Pseudovax - A Cancer Vaccine for Patients With Pseudomyxoma Peritonei

NCT07341360 | Recruiting Early Phase 1 DMC

• 1 other identifier: 2024-517047-30-01
• Study Type: interventional
• Target: 10
• Locations: 1 country
• Sites: 1

Brief Summary

Participants will receive vaccination with Pseudovax/GM-CSF in combination with PD-1 inhibitor tislelizumab over a period of up to two years. The vaccine is expected to reactivate measurable immune response, and tislelizumab to restore anticancer immunity in patients with GNAS mutated pseudomyxoma peritonei.

Conditions

Pseudomyxoma Peritonei

Keywords

Pseudovax; PMP; Peptide vaccine; GNAS mutation; pseudomyxoma peritonei

Outcome Measures

Primary Outcomes (2)

• Safety and tolerability of sequential treatment with Pseudovax/GM-CSF and tislelizumab

  Incidence of Investigative Medicinal Product-related adverse events. All ≥ Grade 3 adverse events and all grades vaccine-related adverse events will be reported and graded using CTCAE v 5.0.

  From start treatment to 6 months after last dose of study drug.

• Immune responses following sequential treatment with Pseudovax/GM-CSF and tislelizumab

  Count of circulating vaccine-specific T cells

  From enrollment to end of treatment (2 years).

Secondary Outcomes (1)

• Progression-free survival, measured as the number of months from date of first treatment until disease progression or death from any cause

  From start treatment to disease progression, death or last follow-up 6 months after last dose of study drug (whichever comes first).

Study Arms (1)

Pseudovax peptide, adjuvant and PD-1 inhibitor

EXPERIMENTAL

Participants will be administered the Pseudovax peptide vaccine + adjuvant, granulocyte-macrophage colony-stimulating factor (GM-CSF). From study week 13, the programmed cell death 1 (PD-1) inhibitor tislelizumab will be administered in addition, for a maximum of 21 months, until confirmed progression, unacceptable toxicity, withdrawal of consent, or Investigator decision, whichever happens first.

Other: Pseudovax; Biological: Molgramostim; Biological: Tislelizumab

Interventions

Molgramostim BIOLOGICAL

Molgramostim, 100 μg recombinant human GM-CSF, powder, to be reconstituted in 0.33 mL water for injection

Pseudovax peptide, adjuvant and PD-1 inhibitor

Tislelizumab BIOLOGICAL

100 mg of humanized IgG4 mAb in 10 mL of isotonic solution

Pseudovax peptide, adjuvant and PD-1 inhibitor

Pseudovax OTHER

Pseudovax peptide dissolved in 0.5 mL water for injection to 1 mg/mL (+/- 0.1 mg/mL)

Pseudovax peptide, adjuvant and PD-1 inhibitor

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• The subject is ≥ 18 years of age on the day of signing the informed consent form, able to provide written informed consent and can understand and agree to comply with the requirements of the study and the schedule of assessments.
• Confirmed diagnosis of recurrent or non-resectable PMP with no other available treatment options that are expected to be efficacious.
• The subject's tumor must carry a mutation in the GNAS oncogene\*
• Subjects must have peritoneal tumor distribution at screening that, in the opinion of the Investigator, is suitable for repeat biopsies: Up to 3 biopsies of target tissue are planned for subjects that complete the study.
• Adequate organ, bone marrow, liver, and renal function at screening, including:
• Absolute neutrophil count: ≥ 1,5 x109/L
• Platelets: ≥ 100 x109/L
• Hemoglobin: ≥ 9 x109/L
• Creatinine ≤ 1,5 upper limit normal (ULN) OR measured/calculated GFR ≥60 mL/min
• Albumin ≥ 30 g/L
• Total bilirubin ≤ 1,5 ULN
• ASAT and ALAT ≤ 3 ULN
• International Normalized Ratio (INR) ≤ 1,5 ULN and Activated Partial Thromboplastin Time (aPTT) ≤ 1,5 ULN unless subject is receiving anticoagulant therapy.
• ECOG performance status of 0 or 1.
• Life expectancy of \>6 months, at the time of signing the informed consent.

