An Open-Label, Phase II Efficacy Trial of Doxorubicin in Combination With Dual Checkpoint Blockade Using Zalifrelimab (AGEN1884) or Botensilimab (AGEN1181) With Balstilimab (AGEN2034) for Advanced or Metastatic Soft Tissue Sarcomas

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Investigational drug late phase More information Active drug More information Started >3 years ago More information High burden on patient More information

Trial Details

Sponsor: University of Colorado, Denver (other)

Phase: 2

Start date: Jan. 28, 2020

Planned enrollment: 65

Trial ID: NCT04028063
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More trial details at ClinicalTrials.gov More info

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Investigational Drug AI Analysis

chevron Show for: Balstilimab (AGEN2034, BAL)

chevron Show for: Botensilimab (AGEN1181, BOT)

chevron Show for: Zalifrelimab (AGEN1884, UGN-301, RebmAb-600)

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Goal: Evaluate whether adding dual checkpoint blockade to doxorubicin improves 6‑month progression‑free survival (PFS6mo) over historical doxorubicin monotherapy in advanced or metastatic soft tissue sarcomas, and characterize safety and immunologic correlates.

Patients: Adults (ECOG 0–1) with advanced or metastatic soft tissue sarcoma not curable by surgery and appropriate for doxorubicin. Multiple histologies allowed, including leiomyosarcoma, liposarcoma subtypes, synovial sarcoma, MPNST, UPS/MFH, myxofibrosarcoma, angiosarcoma, fibrosarcoma, SFT/HPC, epithelioid hemangioendothelioma, malignant phyllodes, spindle/undifferentiated NOS, and others per PI review. Measurable or evaluable disease by RECIST 1.1 required. No prior anthracyclines or checkpoint inhibitors. Part 1 permits 0–1 prior systemic lines; Part 2 allows any number of prior lines provided no prior anthracycline or checkpoint inhibitor. Adequate organ function, LVEF ≥50%, and ability to undergo serial core biopsies are required; key exclusions include active autoimmune disease requiring systemic therapy, significant cardiac disease, uncontrolled comorbidities, active CNS disease, and chronic infections.

Design: Open‑label, single‑institution, non‑randomized, single‑arm phase II using a Simon two‑stage design with an initial 6‑patient safety lead‑in (9‑week DLT window), followed by stage 1 (total 15) and expansion to stage 2 if futility criteria are not met. Historical control for PFS6mo is 43.4%; the study is powered to detect improvement to 63.4%. Planned enrollment up to 65 to yield approximately 28 evaluable for the primary endpoint in Part 1, with additional cohorts in Part 2 exploring botensilimab‑based combinations.

Treatments: Part 1 evaluates doxorubicin with dual checkpoint blockade using balstilimab (anti–PD‑1) plus zalifrelimab (anti–CTLA‑4). Safety lead‑in: balstilimab 300 mg every 3 weeks up to 2 years; zalifrelimab 1 mg/kg every 6 weeks; doxorubicin 75 mg/m2 every 3 weeks beginning cycle 2 for 2 cycles during DLT window. Expansion: balstilimab 300 mg every 3 weeks up to 2 years; zalifrelimab 1 mg/kg every 6 weeks up to 2 years; doxorubicin 75 mg/m2 every 3 weeks for 6 cycles. Part 2 explores botensilimab (Fc‑enhanced anti–CTLA‑4) with doxorubicin at 60 or 75 mg/m2, and a triplet of doxorubicin plus botensilimab 75 mg every 6 weeks with balstilimab 450 mg every 3 weeks, all up to 2 years for immunotherapy. Balstilimab (AGEN2034) is a human IgG4 anti–PD‑1 antibody that restores T‑cell activity by blocking PD‑1 interaction with PD‑L1/PD‑L2. In phase II cervical cancer, balstilimab monotherapy achieved an ORR near 15% with durable responses, and combination with CTLA‑4 blockade increased ORR to approximately 25%. Safety is consistent with PD‑1 agents, with mainly endocrine and gastrointestinal immune‑related events. Zalifrelimab (AGEN1884) is a human IgG1 anti–CTLA‑4 that enhances T‑cell priming and may deplete intratumoral Tregs via Fc‑mediated mechanisms. In combination with balstilimab in cervical cancer, confirmed ORR has been around 25–37% with manageable immune‑related toxicities typical of PD‑1/CTLA‑4 combinations. A prior single‑arm phase II in soft tissue sarcoma using doxorubicin plus balstilimab and zalifrelimab reported a 6‑month PFS rate around mid‑40% and ORR about one‑third, suggesting activity but not superiority to historical control, warranting further evaluation by subtype. Botensilimab (AGEN1181) is an Fc‑enhanced anti–CTLA‑4 engineered to improve T‑cell priming and Treg depletion, engage myeloid cells, and reduce complement‑mediated toxicity. In early studies, particularly when combined with balstilimab, clinical activity has been observed across multiple solid tumors including traditionally immunotherapy‑resistant MSS colorectal cancer, with reported response rates near the 20% range in select cohorts and a manageable safety profile dominated by gastrointestinal immune‑related events.

Outcomes: Primary: 6‑month progression‑free survival by RECIST 1.1. Secondary: overall response rate, clinical benefit rate, duration of response, and safety/adverse event profile. Exploratory/other: changes in tumor‑infiltrating and circulating immune cell subsets and correlation with outcomes.

Burden on patient: Moderate to high. Patients receive intravenous doxorubicin every 3 weeks for up to 6 cycles with concurrent IV checkpoint inhibitors for up to 2 years, requiring frequent infusion visits, labs, and toxicity monitoring. A prolonged 9‑week DLT window increases early visit intensity. Mandatory image‑guided core biopsies at baseline and on cycle 2 day 5 add procedural burden and potential risks. Cardiac monitoring (baseline echocardiogram and ongoing assessments due to anthracycline exposure) and regular laboratory evaluations are required. Travel frequency is every 3 weeks during active treatment, with additional visits for adverse event management typical of PD‑1/CTLA‑4 combinations, including potential need for corticosteroid management of immune‑related toxicities.

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University of Colorado Hospital

Aurora, Colorado, 80045, United States

[email protected] / (720)848-0741

Status: Recruiting

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