SAN DIEGO, CA, USA I November 2, 2023 I Inhibrx, Inc. (Nasdaq: INBX), a clinical-stage biopharmaceutical company dedicated to the development of therapeutics for oncology and rare diseases, today announced preliminary efficacy and safety data from the Phase 1 trial of INBRX-109 in combination with Irinotecan and Temozolomide (IRI/TMZ) for the treatment of advanced or metastatic, unresectable Ewing sarcoma. Inhibrx presented this dataset as of the data cut of September 8th, 2023 at the Annual Connective Tissue Oncology Society (CTOS) Conference today.

Among the 13 patients evaluable, which included 7 classical Ewing sarcoma patients (EWS) and 6 round cell sarcoma patients (RCS), the observed disease control rate was 76.9%, or 10 out of 13 patients as measured by RECISTv1.1. There were 7 patients who achieved partial responses (53.8%), 5 of which were observed in classical EWS patients (71.4%) and 2 of which were observed in RCS patients (33.3%). Durable clinical benefit was observed in 4 patients (30.8%) who achieved disease control lasting greater than 6 months. As of September 8, 2023, the longest duration of stable disease was over 10 months and ongoing and 7 of the 13 patients remained in the study.

Overall, INBRX-109 in combination with IRI/TMZ was well tolerated. The most common adverse events were diarrhea, nausea and fatigue, all consistent with the known safety profile of IRI/TMZ. No grade 3 or higher liver-related events occurred.

“I am encouraged by these initial data in relapsed/refractory Ewing sarcoma patients. This is a patient population with a high unmet need and limited effective treatment options,” said Dr. Rashmi Chugh, MD, a Professor of Internal Medicine in the Division of Hematology/Oncology at University of Michigan Rogel Comprehensive Cancer Center.  “I look forward to ongoing recruitment in this cohort of patients and seeing the results of the further expansion.” 

About Ewing Sarcoma

Ewing sarcoma, a round cell sarcoma, is a rare, aggressive tumor that occurs in children and adults. It is frequently metastatic at diagnosis with a poor prognosis and commonly relapses. Few effective treatments are available. IRI with TMZ is frequently used in the relapsed setting but response rates are low.

About INBRX-109

INBRX-109 is a precision-engineered, tetravalent death receptor 5 (DR5) agonist antibody designed to exploit the tumor-biased cell death induced by DR5 activation.

In January 2021, the FDA granted Fast Track designation to INBRX-109 for the treatment of patients with unresectable or metastatic conventional chondrosarcoma and orphan-drug designation to INBRX-109 for chondrosarcoma in the United States.

In June 2021, Inhibrx initiated a randomized, blinded, placebo-controlled, registration-enabling Phase 2 trial of INBRX-109 in conventional chondrosarcoma, which is currently ongoing. Additionally, in a Phase 1 trial, Inhibrx is currently investigating INBRX-109 in other indications in combination with certain chemotherapies, including Ewing sarcoma.

About Inhibrx, Inc.

Inhibrx is a clinical-stage biopharmaceutical company focused on developing a broad pipeline of novel biologic therapeutic candidates in oncology and orphan diseases. Inhibrx utilizes diverse methods of protein engineering to address the specific requirements of complex target and disease biology, including its proprietary protein engineering platforms. For more information, please visit

SOURCE: Inhibrx