Press Releases

Promising Results of Next-Generation Intranasal COVID-19 Booster Vaccine: Implications for Infection Prevention and Transmission

The Icahn School of Medicine at Mount Sinai in New York, NY is pleased to announce that CastleVax, Inc. has completed enrollment and a preliminary analysis of a phase 1 trial of its licensed Newcastle disease virus (NDV)-based COVID-19 booster vaccine.

The phase 1 study evaluated two dose levels of the live, recombinant vaccine, NDV-HXP-Spike(S), delivered intranasally, intramuscularly, or via both routes in combination, in participants previously vaccinated with an authorized intramuscular COVID-19 vaccine.

Interim results show that intranasal delivery resulted in a robust S-specific, secretory IgA response in saliva relative to pre-booster levels, which is important for conferring mucosal immunity and has the potential to prevent infection and/or transmission of COVID-19. In addition, a strong boosting of serum neutralizing-antibody response was observed, which is important for conferring systemic immunity and prevention of severe disease, hospitalization, and death (the efficacy endpoint(s) for currently authorized intramuscularly delivered vaccines). The safety profile was also acceptable, successfully clearing Data Safety Monitoring Board reviews.

“The initial observations from our phase 1 trial of NDV-HXP-S as a COVID-19 booster vaccination suggest that it is safe and well-tolerated when delivered intranasally and/or intramuscularly to healthy adults. The preliminary exploratory findings looking at mucosal and systemic antibody responses are encouraging, particularly when NDV-HXP-S is administered intranasally. There is a growing interest in developing vaccines that not only protect against the severe illnesses caused by respiratory pathogens but also limit host susceptibility and decrease person-to-person transmissions by enhancing the mucosal immune response. I am excited to watch as the NDV-vectored vaccine platform matures to address newer variants of concern in larger randomized controlled trials,” said Sean Liu, MD, PhD, Assistant Professor of Medicine (Infectious Diseases and Hospital Medicine) at Icahn Mount Sinai.

“We are thrilled with the progress led by Dr. Liu and our colleagues at the Mount Sinai Health System, and are both excited and encouraged by these preliminary results,” said Michael Egan, PhD, CastleVax Chief Scientific Officer and acting Chief Executive Officer. “Dr. Liu’s preliminary findings complement those of our development partners in Mexico, Avimex, whose interim phase 3 results showed their live, attenuated NDV-based vaccine (Patria® (AVX/COVID-12), licensed from CastleVax, was effective as a booster against COVID-19.”

The Mount Sinai NDV-vectored vaccine platform was developed by Mount Sinai scientists Peter Palese, PhD, Horace W. Goldsmith Professor and Chair Emeritus of Microbiology; Adolfo García-Sastre, PhD, Irene and Dr. Arthur M. Fishberg Professor of Medicine and Director of the Global Health and Emerging Pathogens Institute; Florian Krammer, PhD, Professor of Microbiology, and Pathology, Molecular and Cell Based Medicine; and Weina Sun, PhD, Assistant Professor of Microbiology, Icahn Mount Sinai, and was licensed by Mount Sinai to CastleVax Inc. Mount Sinai has a financial interest in this technology and in CastleVax. Drs. Palese, García-Sastre, Krammer, and Sun also have a financial interest in this technology and in CastleVax pursuant to the Mount Sinai Intellectual Property Policy. Mount Sinai is represented on the CastleVax Board of Directors by Erik Lium, PhD, Chief Commercial Innovation Officer, Mount Sinai Health System, and President, Mount Sinai Innovation Partners; Mr. Matthew Rosamond, Chief Financial Officer, Icahn Mount Sinai; and Mr. Stephen Harvey, MBA, Chief Financial Officer, Mount Sinai Health System. The phase 1 clinical trial mentioned herein is led by independent faculty investigators (Dr. Liu and Judith A. Aberg, MD, Chief of the Division of Infectious Diseases, Mount Sinai Health System) who have no financial interests in either the vaccine or CastleVax.

About NDV-HXP-S: The NDV-based vaccine technology was developed at Icahn Mount Sinai in the laboratories of Drs. Palese, García-Sastre, Krammer, and Sun.

About CastleVax: In August 2022, the Mount Sinai Health System launched CastleVax, Inc., a clinical-stage vaccine research and development company devoted to the commercial development of the NDV vaccine platform technology.

For more information on CastleVax and the NDV vaccine platform, visit