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Malignant Pleural EffusionPhase 1/2NCT05278975

Study of RSO-021 in Patients With Malignant Pleural Effusion Due to Advanced/Metastatic Solid Tumors Including Mesothelioma

A Phase 1/2 study testing RSO-021 in people with Malignant Pleural Effusion and Malignant Pleural Mesothelioma, run by RS Oncology LLC at 10 sites in United Kingdom.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

This is an open-label, non-randomized, multicenter, translational Phase 1/2 dose-escalation and expansion study designed to determine the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of RSO-021 after intrapleural (IP) administration in patients with malignant pleural… Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
RSO-021
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
50 participants
Where
10 sitesUnited Kingdom
Study dates
31 Mar 2022to 7 May 2026
Phase
Phase 1/2
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Male or female ≥ 18 years old.
  • ECOG performance status 0-1.
  • Histological diagnosis of solid tumor/mesothelioma with MPE.
  • Expansion Cohort 2:
  • only patients with breast cancer, ovarian cancer or non-small cell lung cancer.
  • patients for whom paclitaxel is a recommended SoC therapy.
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  • no contraindications to paclitaxel.
  • Patients with a disease burden that is predominantly pleural, and a pleural space that is accessible.
  • Expansion Cohorts 1 and 2: MPE (non-mesothelioma): patients must have received at least 1 prior standard of care treatment regimen for advanced, unresectable malignancy, with documented progression.
  • Expansion Cohort 3:
  • MPE mesothelioma: patients must have received at least 1 prior standard-of-care treatment regimen for advanced, unresectable malignancy, with documented progression and there is no approved life extending alternative available.
  • Expansion Cohort 4: MPE mesothelioma 'window of opportunity': patients should be treatment naïve, have refused or not be immediately requiring of systemic therapy and should be patients for whom drainage is planned immediately while further treatment options are arranged. It must be documented for each patient that protocol participation will not affect their subsequent ability to access standard systemic first line therapy due to RSO-021 being a local therapy.
  • 6. Resolution of all acute reversible toxic effects of prior therapy or surgical procedure to Grade ≤1 (except alopecia).
  • 7. For dose escalation: Archival paraffin block, ideally from the patient's most recent biopsy, should be provided prior to the first dose of study therapy, if sufficient tissue is available.
  • For dose expansion cohorts: fresh tumor biopsy must be obtained.
  • Patients enrolled in the mesothelioma expansion phase will be requested to undergo a tumor biopsy during the screening period and after the third dose.
  • Patients enrolled in the non-mesothelioma expansion phase will be requested to undergo a tumor biopsy during the screening period and after the third dose only if medically feasible.
  • 8. Patients must have adequate organ function.

Who cannot join

  • Last dose of prior anti-cancer therapies:
  • Systemic anti-cancer therapy within 3 weeks or 5 half-lives prior to study entry, whichever is shorter.
  • Thoracic radiation therapy or significant surgery within 3 weeks prior to study entry. Localized palliative radiotherapy for pain control in non-target lesions is allowed during the screening period.
  • Received an investigational product or been treated with an investigational device within 30 days prior to first drug administration or plans to participate in any other clinical trial while on this study.
  • Previous or concurrent malignancy that would prevent evaluation of the primary endpoint (e.g. R/R hematological malignancy).
  • Patients whose extent of tumor or loculations would render intrapleural administration incomplete and/or ineffective.
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  • Known hypersensitivity to the active ingredient or any excipient contained in the drug formulation.
  • History or clinical evidence of any surgical or medical condition which the investigator and/or medical monitor judges as likely to interfere with the results of the study or pose an additional risk in participating, e.g., rapidly progressive or uncontrolled disease involving a major organ system-vascular, cardiac, pulmonary, gastrointestinal, gynecologic, hematologic, neurologic, neoplastic, renal, endocrine, or an immunodeficiency, or clinically significant active psychiatric or abuse disorders.
  • Active infection with human immunodeficiency virus (HIV) and CD4+ T-cell count < 350/μL. Patients not on established anti-retroviral therapy for at least four weeks prior to first dose of study drug and having a detectable HIV viral load. Testing is not required for eligibility.
  • Active infection with hepatitis B (surface antigen); or infection with hepatitis C in absence of sustained virologic response. Testing is not required for eligibility.
  • Pregnant or breast-feeding patients.
  • Patients with symptomatic or unstable CNS primary tumor or metastases and/or carcinomatous meningitis. Patients with documented treated CNS metastases stable off steroids may be enrolled at the discretion of the investigator.
  • Therapeutic oral anticoagulation for a thromboembolic event (prophylactic anticoagulation is allowed as long as patient can undergo catheter placement and biopsy). LMWH is allowed on condition that it is medically acceptable to interrupt LMWH therapy for all study procedures.
  • Use of systemic corticosteroids to treat inflammatory or autoimmune symptoms within 15 days or other immunosuppressive drugs within 3 weeks prior to start of the study. Inhaled and topical corticosteroids are permitted. Up to 10 mg/day prednisone or equivalent is permitted.

