Vaccinex to Report Promising New Clinical Data Revealing Pepinemab’s Unique Mechanism to Enhance Immunotherapy

Vaccinex, Inc. recently announced it will present exciting new data characterizing the unique mechanism of pepinemab to enhance immune responses to checkpoint therapies, corresponding with improved survival benefit in patients with melanoma and head and neck cancer at the 2025 Annual Meeting of American Association for Cancer Research (AACR) in Chicago on April 29, 2025. Elizabeth Evans, PhD, Senior VP Discovery and Translational Medicine, will present results of these studies in two presentations.

Previously reported data from these two clinical studies suggest a crucial role of pepinemab to facilitate immune cell interactions within highly organized and robust centers of immunity, called tertiary lymphoid structures, or TLS. By blocking the SEMA4D inhibitory signal to Dendritic Cells (DC), pepinemab allows productive, coordinated interactions between SEMA4D+ T cells, key effector cells capable of eradicating tumors, and DC, regulatory cells that promote immune cell interactions within TLS so as to amplify mature T cell responses. New data will characterize clinical outcomes, biomarkers, and mechanisms of these interactions in patients treated with pepinemab in combination with immune checkpoint therapy.

Boosting TLS within tumors is an area of growing excitement because the presence of TLS has been shown to correlate with clinical benefit and positive response to immune checkpoint therapy. A limitation in the field has been identification of safe and effective therapies that can induce formation and harness the potential of TLS to enable durable benefit to patients. Pepinemab may represent a solution to this problem, as our data demonstrate the potential of pepinemab to turn immunologically cold tumors, such as HPV-negative and PD-L1-low head and neck cancer, into hot immune centers by inducing robust and mature TLS.

Neoadjuvant immunotherapy has emerged as a promising approach in the treatment of various cancers, showing improved immune and clinical benefit in the preoperative setting compared to standard post surgery adjuvant treatments. Despite these advances, many patients who initially benefit from antibodies that block inhibitory checkpoint molecules (e.g. PD-1, CTLA 4) will progress. More effective combination therapies are needed. Neoadjuvant treatment with pepinemab enhanced TLS maturity and correlated with longer recurrence-free survival when combined with immune checkpoint inhibitors in patients with metastatic melanoma. Evaluation of pepinemab in the neoadjuvant setting for patients with head and neck cancer is ongoing and will be reported at upcoming scientific meeting this Spring.

Pepinemab is a humanized IgG4 monoclonal antibody designed to block SEMA4D, which can otherwise bind to plexin-B1 receptors to trigger collapse of the actin cytoskeleton in cells and lead to loss of homeostatic functions of dendritic cells in immune tissue and of astrocytes and other glial cells in the brain. Pepinemab appears to be well-tolerated with a favorable safety profile in multiple clinical trials in different cancer and neurological indications.

Vaccinex, Inc. is pioneering a differentiated approach to treating slowly progressive neurodegenerative diseases and cancer through the inhibition of semaphorin 4D (SEMA4D). The Company’s lead drug candidate, pepinemab, blocks SEMA4D, a potent biological effector that it believes prevents infiltration and activation of immune cells in tumors and triggers damaging inflammation in neurodegenerative diseases. In oncology, pepinemab is being evaluated in combination with KEYTRUDA in the Phase 1b/2 KEYNOTE-B84 study in recurrent or metastatic head and neck cancer (HNSCC) and in combination with BAVENCIO in a Phase 1b/2 study in patients with metastatic pancreatic adenocarcinoma (PDAC). The oncology clinical program also includes several investigator-sponsored studies in solid tumors including breast cancer and melanoma. We believe pepinemab has also given promising results as a monotherapy in the Phase 1b/2 SIGNAL-AD study in Alzheimer’s Disease, and the Company has previously published promising Phase 2 data suggesting a slowing of cognitive decline in Huntington’s disease.

Vaccinex has global commercial and development rights to pepinemab and is the sponsor of the KEYNOTE-B84 study which is being performed in collaboration with Merck Sharp & Dohme Corp, a subsidiary of Merck and Co, Inc. Kenilworth, NJ, USA. Additional information about the study is available at: clinicaltrials.gov.

KEYTRUDA is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co. Inc., Kenilworth, NJ, USA. BAVENCIO/avelumab is provided by Merck KGaA, Darmstadt, Germany, previously as part of an alliance between the healthcare business of Merck KGaA, Darmstadt, Germany and Pfizer.