The Senate narrowly rejected an amendment geared toward criminalizing participation in research that created certain chimeras, or human-animal hybrids, in expectation that the federal government could lift a moratorium on funding for those projects.

A party line vote saw 48 Republicans supporting the measure. The 49 nays included 47 Democrats and two left-leaning independents --Sens. Bernie Sanders, I-Vt., and Angus King, I-ME. Sens. Thom Tillis, R-N.C., Joe Manchin, D-W.Va., and Marsha Blackburn, R-Tenn., didn't vote. 

Proposed this week, the Endless Frontier Act also contained language barring the transfer of a human embryo to a non-human womb and vice versa. 

"We shouldn't need to clarify in law that creating animal-human hybrids or ‘chimeras’ is ethically unthinkable, but sadly the need for that very clear distinction has arrived," said Sen. James Lankford, R-Okla., who co-sponsored the bill with Sens. Mike Braun, R-Ind., and Steve Daines, R-Mont.

STANFORD FAILED TO DISCLOSE FUNDING FOR RESEARCH USING FETAL TISSUE IN MICE, GROUP ALLEGES IN NIH COMPLAINT

Braun said: "Human life is distinct and sacred, and research that creates an animal-human hybrid or transfers a human embryo into an animal womb or vice versa should be completely prohibited, and engaging in such unethical experiments should be a crime."

The legislation would impose penalties as high as $1 million or "the amount equal to twice the amount of the gross pecuniary gain." It also provided for up to 10 years in prison.

The bill was intended as a check on the National Institutes of Health (NIH) potentially lifting its moratorium on research utilizing chimeras.

On Wednesday, the International Society for Stem Cell Research released guidance backing chimeric research.

"Chimeric embryo and in utero research … should proceed for the minimum time necessary to achieve the scientific aim," the organization's guidelines read.

"This research must proceed incrementally, stopping at well-defined timepoints to assess the degree and scope of chimerism during development before proceeding to full gestation, if full gestation is among the well-justified goals of the research. To avoid unpredictable and widespread chimerism, researchers should endeavor to use targeted chimerism strategies to limit chimerism to a particular organ system or region of the gestating chimeric animal."

CLICK HERE TO GET THE FOX NEWS APP

Thursday's vote came against the backdrop of a growing debate about the use of fetal tissue in scientific research. 

Earlier this month, Pennsylvania's legislature held hearings discussing, in part, the University of Pittsburgh's fetal tissue practices. Amid a raging debate about fetal cell lines and COVID-19 vaccines, a Pitt study gained attention for grafting fetal scalps onto mice.