Orbus Therapeutics Highlights Phase 3 STELLAR Clinical Study Results Showing Clinically Meaningful Benefits in Rare Brain Tumor at Society for Neuro-Oncology (SNO) Annual Meeting

– Updated results based on molecular classification and blinded independent central review demonstrate clinically meaningful survival benefits for patients with recurrent grade 3 astrocytoma who were treated with eflornithine plus standard of care –

PALO ALTO, Calif., Nov. 20, 2025 (GLOBE NEWSWIRE) -- Orbus Therapeutics, Inc., a private pharmaceutical company, today announced the presentation of the Phase 3 STELLAR clinical study results showing clinically meaningful benefits in patients with grade 3 astrocytoma—an aggressive brain tumor with a median survival of only two to five years post-diagnosis. The results will be presented at the Society for Neuro-Oncology (SNO) Annual Meeting on November 22, 2025.

The Company's clinical candidate, eflornithine, when combined with lomustine, achieved improvements in overall survival (OS) and progression-free survival (PFS) compared to lomustine alone in patients with recurrent IDH mutant, grade 3 astrocytoma. This subset of patients from the STELLAR Study is a molecularly-defined population representing all diagnosed patients with grade 3 astrocytoma. No benefits were observed in patients with grade 4 disease or the primary endpoint in the intent-to-treat (ITT) population.

“For 30 years, SNO has been at the forefront of neuro-oncology, driving discovery and improving patient care, which is why we are excited to have these encouraging results from the STELLAR Study presented at this meeting," said Jason Levin, President and Chief Executive Officer at Orbus. "In patients with recurrent WHO 2021 grade 3 IDH-mutant astrocytoma, eflornithine not only improved overall survival but, as determined by a blinded independent central review, improved progression-free survival as well. I believe these data, while taken from a subset analysis, represent one of the first meaningful advances for a patient population in which outcomes have been poor for years."

The STELLAR study (NCT02796261) was designed to evaluate the efficacy and safety of eflornithine in combination with lomustine compared to lomustine alone in patients with grade 3 anaplastic astrocytoma that recurs after surgery, irradiation and adjuvant temozolomide chemotherapy. The study enrolled a total of 343 patients who were stratified by key characteristics, including IDH mutation status. In the overall intent-to-treat (ITT) population, which was defined per the previous WHO CNS4 tumor classification (2016) and included patients currently defined as having both grade 4 astrocytoma and glioblastoma and grade 3 astrocytoma, there was no overall difference in the primary endpoint of OS (HR = 0.95) or in PFS between arms.

Of the total number of patients enrolled in the STELLAR Study, a majority (n=196/343) had grade 3 IDH mutant astrocytoma tumors, as defined by the current WHO CNS5 tumor reclassification (2021). The SNO presentation describes both a prospective analysis (prior to unblinding) performed in the intended target tumor population, patients with IDH mutant grade 3 (without CDKN2A/B homozygous deletion) astrocytoma per the WHO CNS5 tumor reclassification (2021), along with a retrospective analysis of radiographic results using a blinded independent central review (BICR):

• In the 196 patients with recurrent grade 3 IDH mutant astrocytoma, clinically meaningful improvements in both OS and PFS were observed.
• Median OS in the eflornithine + lomustine arm was 34.9 months compared to 23.5 months in the lomustine alone arm with HR = 0.64 (log rank p = 0.01).
• Physician determined PFS, as previously reported, showed a correlating benefit with median PFS of 15.8 months in the eflornithine + lomustine arm and 7.2 months in the lomustine alone arm with HR = 0.57 (log rank p = 0.01). BICR results confirmed this benefit with a HR = 0.61 (log-rank p = 0.03).
• The combination of eflornithine + lomustine was generally well-tolerated. The known side effect profile of eflornithine combined with lomustine was consistent with data from earlier studies and no new safety signals were identified. The most common Grade 3+ treatment emergent adverse events of relevance were related to myelosuppression and hearing impairment. Similarly, the proportion of patients with Grade 3+ hematology parameters and those with Grade 3 + clinical chemistry parameters were as expected.

About WHO Tumor Classification

The WHO tumor classification system is a globally recognized framework used to categorize tumors—especially cancers—based on histology, genetic features, and their grade. This system is published and updated by the WHO to ensure that diagnoses are standardized across the world and to help guide treatment decisions. For tumors of the central nervous system, based on improved understanding of biomarkers, the 2021 WHO update reclassified gliomas to incorporate a fully-integrated and molecular-based classification, defined by IDH mutation status and grade. The STELLAR study began prior to 2021 and, consequently, had two subsets of previously classified and enrolled “grade 3” patients change designation to grade 4 under the updated 2021 WHO CNS tumor reclassification.

About Eflornithine

Eflornithine is a novel cytostatic agent that irreversibly inhibits ornithine decarboxylase, a key enzyme in mammalian polyamine biosynthesis that is upregulated in certain types of cancer.

Eflornithine has been granted Orphan Drug Designation and Breakthrough Therapy Designation for the treatment of patients with anaplastic glioma by the U.S. Food and Drug Administration (FDA) and has also been granted Orphan Medicinal Product status for the treatment of glioma by the Committee for Medicinal Products for Human Use (CHMP) at the European Medicines Agency (EMA).

About Orbus Therapeutics

Orbus Therapeutics Inc. is a late-stage, private biopharmaceutical company that is dedicated to developing products that treat rare diseases for which there are few, if any, effective therapies. The Company’s lead product candidate, eflornithine, has completed one Phase 3 clinical study in patients with recurrent anaplastic astrocytoma, a rare form of central nervous system cancer. For more information, please visit the Company's website at http://www.orbustherapeutics.com.

Contact Information:
Jason Levin
jason.levin@orbustherapeutics.com

Media:
Kelli Perkins
kelli@redhousecomms.com

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