While waiting for an organ donor, patients in need of a transplant may one day have the option of taking out a loaner organ—from a pig.

Researchers report Tuesday that they were able to keep pig hearts alive and beating in the abdomens of five baboons for record amounts of time—a median of 298 days and a max of 945 days. Previous benchmarks were set at a median of 180 and a max of 500 days, respectively.

Data from the prolonged ticker swap, published in Nature Communications, highlights scientists’ progress at breaking down the biological barriers of cross-species organ donation, inching closer to using animal organs in humans in desperate need of transplants. Currently in the US, 22 people die every day just waiting for organs, which are in constant short supply.

To help solve the problem, researchers turned to pigs years ago to see if they could lend useful organs or at least provide temporary “bridge” tissue to those on wait-lists. Pigs were a good fit mainly because their organs’ sizes are similar to that of human’s. But, there are a lot of molecular snags that make the exchange difficult, if not immediately deadly.

In early studies, successful survival time in pig-to-primate transplants, generally called xenotransplants, were measured in minutes. The swine substitutes naturally have a molecular marker, called alpha 1-3-galactosyltransferase (gal), which triggers deadly blood clots in primates. And of course, a range of other cellular components on the pig parts appear as foreign invaders to a primate immune system, sparking battles-to-the-death of both the organ and the transplant recipient.

Researchers have since genetically engineered pigs to lack gal and used powerful immune-suppressing drugs to keep the peace between the transplant and its primate host.

In the new study, researchers at the National Institutes of Health and colleagues, tweaked the approach; they engineered the gal-knock out pigs to have extra anti-clotting genetic features and used an antibody to selectively shut down the part of the primate’s immune system that responds to pig organs.

To avoid needlessly killing the baboons and doing extensive surgery, the researchers opted to transplant the pig hearts into the baboon’s abdomens, leaving the primates’ hearts in place. In the abdomen, the pig tickers hooked up to circulatory system and beat for a record-breaking amount of time.

While the authors stress that the results need to be repeated with more animals—and in animals without their natural hearts—they are encouraged by the data. “If successful, the approaches described here could help translate xenotransplantation of the heart and other organs into a potentially transformative therapeutic option for the thousands of transplant candidates who may benefit from the timely availability of a porcine organ,” they conclude.

Nature Communications, 2015. DOI: 10.1038/ncomms11138 (About DOIs).