Abemaciclib in Newly Diagnosed Meningioma Patients

Inclusion Criteria:

• Participants with newly diagnosed intracranial WHO Grade 3 meningioma; or,

• Participants with previous lower grade meningioma and histopathologically confirmednewly transformation to Grade 3.

• Plan to receive or have received upfront standard of care radiation therapy (RT) forthe newly diagnosed WHO Grade 3 meningioma.

• No prior treatment for Grade 3 meningioma other than surgical resection or biopsyand upfront RT. If previously diagnosed with a lower grade meningioma, no priortreatment other than surgical resection or biopsy and no prior RT.

• Ability to understand and the willingness to sign a written informed consentdocument (personally or by the legally authorized representative, if applicable).

• Participant has voluntarily agreed to participate by giving written informed consent (personally or via legally authorized representative[s], and assent, if applicable).Written informed consent for the protocol must be obtained prior to any screeningprocedures. If consent cannot be expressed in writing, it must be formally documentand witnessed, ideally via an independent trusted witness. Participant must bewilling and able to comply with scheduled visits, treatment plans, laboratory testsand other procedures.

• Age ≥18 years at time of consent.

• Have a performance status (PS) of ≤2 on the Eastern Cooperative Oncology Group (ECOG) scale.

• Ability to swallow oral medications.

• Participant has adequate bone marrow and organ function as defined by the followinglaboratory values (as assessed by the local laboratory for eligibility):

• Adequate Bone Marrow Function: absolute neutrophil count ≥1,500/mcL, platelets ≥100,000/mcL, and hemoglobin ≥8.0 g/dL (individual may receive erythrocytetransfusions to achieve this hemoglobin level at the discretion of theinvestigator; initial treatment must no begin earlier than the day after anyerythrocyte transfusion).

• Adequate Hepatic Function: total bilirubin ≤1.5x ULN (individuals withGilbert's syndrome with a total bilirubin ≤2.0x ULN and direct bilirubin withinnormal limits are permitted), AST/SGOT ≤3x ULN, and ALT/SGPT ≤3x ULN.

• Confirmed negative serum pregnancy test (β-hCG) before starting study treatment orparticipant who is no longer of childbearing potential due to surgical, chemical, ornatural menopause.

• For females of reproductive potential: use of highly effective contraception duringstudy participation and for an additional 3 weeks after the end of treatmentadministration.

• For males of reproductive potential: use of condoms or other methods to ensureeffective contraception with partner and for an additional 3 weeks after the end oftreatment administration.

Exclusion Criteria:

• Prior history of cancer with ongoing treatment of disease.

• Pregnancy or breastfeeding.

• Known allergic reactions to components of the abemaciclib.

• Active infection or fever >38.5°C requiring systemic antibiotic, antifungal orantiviral therapy within 4 weeks of Day 1.

• Known to have active (acute or chronic) or uncontrolled severe infection, liverdisease such as cirrhosis, decompensated liver disease, and active and chronichepatitis.

• Known active systemic bacterial infection (requiring IV antibiotics at time ofinitiating study treatment), fungal infection, or detectable viral infection (suchas known HIV positivity or with known HBV or HCV). Screening is not required forenrollment.

• Participant has serious and/or uncontrolled preexisting medical condition(s) that,in the judgment of the investigator, would preclude participation in this study.

• Prior therapy with any CDK4/6 inhibitor. Prior therapy is defined as therapeuticdosing.

• Treatment with another investigational drug within 5 half-lives of theinvestigational product.