PaxVax Announces the Initiation of Phase 2b Trial for Its Chikungunya Vaccine

PaxVax announced the enrollment of the first patient in its Phase 2b dose-finding trial of the chikungunya virus-like particle (VLP) vaccine, building upon a Phase 2a study by the National Institutes of Health (NIH) with 400 subjects. The Phase 2b study will enroll 400 subjects to evaluate multiple dosing regimens. PaxVax expects results in early 2019. The vaccine was licensed from the National Institute of Allergy and Infectious Diseases (NIAID) at NIH.

"We are pleased to advance our chikungunya clinical trial program and continue our progress toward developing and commercializing a new vaccine to protect against this debilitating and highly-infectious disease," said Nima Farzan, Chief Executive Officer and President of PaxVax. "This significant milestone underscores our commitment to addressing overlooked, recalcitrant global health threats."

Chikungunya represents a significant unmet public health need. The chikungunya virus leads to an acute febrile disease with headache, muscle pain, and skin rashes, with severe, often debilitating, joint pain in infected patients that can persist for years, especially in adults. It has caused millions of infections worldwide in the past few years. In late 2013, the first local transmission in the Americas was identified in Caribbean countries and territories. Since then, chikungunya has been identified in 45 countries in the Americas alone with more than 1.7 million suspected cases reported to the Pan American Health Organization, increasing the incidence of the disease and risk to U.S. travelers. In 2016 and 2017, cases were reported in the United States, Italy and France. Additionally, in 2016 there were approximately 60,000 cases of chikungunya across India, posing a large burden on the healthcare system. Beyond the Indian subcontinent, the Caribbean, Central America and South America, inhabitants and travelers visiting sub-Saharan Africa and Southeast Asia are also at risk.

VLP vaccines are multi-protein structures that mimic the organization and conformation of naturally occurring viruses, but lack the viral genome. There are two main advantages of the chikungunya VLP approach over other vaccine approaches. First, VLP vaccines are non-infectious and therefore avoid safety concerns during production or use. Additionally, the chikungunya VLP vaccine maintains natural epitopes to mimic natural infection and derives high immunogenicity.

Chikungunya virus is an arthropod-borne virus (arbovirus), closely related to other viruses in Africa, South America and Australia that cause similar symptoms. Chikungunya virus is a small, spherical RNA virus and a member of the Alphavirus genus in the family Togaviridae. The virus is vectored by the daytime-biting Aedes aegypti mosquito, which also transmits yellow fever, Zika and dengue viruses. The virus originated in sub-Saharan Africa, but has variants that spread throughout tropical areas of the world.

Chikungunya can also be transmitted by Aedes albopictus mosquitoes, a more cold-tolerant mosquito – this could result in the spread of chikungunya to more temperate areas of the world. Individuals who are at higher risk for more serious complications include infants, the elderly and those with chronic medical conditions. There are currently no FDA approved vaccines to prevent chikungunya and no specific treatments for the complications of the infection. Non-vaccine interventions to prevent infection are limited to using insect repellent, wearing long sleeves and pants and otherwise restricting exposure to vector mosquitos.