You may not qualify if:

• Patient has Eastern Cooperative Oncology Group performance status 2 or worse.
• Blood transfusion or growth factor support ≤ 14 days before sample collection at screening.
• Active malignancy the past 3 years except for the specific cancer under investigation in this study and any locally recurring cancer that has been treated curatively (e.g., resected basal or squamous cell skin cancer, superficial bladder cancer, carcinoma in situ of the cervix or breast)
• Enrollment in another interventional trial that, in the opinion of the Investigator, could influence the outcome of this study.
• Subject has within the last 30 days received any other interventional therapy that, in the opinion of the Investigator, could influence the outcome of this study.
• Pregnancy or lactating female.
• Known active hepatitis B or C, or is known to be HIV-positive.
• Any condition that required systemic treatment with either corticosteroids (\> 10 mg daily of prednisone or equivalent) or other immunosuppressive medication ≤ 14 days before the first dose of IMP.
• Note: Subjects who are currently or have previously been on any of the following steroid regimens are not excluded: Adrenal replacement steroid (dose ≤ 10 mg daily of prednisone or equivalent); Topical, ocular, intra-articular, intranasal, or inhaled corticosteroid with minimal systemic absorption; Short course (≤ 7 days) of corticosteroid prescribed prophylactically (e.g., for contrast dye allergy) or for the treatment of a non-autoimmune condition (e.g., delayed-type hypersensitivity reaction caused by contact allergen).
• Active autoimmune diseases or history of autoimmune diseases that may relapse. Note: Subjects with the following diseases are not excluded and may proceed to further screening, controlled Type I diabetes, hypothyroidism (provided it is managed with hormone replacement therapy only), controlled celiac disease skin diseases not requiring systemic treatment (eg, vitiligo, psoriasis, alopecia), any other disease that is not expected to recur in the absence of external triggering factors.
• Diagnosis of immunodeficiency.
• History of interstitial lung disease, non-infectious pneumonitis or uncontrolled diseases including pulmonary fibrosis, acute lung diseases, etc.
• Severe chronic or active infections requiring systemic antibacterial, antifungal or antiviral therapy, including tuberculosis infection, etc.
• Severe infections within 4 weeks before first dose of IMP, including but not limited to hospitalization for complications of infection, bacteremia, or severe pneumonia.
• Therapeutic oral or intravenous antibiotics within 2 weeks before first dose of IMP.

Sponsors & Collaborators

• Oslo University Hospital: lead
• BeiGene: collaborator

Study Sites (1)

Oslo University Hospital HF, Radium

Oslo, Oslo County, 0379, Norway

RECRUITING

MeSH Terms

Conditions

Pseudomyxoma Peritonei

Interventions

molgramostim; tislelizumab

Condition Hierarchy (Ancestors)

Adenocarcinoma, Mucinous; Adenocarcinoma; Carcinoma; Neoplasms, Glandular and Epithelial; Neoplasms by Histologic Type; Neoplasms; Neoplasms, Cystic, Mucinous, and Serous

Central Study Contacts

Geir Olav Hjortland, Medical Doctor - Oncologist

CONTACT

+47 22934000; kreftstudier@ous-hf.no

Study Design

• Study Type: interventional
• Phase: early phase 1
• Allocation: NA
• Masking: NONE
• Masking Details: Open label
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Model Details: Study Design: A phase 1, first-in-human open label, single-arm trial, combining the novel peptide vaccine Pseudovax against mutated GNAS (Gsα) with adjuvant granulocyte macrophage - colony stimulating factor (GM-CSF) and subsequent treatment with the immune checkpoint inhibitor tislelizumab (anti-PD-1) in adult subjects with recurrent or non-resectable GNAS-mutated pseudomyxoma peritonei (PMP). Study treatment: Participants will be administered the Pseudovax peptide vaccine + adjuvant, granulocyte-macrophage colony-stimulating factor (GM-CSF). From study week 13, the programmed cell death 1 (PD-1) inhibitor tislelizumab will be administered in addition, for a maximum of 21 months, until confirmed progression, unacceptable toxicity, withdrawal of consent, or Investigator decision, whichever happens first.

Study Record Dates

• First Submitted: November 20, 2025
• First Posted: January 14, 2026
• Study Start: October 13, 2025
• Primary Completion (Estimated): December 31, 2029
• Study Completion (Estimated): December 31, 2034
• Last Updated: January 14, 2026

Record last verified: 2026-01

Data Sharing

• IPD Sharing: Will not share

Locations

NO (1)