Inhibrx Announces Positive Interim Results from Chondrosarcoma Trial

Inhibrx has announced updated interim results from a Phase 1 clinical trial evaluating the efficacy and safety of INBRX-109 in patients with chondrosarcoma. Chondrosarcoma is an orphan disease and bone cancer with approximately 2,800 new patients diagnosed annually in the United States and the European Union. There are currently no therapeutics approved for the treatment of chondrosarcoma.

Inhibrx's most advanced program, INBRX-109, is a precision-engineered, tetravalent DR5 agonist antibody designed to exploit the tumor-biased cell death induced by DR5 activation.

Of the 12 patients evaluable for efficacy within the ongoing chondrosarcoma expansion cohort to date, disease control was observed in 11 of 12 patients (92%) and 8 of 12 patients (67%) had a decrease in their tumor burden by RECIST.

Two of the patients achieved partial responses with reductions in tumor size of 60% and 32% as of October 2020.

Based on these preliminary results, the observed disease control rate at the four-month follow-up was 8 of 12 subjects (67%) with 7 of 12 patients continuing on study. The longest disease control duration observed to date for a patient in this cohort was 33 weeks, or approximately eight months.

The safety and tolerability profile continued to be favorable with most patients, approximately 90%, experiencing no signs of hepatotoxicity. There have been no new serious or severe adverse events since Inhibrx's last safety update in July 2020.

The trial is ongoing and an additional 10 patient slots were added, per investigator requests, to the chondrosarcoma cohort.

"I am quite pleased to see prolonged progression free survival in a disease that has been unresponsive to conventional therapies," said Dr. Sant P. Chawla, one of the principal investigators conducting the Phase 1 trial at the Sarcoma Oncology Center in Santa Monica, California.

"We believe the results in chondrosarcoma, a disease with a significant unmet need, are very promising. We are meeting with the Food and Drug Administration in the near future to discuss the design of a registration-enabling study that we anticipate initiating in the second quarter of next year," said Mark Lappe, CEO for Inhibrx. "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."

INBRX-109 is a precisely engineered tetravalent single domain antibody (sdAb) based therapeutic candidate that agonizes DR5 to induce tumor selective programmed cell death. A three-part, Phase 1 clinical trial was initiated in November 2018. Part 1, dose escalation, was completed in August 2019 with enrollment of 20 patients. INBRX-109 was well-tolerated, with no significant toxicities observed at doses up to and including the maximum administered dose of 30 mg/kg. No maximum tolerated dose was reached. Part 2, single agent dose expansion, commenced in September 2019, while Part 3, chemotherapy combination cohorts, initiated this month in epithelioid subtype malignant pleural mesothelioma and pancreatic adenocarcinoma.