Inhibrx Biosciences’ antibody ozekibart has notched a key phase 2 win in a rare bone cancer that currently has no approved treatments, prompting the San Diego biotech to plot a submission to the FDA in the second quarter of 2026.
Ozekibart reduced the risk of disease progression or death by 52% compared to placebo, Inhibrx announced in an Oct. 23 release, hitting the primary endpoint of the ChonDRAgon trial. What’s more, the treatment more than doubled the 2.66-month median progression-free survival of the placebo arm to 5.52 months.
The trial enrolled 206 patients with advanced or metastatic chondrosarcoma that could not be removed with surgery, the go-to treatment for the disease. Chondrosarcoma is cancer of the bone’s cartilage that affects about one in every 200,000 people in the U.S. Disease usually starts in the arms, legs, pelvis, breastbone or ribs.
Ozekibart is designed to bind to death receptor 5 on the surface of cancer cells, triggering a cell death pathway.
One patient died from liver toxicity early in the ChonDRAgon study, after which Inhibrx began excluding patients with severe liver problems and imposed stricter monitoring for early signs of liver trouble. Overall, the treatment arm had a liver adverse event rate of 11.8% compared to 4.5% in the placebo arm, the company said, with most adverse events being grade 1 or 2.
Inhibrx said intravenous infusion of ozekibart every three weeks was otherwise well tolerated by patients, with the most common side effects being fatigue, constipation and nausea.
"I am very encouraged and enthusiastic about ozekibart and the impact I have seen on my sarcoma patients," Robin Jones, M.D., head of the sarcoma unit at The Royal Marsden Hospital in London, said in the release. "With no approved treatments available, we have observed that ozekibart helps to keep the cancer from growing, improves how patients feel and restores a sense of hope.”
Alongside the chondrosarcoma data, Inhibrx also reported that ozekibart had hit a 64% overall response rate in 25 patients enrolled in an expanded phase 1 cohort for Ewing sarcoma, another rare bone cancer, in combination with irinotecan and temozolomide.
In that same phase 1 trial, a similarly expanded cohort for colorectal cancer, in combination with the FOLFIRI chemotherapy regimen, has scored a 23% overall response rate so far, Inhibrx said. For both phase 1 cohorts, the treatment has shown a safety profile consistent with the treatment paired with ozekibart given alone, the biotech added.
"We are excited by these results which suggest the potential of ozekibart to expand not only in sarcomas but also in high unmet need solid tumor indications," Mark Lappe, Inhibrx’s co-founder and CEO, said in the release. "We look forward to working with the FDA to deliver ozekibart to patients as swiftly as possible."
Ozekibart was one of three cancer assets Inhibrx was left with after a $1.7 billion buyout from Sanofi in January 2024. The French pharma giant wanted to get its hands on the rare disease drug INBRX-101, a candidate for alpha-1 antitrypsin deficiency. To do so, Sanofi absorbed the company but then spun the unwanted assets back out into a new-look Inhibrx.
One of those candidates, an anti-PD-L1 x 4-1BB bispecific called INBRX-105, was later revealed to have been canned around the time of the Sanofi sale due to lackluster data from a phase 1/2 solid tumor trial, with Inhibrx ending the trial early.
Besides ozekibart, Inhibrx’s other remaining asset is INBRX-106, a hexavalent OX40 agonist currently being tested in combination with Merck’s Keytruda in a phase 2/3 head and neck squamous cell carcinoma trial and a phase 1/2 solid tumor trial.