).

11. Concurrent congestive heart failure or prior history of New York Heart Association (NYHA) class III/IV cardiac disease.

12. Any condition or illness that, in the opinion of the investigator or the medicalmonitor, would compromise the safety of the patients or interfere with theevaluation of the safety of the investigational medicinal product.

13. In the investigator's opinion not able to comply with study procedures. Any medicalor psychological condition that would preclude participation in the study orcompromise the ability to give informed consent.

14. Administration of an investigational medicinal product within 4 weeks, or at least 5times the half life, prior to enrolment.

15. Concurrent administration of any cancer therapy other than planned study treatmentwithin 4 weeks prior to, and up to 4 weeks after the surgery.

16. Treatment with bevacizumab within 5 weeks prior to IDS.

17. Known hypersensitivity to any of the excipients of the study drug.