If you’re a chemist working with peptide coupling agents, you can literally become allergic to the lab, according to a new report. Over the course of three years, graduate student Kate McKnelly of the University of California, Irvine, developed an allergy to the coupling agents HATU, HBTU, and HCTU so severe that she can no longer be in the building where they’re used. She and her research adviser James Nowick found that her allergy to the uronium coupling agents is not an isolated incident, and that many peptide coupling reagents are sensitizers and should be handled with extreme care (J. Org. Chem. 2019, DOI: 10.1021/acs.joc.9b03280).
Peptide coupling agents help form amide bonds between a carboxylic acid and an amine, so the compounds have the potential to modify human proteins. This property makes the agents potential sensitizers, chemicals that can cause people who are regularly exposed to them to develop an allergy. “This is something that has been passed around anecdotally and in the toxicological literature, but has not been published in places that organic chemists would see,” Nowick says. The authors found about 10 other examples of the allergy in the toxicology literature, but don’t have exact numbers on how common the allergy is.
After years of repeated exposure to the agents, McKnelly has to carry an epipen, can no longer work in the lab, and has to ask labmates to change their clothes before coming into contact with her. At first, McKnelly didn’t know where her symptoms were coming from, but she began to suspect it was lab-based after she’d notice her reactions while weighing out the coupling reagents in the lab. “Sometimes I would sneeze or my nose would get runny,” she says, but she was trying not to jump to conclusions. “I didn’t really know for sure until I had my anaphylactic reaction.”
One day when McKnelly sat down in her office adjacent to the lab, her throat began to constrict, and she started wheezing. She was fine after leaving the lab and taking diphenhydramine (generic Benadryl), but in hindsight, she should have called 911, she and Nowick now say.
Since the incident, Nowick has instituted new safety rules for handling peptide coupling agents in the lab. They now have a dedicated hood where the researchers weigh the coupling agents and amino acids and dispose of any contaminated weighing paper or other waste. There was another lab member who also showed signs of an allergy to peptide coupling agents, but caught it early and was able to manage it by limiting his use and having labmates weigh out the compound, McKnelly says. She’s now switched her focus to teaching because her allergist told her it’s probably not safe to work in a lab ever again, although it’s not necessarily due to the presence of peptide coupling reagents. “My lungs are sensitive now, so any irritants can set me off,” McKnelly says. “Unfortunately, most labs have irritants.”
This is a tragic event for McKnelly, but it’s good that the researchers published this account, says Craig Merlic, an organic chemist at the University of California, Los Angeles, and the executive director of the University of California Center for Laboratory Safety. Chemical sensitizers currently aren’t on the list of chemicals that safety experts typically train on, but they should probably be added, he says. An allergy like this is a “complete life-changing incident for a researcher and the article presents the clinical issues, but certainly there are personal challenges for the woman that must be substantial.”
Merlic applauds the steps the Nowick lab has taken to reduce the lab members’ exposure to these peptide coupling agents, but feels like it’s a good beginning rather than extent of what they can do. He suggests additional steps, such as weekly laundering of lab coats, cleaning of the lab, and neutralization and hydrolysis protocols to destroy the uronium coupling agents.
“I really don’t want this to happen to anyone else,” McKnelly says. “If I wasn’t as teaching-oriented as I am, it could have been kind of detrimental to my career as a chemist.” She notes that people who work with these compounds need to protect themselves. HATU, HBTU, and HCTU haven’t been nominated for testing through the US National Toxicology Program, but she intends to submit them, she says.