Inclusion Criteria:

          1. Diagnosis of soft tissue sarcoma or conventional chondrosarcoma, dedifferentiated
             chondrosarcoma, osteosarcoma (see exclusion criteria below)

          2. Metastatic or locally advanced disease that is unresectable

          3. There is no limit to the number of prior therapies a subject may have had, but the
             following requirements must be met:

               1. Conventional chondrosarcoma and low-grade osteosarcoma: No requirements regarding
                  prior therapy

               2. Osteosarcoma (high-grade), Dedifferentiated chondrosarcoma: at least 1 prior
                  anthracycline chemotherapy, alone or in combination, required either as adjuvant,
                  neoadjuvant or in the metastatic setting.

               3. Soft tissue sarcoma: at least 1 line of systemic therapy, unless the sarcoma
                  subtype is one that is generally considered unresponsive to standard
                  chemotherapy.

          4. Age ≥ 18 years.

          5. Provide study specific informed consent prior to study entry

          6. Documented CDK pathway abnormality on a commercially available mutation profiling test
             (Foundation, Tempus xT, etc), if performed previously as part of routine/standard care
             on tumor (metastatic or primary), having at least one of the following (a and/or b)

               1. Cyclin D1 (CCND1), cyclin D2 (CCND2), cyclin D3 (CCND3), cyclin dependent kinase
                  4 (CDK4), and/or cyclin dependent kinase 6 (CDK6) amplification

               2. Cyclin Dependent Kinase Inhibitor 2A (CDKN2A) homozygous loss

          7. Rb positive confirmed by immunohistochemistry testing of archived tumor tissue
             specimen (metastatic or primary site) performed centrally at Medical College of
             Wisconsin Precision Medicine Laboratory.

          8. All subjects must have measurable disease as defined by RECIST 1.1. (See RECIST 1.1
             criteria in Appendix 10.

          9. Subjects must also have had evidence of disease progression by RECIST 1.1 within 6
             months of enrollment, or newly diagnosed within the last 6 months (refer to step 1
             criteria regarding previous lines of therapy).

         10. A washout period of at least 21 days is required between last chemotherapy dose and
             enrollment.

         11. A washout period of at least 14 days is required between end of radiotherapy and
             enrollment.

         12. At least 14 days after surgery, and absence of significant wound healing issues that
             would pose infection risk.

         13. Subjects with brain metastasis that have been treated with definitive surgery or
             radiation and have been clinically stable for 3 months are eligible.

         14. Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1

         15. Adequate organ and marrow function as defined below (ULN indicates institutional upper
             limit of normal):

               -  Absolute neutrophil count ≥ 1.5 x 10^9/L

               -  Hemoglobin ≥ 8.0 g/dL

                  a. Patients may receive erythrocyte transfusions to achieve this hemoglobin level
                  at the discretion of the investigator. Initial treatment must not begin earlier
                  than the day after the erythrocyte transfusion.

               -  Absolute neutrophil count ≥ 1.5 x 10^9/L

               -  Platelets ≥ 100 x 10^9/L

               -  Total bilirubin ≤ 1.5 x ULN

                  a. Patients with Gilbert's syndrome with a total bilirubin ≤2.0 times ULN and
                  direct bilirubin within normal limits are permitted.

               -  Aspartate aminotransferase (AST)(SGOT)/alanine aminotransferase (ALT)(SGPT) ≤ 3 x
                  institutional ULN

               -  Renal function (at least one of the following): Estimated Creatinine Clearance
                  (CrCl) ≥ 30 mL/min (Cockcroft-Gault), estimated glomerular filtration rate (eGFR)
                  ≥ 30 mL/min/1.73 m^2 (MDRD or Chronic Kidney Disease Epidemiology Collaboration
                  (CKD-EPI) formula), or actual CrCl as determined by 24-hour urine collection

         16. Female subjects must meet one of the following:

               -  Postmenopausal for at least one year before enrollment, OR

               -  Surgically sterile (i.e. undergone a hysterectomy or bilateral oophorectomy), OR

               -  If subject is of childbearing potential (defined as not satisfying either of the
                  above two criteria), must have a negative serum pregnancy test within 21 days of
                  step 2 enrollment AND

                    -  Agree to practice two acceptable methods of contraception (combination
                       methods requires use of two of the following: diaphragm with spermicide,
                       cervical cap with spermicide, contraceptive sponge, male or female condom
                       with spermicidal agent added, hormonal contraceptive) from the time of
                       signing of the informed consent form through 90 days after the last dose of
                       study agent, OR

                    -  Agree to practice true abstinence when this is in line with the preferred
                       and usual lifestyle of the subject. (Periodic abstinence [e.g., calendar,
                       ovulation, symptothermal, postovulation methods] and withdrawal are not
                       acceptable contraception methods.)

         17. Male subjects, even if surgically sterilized (i.e., status post vasectomy), must agree
             to one of the following:

               -  Practice effective barrier contraception during the entire study period and
                  through 60 calendar days after the last dose of study agent, OR

               -  Agree to practice true abstinence when this is in line with the preferred and
                  usual lifestyle of the subject. (Periodic abstinence [e.g., calendar, ovulation,
                  symptothermal, post ovulation methods] and withdrawal are not acceptable methods
                  of contraception.)

         18. Subjects must be deemed able to comply with the study plan by the local PI.

         19. Ability to swallow oral medications

        Exclusion Criteria:

          1. Diagnosis of well differentiated (WD) or dedifferentiated (DD) liposarcoma

          2. Any bone sarcoma other than osteosarcoma, conventional or dedifferentiated
             chondrosarcoma.

          3. Prior treatment with a specific CDK 4 or CDK 6 inhibitor - (such as palbociclib,
             abemaciclib, or ribociclib).

          4. Subjects who have not recovered (Common Terminology Criteria for Adverse Events [CTCAE
             v5.0] Grade ≤1) from the acute effects of chemotherapy (except for residual alopecia
             or Grade 2 peripheral neuropathy) prior to enrollment, or other toxicity or serious
             preexisting medical condition(s) (for example, interstitial lung disease, severe
             dyspnea at rest or requiring oxygen therapy, history of major surgical resection
             involving the stomach or small bowel, or preexisting Crohn's disease or ulcerative
             colitis or a preexisting chronic condition resulting in baseline Grade 2 or higher
             diarrhea) that in the opinion of the site PI is expected to preclude participation in
             this study.

          5. Subjects currently receiving any other investigational agents.

          6. Current ongoing treatment with strong Cytochrome P450, family 3, subfamily A (CYP3A)
             inducers or inhibitors.

          7. Uncontrolled intercurrent illness including, but not limited to, known ongoing or
             active bacterial infection (requiring IV antibiotics), fungal infection, detectable
             viral infection (such as known HIV or active hepatitis B or C) (screening tests is not
             required for enrollment), symptomatic congestive heart failure, unstable angina
             pectoris, cardiac arrhythmia (specifically, atrial fibrillation or ventricular
             dysrhythmias except ventricular premature contractions), or psychiatric illness/social
             situations that would limit compliance with study requirements.

          8. The subject has a personal history of any of the following conditions: syncope of
             cardiovascular etiology, ventricular arrhythmia of pathological origin (including, but
             not limited to, ventricular tachycardia and ventricular fibrillation), or sudden
             cardiac arrest.

          9. Pregnant women and women who are breast-feeding.

         10. Subjects must not have current evidence of another malignancy that requires treatment.

         11. Subjects who received treatment with live attenuated viruses within 30 days prior to
             eligibility confirmation or might receive the treatment through the duration of the
             trial.