Phase 1 Open-label Study of 123I-ATT001 in Subjects With Relapsed Glioblastoma (CITADEL-123)

Citadel-123: A Phase I Clinical Trial to Assess the Activity of I-123 Poly Adenosine Diphosphate Ribose Polymerase I Inhibitor (123I-ATT001) Directly Administered in Subjects With Relapsed Glioblastoma.

Phase I open-label trial of 123I-ATT001 monotherapy and in combination with treatment therapies in subjects with relapsed glioblastoma.

Study Overview

• Status: Completed
• Conditions: Glioma Glioblastoma Multiforme
• Intervention / Treatment: Drug: 123I-ATT001

Detailed Description

The main goals of this study are to understand if 123I-ATT001 is safe and tolerable to treat participants with relapsed glioblastoma and to determine the maximum tolerated dose that can be given to participants without any unacceptable side effects.

The study consists of two parts:

- Part 1 is a dose escalation study where three doses of 123I-ATT001 will be tested, starting with the lowest dose. When a recommended dose (RD) has been declared, a monotherapy expansion cohort will be open at that dose level.

In Part 1 participants will receive a 123I-ATT001 dose, once per week, for four weeks (+ two optional extra cycles).

• Part 2 is a dose expansion study where one dose of 123I-AT001 will be tested in combination with other therapies. Part 2 will begin after the Part 1 has completed and a recommended part 2 dose has been chosen.

The specific details and combination therapies for Part 2 of the study will be added via a protocol amendment at a later date.

• Study Type: Interventional
• Enrollment (Actual): 7
• Phase: Phase 1

Contacts and Locations

Study Locations

• United Kingdom
  • London, United Kingdom
    • University College London Hosptial
  • Southampton, United Kingdom
    • University Hospital Southampton

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. written informed consent
2. Men and women over 18 years of age.
3. Histologically confirmed recurrent glioblastoma (grade IV) as per WHO criteria 2021 (IDH- wild type only) where the subjects have an Ommaya reservoir in an intralesional cavity of at least 5 mL volume.
4. Documented recurrent disease (radiological, based on RANO v.1.0) within 3 months prior to first study drug administration with no suitable standard of care options available.
5. Eastern Cooperative Oncology Group Performance status of 0 or 1.
6. Adequate organ function
7. Women of childbearing potential must use two forms of reliable contraception before starting 123I-ATT001 treatment, during therapy and for 6 months after receiving the last dose of 123I-ATT001. All male subjects must agree to not donate sperm during the study and for 6 months after the last dose of study drug.
8. Be able to understand and comply with the requirements of the study, as judged by the Investigator.

Exclusion Criteria:

1. Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks of the first dose of treatment.
2. Diagnosis of immunodeficiency or receiving systemic steroid therapy of up to 4 mg/ day dexamethasone or equivalent or any other form of immunosuppressive therapy within 7 days prior to the first dose of study treatment.

3. Prior anticancer treatments within the following time periods:

   1. Chemotherapy within 4 weeks of enrolment or 5 half-lives, whichever is shorter.
   2. Targeted small molecule therapy within 4 weeks of enrolment or 5 half-lives, whichever is shorter.
   3. Immunotherapy (including monoclonal antibody therapy) or radiation therapy within 4 weeks prior to study day 1.
4. Unresolved NCI-CTCAE grade 2 or higher toxicity (except stable neurological toxicities/deficits related to disease process, alopecia).
5. Patients with a known allergy to Olaparib or Iodine.
6. Known additional malignancy that is progressing or requires active treatment excepting basal cell carcinoma of the skin, squamous cell carcinoma of the skin that has undergone potentially curative therapy, or in situ cervical cancer.
7. Any condition that precludes the proper performance of SPECT and/or MRI scan
8. Any clinically significant abnormalities in resting ECG at the time of screening including prolonged QTcF (>450 ms for males; >470 ms for females) and cardiac arrhythmias, as judged by the Investigator or designee.
9. Unstable systemic disease (including but not limited to active infection, uncontrolled hypertension, unstable angina, congestive heart failure, myocardial infarction within the previous year, serious cardiac arrhythmia requiring medication, hepatic, renal, or metabolic disease).
10. Psychiatric, substance misuse or functional disorders that prevent subjects from providing informed consent, following protocol instructions or cooperating with the requirements of the study.
11. Active infection requiring systemic therapy.
12. Pregnant, breastfeeding, or expecting to conceive or father children within the projected duration of the study, starting with the pre-screening or screening visit through 3 months after the last dose of study treatment.
13. Subject that has a condition or is in a situation, which in the Investigators opinion may put the subject at significant risk, may confound the study results, or may interfere significantly with the subject's participation in the study.
14. History of non- infectious pneumonitis within the last 3 years.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part 1 Dose Escalation & Dose Expansion; Dose Escalation: 123I-ATT001 Dose Level 1 123I-ATT001 Dose Level 2 123I-ATT001 Dose Level 3 Dose Expansion: 123I-ATT001 Recommended Dose from Dose Escalation	Drug: 123I-ATT001; 123I-ATT001

