In a Phase 1 expansion of ragistomig, a 4-1BB × PD-L1 bispecific, the 3 mg/kg every-six-weeks regimen delivered an 11.8% objective response rate and 58.8% disease control rate across 17 evaluable, heavily pretreated solid tumor patients previously exposed to immuno-oncology therapies. Safety improved meaningfully versus the prior every-two-weeks schedule: Grade ≥3 liver function test elevations occurred in 5% of patients on Q6W compared with 40% on Q2W, with Grade ≥3 TEAEs at 50% versus 66.7%, respectively, and no cytokine release syndrome in either cohort. Immunophenotyping showed proliferation of effector and memory CD8+ T cells with attenuated Treg expansion on Q6W dosing. By contrast, the Q2W cohort (n=14 evaluable) posted a higher ORR of 28.6% and DCR of 64.3%.
The core update, presented at ESMO-IO 2025, positions the extended-interval 3 mg/kg regimen as the provisional monotherapy “sweet spot” on tolerability, intended to open the door to combination studies without compounding hepatic risk. Enrollment is underway in a 5 mg/kg Q6W cohort to probe the margin between immunologic durability and dose-limiting toxicity. The program continues in the United States and South Korea and targets patients relapsed or refractory to PD-(L)1 inhibitors, a setting where resistance is entrenched and combination complexity often undermines operational cadence.
Strategically, extending the dosing interval is a defensive optimization aimed at widening the therapeutic window for a class still shadowed by historical 4-1BB liver toxicity. Ragistomig’s conditional 4-1BB activation tethered to PD-L1 engagement, plus an Fc-silent backbone, is designed to confine costimulation to the tumor microenvironment; the Q6W signal suggests that schedule can further blunt off-tumor stress. The trade-off is visible: lower monotherapy ORR on Q6W relative to Q2W, offset by a materially better hepatic profile that is more compatible with add-on regimens. For NovaBridge, which is also advancing a Claudin 18.2 × 4-1BB asset, the emerging theme is a portfolio bet on 4-1BB as a modular T-cell activator, with dosing and conditional gating as the levers to make combinations clinically and regulatorily feasible.
For sites, a Q6W infusion cadence reduces chair time and visit frequency, but liver surveillance remains non-negotiable; protocols will still demand tight early-cycle lab monitoring and rapid turnaround on LFTs. As combinations roll in, operational simplicity will erode: overlapping hepatotoxicity risks, more intensive AE adjudication, and expanded correlative sampling for CD8/Treg dynamics will increase coordinator load and central lab dependencies. CROs can expect complex DLT schemas and adaptive dose-modification rules tuned to hepatic signals. Regulators have been consistently cautious with 4-1BB; any path forward will hinge on reproducible hepatic safety in combinations and clear, prespecified management algorithms.
Near term, the key readouts will be the 5 mg/kg Q6W safety and immunologic durability, confirmation of an RP2D, and early combination data that maintain the improved hepatic profile while restoring or surpassing the Q2W efficacy signal. Program risk concentrates in three areas: whether ORR and depth of response can be lifted in combinations without triggering liver toxicity, whether PD-L1 expression or other biomarkers can rationalize patient selection beyond a broad refractory label, and how ragistomig differentiates within a crowded class of PD-L1 × 4-1BB bispecifics pursuing the same conditional-activation thesis. Watch for randomized expansion designs, more granular durability data, and explicit liver monitoring frameworks embedded in upcoming protocols—these will signal how confidently the program is navigating the 4-1BB safety–efficacy trade space.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
