This study will recruit participants with Grade 2 and 3 meningiomas who have failed prior therapy. Participants will receive oral doses of JZP3507. The antitumor activity and safety of JZP3507 will be evaluated.

Key Inclusion Criteria:

Age

1. Is ≥ 18 years of age at the time of signing the informed consent.

   Type of Participant and Disease Characteristics

2. Has histologically confirmed Grade 2 or 3 meningioma.

3. Has failed, is not a candidate for, or has declined standard of care treatment for meningioma. Note: There is no limit on the number of prior systemic therapies.

4. Has measurable disease, as assessed by the investigator. Measurable disease is defined as at least one lesion measuring ≥ 10 mm on perpendicular dimensions by contrast-enhanced MRI performed within 28 days prior to study enrollment.

5. Has progressive disease (PD) per Response Assessment in Neuro-Oncology (RANO) criteria, as assessed by the investigator using axial, contrast-enhanced T1-weighted magnetic resonance imaging (MRI). PD is defined as an increase in size of the measurable primary lesion on imaging by at least 15% in sum of product of target lesions since last treatment or between scans separated by no more than 6 months. The presence of a new lesion would also qualify as PD.

6. Is able to submit historic disease-related imaging from at least 9 months prior to study entry to central imaging vendor (preferably all available disease-related imaging from initial diagnosis onwards).

7. Is able to swallow oral tablets.

8. Has a Karnofsky Performance Status (KPS) of at least 70.

9. Has laboratory test results meeting the following parameters within 14 days before the start of study intervention:

   1. Absolute neutrophil count ≥ 1.0 × 109/L and platelets ≥ 75 × 109/L.
   2. Total bilirubin ≤ 1.5 × upper limit of normal (ULN) (participants with Gilbert's syndrome may be included with total bilirubin > 1.5 × ULN if direct bilirubin is ≤ 1.5 × ULN).
   3. Aspartate (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN. Note: For participants with documented baseline liver metastasis, the following limits will apply: ≤ 5 × ULN for transaminase.
   4. Creatinine clearance ≥ 50 mL/min as calculated by the Cockcroft Gault equation (or estimated glomerular filtration rate [eGFR] > 60 mL/min/1.73 m2) or serum creatinine ≤ 1.5 × ULN.

10. Has an expected survival of at least 12 weeks, as predicted by the physician.

11. Is able to submit at least 10 (preferably ≥ 15 slides, if available) unstained formalin-fixed paraffin-embedded (FFPE) slides or a tissue block with sufficient material for ~15 slides from participant's tumor tissue to the sponsor.

12. Has had an MRI within 28 days before the start of study intervention, with the corticosteroid dose stable or decreasing at least 5 days prior to the scan.

    Sex and Contraceptive/Barrier Requirements

13. Agrees to the following based on sex assigned at birth: is not of child-bearing potential or agrees to use appropriate contraception, as defined in protocol, for males and females.

Key Exclusion Criteria:

Medical Conditions

1. Has known hypersensitivity to JZP3507, dordaviprone, or any excipient used in the JZP3507 study intervention formulation.

2. Has active cardiac disease/condition as defined in the protocol.

3. Has a known additional malignancy that is progressing or has required active treatment within the past 2 years. Exceptions include participants with basal cell carcinoma of the skin, squamous cell carcinoma of the skin that has undergone potentially curative therapy or in situ cervical cancer.

4. Has an active infection that requires systemic therapy.

   Prior/Concomitant Therapy

5. Has received any of the following interventions within the specified time periods before the first dose of study intervention or plans to receive any of the following interventions during study participation:

   1. Prior anticancer therapy or investigational agents within 28 days or 5 half-lives, whichever is shorter.
   2. Antibody-based anticancer therapy within 42 days.
   3. Radiotherapy within 24 weeks (~6 months).
   4. Strong CYP3A4 inhibitors within 14 days.
   5. Strong CYP3A4 inducers within 14 days.
   6. Major surgery, open biopsy, or significant traumatic injury within 30 days.

6. Has uncontrolled intercurrent illness or any other medical, psychiatric, or social condition that, in the opinion of the investigator, may interfere with participant safety or the ability to comply with study requirements.

   Prior/Concurrent Clinical Study Experience

7. Has previous exposure to JZP3507 or dordaviprone from any source.

   Diagnostic Assessments

8. Has optic nerve sheath meningioma, extracranial meningioma, or meningioma primarily localized spinal cord.

9. Has more than 3 measurable lesions.

In accordance with ICMJE requirements, Jazz Pharmaceuticals may provide qualified external researchers access to individual participant data (IPD) and clinical trial data that underlie the results of this trial upon request. Qualified researchers can submit a request on https://www.jazzpharma.com/science/clinical-trial-data-sharing/ as outlined. Jazz Pharmaceuticals reserves the right not to consider a request. For inquiries about Jazz's data sharing policy, contact clinicaldatasharing@jazzpharma.com