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part 1 - Dose Escalation: Frequency and severity of treatment emergent adverse events (TEAEs) and serious adverse events (SAEs)	To assess safety and tolerability of 123I-ATT001	Screening to end of treatment visit (28 days after last dose of 123I-ATT001)
Part 1- Dose Escalation: Incidence of Dose Limiting Toxicity (DLT)	Evaluated by monitoring of Adverse Events.	Day 1 to Day 14 of 123I-ATT001 administration

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part 1 - Dose Escalation: biodistribution and pharmacokinetics of 123I-ATT001 in blood	Blood samples will be collected from the first 6 patients in Part 1.	Collected 1 hour, 4 hours and 24 hours post each dose and optionally at 48 hours post first dose.
Part 1- Dose Escalation: biodistribution and pharmacokinetics of 123I-ATT001 in urine.	Urine samples will be collected from the first 6 patients in Part 1.	Collected 24 hours post first dose
Part 1 - Dose Escalation: radiation dosimetry of 123I-ATT001 (exposure of each organ to radiation)	SPECT/CT and or whole body planar imaging	1 and 4 and 24 hours post first dose and 4 hours post fourth dose.
Part 1- Dose Escalation: preliminary assessment of the antitumour activity of 123I-ATT001	Efficacy will be assessed according to the RANO response criteria using MRI Scans	Screening, Day 14 post each dose, 28 days after last dose, then a further 3 times every 8 weeks at follow up.
Part 1 - Dose Escalation: effect of 123I-ATT001 on neurological function	Neurological function will be assessed by the principal investigator according to NANO criteria.	Screening, the day of the 1st, 3rd and 5th (if given) dose, may also be performed within 48 hours prior to dose administration. It will also be performed on the End of Treatment visit which takes place 28 days post last dose.
Part 1 - Dose Escalation: effect of 123I-ATT001 on neurological function	Patients will complete the MDASI-BT questionnaire	Screening, the day of the 1st, 3rd and 5th (if given) dose, may also be performed within 48 hours prior to dose administration. It will also be performed on the End of Treatment visit which takes place 28 days post last dose.

Collaborators and Investigators

• Sponsor: Theragnostics Ltd
• Investigators: Principal Investigator: Paul Mulholland, University College London Hospital

Publications and helpful links

Helpful Links

• Related Info

Study record dates

Study Major Dates

• Study Start (Actual): July 4, 2024
• Primary Completion (Actual): March 1, 2026
• Study Completion (Actual): March 1, 2026

Study Registration Dates

• First Submitted: July 16, 2024
• First Submitted That Met QC Criteria: October 18, 2024
• First Posted (Actual): October 21, 2024

Study Record Updates

• Last Update Posted (Actual): March 31, 2026
• Last Update Submitted That Met QC Criteria: March 26, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms; Neoplasms by Histologic Type; Neoplasms, Glandular and Epithelial; Astrocytoma; Glioma; Neoplasms, Neuroepithelial; Neuroectodermal Tumors; Neoplasms, Germ Cell and Embryonal; Neoplasms, Nerve Tissue; Glioblastoma
• Other Study ID Numbers: PIL101; 1006521 (Other Identifier: IRAS)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: no current plans to share any data with other researcheers

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No