Inhibrx Initiates a Potential Registration-Enabling Phase 2 Study of INBRX-109 in Conventional Chondrosarcoma Patients, Updates Data for Ongoing Phase 1 Study and Announces Amended Loan Agreement with

Inhibrx, Inc. (Nasdaq: INBX), a biotechnology company with four clinical programs in development, announced initiation of a potential registration-enabling Phase 2 study of INBRX-109 in conventional chondrosarcoma.

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.

Chondrosarcoma is an orphan 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.

In January 2021, the U.S. Food and Drug Administration (FDA) granted Fast Track designation to INBRX-109 for the treatment of patients with unresectable or metastatic conventional chondrosarcoma.

Inhibrx provided updated results from an ongoing Phase 1 clinical trial evaluating the efficacy and safety of INBRX-109 in patients with conventional chondrosarcoma. Additional data will be presented at the Annual Connective Tissue Oncology Society (CTOS) Conference taking place on November 10-13, 2021.

• Disease control was observed in 14 of 16 patients (87.5%). Two patients (12.5%) achieved partial responses and 12 of 16 patients (75%) had stable disease measured by RECISTv1.1.

• Based on preliminary results of the ongoing Phase 1 study, the median progression-free survival (PFS) is 7.6 months, and the median overall survival has not been reached.

• Three patients have exceeded 52 weeks on treatment with INBRX-109, with 62 weeks being the longest duration of stable disease observed to date, with the patient still on study.

• The safety and tolerability profile in conventional chondrosarcoma was favorable with only 1 out of 16 patients experiencing a transient low grade and fully reversible sign of hepatotoxicity.

• The trial is ongoing with an additional 12 slots added for patients with IDH1 or IDH2 mutations to support ongoing biomarker discovery efforts.

A randomized, blinded, placebo-controlled, potential registration-enabling Phase 2 trial of INBRX-109 in conventional chondrosarcoma initiated this month. The primary objective of this trial is to evaluate the anticancer efficacy of INBRX-109, as measured by PFS per RECISTv1.1 and assessed by central independent radiology review. Patients with disease progression on placebo will be able to crossover to INBRX-109. An interim analysis will occur after 50% of the planned PFS events are observed.

Additionally, upon initiation of this study, Inhibrx's loan agreement with Oxford Finance was amended and $40M in additional principal was received by Inhibrx on June 18, 2021.

About Inhibrx, Inc.

Inhibrx is a clinical-stage biotechnology 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 sdAb platform. Inhibrx has collaborations with bluebird bio, Bristol-Myers Squibb and Chiesi.