Soligenix Inc. (NASDAQ: SNGX) Working to Advance Heat-Stable Ricin Vaccine with Promising Efficacy

• Ricin toxin is a potent biothreat, so lethal that even a dose the size of a grain of salt can be fatal within 48 to 72 hours.
• RiVax(R) is a subunit protein vaccine that incorporates Soligenix’s ThermoVax(R) technology, which eliminates the need for cold-chain storage. 
• Soligenix reports that the RiVax antigen has been shown to be safe in phase 1 studies in humans, with future steps including pivotal animal efficacy studies.

With global security threats driving demand for advanced biodefense solutions, Soligenix (NASDAQ: SNGX) is advancing RiVax(R), a heat-stable recombinant vaccine candidate aimed at protecting against deadly ricin toxin exposure. Supported by proprietary stabilization technology and robust preclinical data demonstrating long-lasting immunity, SNGX’s RiVax represents both a critical public safety innovation and a significant market opportunity in the specialized vaccine sector.

Ricin toxin, derived from castor beans, is a potent biothreat, so lethal that even a dose the size of a grain of salt can be fatal within 48 to 72 hours, depending on the route of exposure (https://ibn.fm/H5pl6). RiVax is a subunit protein vaccine composed of a genetically inactivated version of the ricin A-chain (“RTA”) with two mutations that nullify toxicity while preserving immunogenicity (https://ibn.fm/15PuI).

The vaccine incorporates Soligenix’s ThermoVax(R) formulation, thermostabilized platform that eliminates the need for cold-chain storage. This means RiVax, can remain stable and effective for at least a year even when stored at high temperatures such as 40°C (104°F), making it highly practical for stockpiling and deployment in remote or resource-limited settings.

Clinical evaluations have shown safety and immune response in humans. In phase 1A trials without adjuvant, RiVax demonstrated dose-dependent seroconversion and no toxicity up to 127 days post-vaccination. A follow-up Phase 1B trial formulated with adjuvant revealed an enhanced immunogenic profile, where the adjuvanted version elicited higher and more durable neutralizing antibody levels in human volunteers, along with a favorable safety profile (https://ibn.fm/zgbEL).

The company plans on pursuing approval for RiVax under the Animal Rule, noting that work to date has “focused on improving manufacturing processes and identifying correlates of immune protection that can demonstrate that protection observed in animals is likely to translate to humans” (https://ibn.fm/qJtbv). Soligenix reports that the RiVax antigen has been shown to be safe in two phase 1 studies in humans, with future steps including pivotal animal efficacy studies to demonstrate potency in animals, as well as a phase 2 clinical study in humans to confirm safety and correlate immune markers of protection with outcomes from animal studies.

The efficacy of RiVax in animal models has been especially noteworthy. Soligenix reported statistical protection of up to 100% in mice and nonhuman primates exposed to lethal doses of ricin via injection or aerosol, all with no signs of lung damage. Remarkably, a prime-boost regimen with two doses protected mice against ricin challenge equivalent to 10 times the lethal dose, maintaining immunity for at least one year. Further, correlates of protection identified in nonhuman primates versus humans bolster the case for efficacy under the FDA’s Animal Rule, enabling the company to advance RiVax under regulatory pathways designed for ethical and rare exposures (https://ibn.fm/MNErD).

RiVax has been granted both Orphan Drug and Fast Track designations by the U.S. Food and Drug Administration, as well as Orphan status in Europe. If approved, the treatment may be eligible for a biodefense Priority Review Voucher (“PRV”), a potentially valuable incentive that offers transferable market value. The program’s development is backed by nondilutive funding, more than $40 million to date, from institutions including the National Institute of Allergy and Infectious Diseases (“NIAID”), reflecting federal support for biodefense countermeasures.

RiVax was originally licensed from researchers at UT Southwestern, and Soligenix holds a U.S. patent covering RiVax(R) as well as other biothreat antigens such as anthrax as well as multivalent compositions for filovirus infections like ebola, highlighting the vaccine candidates’ versatility in broader defense and public health strategies.  The company is also exploring potential inclusion in the U.S. Strategic National Stockpile and further formulation for biodefense readiness.

RiVax represents a strategic combination of innovative science, practical formulation and strong preclinical and early clinical validation. Its unique approach — leveraging thermostability, clear safety and durable, and broad-spectrum protection — sets a new standard for biodefense vaccines. For Soligenix, RiVax embodies the company’s commitment to address critical public health threats with advanced solutions. As Soligenix continues to advance this vaccine through pivotal trials, RiVax stands as a milestone in preparedness against ricin toxin and potentially other biothreats.

For more information, visit www.Soligenix.com.

NOTE TO INVESTORS: The latest news and updates relating to SNGX are available in the company’s newsroom at https://ibn.fm/SNGX

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