It’s getting cold out there! And while winter temperatures may have us yearning for a warm spot by the fireside, cold is a good thing for cell and gene therapies—in many cases, the colder the better. Logistics dictate that international shipping of cellular therapeutics often means freezing them first. Cryopreservation protects fragile cellular material from loss of viability or functionality during transit and storage, by halting chemical and biological degradation processes. To understand how important that is, it is worth noting that two of the hottest cell therapy drugs on the market this year (Yescarta® and Kymriah®) are both cryopreserved prior to infusion into the patient. But how cold does it really need to be to protect the efficacy of these cellular therapeutics? We decided to put that question into perspective.
Winter, of course, is the coldest time of year in the Northern climes. The village of Oymyakon in Siberia, Russia is the coldest permanently inhabited place on Earth, averaging an eyelash freezing -62°C in December. This makes the North Pole, where Santa manages his toy enterprise, almost balmy by comparison at -40°C. But these temperatures still aren’t the coldest on the planet. Vostok Station, in Antarctica, averages -88°C in winter, enough to make your teeth chatter just thinking about it.
How do these numbers compare to the temperatures needed to maintain the integrity of cell-based pharmaceuticals during shipping? Well, we all know water freezes when it reaches 0°C, but that temperature isn’t nearly enough to prevent damage to living biological systems. To prevent damage to living cells, they should be frozen at a slow, steady cooling rate (approximately 1°C/min for many cell types), aided by the presence of cryopreservative agents such as ethylene glycol and dimethyl-sulfoxide (DMSO) that help stabilize cell membranes against osmotic pressure. “Glass transition”, the temperature at which water transitions directly from a liquid to a solid without damaging crystal formation, is -135°C. This temperature is enough to significantly halt any biological activity, but it is still not an ideal storage temperature. Most scientists recommend storing cells in the vapor phase of liquid nitrogen, at a frigid -196°C.
Protecting therapeutic cells from unintended changes in temperature is just as important as freezing them in the first place. Even a short foray into warmer temperatures can result in a decrease in efficacy, as stressed or damaged cells succumb to loss of functionality or even cell death. To prevent such occurrences, smart cell and gene therapy institutions embrace meticulously controlled cold chain practices. At HemaCare, full oversight of cell therapy starting materials is maintained from collection through to delivery. HemaCare offers packaging solutions designed for consistent temperature stability between 2°-8°C, 15°-25°C, and -196°C.
Here in southern California, winter temperatures rarely drop below “chilly”, with an average temperature of 18°C even in December. All the more reason to protect cell-based products from the sunny outdoors that we enjoy throughout the holiday season.