(CNN) — Scientists continue to make progress with research on how well pig organs might perform in humans, and now they’re ready for the next step: larger-scale clinical trials.

eGenesis, one of the biotech companies developing gene-edited pigs whose organs are transplanted into humans, said Monday that the US Food and Drug Administration has given the green light to human trials involving kidneys from its pigs.

“It’s a very optimistic period,” said Paul Conway, chair of policy and global affairs for the American Association of Kidney Patients, the country’s largest kidney patient advocacy group.

eGenesis’ pigs are genetically modified so that their organs are more compatible with human recipients. Key to this effort is using a tool called CRISPR to knock out the gene responsible for

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