Health/Life Sciences

Seattle biotech startup backed by Gates Basis launches trial for snail fever vaccine

The first patient is dosed in a phase 1 trial for the SchistoShield vaccine against schistosomiasis. ( Kaiser Permanente Washington Health Research Institute Photo)

The first patient has been dosed with a vaccine for the tropical disease schistosomiasis, developed by Seattle biotech company PAI Life Sciences.

The phase 1 trial will assess the safety and immune response in healthy volunteers at Kaiser Permanente Washington Health Research Institute in Seattle.

Schistosomiasis, also called snail fever, is caused by parasitic flatworms that enter human skin in contact with contaminated water. Long term infections can cause damage to livers and kidneys, infertility, and bladder cancer.

A vaccine would build up the arsenal against the disease, which affects almost 240 million people in sub-Saharan Africa, the Middle East, Southeast Asia and the Caribbean. Treatments are available but often don’t shield against symptoms like headache and malaise, and many people experience recurrence, said PAI CEO Darrick Carter.

The condition “is second only to malaria among parasitic diseases with the greatest devastating economic impact,” said PAI’s vice president Sean Gray in a statement Tuesday announcing the trial launch. Many vaccine candidates have been tested, but “few have offered any significant protection,” said Gray.

The new protein-based vaccine can confer protection for up to eight years in primates, and antibodies are transmitted from mother to child, said Carter.

The advantage of PAI’s vaccine is that it is designed to affect all life cycles of the parasite in the body, from eggs to juveniles to adult worms. The vaccine targets a protein called calpain that cleaves other proteins and is thought to “remodel” the worm’s surface to help it evade the immune system.

Isolated schistosome worms under the microscope. (Afzal Siddiqui lab Image)

“By targeting this protein there would be less immune evasion. We are hitting a potential Achilles heel,” said Carter. The vaccine aims for eggs by killing almost all females, which have high levels of calpain on their surface and cause most of the pathology. And the worms that hatch are also damaged, interrupting transmission cycles.

Not all the males are killed by the vaccine, but that is an advantage, said Carter. The males do not cause disease. And if a few stick around, they can keep the immune system activated and ready to attack any incoming females.

Texas Tech University Health Sciences Center researcher Afzal Siddiqui and his colleague invented the vaccine, which is licensed it to PAI.

PAI is also developing vaccines and treatments for other neglected conditions including tuberculosis and leishmaniasis, and sells adjuvants, immune-boosting substances added to vaccines. The 6-person company was founded in 2004 by Carter, who is also chief scientific officer at another Seattle vaccine company, HDT Bio.

The new “SchistoShield” vaccine is PAI’s first clinical trial. The trial is funded by the U.S. National Institute of Allergy and Infectious Diseases, the Bill & Melinda Gates Foundation, and a public-private partnership, the RIGHT (Research Investment for Global Health Technology) fund.

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