Ozekibart Shows Activity in Late-Line Colorectal Cancer

Updated interim findings from a phase 1/2 study evaluating ozekibart (INBRX-109) in combination with FOLFIRI demonstrate encouraging clinical activity in patients with locally advanced or metastatic, unresectable colorectal cancer, according to data reported by Inhibrx Biosciences, Inc.

As of the April 10, 2026, data cutoff, the combination yielded an objective response rate of 20% among 45 evaluable patients. This compares favorably with historical response rates of approximately 1% to 6% observed with currently available therapies in similar late-line settings. Additionally, the regimen demonstrated a median progression-free survival of 5.5 months and a disease control rate of 87%, supporting further clinical development.

Key efficacy outcomes support continued development

Among the 45 evaluable patients, ozekibart in combination with FOLFIRI produced an objective response rate of 20% per RECIST version 1.1 criteria. Notably, nearly half of these responses were durable, with durations exceeding six months. Responses were observed irrespective of RAS or RAF mutation status, suggesting potential activity across molecular subgroups.

The median progression-free survival was reported at 5.5 months. At the six-month landmark, 42% of patients remained progression-free, and nine patients continued on active therapy, indicating sustained disease control in a subset of patients beyond the median.

The disease control rate, defined as the proportion of patients achieving either partial response or stable disease, reached 87%. These findings collectively underscore the potential of ozekibart to provide clinically meaningful benefit in a population with significant unmet need.

Mechanism of action and Prior pevelopment of ozekibart

Ozekibart is a precision-engineered, tetravalent death receptor 5 agonist antibody designed to induce tumor-selective apoptosis through activation of the death receptor 5 pathway. This mechanism aims to exploit tumor-biased cell death signaling, differentiating it from conventional cytotoxic and targeted therapies.

The agent has previously demonstrated clinical activity in other malignancies, most notably in conventional chondrosarcoma. In the randomized phase 2/3 ChonDRAgon trial, ozekibart significantly improved progression-free survival compared with placebo, achieving a hazard ratio of 0.479 and more than doubling median progression-free survival to 5.52 months vs 2.66 months.

These findings supported regulatory engagement, including a biologics license application submitted in April 2026.

Study design and treatment approach

The ongoing phase 1/2 study evaluates ozekibart in combination with FOLFIRI, a standard chemotherapy regimen consisting of folinic acid, fluorouracil, and irinotecan. The trial includes patients with locally advanced or metastatic colorectal cancer who are not candidates for surgical resection.

Efficacy assessments were conducted using RECIST version 1.1 criteria. Key end points include objective response rate, progression-free survival, and disease control rate. Safety and tolerability were also closely monitored to characterize the feasibility of combining ozekibart with chemotherapy in this setting.

The study population represents a heavily pretreated cohort. Approximately 70% of patients received ozekibart as a fourth-line therapy, underscoring the advanced stage of disease at treatment initiation. Additionally, 80% of patients had previously experienced disease progression on irinotecan-based regimens, indicating resistance to a key component of the FOLFIRI backbone.

A substantial proportion of patients, 68%, presented with liver metastases at baseline, reflecting a population with high disease burden and limited prognosis. This context is critical when interpreting the observed efficacy outcomes.

Safety profile and future clinical directions

The combination of ozekibart and FOLFIRI demonstrated a manageable safety profile consistent with known toxicities of chemotherapy. The most common treatment-related adverse events included diarrhea, fatigue, and nausea, predominantly grade 1 or 2 in severity. Importantly, no significant liver toxicity was observed despite the high prevalence of baseline hepatic metastases.

These findings support further clinical evaluation. Inhibrx Biosciences plans to engage with the FDA in the second half of 2026 to discuss initiation of a first-line registrational trial in colorectal cancer. Additional discussions will explore potential accelerated regulatory pathways in the fourth-line setting, as well as expansion into other indications, including refractory Ewing sarcoma.

For oncology nursing professionals, these data highlight a potentially emerging therapeutic option in late-line colorectal cancer, emphasizing the importance of monitoring for manageable gastrointestinal toxicities and recognizing the clinical significance of durable responses in heavily pretreated populations.