A Phase 1 interventional study of Palbociclib and Pembrolizumab in Sarcoma, sponsored by John Rieth. Recruiting at 1 site in United States. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-05-22.
Sponsored by John Rieth · Phase 1, Interventional, and Treatment
This is a single-arm open-label window of opportunity clinical study assessing the impact of pre-treatment with palbociclib in patients with soft tissue sarcomas for which PD-1 inhibitors are approved (includes undifferentiated pleomorphic sarcoma, myxofibrosarcoma, angiosarcoma, pleomorphic rhabdomyosarcoma, pleomorphic liposarcoma, or alveolar soft part sarcoma).
Patients will be given palbociclib for 2 weeks following a pre-treatment ultrasound guided biopsy used to establish immunological baseline of the tumor microenvironment. After 2 weeks of palbociclib therapy, a second biopsy will be performed to assess the impact of palbociclib on the tumor microenvironment. Pembrolizumab will be started the same day as the second biopsy. After 2 doses of pembrolizumab, a third (optional) biopsy may be performed if the subject consents. At 8 weeks of therapy disease response will be assessed as per standard of care.
1,667 studies on the registry are indexed under Sarcoma; 393 are open to participants now.
This study's planned enrollment of 8 is below the median of 40 across 1,283 interventional studies indexed under Sarcoma.
Browse Sarcoma studies →John Rieth is the lead sponsor of 4 studies on the registry; 1 is open to participants now.
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A potential subject must meet all the following inclusion criteria to be eligible to participate in the study:
Exclusion Criteria
A potential subject who meets any of the following exclusion criteria is ineligible to participate in the study:
Palbociclib given for 2 weeks following a pre-treatment ultrasound guided biopsy used to establish an immunological baseline of the tumor microenvironment. After the conclusion of palbociclib therapy, a post-treatment biopsy will be performed to assess the impact of palbociclib on the tumor microenvironment; pembrolizumab will be started the same day as the second biopsy. After 2 doses of pembrolizumab, a third (optional) biopsy could be performed.
Drug: Palbociclib · Drug: Pembrolizumab
Palbociclib is a CDK4/6 inhibitor. Palbociclib, 125 mg, (pediatric dose 75mg/m2 up to 125mg) daily for 21 days out of every 28 days, PO (orally) starting 14 days prior to Pembrolizumab
Pembrolizumab is a PD-1 blocking antibody. Given 14 days following Palbociclib: Pembrolizumab, 200 mg, once every three weeks, intravenously (IV)
Dose limiting toxicities (DLTs) and adverse events (AEs) per CTCAE v5
Confirm the safety of the combination of Palbociclib and pembrolizumab in sarcomas for which PD-1 inhibitors are approved as defined by the incidence of DLTs
Time frame: The dose limiting toxicity period is 4 weeks after starting the first dose of pembrolizumab
Response rate per RECIST 1.1 criteria
To assess the response (per RECIST 1.1 criteria) of patients with advanced UPS with the combination of CDK4/6 inhibitor and anti-PD-1 immunotherapy
Time frame: 8 weeks following treatment intiation
Progression free survival
To assess progression free survival as calculated by the time from start of treatment until the time of progression of disease or death due to any cause
Time frame: Up to two years following completion of treatment
Plan to share: No
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