Testing the Addition of Cemiplimab to Palbociclib for the Treatment of Advanced Dedifferentiated Liposarcoma

This phase II trial compares the effect of treatment with palbociclib alone to treatment with palbociclib plus cemiplimab for treating patients with dedifferentiated liposarcoma that may have spread from where it first started to nearby tissue, lymph nodes, or distant parts of the body (advanced). Palbociclib may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth. Cemiplimab is a monoclonal antibody that may interfere with the ability of cancer cells to grow and spread. The combination of these two drugs may be more effective in shrinking or stabilizing advanced dedifferentiated liposarcoma compared to palbociclib alone.

PRIMARY OBJECTIVES: I. To perform a safety lead-in among 6 patients to confirm that the combination of palbociclib and cemiplimab is safe and tolerable. II. To evaluate whether palbociclib in combination with cemiplimab (Arm 2) demonstrates a superior progression-free survival (PFS) compared to palbociclib monotherapy (Arm 1) for patients with advanced dedifferentiated liposarcoma (DDLPS). SECONDARY OBJECTIVES: I. To evaluate the toxicity profile in and across each treatment arm as determined by both Common Terminology Criteria for Adverse Events (CTCAE) and Patient Reported Outcomes (PRO)-CTCAE criteria. II. To evaluate and compare the objective response rate (ORR) and duration of response (DOR) in and across each treatment arm. III. To evaluate and compare the overall survival (OS) in and across each treatment arm. IV. To evaluate and compare progression-free rate at 8 weeks (PFR8) in and across each treatment arm. EXPLORATORY OBJECTIVES: I. To collect genomic sequencing data previously collected as standard of care, including data on CDK4 copy number (as determined by fluorescence in situ hybridization \[FISH\] or other molecular testing). II. To conduct multiplex immunohistochemistry using archival tumor tissue (where available) to define densities of infiltrating immune cell subsets and tumor and immune cell major histocompatibility complex (MHC) and PD-L1 expression. III. To perform an exploratory analysis to evaluate for any relationship between CDK4 copy number and (a) the tumor immune microenvironment as defined by multiplex immunohistochemistry and (b) clinical outcomes from study treatment. IV. To explore efficacy and toxicity endpoints, including PFS and ORR, for patients who progress on palbociclib monotherapy and crossover to the palbociclib plus cemiplimab combination. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive palbociclib orally (PO) on study. Patients will be allowed to cross over to Arm II following documentation of disease progression. Patients undergo magnetic resonance imaging (MRI) or computed tomography (CT) scans throughout the trial. Patients may also undergo blood sample collection on study. ARM II: Patients receive palbociclib PO and cemiplimab intravenously (IV) on study. Patients undergo MRI or CT scans throughout the trial. Patients may also undergo blood sample collection on study.