Trial locations and contacts

10 sites in 1 country.

10 sites in 1 country

United Kingdom10 sites

  • South Mead North Bristol Hopsital

    Bristol, Bristol, BS105NB

  • NHS Greater Glasgow & Clyde

    Glasgow

  • Leeds Teaching Hospital

    Leeds, Leeds, LS970F

  • Facility: HOPE Clinical Trials Facility, Leicester Royal Infirmary

    Leicester, LE1 5WW

  • Barts Health NHS Cancer Institute

    London, EC1A7BE

  • Guys and St Thomas NHS Foundation Trust

    London, SE19RT

  • The Royal Marsden

    London, SW3 6JJ

  • The Christie NHS

    Manchester, M204BX

  • Northumbria NorthTyne Side General Hospital

    North Shields, North Shields, NE29 8NH

  • Oxford University Hospitals NHS Foundation

    Oxford, OX42PG

Other trials in United Kingdom

About this study

Official title: A Translational Phase 1/2 Dose-Escalation and Expansion Study to Determine Safety, Tolerability, and Recommended Phase 2 Dose of RSO-021 in Patients With Malignant Pleural Effusion Due to Advanced/Metastatic Solid Tumors Including Mesothelioma

This is an open-label, non-randomized, multicenter, translational Phase 1/2 dose-escalation and expansion study designed to determine the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of RSO-021 after intrapleural (IP) administration in patients with malignant pleural effusion (MPE) (non-mesothelioma) and MPE from mesothelioma.

Read the detailed description

This is a Phase 1/2, open-label, multi-center study whose primary Phase 1 stage objective is to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of RSO-021 (thiostrepton), a naturally-occurring, sulfur-rich, cyclic oligopeptide antibiotic of the thiopeptide class, in patients with MPE from any solid tumor, including mesothelioma.

In the Phase 2 stage, once the RP2D has been identified, the antitumor activity of RSO-021 will be evaluated in four recruitment arms; (1) in patients with MPE (non-mesothelioma), (2) in patients with MPE (non-mesothelioma) in combination with paclitaxel, (3) in patients with MPE from mesothelioma after first-line SoC, and (4) in patients with MPE from mesothelioma who have a 'window of opportunity' for treatment prior to first-line systemic therapy.

Being tested
RSO-021
Medical subject headings
Pleural Effusion, Malignant, Mesothelioma, Malignant, Mesothelioma

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • RSO-021Drug

    Also called Thiostrepton

    A naturally-occurring, sulfur-rich, cyclic oligopeptide antibiotic of the thiopeptide class.

