A Stony Brook University professor pilfered grant money meant for cancer research and used it to pay for personal expenses, including mortgage payments on his house, federal prosecutors said Thursday.

Associate Professor Geoffrey Girnun, director of cancer metabolomics at Stony Brook’s Renaissance School of Medicine, was charged with wire fraud and money laundering after allegedly siphoning over $200,000 from cancer-research grants issued by the National Institute of Health, the Department of Justice said.

“Professor Girnun’s alleged theft of federal and state grant funds earmarked for cancer research can be explained in two words: pure greed,” US Attorney Richard Donoghue said. “He will now be held to account in a federal courtroom.”

Girnun, 48, allegedly made shell companies that claimed to be providing research materials and equipment for his cancer-research projects — then submitted phony invoices to the university for grant money, prosecutors said.

Once he had his hands on the money, Girnun transferred it into his personal bank account, which he used to pay off his mortgage, among other expenses. The payments were made over four years, from 2013 to 2017.

“As millions of Americans place their faith in programs established to fund cancer-related research, Geoffrey Girnun, a professor, allegedly siphoned money from grant funds established for this very purpose,” added FBI Assistant Director-in-Charge William Sweeney. “While people continued to suffer from their illnesses, Girnun made payments toward his personal mortgage with the money he stole. His conduct is despicable, and it won’t be tolerated.”

The professor was arraigned in federal court on Long Island Wednesday afternoon. He pleaded “not guilty,” posted a $250,000 bond against his parents’ home in Florida and was released Thursday.

Among his bail conditions, he is not allowed in any Stony Brook facility.

“Geoffrey was completely shocked by these charges. At this time, these are merely allegations,” his attorney Steven Metcalf said. “I ask for everyone to hold off in rushing to judgement. We will be zealously and vigorously defending against these charges.”

His lawyer Steven Seigel added, “What you have here is a remarkably fine man, a Harvard-educated scientist who has made remarkable improvements in the lives of cancer patients. And I believe that when everything is resolved, there will be a whole different picture.”

If convicted, Girnun faces up to 20 years in prison.

The government is also seeking the forfeiture of the Woodmere, LI, house whose mortgage he is accused of paying with the ill-gotten grant money.