that can develop hemophilia B
A plant-made therapy has demonstrated safety and efficacy in dogs with hemophilia B, according to research published in Molecular Therapy.
Previously, researchers found they could produce freeze-dried lettuce cells expressing human coagulation factor IX (FIX) fused with cholera toxin B subunit (CTB).
These cells were able to prevent inhibitor formation and allergic reactions to intravenous FIX therapy in mice with hemophilia B.
With the current study, the researchers showed that lettuce cells expressing CTB-FIX were safe and could prevent anaphylaxis and inhibitor formation in dogs receiving intravenous FIX to treat hemophilia B.
“The results were quite dramatic,” said study author Henry Daniell, PhD, of the University of Pennsylvania in Philadelphia.
“We corrected blood clotting time in each of the dogs and were able to suppress antibody formation as well. All signs point to this material being ready for the clinic.”
This study made use of Dr Daniell’s patented plant-based drug-production platform, in which genetic modifications enable the growth of plants that have specified human proteins in their leaves.
The researchers grew lettuce that had been modified to produce a fusion protein of human FIX and CTB. CTB helps the fused protein cross the intestinal lining as the lettuce cells are digested by gut microbes, while the plant cell walls protect FIX from digestion.
The researchers said they were able to achieve commercial-scale production of CTB-FIX fusions expressed in lettuce chloroplasts by growing the plants in a hydroponic facility.
The team first tested their product in 2 dogs with hemophilia B. Twice a week for 10 months, the dogs consumed the freeze-dried lettuce material, which was spiked with bacon flavor and sprinkled on their food.
Observing no negative effects of the treatment, the researchers went on to a more robust study, including 4 dogs that were fed the lettuce material and 4 that served as controls.
The 4 dogs in the experimental group were fed the lettuce material for 4 weeks. At that point, they also began receiving weekly injections of FIX, which continued for 8 weeks. The control dogs only received the FIX injections.
All 4 dogs in the control group developed significant levels of antibodies against FIX, and 2 had visible anaphylactic reactions that required the administration of antihistamine.
In contrast, 3 of the 4 dogs in the experimental group had only minimal levels of one type of antibody, IgG2, and no detectable levels of IgG1 or IgE.
The fourth dog in the experimental group had only a partial response to the lettuce cells expressing CTB-FIX. The researchers believe this was due to a pre-existing antibody to human FIX.
Overall, levels of IgG2 were 32 times lower in the experimental group than in the controls.
In addition, the dogs showed no negative side effects from ingesting the lettuce material, and blood samples taken throughout the experiment revealed no signs of toxicity.
“Looking at the dogs that were fed the lettuce material, you can see it’s quite effective,” Dr Daniell said. “They either developed no antibodies to factor IX, or their antibodies went up just a little bit and then came down.”
The next steps for the researchers include additional toxicology and pharmacokinetics studies before applying for an investigational new drug application with the US Food and Drug Administration, a step they hope to take before the end of the year.
