March 15, 2008 (Vol. 28, No. 6)

Ability to Tackle Serious Infectious Disease Outbreak Still Not Where It Should Be

The fear of bioterrorism and avian flu are driving a healthy new interest by biotech firms in developing products in the field of infectious diseases. “Even though we were developing a smallpox vaccine in 2000, there is no doubt that 9/11 was the moment that biodefense suddenly came up the funding ladder in the U.S.,” said Clement Lewin, Ph.D., vp of marketing policy and strategy at Acambis, who spoke at “EuroBio” late last year.

Acambis’ vaccine for smallpox, ACAM2000, was approved by the FDA at the end of August. ACAM2000 is based on a vaccinia pox virus related to variola and is manufactured in cell culture in Vero cells rather than from calf lymph, as previous smallpox vaccines have been.

“ACAM2000 is the first biodefense vaccine to come to market and has drawn on all the available cell culture technologies we have today,” Dr. Lewin said. “The vaccine’s approval took 60 months from the start of development, and we have now made over 200 million doses available around the world.”

Despite product success Acambis has had a bumpy ride with its funding. “Any biotech that believes developing products to serve public health emergencies is access to easy money needs to think again,” Dr. Lewin cautioned. “Collaborating with the U.S. government is different from working in the biotech world. You have to produce a proposal for the government to digest, a cost of around $400,000, and if you don’t get the contract that’s all money down the drain.”

Drinking Water Test

Another company mining the bioterrorism threat is Pharmaleads, which is developing a fluorescence-based diagnostic test for detecting botulinum toxin in drinking water. “Botulinum toxin is easy to make and introduce into liquid,” explained Jean-Pierre Rogala, COO. “Also the botulinum A and B toxins are lethal in doses as small as 5 ng/mL and 200 ng/mL, respectively. To be able to monitor drinking water requires a test that is robust and fast, and can be used either by security forces or other nonscientifically trained personnel in the field.”

To fulfill these needs the company developed a test that utilizes botulinum toxin’s zinc metalloprotease activity. The firm generated a zinc metalloprotease substrate containing a fluorescent reagent known as Fluofast®. Since botulinum toxins can recognize and cleave specific amino acids in the Fluofast substrate to release a fluorescent signal, the toxin’s presence can be detected via a fluorometer. To make field detection possible, Pharmaleads also tested a number of hand-held fluorometers and included one in a full diagnostic kit called EzyBot®.

“EzyBot contains everything necessary to test water samples in situ including the reagents and a portable fluorometer,” Rogala commented. “We have even added a portable incubator that can be plugged in a car’s cigarette lighter socket to ensure the reaction can be carried out at 37ºC. Using EzyBot, anyone can find out for certain within an hour if there is botulinum A or B toxin in their drinking water.”

To show the efficacy of the EzyBot system, Rogala presented data on many different types of drinking water samples including those that had been spiked with pollutant compounds containing iron, zinc, manganese, calcium, nitrate, and nitrite. “To prove that our technology works, we have tested it on thousands of different water samples, taken from different seasons and moments in the day, as well as those spiked with unusual pollutants such as humic acid,” Rogala explained.

“We are so confident in the core technology that we would like to extend the kit to test for Legionella and anthrax but we require more funding for the amount of work this will require.”

Avian Flu

Another area where there is concern about the possibility of a sudden outbreak is avian flu, and Novavax claims to have a solution to address this threat. “All the major pharmas are working on avian flu vaccines, but many are using their existing technology and trying to adapt it to fit the problem,” Rahul Singhvi, Sc.D., CEO of Novavax, said. “At Novavax, we are starting from scratch and integrating all the current recombinant strategies and manufacturing innovations to provide a totally different approach.”

The company is using a virus-like particle (VLP) to build a structure similar to an avian flu virus but without the genetic material required for viral replication. Once injected into the body, VLPs are expected to trigger an immune response sufficient enough to protect a person if they are exposed to the virus.

“VLPs have the same size and outside viral surface protein decorations but without any of the virus’ guts, and because the virus cannot replicate this is safe technology,” Dr. Singhvi stated. “In fact, Merck’s cervical cancer vaccine, Gardasil, is made this way so a track record of safety does exist.”

Dr. Singhvi presented preclinical data on Novavax’ H5N1 VLP vaccine that showed it was effective in ferret models. “We use ferrets as well as mice in our preclinical studies because ferrets display human-like flu symptoms such as sneezing and runny noses.”

“We performed a challenge experiment in ferrets with wild type H5N1 Indonesian and Vietnamese avian flu virus. Of those ferrets that had been immunized with 0.6, 3, or 15 µg of H5N1 VLP vaccine made using an Indonesian strain of H5N1 all survived after they were challenged with a lethal dose of the H5N1 virus, but those that received a placebo died.
“Research has been so promising that we have initiated a Phase I/II study that will enroll 230 volunteers. We expect to receive interim safety and immunogenicity results from 70 subjects by the end of this year.”

For large-scale clinical production, Novavax’ H5N1 vaccine will be manufactured in insect cells with recombinant baculovirus expression technology using totally disposable bioreactors. “Traditionally,” Dr. Singhvi adds, “influenza vaccines are made in eggs, taking as long as six months to produce a vaccine. As avian flu attacks chickens, many chickens may well be dead before we have the millions of eggs required for large-scale vaccine production, so it makes sense to use cell culture instead.”

According to Dr. Singhvi, Novavax is going to rely 100% on disposables in manufacturing, as the company believes it will take too long and cost too much to set up and run fixed stainless steel plants. Using disposable processing equipment, Dr. Singhvi estimates the firm could produce economic quantities in 100–500 L batches.  Production plants manufacturing the same number of doses as stainless steel plants could be built for 60% less capital expenditure, said Dr. Singvi.

“Since our manufacturing approach is small scale, it is more portable and could easily be franchised to other countries to address local market needs and produce a vaccine in large quantities in as little as two to three months. This is quicker than the current egg-based vaccine production and could save many lives in a global pandemic situation.”

Are We Ready?

Speakers presenting at “EuroBio” concluded that although interest and, as a consequence, the funding to develop products to detect or treat infectious diseases have increased, there is still a long way to go if public health is not going to be seriously compromised in the event of a spontaneous or terrorist-driven pandemic.

“Setting up and running Biomedical Advanced Research and Development Authority (BARDA) in the U.S. to provide an integrated approach to ensure drugs and diagnostics tools are available for public health emergencies is a step in the right direction,” Dr. Lewin commented. “However, we need to ensure that BARDA is staffed by people with industry experience and is also more flexible with its procurement policies or they will not be able to do this effectively.

“The preparedness for pandemic infections has improved, but if you look at the $560 million set aside each year by the Bioshield legislation, for example, this is still only $2 for every American. I would say in terms of being ready, we’re now moving from neutral to first gear, but we need to be in third gear to have a real ability to deal with serious outbreaks of infectious diseases.”

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