Phase 1 Trial Exhibits Positive Interim Results in Chondrosarcoma

Treatment with the investigation agent INBRX-109 induced responses and decreased the tumor burden in a cohort of patients with chondrosarcoma, according to interim efficacy and safety findings a phase 1 trial in patients with chondrosarcoma, Inhibrx, Inc announced in a press release.

The results from the study will be presented at the Annual Connective Tissue Oncology Society Conference on November 20, 2020 and Inhibrx, Inc also plans to share the findings with the FDA.

Of the 12 evaluable patients in the ongoing expansion cohort, 8 (67%) showed a decrease in their tumor burden by RECIST with INBRX-109. As of October 2020, 2 patients achieved partial responses with reductions in tumor size of 60% and 32%. Eleven (92%) patients were observed to have disease control. At 4-month follow-up, 7 patients were still on the study. To date, the longest disease control duration for a patient in this cohort was 33 weeks.

"I am quite pleased to see prolonged progression-free survival in a disease that has been unresponsive to conventional therapies," Sant P. Chawla, MD, a principal investigator conducting the phase 1 trial at the Sarcoma Oncology Center in Santa Monica, California, said in a statement.

INBRX-109, a precision-engineered, tetravalent DR5 antagonist antibody or single domain antibody, is designed to exploit the tumor-biased cell death induced by DR5 activation.

In most patients, there was a favorable safety and tolerability profile. About 90% did not show signs of hepatotoxicity. No new serious or severe adverse events were observed since the last safety update in July 2020.

This 3-part study is ongoing and has been updated to have 10 more patient slots to the chondrosarcoma cohort per investigator requests. Originally, the trial was initiated in November 2018. Part 1 was a dose escalation up to the maximum dose of 30 mg/kg, which was completed in August 2019 with enrollment of 20 patients. The study drug was well tolerated in part 1; then part 2 was a single agent dose expansion starting in September 2019. Part 3 looked at chemotherapy combination cohorts in patients with malignant pleural mesothelioma and pancreatic adenocarcinoma. This was initiated in November 2020.

"We believe the results in chondrosarcoma, a disease with a significant unmet need, are very promising. Mark Lappe, CEO for Inhibrx, said in a press release.

In terms of next step for the phase 1 study, Lappe announced intiaion of treatment in another subset of patient, stating, "additionally, this month, we will initiate dosing in patients with synovial sarcoma, as well as our first chemotherapy combination cohorts with INBRX-109 in pancreatic adenocarcinoma and epithelioid subtype malignant pleural mesothelioma."

_Reference

_{Inhibrx Announces Positive Interim Results from the Phase 1 Trial of INBRX-109 in Chondrosarcoma Patients. News release. Inhibrx, Inc. Published November 11, 2020. Accessed November 13, 2020. https://bit.ly/3kqzbCt}