Bria-IMT (SV-BR-1-GM whole-cell vaccine + GM-CSF) + PD-1 blockade shows 44% 12-mo OS in heavily pretreated MBC

Bria-IMT pairs SV-BR-1-GM (an irradiated allogeneic breast cancer cell-line vaccine engineered to secrete GM-CSF; given as IFNγ-stimulated vs unstimulated formulations) with PD-1 checkpoint inhibition (pembrolizumab or retifanlimab) in a randomized Phase II sequencing study (CPI start cycle 1 vs cycle 2) in heavily pretreated metastatic breast cancer (n=32; median 6 prior lines). Median PFS was 3.5 months (95% CI 3.0–4.2) and median OS was 9.5 months (95% CI 7.0–17.4), with Kaplan–Meier OS probability 44.0% at 12 months (95% CI 26.2–59.7%) and 26% at 24 months (95% CI 12.1–42.4%); exploratory subgroup signals favored earlier CPI start (mOS 13.3 vs 7.4 months; HR 0.8, p=0.6), unstimulated (≠IFγ) formulation (mOS 16.6 vs 9.1 months; HR 0.58, p=0.23), DTH positivity (mOS 11.9 vs 4.7 months; p<0.001), and lower baseline CTC burden (<5 vs >5; mOS 16.6 vs 5.5 months; p<0.001). Grade≥3 AEs occurred in 47% (most commonly injection-site reaction, nausea, fatigue), with no treatment-related discontinuations and no unexpected safety signals; an ongoing Phase III study is Bria-ABC (NCT06072612). Compared with common late-line single-agent options (eribulin “treatment of physician’s choice” control mOS ≈10.6 months in EMBRACE) and pembrolizumab monotherapy in previously treated mTNBC (KEYNOTE-119 mOS ≈10.7 months in CPS≥1), the overall mOS here looks in-family overall—so the real story is whether the biomarker-enriched “long-survivor” tail is reproducible rather than the median shifting.