Study groups in NCT05278975
Study groupRoleWhat they receive
Phase 1 - Dose EscalationExperimentalRSO-021 administered in increasing doses as a solution for pleural infusion through an indwelling IP catheter, administered as a single dose on Day 1 of each week of a 21-day treatment cycle.
Receives: Drug: RSO-021
Ph2 - Dose Expansion - MPE from non-mesothelioma solid tumorsExperimentalRSO-021 administered at the MTD/RP2D as a solution for pleural infusion through an indwelling IP catheter, administered as a single dose on Day 1 of each week of a 21-day treatment cycle in patients with MPE from non-mesothelioma solid tumors.
Receives: Drug: RSO-021
Ph2 - Dose Expansion - MPE from mesotheliomaExperimentalRSO-021 administered at the MTD/RP2D as a solution for pleural infusion through an indwelling IP catheter, administered as a single dose on Day 1 of each week of a 21-day treatment cycle in patients with MPE from mesothelioma.
Receives: Drug: RSO-021
P2 - Dose Expansion - mesothelioma -First line treatment prior to Ipi/NivoExperimentalRSO-021 administered at the MTD/RP2D as a solution for pleural infusion through an indwelling IP catheter, administered as a single dose on Day 1 of each week of a 21-day treatment cycle in patients with mesothelioma. This local treatment with RSO-021 is prior to systemic treatment of Ipi/Nivo.
Receives: Drug: RSO-021
Ph2 - Dose Expansion - MPE from non-mesothelioma solid tumors combination with PaclitaxelExperimentalRSO-021 administered at the MTD/RP2D as a solution for pleural infusion through an indwelling IP catheter, administered as a single dose on Day 1 of each week of a 21-day treatment cycle in patients with MPE from non-mesothelioma solid tumors. In combination with Paclitaxel. Paclitaxel will be administered as a systemic therapy per SoC and the approved labeling based on the tumor type being treated. Paclitaxel is commercially available in the UK
Receives: Drug: RSO-021

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Dose-limiting Toxicity

    The incidence of DLTs during the DLT assessment period.

    Measured: First 21 days of treatment.

  2. Frequency and Severity of Adverse Events (AE)

    The incidences and percentages of patients experiencing AEs summarized by NCI CTCAE version 5.0 grade and by causality.

    Measured: Screening to 90 days from last dose.

  3. Dose Finding

    Determination of the MTD and/or the RP2D.

    Measured: Screening to 90 days from last dose.

Secondary outcomes (5)

  1. Pharmacokinetics of RSO-021

    Maximum Plasma Concentration (Cmax)

    Measured: Day 1 of dosing through 21 days post last dose.

  2. Pharmacokinetics of RSO-021

    Area Under the Curve (AUC)

    Measured: Day 1 of dosing through 21 days post last dose.

  3. Objective Response Rate (ORR)

    ORR according to RECIST v1.1.

    Measured: Day 1 of dosing through day 90 after the last dose.

  4. Disease Control Rate (DCR)

    The percentage of subjects with a complete response, partial response, or stable disease for at least 2 consecutive tumor assessments.

    Measured: Day 1 of dosing through day 90 after the last dose.

  5. Progression Free Survival (PFS)

    Time from the date of initiation of study therapy to the date measurement criteria are first met for PD or death from any cause, whichever occurs first.

    Measured: Day 1 of dosing through day 90 after the last dose.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted15 Mar 2022
  2. Study start31 Mar 2022
  3. Primary completion30 Nov 2025
  4. Study completion7 May 2026

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 1/2
Primary purpose
Treatment
Allocation
Non-randomised
Intervention model
Sequential
Masking
None (open label)
Enrolment
50 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05278975
Sponsor's protocol ID
RS-TS-101-01
Status last verified
Jul 2026
First submitted
7 Feb 2022
Last updated
24 Jul 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Publications

  • Gibson V, Dzialo J, Messier T, Bzura A, Poile C, Rogel J, Hahne JC, Habibovic A, Stead S, Saaman A, Blyth KG, Szlosarek PW, Lord S, Thistlethwaite F, Zhang M, Nakas A, Wells-Jordan P, Kutywayo K, Butnor KJ, Heintz NH, Naumov GN, Dungey M, Colomina JH, Aktas B, Dulloo S, Spicer J, Fennell DA, Cunniff B. Preclinical characterization and phase 1 clinical testing of targeting mitochondrial peroxiredoxin 3 in cancer. Nat Commun. 2026 Jul 14;17(1):5929. doi: 10.1038/s41467-026-75153-y.

    PubMed 42448681

Questions about this trial

What is this clinical trial studying?

A Phase 1/2 study testing RSO-021 in people with Malignant Pleural Effusion and Malignant Pleural Mesothelioma, run by RS Oncology LLC at 10 sites in United Kingdom.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 18 inclusion and 14 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 24 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 10 sites in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Dose-limiting Toxicity (time frame: First 21 days of treatment.). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05278975, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Jul 2026.

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