A novel approach to cancer immunotherapy that inverts the conventional role of regulatory T cells is set to enter first-in-human testing, with CoRegen, Inc. registering a Phase I/IIa study of CRG-150, an autologous CRISPR-edited regulatory T cell (Treg) therapy, in patients with relapsed or refractory breast and prostate cancers. The study appears set to become the first clinical evaluation of a therapy targeting steroid receptor coactivator 3 (SRC-3) in Tregs, an approach that could add a distinct mechanistic class to the crowded solid tumor immunotherapy landscape.
The open-label, multicenter study (NCT07730125) will enroll up to 67 adults with metastatic HR+/HER2-negative breast cancer, triple-negative breast cancer (TNBC), or prostate cancer who have received at least two specified classes of prior systemic therapy and experienced progression or intolerance. Phase I will use a Bayesian Optimal Interval (BOIN) design to establish a recommended Phase II dose (RP2D), followed by Phase IIa expansion cohorts of 10 patients per tumor type.
One unusual feature is the absence of lymphodepleting chemotherapy before CRG-150 infusion, a conditioning strategy commonly used in adoptive cell therapy to support expansion of transferred cells. Patients will undergo apheresis followed by an anticipated 28-day manufacturing period, during which bridging therapy is permitted at investigator discretion. Long-term safety follow-up will extend to 15 years, consistent with the FDA's framework for genome-edited gene therapies. The study is expected to begin in Q4 2026, with primary completion targeted for June 2029.
SRC-3, also known as NCOA3, is a transcriptional coactivator that is highly expressed in Tregs and has been shown preclinically to be important for their immunosuppressive activity. CRISPR-mediated knockout of SRC-3 is intended to reprogram autologous Tregs from tumor-protective immunosuppressors into promoters of anti-tumor immunity. CoRegen said SRC-3 disruption also affects transcriptional programs involving immune checkpoint targets including PD-1, PD-L1, CTLA-4, LAG3, and CCR4.
The approach has produced striking results in immune-intact mouse models. A 2023 PNAS study found that adoptive transfer of SRC-3-knockout Tregs eradicated established breast tumors in mice and produced durable protection against recurrence, while related genetic models showed similar activity in prostate cancer without an apparent systemic autoimmune phenotype. A 2026 OncoImmunology paper extended the findings to syngeneic models of glioblastoma, melanoma, and lung cancer. The platform originated from research in the O'Malley Laboratory at Baylor College of Medicine, where work led by the late Bert O'Malley laid the scientific foundation for CRG-150.